J.-P Pérez

Keywords: Techniques, interferometric -Astrometry -Stars, binaries, close, visual -Stars, composite spectrum

We present speckle interferometry observations of 47 composite spectrum stars obtained between 1993 and 1998 at the Pic du Midi Observatory with the PISCO speckle camera. 76% of over 150 independent 10-min sequences of observations led to a companion detection. Binary component angular separations ranged from 0.05 ′′ to 1.2 ′′ . We also obtained a series of 23 measurements of an additional 9 close binaries. PISCO observations confirm, for the first time since their discovery, the duplicity of HD 29104 (L 4), HD 83808 (WGT 1Aa), HD 183912 Aa' (BON Ap), and HD 156729 (HR 6436). Discovered as double by Hipparcos, the particularly difficult to resolve HD 156729 was observed despite the large magnitude difference, ∆m = 4.2, between its two components.

Introduction

Composite spectrum stars are binary stars (often spectroscopic binary stars) comprising in most cases a dwarf hot star (B or A-type) and a cool evolved star (G, K or M) [START_REF] Ginestet | Atlas de spectres stellaires[END_REF]). The study of these systems is of great astrophysical interest (i) to improve estimates of the mass of red giant stars, and (ii) to constraint stellar evolution models (Schröder et al. 1997). A major problem arises when it comes to identifying the spectral types of the two components. As speckle interferometry can resolve some of these objects, we have undertaken an observational program with PISCO1 at the Pic du Midi Observatory and we report here on the astrometry done on some of them. The photometry and the spectra of the individual components will be presented elsewhere (Prieur et al., in preparation).

In 1993, we established the list of our targets from the following sources: -Hynek's catalogue of composite spectrum stars (Hynek 1938), -McAlister's catalogue of interferometric binaries (38), -Griffin's list of spectroscopic binaries where he suggests that most of them are likely to be resolved with speckle interferometry (Griffin 1990), -a list of stars with composite spectra from Markowitz (1969).

Additional objects suspected to be composite stars -e.g., stars with abnormal color indices in the Bright Star Catalogue [START_REF] Hoffleit | The Bright Star Catalogue[END_REF] -have also been incorporated to our list.

When starting this project, most of the objects had already been resolved by speckle interferometry but their orbits were undetermined. To obtain a good determination of the spectral types of the two components, two of us (N.G. and J.-M.C.) have carried out a spectroscopic survey of these binaries with the Carélec and Aurélie spectrographs at the Haute-Provence Observatory. The results concerning the cool components were presented in [START_REF] Ginestet | [END_REF](Ginestet et al., , 1999)). The classification of the hot components is in progress (Ginestet & Carquillat, in preparation).

During the 1993-1998 exploitation phase of PISCO, we applied a "flexible" scheduling to maximize the scientific return. Depending on the weather conditions, we selected the astrophysical program best suited for these conditions. Since part of our observations could be done when the FWHM seeing was larger than 1.2 arcsec, our program was often used as a backup for observations requiring good atmospheric conditions (e.g., high resolution imaging of complex or faint objects). As a consequence, multiple observations of our targets were performed during the 1993-1998 period, which permitted a follow-up of the astrometry over 6 years for some of them.

Observations

The observations (Table 1) were carried out with the PISCO speckle camera (44) developed at the Midi-Pyrénées Observatory and operated at the Cassegrain Focus of the 2-meter Bernard Lyot Telescope (TBL) at Pic du Midi. PISCO is a remotely controlled versatile instrument whose observing modes (e.g., imaging or spectroscopy) can be configured in real time. It constitutes a powerful tool for investigating the field of close binary stars, as demonstrated in previous works (Aristidi et al. 1999;48;45).

In this program, the PISCO speckle camera was used in its full pupil imaging mode. The atmospheric chromatic dispersion was corrected in real time with computer controlled Risley prisms. Except when the wind was strong and caused an elongation of the autocorrelation peaks (e.g. for HD 33883), these peaks were circular which is a good indication of the quality of the dispersion correction.

PISCO can make use of various detectors, as described in [START_REF] Prieur | [END_REF]. The observations presented here were performed with three detectors: the CAR (Caméra à Anode Résistive or Ranicon detector), the ICCD (Intensified CCD with a micro-channel plate) and the PAPA (photon-counting detector, derived from the version described in Papaliolios et al., 1985).

In Table 1, the nights are qualified as "used" when we could open the dome; however the FWHM seeing was generally much poorer than the yearly average TBL value of ∼1.2 ′′ . During the period 1993-1998, over one hundred nights were allocated to the projects studied with PISCO, with a usability rate of 33% that is significantly less than the average rate of ∼50% for this site.

Data reduction

The data reduction of a given observing sequence started with a detector-dependent pre-processing phase that generated an autocorrelation according to the method described in Worden (1977). The mean inter-correlation of two frames separated by a delay larger than the coherence time was subtracted from the mean autocorrelation of the elementary frames. This removed the background of the mean autocorrelation and nicely increased the contrast of the secondary peaks of binary stars. Astrometry parameters were then derived from this autocorrelation following the procedure described in Prieur et al. (2001).

Calibration

The orientation of the frames was calibrated by combining two methods: (i) by using the star tracks obtained by moving the telescope along the declination and right ascension axes, and (ii) by using wide pairs with slow orbital motion as "astrometric standards": HIP 1447 and HIP 4065 (Cuypers & Seggewiss, 1999, Prieur et al, 2001). The resulting angular uncertainty was found to be ±0.4 • and was included in the error on the position angle measurements displayed in Tables 3 and4.

Likewise, the magnification scale was obtained both by the "astrometric standards" and by measuring a calibration grid placed at the entrance focal plane of PISCO. A value of 50.4±0.1 m was used for the focal length of the TBL, as determined by the Pic du Midi optics group. This grid was also used to measure and correct the geometric distortion.

Pre-processing data collected with the CAR detector

The CAR detector produces no frames, but a continuous flow of photon coordinates in chronological order. With this camera, the mean autocorrelation was computed by correlating each photon coordinate with the N others collected during a given time interval. For each photon, this time interval, dubbed "the sliding window", starts after the photon is detected and ends after a chosen "frame time" has elapsed. This "frame time" can be chosen and adjusted during off-line data processing. If the frame time is significantly larger than the coherence time τ c of the atmospheric turbulence, noise is added to high resolution structures, and this prevents any detection of the companion. If the frame time is too small, the signal to noise ratio is degraded by photon noise, which may also impede companion detection.

To determine the optimum frame time, which maximizes the contrast of the secondary peaks in the autocorrelation function of the binary star, we computed from the same data a series of autocorrelations with frame times spanning the range 2-20 ms. Optimal values were 5-8 ms, which implies that the turbulence was fast (τ c =3-5 ms).

Another important parameter of the reduction procedure was the spatial sampling factor (re-binning) of the autocorrelations. For each data set, a compromise had to be found since a large spatial sampling increases the signal-to-noise ratio (by reducing the photon noise), while decreasing the angular resolution. Hence, by providing a list of photo-events coordinates, the CAR detector offers a high flexibility and the possibility to determine during the data processing phase the optimum values for the frame time and the sampling factor.

Unfortunately, this detector presents two defects which had to be calibrated and corrected:

1) A small geometric distortion: the detector axes (i.e. those of the resistive anode)

were not strictly perpendicular relative to each other (difference up to 2.5 • ), and at a different scale (up to 2%). To correct this geometric distortion, two-dimensional polynoms were fitted each night to images of the scaling grid available in PISCO, and applied to the CAR data.

2) A hole in the center of the autocorrelation function commonly appears when using detectors coupled to a micro-channel plate. This hole is due to the electronic depletion of a channel that appears after the detection of a photo-event in that channel. This depletion can last a few milliseconds and is a limitation to working at high illuminations.

We thus limited the illumination to 10 4 photons/s by inserting neutral densities for bright objects (V<7). We also modified the sliding window, shifting it by one or several milliseconds towards the future. In such a situation, each photon is not correlated with those immediately following, but correlated only with other photons detected at a time when the microchannels have partially recovered from depletion. The "photon counting hole" effect mainly affects the photometric measurements. Although it can reduce the detectability of very close binaries, it does not introduce artefacts on the astrometric measurements.

Pre-processing data collected with the ICCD detector

The data from the ICCD were stored as frames in SVHS tapes with a rate of 50 frames/s. For the ICCD, the exposure time of elementary frames could take any value between 64 µs and 16 ms, but the time interval between two successive frames was fixed (20 ms). This detector could not work in genuine photon counting mode and thus did not provide the coordinates of individual photo-events. A specially designed program (by JLP), controlled a video-tape recorder and a digitizing board, allowing a fully automatic processing of these tapes (Prieur et al., 2001).

Pre-processing data collected with the PAPA detector

The pre-processing phase of the data obtained with the PAPA detector is described in (Aristidi et al. 1999) and concerns here only a few measurements.

Astrometric measurements

The treatment of the mean autocorrelations was identical for all detectors. It consisted in accurately measuring the position of the secondary peaks of the binary stars, from which the position angles and angular separations of the components were derived. This was interactively done by a set of procedures described in Prieur et al. (2001).

Results

The astrometric measurements are displayed in Tables 3 and4. The HD name is in Col. 1 and the corresponding WDS name (Washington Double Star Catalogue, http://ad.usno.navy.mil/wds/wds.html) is given in Col. 2. For each observing sequence, we give the epoch of observation (Col. 3) in Besselian years, the filter (Col. 4) (whose characteristics are listed in Table 2), the detector used (Col. 5), the position angle θ in degrees (Col. 6), relative to North increasing in the direction of increasing right ascension, and the angular separation ρ in arcseconds (Col. 7).

In Cols. 8 and 9 are indicated the residuals O -C (Observed minus Computed) for the objects with a known orbit, whose origin is given in Col. 10: HP64 [START_REF] Hopmann | [END_REF], HP73 (Hopmann, 1973), HZ82 (Heintz, 1982), SC83 (Scardia, 1983), DC84 (Docobo & Costa, 1984), HZ86 (Heintz, 1986), HK89 (Hartkopf et al., 1989), MS97 (Mason, 1997), BG99 (Balega et al., 1999), HK99 (Hartkopf, 1999), MS99 (Mason et al., 1999a), SJ99 (Soderhjelm, 1999), HK00 (Hartkopf & Mason, 2000) OJ00 (Olevic & Jovanovic, 2000), PB00 (Pourbaix, 2000), and SC00 (Scardia et al., 2000b).

In some cases (noted as "Marginal detection" in Col. 11), although the companion could be detected, the measurements are not given as they would be too uncertain to be of any use. Note that the V and R measurements of the position angle of HD 49618 have large errors; they are given between brackets. In Col. 11, we also indicate if the object is known to be a spectroscopic binary (SB) and, when applicable, give its orbital period.

The position angle θ of the companion was measured from the autocorrelation function, which leaves a 180 • ambiguity. When the signal-to-noise ratio was good enough, the restricted triple-correlation technique described in Aristidi et al. (1997a), or the image restoration with bispectral techniques [START_REF] Prieur | Proc. of the ESO conf. High Resolution Imaging by interferometry II[END_REF], allowed us to remove this ambiguity. This is noted with an asterisk in Col. 6. We note that for HD 8036, the brightest component in the B image is at 180 • relative to that found in the V and R images.

To have a more comprehensive view of our program on composite spectrum stars, we have included in The smallest (one-sigma) errors for the angular separation (Col. 6) were estimated at 0.002 ′′ for close pairs (i.e., ρ < 1 ′′ ) and 0.2% for wide pairs (i.e., ρ > 1 ′′ ) on the basis of the uncertainties coming from the determination of the center of the autocorrelation peak and those affecting scale calibration. Similarly, the smallest (one-sigma) error found for the angle position (Col. 7) was 0.5 • .

To evaluate systematic errors (e.g. a wrong value of the focal length), we plotted in Fig. 1 the residuals relative to the ephemerides for objects with known orbits (Cols. 8 and 9 of Tables 3 and4). In this plot, we excluded the case of HD 196088 whose latest orbit lead to particularly large residuals (discussed in Sect. 5.1). Although some residuals are rather large -due to the poor knowledge of the orbits for these objects -, they are globally centered at (∆θ=0; ∆ρ= 0), which indicates the absence of systematic errors.

Discussion

We compared our measurements with those from other observers, making an extensive use of the CHARA Third Catalogue (http://ad.usno.navy.mil/dsl/Speckle/intro.html, hereafter CHARA3), which includes all published measures of binary stars obtained with interferometric techniques.

Composite spectrum stars: particular cases

In this section, we successively examine the binaries (L 4, WGT 1Aa and BON Ap), whose duplicity is confirmed for the first time since their discovery, and the objects HD 49618 and HD 196088 which exhibit the largest residuals in Table 3 (Cols. 8 and9).

The companion of HD 29104 (L 4, ADS 3316) was discovered by Thomas Lewis in 1902 with the 28-inch refractor of the Greenwich Observatory, with θ = 192 • and ρ = 0.34 ′′ [START_REF] Dyson | Catalogue of double stars from observations made at the Royal Observatory[END_REF], and was never detected again, despite numerous attempts, especially in the period 1910-1922[START_REF] Aitken | New General Catalogue of Double Stars[END_REF] concluded in his famous "New General Catalogue of Double Stars" by the comment: "It is very doubtful whether the star is double". Only one observation (negative detection) is reported in CHARA3 (Bonneau et al., 1984). Our measurement in 1994.720 with θ = 134.0 • and ρ = 0.065 ′′ is then the first confirmation of the duplicity of HD 29104, more than 90 years after its discovery.

Likewise, our observations of HD 83808 (WGT 1Aa, ADS 7480) and HD 183912 Aa' (BON Ap) are the first successful detections since the discovery of the companions for both objects, respectively with θ = 17.0 • , ρ = 0.463 ′′ in 1980 (Weigelt & Wirnitzer, 1983) and θ = 163 • , ρ = 0.125 ′′ in 1978 (Bonneau & Foy, 1980).

For HD 49618 (STF 963 AB, ADS 5514), the orbit computed by Docobo & Costa (1984) fits better our measurements than Heintz' (1986) orbit, although the residuals are large in both cases. This was unexpected since Heintz' orbit is more recent and should be more accurate.

The O -C residuals of HD 196088 (MCA 61, BD+49 3310, HD 196089) are the largest seen in Fig. 1. This is surprising since the orbit was computed in 2000 (Olevic & Jovanovic, 2000) and should be compatible with our observation, made in 1998.665. We are quite confident about the quality of our measurement since it is in good agreement with the previous speckle observations reported in CHARA3. The angular separation has been increasing rather regularly from 0.047 ′′ to 0.074 ′′ during the period 1989-1996. Our measurement shows that the periastron passage predicted in 1998.49 by Olevic & Jovanovic did not occur.

As a general remark, our measurements will be very useful for future orbit determinations, because the number of speckle measurements of composite stars, and of binaries in general, has been decreasing in the 1990's. For example, since the Hipparcos measurement of 1991.25 [START_REF] Esa | Hipparcos Catalog[END_REF], only one measurement is given in CHARA3 for the objects HD 195692 (STF 2695, ADS 13971) andHD 214606 (CHR 113, BD+68 1319), obtained by Hartkopf et al. (2000Hartkopf et al. ( ) in 1996Hartkopf et al. ( and 1994, respectively. , respectively. This decrease of the occurrence rate of speckle observations is of particular importance for the small angular separations, due to a lack of observations with large telescopes.

Complementary list: particular cases

For ADS 9701 (WDS 15348+1032), the orbit computed by Hopmann (1973) leads to large residuals (ρ (O-C) =-0.254 ′′ ) and clearly needs revision. The orbit of this double star is still undetermined because the companion has moved along an orbital arc of only 26 • between 1822 and 1990. The relative motion of the two components is very slow and the period is thus expected to be very large. In the hypothetical case (quite unlikely) of a circular orbit, the orbital period would be about 2300 years. Our measurement is in agreement with the Hipparcos data: θ=174.8 • , ρ=4.012 ′′ .

During the data reduction, the objects HD 156729 and HD 196178 that we intended to use as reference stars were subsequently found to be double stars (Table 4).

HD 196178 (HIP 101475, WDS 20339+4642) was discovered as a double system by Hipparcos with ρ=0.311 ′′ and θ=56 • . In CHARA3, only one ground-based observation is reported in 1996.699, with ρ=0.302 ′′ and θ=60.2 • (Mason et al., 1999b).

HD 156729 (HR 6436, HIP 84606) was also found double by Hipparcos: ρ=0.844 ′′ , θ=141 • , with ∆m ∼4.2. This large magnitude difference between the two components explains why all speckle detection attempts of the companion have failed in 1988.169 (ρ < 0.038 ′′ , McAlister et al., 1993), in 1997.269 (ρ < 0.054 ′′ , Mason et al., 1999b) and in 1997.460 (ρ < 0.054 ′′ , Mason et al., 1999b). Our measurement in 1994.720 (ρ=0.906 ′′ , θ=139 • ) agrees well with the Hipparcos data. We also found a large magnitude difference, the companion brightness being close to our detection limit.

Composite spectrum stars not resolved by PISCO

We now examine the possible reasons which may account for the non-detection of the companion of some targets. Let us recall that we could not resolve all the binary stars with angular separations less than the TBL diffraction limit ρ d (ρ d =0.05 ′′ in V ).

The objects that were never resolved during our observations are listed in Table 5. If we take into account the last measurements by other observers (Cols. 2-5), the objects of this table belong to three groups (cf. Col. 6):

(1) binaries with a very small angular separation ρ < ρ d ,

(2) binaries with ρ d ≤ ρ ≤ 2 * ρ d , that can be resolved when atmospheric conditions are good,

(3) objects whose duplicity poses problem because it was never confirmed since their discovery.

Objects with small angular separations

Among our sample of composite spectrum stars, there are binaries whose components are closer than the TBL diffraction limit over part of their orbit. Hence the absence of a companion detection by PISCO is not surprising. An extreme case is HD 192577 (WRH 33Aa) which was always observed with angular separations smaller than 0.03 ′′ .

With angular separations larger than ρ d , the objects of the second group should have been resolved by PISCO. Let us remark that all of these objects were only observed once by PISCO and this absence of detection is not meaningful. It must be due to bad seeing. Actually, the performances of speckle interferometry are tightly related to the coherence time τ c and radius r 0 of the atmospheric turbulence (cf., e.g., [START_REF] Roddier | The effects of atmospheric turbulence in optical astronomy[END_REF]. As the turbulence can vary quickly, τ c and r 0 can quickly reach values small enough to impede the resolution of close binaries. This explains why in Table 3, there are many negative detection reports associated with positive detections for the same object (e.g., HD 9352, HD 82072, and HD 183912 Aa), sometimes on the same night.

Dubious or difficult cases

There are objects that were never resolved with PISCO at the TBL, despite multiple attempts made during the 1993-1998 period, and whose duplicity has never been confirmed either by other observers since they were discovered: HD 17245 (CHR 7): 3 observations were made in 1980-1984, with only one positive detection, by the discoverer (McAlister et al., 1987). We observed HD 17245 four times in 1997-1998 without success.

HD 17378 (MCA 9): Only two observations are reported in CHARA3. The companion was found in 1980 by [START_REF] Mcalister | Catalog of Interferometric Measurements of Binary Stars[END_REF] and was not detected in 1984 with a 6-meter telescope (Balega & Balega, 1987). Our three observations in 1994-1998 led to a negative result.

HD 109358 (BNU 4Aa): It was discovered as double with ρ = 0.110 ′′ by Bonneau et al. (1980), but was never detected in any of the 17 other observations performed from 1921 to 1989. Our two observations in 1997 also led to a negative result.

HD 169985 (STF 2316 Aa): The companion was observed twice in 1951, with ρ = 0.06 ′′ (Wilson, 1952), and 1976, with ρ = 0.250 ′′ (McAlister & Hendry, 1982). All 8 subsequent observations in 1976-1992 have failed.

HD 192909 (V1488 Cyg): The 20 observations made during the period 1921-1992 have failed to detect the companion.

HD 197177 (BNU 7Aa): The companion was only observed once by the discoverers with ρ = 0.244 ′′ (Bonneau et al., 1980). Nine other detection attempts made in 1949-1986 led to negative results. HD 208816 (WRH 36): The companion was only seen by Wilson (1951), with a very small separation: ρ = 0.05 ′′ , and never confirmed despite 17 other attempts in 1949-1992.

Hence, in the last twenty years or so, all the efforts made to resolve these objects with speckle interferometry have failed. One can then wonder whether the companions are detectable by speckle interferometry. As the spectra of all these objects are composite, their binary nature is certain and the magnitude difference between their two components is not very large (≤ 3). Hence the non-detection of the companion by speckle interferometry likely means that the two components are closer than the diffraction limit of the telescopes used.

Conclusion

The PISCO speckle camera of the Midi-Pyrénées Observatory has proven to be an efficient tool to study binary and multiple stars. Despite bad weather conditions, campaigns led with PISCO have produced a large number of astrometric measurements of binary systems, many of which could be followed during six years.

Three very different detectors were used (CAR, ICCD, PAPA), with different processing procedures. However, the results are homogeneous. The very good agreement both internally -measurements obtained with those three detectors agree -and externally -agreement with speckle interferometry observations by other authors -shows the absence of systematic errors when operating PISCO.

We confirm the duplicity of HD 156729 (HR 6436) discovered by Hipparcos as having a large magnitude difference between the two components (∆m = 4.2). PISCO is the first ground-based instrument that has been able to resolve this difficult object. Indeed, in most books, it is said that the speckle technique is limited to ∆m ≤ 3. The CAR detector, that was used for this detection, appears then particularly sensitive, and exhibits a high dynamical range. We also confirm the duplicity of HD 29104 (L 4), HD 83808 (WGT 1Aa), and HD 183912 Aa' (BON Ap). For these objects, the measurements with PISCO are the first successfully performed since the discovery of their duplicity, in 1902, 1980 and 1978, respectively. Some objects were not resolved during our observations. A close analysis of the results obtained by previous observers yields a logical explanation. For most objects, the angular separation was very close to, or smaller than, the diffraction limit of the TBL whose diameter is too small to perform continuous measurements during an orbital revolution. For others, the companion was observed only once, by their discoverers. As the presence of these companions has never been confirmed in the last 20 years or so, even with large telescopes, the two components responsible for the composite spectrum of these objects must be too close to be detected by 2-6 m class telescopes. To resolve them, interferometric arrays are required. Since these objects are very close binaries whose components are rather bright and have a small magnitude difference, they should be useful for testing the capabilities of these arrays.

Due to a change in policy of the TBL time committee, PISCO was de-commissioned in 1998 and this paper is the last of a series that has produced numerous results (Carbillet et al. 1996;Aristidi et al. 1997b;Aristidi et al. 1999;48;45). PISCO has contributed measurements of binary stars during the particularly critical period of the 1990's during which the frequency of speckle measurements with 2-m class, or larger, telescopes significantly decreased. Continuous observations are essential for establishing reliable orbits. In particular, measurements obtained during the periastron passage are crucial for accurate orbit determinations. The case of HD 196088 is illustrative of this problem. Our observations obtained close to the predicted periastron invalidate a very recently published orbit. This erroneous orbit was computed after the epoch of our observations, using too scarcely distributed data. We hope the situation will soon improve with new generation speckle cameras being installed on large-size telescopes and adaptive optics systems becoming available on most of medium-size telescopes.

Fig. 1 .

 1 Fig. 1.-Residuals for objects with known orbits (observed -computed).

Table 1

 1

		. Observations
	Dates	Detector	Nights	Program
		Attributed Used
	Aug. 1993 CAR	-	∼1 Backup
	Sept. 1994 CAR	-	<1 Backup
	July 1995 CAR	8	4	Main
	Jan. 1997 CAR	5	2	Main
	" ICCD		1	"
	June 1997 PAPA	-	<1 Backup
	Aug. 1998 ICCD	7	5	Main
	Table 2. Filter characteristics.
	Name Central wavelength Bandwidth
		(nm)		(nm)
	B	447		47
	OIII	501		11
	V	530		57
	R	644		70
	RL	743		69
	I	855		74

Table 3 .

 3 Table 3 two previously published measurements of HD 83808 and HD 186518 made with PISCO (references given in Col. 11). Relative astrometric data (epoch, ρ, θ, resp. in Col. 3, 6 and 7) of the composite spectrum stars. The position angles θ have a 180 • ambiguity except those marked with an asterisc for which triple correlation methods removed this ambiguity.

	HD name WDS name Epoch Filt. Detector	θ	ρ	θ (O-C) ρ (O-C) Orbit	Comments
						•	′′	•	′′
	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
	HD 4775 00507+6415 1998.665 R ICCD	-	-			SB, P=2090 days
	HD 8036 01198-0031 1998.657 B ICCD	196.4±0.5 * 1.598±.005			Inversion of brightest comp.
	"	"	1998.657 V	ICCD	16.3±0.5 * 1.603±.005
	"	"	1998.657 R ICCD	16.5±0.5 * 1.599±.004
	HD 9352 01334+5820 1994.720 R CAR	-	-			SB?
	"	"	1997.071 B ICCD	-	-
	"	"	1997.071 V	ICCD	115.±2. 0.085±0.006
	"	"	1997.071 R ICCD	125.±10. 0.092±0.01			Marginal detection.
	"	"	1997.071 RL ICCD	-	-
	"	"	1997.071 I	ICCD	-	-
	"	"	1997.079 V	CAR	-	-
	"	"	1998.665 R ICCD	-	-
	HD 12447 02020+0246 1998.657 B ICCD	274.4±0.5 * 1.867±.007	1.9	0.035 SC83
	"	"	1998.657 V	ICCD	274.7±0.5 * 1.861±.007	2.2	0.029 SC83
	"	"	1998.657 R ICCD	274.4±0.5 * 1.864±.016	1.9	0.032 SC83
	"	"	1998.660 V	ICCD	274.6±0.5 * 1.867±.007	2.1	0.035 SC83
	HD 13474 02145+6631 1998.665 R ICCD	-	-			SB P=32 yr
	HD 17245 02475+4416 1997.082 R CAR	-	-			SB P=349 days
	"	"	1997.082 I	CAR	-	-
	"	"	1998.657 V	ICCD	-	-
	"	"	1998.657 V	ICCD	-	-
	HD 17378 02945+5705 1994.720 R CAR	-	-
	"	"	1998.657 V	ICCD	-	-			Marginal detection.
	"	"	1998.665 R ICCD	-	-
	HD 18925 03048+5330 1998.657 B ICCD	244.0±1.1 * 0.255±.003	-0.3	0.001 PB00 SB P=5350 days
	"	"	1998.657 V	ICCD	244.9±0.5 * 0.253±.003	0.6 -0.001 PB00
	"	"	1998.657 R ICCD	245.2±1.2 * 0.252±.003	1.1 -0.002 PB00
	HD 23089 03460+6321 1998.665 V	ICCD	-	-			SB P=6150 days
	HD 29104 04357+1953 1994.720 R CAR	134.±3.5 0.065±.002			Marginal det., SB P=488 days
	HD 29140 04357+1010 1997.071 B ICCD	125.9±0.5 * 0.175±.002	-0.7	0.002 BG99 A is SB (P=3.6 days)
	"	"	1997.071 V	ICCD	125.9±0.5 * 0.173±.006	-0.7	0.000 BG99
	"	"	1997.071 R ICCD	126.9±1.5 * 0.164±.01	0.3 -0.009 BG99 Fuzzy autocorr. peaks
	HD 33883 05135+0158 1994.720 R CAR	234±6	0.60±.04	-3.1	0.015 MS99 Elongated autocorr. peaks
	HD 49618 06531+5927 1997.079 B CAR	-	-
	"	"	1997.079 V	CAR	(277±10) 0.239±.017 (-16.5)	0.025 DC84 Very bad seeing
								(-9.7) -0.041 HZ86
	"	"	1997.079 R CAR	(312±10) 0.268±.051	(18.5)	0.054 DC84 Very bad seeing
								(25.3) -0.012 HZ86
	"	"	1997.079 RL CAR	292±3	0.219±.034	-1.5	0.005 DC84
								5.3 -0.061 HZ86

Table 3 -

 3 Continued

	HD name	WDS name	Epoch Filt. Detector	θ	ρ	θ (O-C) ρ (O-C) Orbit	Comments
						•	′′	•	′′
	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
	"	"	1997.079 I CAR	293±2	0.240±.027	-0.5	0.214 DC84
								6.3 -0.040 HZ86
	HD 09296-0307	1997.079 B CAR	-	-
	"	"	1997.079 RL CAR	30.3±0.9 0.895±.010
	"	"	1997.082 B CAR	30.4±0.5 0.868±.024
	"	"	1997.082 V CAR	-	-
	"	"	1997.082 R CAR	-	-				Marginal detection.
	HD 09412+0954	1997.071 V ICCD	267.9±0.5	0.59±0.1				(Aristidi et al., 1999)
	"	"	1997.076 R CAR	-	-				A is SB, P=14 days
	"	"	1997.079 RL CAR	-	-
	"	"	1997.079 I CAR	-	-
	HD 09525-0806	1997.082 B CAR	64.7±2.	0.594±.038	1.0 -0.012 HZ82
	"	"	1997.082 V CAR	-	-				Marginal detection.
	"	"	1997.082 R CAR	63.4±0.5 0.615±.013	-0.3	0.009 HZ82
	HD 12337+4121	1997.079 V CAR	-	-
	"	"	1997.079 R CAR	-	-
	HD 17335+5734	1995.556 B CAR	307.8±0.6 0.099±0.005
	"	"	1995.556 R CAR	308.1±0.7 0.102±0.002
	"	"	1995.561 V CAR	309.2±1.2 0.094±0.004
	HD 18101+1629	1995.553 B CAR	220.1±0.5 1.218±0.008	1.7 -0.023 HP64
	"	"	1995.553 V CAR	221.3±0.5 * 1.221±.019	2.9 -0.020 HP64
	"	"	1995.553 R CAR	220.4±0.5 * 1.210±.002	2.0 -0.031 HP64
	"	"	1998.657 B ICCD	220.6±0.5 * 1.228±.002	2.6 -0.013 HP64
	"	"	1998.657 V ICCD	220.7±0.5 * 1.225±.002	2.7 -0.016 HP64
	"	"	1998.657 R ICCD	220.7±0.5 * 1.229±.002	2.7 -0.012 HP64
	HD 18272+0012	1998.657 V ICCD	-	-				SB P=386 d., triple.
	HD 19082+1215	1995.561 B CAR	181.9±1.5 0.158±.002
	"	"	1995.561 V CAR	183.7±0.8 0.156±.004
	"	"	1998.657 V ICCD	180.9±0.5 0.169±.01				Weak autoc. peaks
	HD 19307+2758 AB 1995.559 B CAR	234.3±1.0 * 34.4±0.2				Albireo
	"	"	1995.559 V CAR	234.9±1.0 * 34.0±0.2
	"	"	1995.559 R CAR	233.2±1.0 * 34.3±0.2
	HD 19307+2758 Aa 1995.556 B CAR	139.0±0.8 0.398±0.009	-1.9	0.008 HK99
	"	"	1995.556 R CAR	140.9±1.0 0.397±0.009	-0.0	0.007 HK99
	"	"	1995.559 V CAR	139.3±1.0 0.397±.007	-1.6	0.007 HK99
	"	"	1998.657 B ICCD	132.7±0.5 * 0.388±.005	0.5	0.018 HK99
	"	"	1998.657 V ICCD	132.7±0.5 * 0.384±.006	0.5	0.007 HK99
	"	"	1998.657 R ICCD	132.3±0.9 * 0.385±.007	0.9	0.008 HK99
	"	"	1998.660 V ICCD	-	-
	HD 19307+2758 Aa' 1995.556 B CAR	-	-				Marginal detection.

Table 3 -

 3 Continued

	HD name WDS name Epoch Filt. Detector	θ	ρ	θ (O-C) ρ (O-C) Orbit	Comments
						•	′′	•	′′
	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
	"	"	1995.556 R CAR	-	-			Marginal detection.
	"	"	1995.559 V	CAR	160.0±4.0 0.045±.003
	HD 19348+2928 1998.657 V	ICCD	-	-			SB P=1572 days
	HD 19426+1150 1993.605 V	CAR	73.±1.	0.39±.01
	"	"	1995.553 R CAR	76.4±1.0 0.421±0.006
	"	"	1995.559 B CAR	76.9±0.5 0.430±.005
	"	"	1995.559 V	CAR	76.7±0.5 0.431±.004
	"	"	1998.657 B ICCD	77.9±0.5 * 0.417±.002
	"	"	1998.657 V	ICCD	77.4±0.5 * 0.417±.002
	"	"	1998.657 R ICCD	77.0±0.5 * 0.420±.002
	HD 19439+2708 1998.657 B ICCD	282.±2.	0.348±.02
	"	"	1998.657 V	ICCD	283.2±0.6 0.360±.003
	"	"	1998.657 R ICCD	283.6±0.5 * 0.349±.004			(Prieur et al., 2001)
	HD 19487+1149 1995.561 B CAR	106.6±0.7 1.499±.020
	"	"	1995.561 V	CAR	106.8±0.8 1.451±.008
	"	"	1995.561 R CAR	107.6±0.8 1.467±.010
	"	"	1998.657 B ICCD	107.3±0.5 * 1.449±.003
	"	"	1998.657 V	ICCD	107.4±0.5 * 1.450±.003
	"	"	1998.657 R ICCD	107.1±0.5 * 1.447±.004
	"	"	1998.660 V	ICCD	107.0±0.5 * 1.447±.010
	HD 19487+1852 1998.657 B ICCD	100.±2. *	0.400±.02			Artefact in central line
	"	"	1998.657 V	ICCD	99.5±0.5 * 0.412±.002
	"	"	1998.657 R ICCD	99.6±0.5 * 0.411±.002
	HD 20136+4644 1998.665 V	ICCD	-	-			SB P=3784 days
	"	"	1998.665 R ICCD	-	-
	HD 20155+4743 1998.665 R ICCD	-	-			SB P=1148 days
	HD 20244+2417 1994.706 OIII CAR	111.5±1.7 0.363±.004			Noisy
	"	"	1998.657 B ICCD	116.4±0.6 * 0.353±.004
	"	"	1998.657 V	ICCD	117.0±0.5 * 0.357±.004
	"	"	1998.657 R ICCD	116.4±0.5 * 0.352±.002
	HD 20320+2548 1995.550 V	CAR	-	-			A is SB (P=11 days)
	"	"	1995.550 R CAR	240.1±1.1 0.161±.005
	"	"	1998.657 B ICCD	244.3±0.5 0.223±.002
	"	"	1998.657 V	ICCD	243.7±0.7 0.226±.006
	"	"	1998.657 R ICCD	242.6±0.8 * 0.227±.006
	"	"	1998.660 V	ICCD	244.0±1.2 * 0.225±.008
	HD 20330+4950 1998.665 R ICCD	220.0±0.7 0.082±.003	7.9	0.065 OJ00 SB
	HD 20339+3515 1994.706 V	CAR	-	-
	"	"	1995.550 R CAR	-	-
	"	"	1998.657 B ICCD	280.±2.	0.317±.04			Artefact in central line

Table 3 -

 3 Continued

	HD name WDS name Epoch Filt. Detector	θ	ρ	θ (O-C) ρ (O-C) Orbit	Comments
						•	′′	•	′′
	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
	"	"	1998.657 V	ICCD	-	-				Marginal detection.
	"	"	1998.657 R ICCD	278.4±1.5 * 0.282±.01
	HD 20410+3218 1998.657 V	ICCD	-	-
	HD 20537+5918 1998.665 R ICCD	97.4±0.5 0.166±.002	-0.1 -0.001 HK89
	HD 21193+5837 1998.665 R ICCD	-	-				Very bad seeing
	HD 21516+6545 1998.665 R ICCD	147.7±0.5 * 1.450±.002
	HD 21567+6338 1998.665 R ICCD	-	-				SB P=7430 days
	HD 22038+6438 1998.665 R ICCD	-	-				SB P=811 days
	HD 22295+4742 1998.657 V	ICCD	-	-				SB P=42 yr
	HD 22330+6955 1998.665 R ICCD	116.0±1.0 0.198±.004	-3.8	0.012 SJ99
	"	"	1998.665 R ICCD	121.2±1.0 0.204±.008	1.4	0.018 SJ99
	HD 22383+4511 1998.657 V	ICCD	-	-				Artefact in central line
	HD 22373+6913 1998.665 R ICCD	0.2±0.5 0.535±.007				A is Am, perhaps SB
	HD 22431+4710									Triple system
	"	AB	1993.605 V	CAR	300.0±1.0 0.462±.01
	"	AC	1993.605 V	CAR	309.0±1.0 0.450±.01
	"	BC	1993.605 V	CAR	42.±6.	0.069±.02
	"	AB	1993.605 R CAR	300.7±1.0 0.453±.01
	"	AC	1993.605 R CAR	308.5±1.0 0.453±.01
	"	BC	1993.605 R CAR	34.±6.	0.054±.01
	"	AB	1993.608 B CAR	-	-				Marginal detection.
	"	AB	1993.611 B CAR	-	-
	"	AB	1995.553 R CAR	-	-				Marginal detection.
	"	AB	1995.556 B CAR	306.0±1.0 0.517±0.01
	"	AB	1995.556 V	CAR	305.2±1.0 0.508±0.01
	"	AB	1995.556 R CAR	305.7±1.0 0.499±0.01
	"	AB	1997.476 R PAPA	302.8±1.0 0.509±.01
	"	AC	1997.476 R PAPA	308.2±1.0 0.507±.01
	"	BC	1997.476 R PAPA	44.0±5.	0.056±.01
	"	AB	1998.657 B ICCD	302.6±1.5 0.496±.005				Fuzzy autocorr. peaks
	"	AB	1998.657 V	ICCD	304.6±0.5 0.501±.002
	"	AB	1998.657 R ICCD	304.4±0.5 * 0.499±.002
	"	AB	1998.660 V	ICCD	304.5±0.5 * 0.499±.002
	HD 23460+4625 1995.550 R CAR	-	-				ψ And; Marginal detection.
	"	"	1995.556 B CAR	282.0±1.7 0.327±.009
	"	"	1995.559 B CAR	282.3±0.7 0.325±.006
	"	"	1995.559 V	CAR	281.6±1.0 0.317±.004
	"	"	1998.657 B ICCD	280.1±0.5 0.351±.008				Artefact in central line
	"	"	1998.657 V	ICCD	280.3±0.5 0.332±.009
	"	"	1998.657 R ICCD	280.2±0.5

* 0.342±.005

Table 3 -

 3 Continued

	HD name WDS name Epoch Filt. Detector	θ	ρ	θ (O-C) ρ (O-C) Orbit Comments
						•	′′	•	′′
	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
	HD 224646 23595+5441 1998.665 R ICCD	86.9±0.5 0.386±.003

Table 4 .

 4 Relative astrometry of our complementary list (same structure as Table3).

	HD name WDS name Epoch Filt. Detector	θ	ρ	θ (O-C) ρ (O-C) Orbit	Comments
						•	′′	•	′′
	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
	ADS 9701 15348+1032 1995.556 B CAR	174.8±0.5 * 4.00±.01	-1.8 -0.254 HP73
	"	"	1995.556 V CAR	174.7±0.5 * 4.00±.01	-1.9 -0.254 HP73
	"	"	1995.556 R CAR	174.7±0.5 * 4.00±.01	-1.9 -0.254 HP73
	ADS 11046 18055+0230 1995.559 B CAR	165.7±0.5 * 2.63±.02	-0.4	0.071 PB00
	"	"	1995.559 V CAR	165.6±0.6 * 2.62±.02	-0.5	0.061 PB00
	"	"	1995.559 R CAR	165.6±0.6 * 2.61±.02	-0.5	0.051 PB00
	HD 895	00134+2659 1993.602 V CAR	172.5±1. 0.347±.01	-3.8	0.005 SC00
	"	"	1993.608 V CAR	172.1±1. 0.342±.01	-4.2	0.000 SC00
	"	"	1993.608 R CAR	172.5±1. 0.335±.01	-3.8 -0.007 SC00
	HD 2913	00324+0657 1993.614 B CAR	-	0.180±.01
	"	"	1993.611 V CAR	286.7±3. 0.198±.015	-5.4	0.007 MS97
	"	"	1993.611 V CAR	290.0±3. 0.183±.015	-2.1 -0.008 MS97
	HD 156729 17177+3717 1994.720 R CAR	139.1±0.8 0.906±.007
	HD 196178 20339+4642 1993.602 V CAR	60.9±3.	0.260±.02
	"	"	1993.605 V CAR	63.0±2.	0.270±.02
	"	"	1993.614 R CAR	62.3±2.	0.305±.03
	HD 197018 20396+4035 1993.602 V CAR	1.6±1.	0.871±.02
	HD 206644 21424+4105 1993.602 V CAR	335.5±2. 0.167±.01	-2.6	0.003 HK00
	HD 214810 22408-0333 1993.614 B CAR	126.2±2. 0.349±.01	-3.3 -0.021 SJ99
	"	"	1993.605 V CAR	126.2±1. 0.348±.01	-3.3 -0.022 SJ99
	"	"	1993.605 R CAR	125.5±1. 0.350±.01	-4.0 -0.020 SJ99
	"	"	1995.550 V CAR	-	-				Marginal detection.
	"	"	1995.550 R CAR	129.0±.9 0.384±.004	-1.1	0.017 SJ99
	V Cyg.	-	1993.605 R CAR	-	-				Asymmetric core

PISCO stands for "Pupil Interferometry Speckle camera and COronagraph".

We would like to thank the technical staff of the "Télescope Bernard Lyot" for providing assistance during the observations. We are grateful to the people who lent us some of the detectors used: Peter Nisenson (Center for Astrophysics, USA) for the PAPA detector and Denis Mourard (Côte d'Azur Observatory, France) for the CAR detector. We also thank Jean-Pierre Barriot (Midi-Pyrénées Observatory), Yves Bresson (Côte d'Azur Observatory), Christine André, Boris Dintrans and Pierre-Antoine Hermange (all students at Midi-Pyrénées Observatory), and Bruno Lopez (Côte d'Azur Observatory) who participated to some of the observations. This work has made use of the "Third Catalog of Interferometric Measurements of Binary Stars" (http://ad.usno.navy.mil/dsl/Speckle/intro.html, CHARA Contribution No4) and of the "Besançon data base of binary stars" (http://bdb.obs-besancon.fr). This research has also made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory.


Nguyen Leroy

M Nguyễn

Leroy Lân

Urbanization and land disputes in Việt Nam : compromises and protests

Keywords: moral economy, urbanization, Việt. Nam, Party-State authoritarianism, resistances

Urbanization is the modus operandi of Việt. Nam 's integration into globalization and the "urban civilization" project is part of the expression of a new authoritarian norm.

The first part of the article discusses how the Vietnamese Party-State justifies its hegemonic urbanization project.

The second part returns to the modalities of strengthening the control of the political-administrative apparatus over the urban manufacturing process by the way of compromise and arrangements between actors.

The last part focuses on the authoritarian nature of urbanization and addresses the increasingly sensitive question of the resistance (material, statuary, ideological) of subordinates to a domination that is no longer bearable for them.

Based on the results of five-year doctoral research in geography conducted in the Red River Delta on the issue of acting in the urban factory in Hanoi, this research has been the subject of a book detailing stakeholder strategies, power relations and the resulting geography 1 .

The objective of this communication is to make Vietnamese political economy clearer in the field of urban manufacturing 2 by identifying the techniques and strategies of the authorities to impose "urban civilization" as a new authoritarian norm and thereby strengthen their legitimacy.

The second objective proposes to underline the existence of resistance and infrapolitics among subordinates.

1 Duchère (Y.), 2019, Hanoi and its region. A geography of compromise in authoritarian regime, Les Indes Savantes, 265 p. 2 "Process by which the interaction between urban society and the city, in its material reality, spaces and territories, produces a specific urban in perpetual transformation" (H. Noizet, 2003).

Yves Duchère

 and Antonio Gramsci's theory of "hegemony". This paper is partly in line with the work of Kleinen [John Kleinen, 2015], B.

Kerkvliet [2014, 2015] on the "dialogical" politic, J. Ségard and M. Gibert [2015] on "negotiated authoritarianism", M. Gainsborough about the non-monolithic organization of the VCP or Marie Lan

systematically being complacent towards the authorities, prefers to give land-based resistance movements an economic meaning rather than question what they tell us about the deterioration of relations between the population and its management structures [START_REF] Hiếu | V đ chuyển mục đích s đất trong quá trình công nghiệp h a, đô thị h a [About the problem of converting agricultural land for industrialization and urbanization], Tạp hí uản Nhà Nước[END_REF]Nguyễn Duy Thăng, 2004 ;[START_REF] Guyễn Văn | Agricultural Land Conversion and Its Effects on Vietnamese Farmers[END_REF].

I.

Urbanization, between voluntarism and state project a.

Urbanization and administrative reforms

The urban growth rate in Việt am (3,5 %/year since 2000) [World Bank, 2015, 2] and the share of urban dwellers (35,2 % in 2017) Đà ẵng (city in the center of the country benefiting from the development of coastal industrialization).

The authorities still operate on a highly centralized model and governed by five-year plans, which does not necessarily make it possible to think of the city in accordance with the speed of its development. The lack of transversality of urban planning (sectoral plans) also does not favour the design of development plans and effective master plans. In any case, these plans are most often bypassed by interest groups (nhóm lợi ích) 4 .

But the Vietnamese city is not only the result of "top-down" urban planning, the inhabitants also take part in the urban factory by sneaking between laws and regulations (lách luật). In situ urbanization, from below or endogenous urbanization, then covers the same reality: urban development that is beyond the control of the authorities and that contributes to urban sprawl and building densification.

Faced with the social, economic and environmental challenges of urban development, the Party-State undertook a decentralization process from the 1990s onwards, aimed at giving local authorities, led by the provinces, more room for manoeuvre. These changes can be analyzed as a draft of decentralization (or rather deconcentration), they can just as easily be likened to a political lure allowing the central power to maintain its hold while giving the impression of opening up 5 . 4 For T . Lê Đăng Doanh "Interests groups in Việt. Nam are characterized by people who have a position, some power and relations with public servants in the budget, banking, investment, real estate, mine, forest, sea fields" (Lê Đăng Doanh ,2012, p 277 and 278). Interests groups aim private and local interest at the expense of public interest and operate in an informal and illegal space. In real estate, interests groups, thanks corruption and their relations, obtain lands and build, for example, ghost residential area, ineffective economic exclusive zones or useless infrastructures (An Giang airport for example : https://tuoitre.vn/them-san-bay-an-giang-khi-san-bay-can-tho-dange-20171004111319674.htm, consulted on 3/10/19). In agreement with guyễn Quang A (former director of the ID research institute), it seems that the first interests group is the Communist Party of Việt. Nam. 5 About decentralization and recentralization, we refer to the reading of Vietnam. Rethinking the State [M. Gainsborough, 2010, chapter 3]. Nevertheless, it's important to keep in mind that localism is very developed in Việt. Nam.

Political decision-making and the room for manoeuvre enjoyed by local authorities are conditioned by their connections with the central government and by their ability to modulate decisions from higher levels. It is therefore an ambivalent system based on a mixture of compromise, ideological voluntarism, trial and error and adaptation to local requirements that is being put in place. b. "Urban civilization", a state project that is a source of legitimacy Hà ội, or rather its metropolitan modernization, is a state project. This modernity project led by the Ministry of Construction and the Prime Minister is embodied by the slogan: "green, civilized, modern and cultural city". This leitmotiv, chanted by the supporters of a metropolis of international standing, semantically and publicly records certain popular expectations of urban modernity (hiện đại). The population and the public authorities discuss and exchange ideas around a more or less shared reference framework. Through persuasion and propaganda, the authorities forge the "common sense" of populations (such as making people believe a civilized society is necessarily an urban society). "Urban civilization" is not only a marketing slogan which emphasizes life quality and lifestyle, it's also the conceptualization of a form of citizenship founded on exclusion [E. Harms, 2016, chapter 2] because it's the result of authoritarian practices such as evictions or changes in functions imposed on land 6 [M. Gibert, J. Ségard, 2016, 6].

The urban project of the Vietnamese capital is presented by the authorities as a bearer of the modern values of a contemporary society integrated into the world economy. The legitimacy of the CPV is not only based on its ability to create wealth, comfort and prosperity. Its legitimacy also depends on its ability to engage 6 Văn minh đô thị (urban civilization), is derived from the chinese wenming (文明). For the regime, as there are some civilized spaces, there are some non-civilized spaces. The concept of văn minh has been used to denigrate ethnic minorities of the margins of Viet Nam. This concept is also part of a process of social distinction, particularly between the rural world populated by nhà quê and the urban world inhabited by civilized city dwellers. This distinction operates between the new urban area (Khu đô thị mới) and the rest of the city too.

in dialogue with the people and to allow a "controlled relaxation of domination in certain spheres of social life" whose purpose is to "provide an escape from the regime's control"[M. [START_REF] Grawitz | Traité de sciences politiques[END_REF]. So, we can define the authoritarianism of the Vietnamese regime as a soft and dialogical authoritarianism. If the discourses 7 praising the merits of a modern city connected to the world can be associated with an obvious process of legitimization of the central power, they can also serve to conceal political and economic mechanisms that are more or less clear and justifiable to the population.

Thus, the expansion of Hà ội (Figure 1) in August 2008 is a striking example in several respects, in particular because it makes it possible to identify the values and semantic field mobilized both by the population and by the authorities through different media such as the press or Internet forums. The slowness with which the authorities communicated on the subject reminds us that this project was an authoritarian measure not intended to be discussed. because it was hiding important political and land deals that benefited a handful of insiders and, at the same time, allowed a recentralization of the power [D. [START_REF] Labbé | L'extension des limites administratives de Hà ội : un exercice de recomposition territoriale en tension[END_REF].

II.

State-party corporatism and decentralization of power a. Urban manufacturing and "state-party corporatism": from the National Assembly to the district 7 See this article (URL: http://tphcm.chinhphu.vn/muon-hien-dai-nghia-tinh-phai-xay-dung-van-minh-do-thi, consulted on 12/5/18) from the city's website Hồ Chí Minh and entitled: "Modernity requires the construction of urban civilization".

The urban fabric in Việt. Nam is ambivalent, revealing consultation mechanisms coupled with forms of authoritarianism that are themselves modulated according to the territories and their challenges. What we call corporatism, once analyzed, offers the possibility of illustrating how the political center maintains its hold on the peripheries, in particular by linking the various actors to each other around political and economic interests. The aim here is therefore to analyze how, like what is observed in Vietnamese society, the administration functions more on the basis of consultation/persuasion than coercion in accordance with the "negociated authoritarianism" [M. Gibert, J. égard, 2016].

The actors of the political-administrative machine are linked to each other by sectoral or regional interests that show a political and territorial administration marked by entryism, corporatism 8 and above all by the control of the center on all its peripheries. Indeed, the transfer of power from which these local authorities benefit is in fact one of the conditions for strengthening the weight and control of central power. This paradox is explained by the Vietnamese electoral process which, as Marie Lan Nguyen Leroy [M. guyễn Leroy Lân, 2015, 60] points out, gives major importance to the provinces in the choice of candidates eligible for a seat as a deputy in the National Assembly (list voting). This mechanism allows reciprocity and creates mutual dependence between the National Assembly and the provinces whose interests are essentially the same.

The proximity between high instances of the party and these same local authorities is also striking. As is the case in the provinces of the region of Hà ội, there are many political executives with a seat on the Central Committee of the Communist Party and responsibilities at the local level. This accumulation creates obvious conflicts of interest which give to some provincial People's Committee 8 However, if the entryism and verticality of power ensures that the centre has control over its peripheries, we must not believe and let believe that the political actors constitute a monolithic bloc. In reality, just as society is diverse, the regime is also affected by different currents and is mainly confronted with factional struggles.

presidents more power than a minister. The development of the metropolitan area of Hà ội is in fact a patchwork of sectoral and regional interests linked to the clienteles that the members of the Central Committee of the Communist Party represent.

The liberalization of the land market and the increasing involvement of market forces9 in the urban factory must not obscure the "fiscal socialism" [A. [START_REF] Kim | Land Takings in the Private Interest : Comparisons of Urban Land Development Controversies in the United States, China, and Vietnam[END_REF]. The relations between the different levels of the administration are characterized by a system of constraints/incentives that systematically places the commune, district and provincial levels in a situation of dependence on the orientations desired by the central authorities.

In this system, if the districts and communes are responsible for implementing provincial guidelines but receive no incentives, they will try to solicit them from the population and construction-promotion companies. It is precisely when incentives are too low that acts of corruption seem to be most prevalent. However, other systems based on obtaining facilities, infrastructure or constructions, in exchange for building land for example, may exist.

b. "Refocusing" of the State at the communal and village level

The commune and ward level is the subject of particular attention by provincial authorities and even by the central State since it is the territory in which planning policies are tested, most often on an ad hoc basis, but also because it is here that representations relating to land use planning and management are the most conflictual.

In recent years, the metropolization of Hà ội has been accompanied by an expansion of urban space that has most often ignored the existing situation and has been accompanied by land conflicts as a result of the absence of private land ownership in a market oriented country. It is in this context that we observe a descent of the State at the village level as well as a confusion of roles and functions at this same level (the population can be an investor and the investor can be a public servant...). district and provincial level. Through a process of nationalization of associations, the public authorities maintain their control over these structures, which are thought to be independent and for which the analogy with a possible counterpower is unthinkable.

Agreeing with a descent the State into the village where it was already present, or a "refocusing" 12 , these new social spaces are nevertheless the place where social changes and innovations are promoted that allow the politicaladministrative machine to delegate certain missions the local level without calling into question the major balances of power.

Finally, development and construction companies, public authorities and residents jointly participate in the urban factory. In some cases, the actors can be at the same time residents, administrators and investors. This is not without a number of conflicts of interest, particularly when local politicians are actively involved in investment projects requiring "land releases". Nevertheless, when local administrators are involved in investment projects, they are most often involved indirectly, as partners, associates or "facilitators" 13 . In fact, members of the local administration try to negotiate their place in the metropolization process, taking advantage of their network of influence and their power of coercion and decisionmaking in municipal affairs. Thus, gradually, we are witnessing a reactivation of relations with local notabilities.

III. Authoritarian urbanization and popular response a. "Liberations" of land or evictions?

12 For M. Gainsbourough, « recentralization » is when the center try to reassert its control on lower levels, as the village level [M. Gainsborough, 2010, chapter 3]. 13 They facilitate the implementation of projects by providing investors with the benefit of their political networks at higher levels or by showing clemency and understanding (thông cảm) with regard to compliance with construction or environmental legislation.

Since the land laws of 2003 and 2014, land recuperations and the feeling of injustice has increased 14 . The land has become a notorious lever of enrichment that allows a small emerging middle class 15 to accumulate capital taking advantage of its relationships with power. The State grants land to investors, sets up a system of dual land prices, facilitates "land liberations" and creates an institutional environment that is largely beneficial to market forces 16 . The prices proposed by the administration (giá nhà nước) are much lower than those of the market and the land then appears to be "priceless" [L. Pandolfi, 2009]. This situation gives rise to a feeling of injustice among the population, particularly in agricultural villages on the outskirts of urban areas where land has become one of the modern levers of capital accumulation. The method of calculating the price of land differs according to the type of land. In this system, agricultural land is significantly undervalued compared to other land.

The need to build "urban civilization" justifies what the authorities call "liberations" of land presented as essential for the modernization of the country.

"Attractiveness", "competitiveness", "investment", "modernization" are all terms 17 used by public authorities to shape representations of the transition to the urban era in which "the power to evict is founded on the right to own" [E. Harms, 2016, introduction]. Vietnamese urban civilization is built on a denial of the right to the 14 The report 304/BC-CP reflects the increase in the population's feeling of injustice and points out that, of the total number of land-related complaints related to expropriations carried out by the State, 70 % relate to the amount of compensation and relocation (compensation is indeed considered too low compared to "free market" prices); 20 % of the complaints concern households that have been expropriated in a less favourable legislative context than that in force at the time of the investigations; 6 % concern land recovered during the bao cấp period which no compensation was paid; 3% concern households that have still not been relocated and 1% concern suspected discrimination and inequalities in land recovery arrangements 15 Above 15 USD per person and per day (7.7 % of the population in 2010 and 13 % of the population in 2016) [World Bank, 2018]. More than a simple range of revenue, the middle class is also a social group which adheres to a certain lifestyle. For more details on the question of middle class in Việt. Nam, please report to The reinvention of distinction : Modernity and the middle class in urban Vietnam [Van Nguyen Marshall and al., 2012]. 16 Truong and Perera [START_REF] Truong | Consequences of the two-price system for land in the land and housing market in HoChi Minh City, Vietnam[END_REF] argued that the land pricing mechanism is intentionally designed by the state to attract investment.

city. The land seizures illustrate the symbolic and physical violence from which it is built. For Erik Harms, "mass evictions and emergence of property rights go hand in hand. Likewise, the production of civilized spaces of new urban living founded on mass dispossession" [E. Harms, 2016, 219]. The expression of this new authoritarian norm is justified in an ambivalent way by the authorities and shows the use of different, even opposing, ideological registers. The phase of justification, awareness and pedagogy borrows from the values and concepts of the market economy, while in response to popular criticism and resistance, the words of the market economy are abandoned in favour of those of nationalism, socialism and revolution.

In a classic way, we also find in the press certain recurring qualifiers that dishonour those who dared to rise up, such as in the town of Đồng Tâm in April 2017 for example. Among these adjectives are: reactionaries (phản động), traitors to the nation, extremists (quá khích) and are described 18 as "disorder professionals"

("nghề ăn nên làm ra của mấy mấy kẻ chính tri") working for the collapse of the state, social instability and the disintegration of national unity while being financed by foreign and reactionary organizations.

b. From daily resistance to revolt

If many peasants in the suburban area of Hà ội appear to be victims of the modalities of land seizure, the analysis of their speeches and representations makes it possible to better define the framework of the exploitation of which they are victims and above all the limits beyond which domination is no longer, for them, "tolerable".

Concealment, cunning, the art of sneaking into the law (lách luật) or even the use of force (phá rào), are the possibilities open to the inhabitants and constitute 18 For example in Nhân Dân newspaper on 11 September 2018 in the article Phản nước, hại dân và phục vụ mưu mưu đồ chính trị cá nhân (Against the State and the People, and in the service of their personal interests).

as many material resistances. But, when the inhabitants of the peri-urban area, for example, put in place spatial strategies for the extension of housing or craft spaces, what is important to highlight is the way in which these strategies are justified (statutory resistance). The inhabitants construct their statements from and within the framework of the dominant ideology according to which the party is the central institution to which authority legitimately belongs. Individuals involved in informal and illegal forms of urbanization on agricultural land do not hesitate to recall that these lands have been won by the struggle:

"We, the humble peasants of the Vietnamese people, had to live under Chinese rule for a thousand years and under colonial oppression for a hundred years. Today, we own the country, we live in a socialist regime, but we become "homeless" in the very place where we fought a few decades ago, in the very place where we sacrificed our lives" (letter of protest sent to Prime Minister M guyễn Tấn Dũng, 2012).

While some well-known national artists such as the singer Mai Khôi 19 or the rappers Son Nah 20 and Sendoh 21 try to echo the "voiceless", it is also important to note that the villagers also produce real protest songs sung during sit-ins, occupations and other demonstrations. The song of the village inhabitants of Đồ ơn (province of Haỉ Phòng) is an example 22 :

Một lũ quan tham, một bọn người người A crowd of gourmet mandarins Một bầy tham nhũng, một một bầy tôi Huge corruption 19 Mai Khôi is constantly harassed and regularly arrested for taking a stand against the regime. We strongly recommend listening to the album "Dissent" produced with his group "The dissidents". 20 Known in particular for his song "Địt Mẹ Cộng Cộng ản" ("Fuck Communism"). 21 Listen « Việt am Lạ Lắm ». with the people modulate the political authoritarianism of the authorities but do not protect them from demonstrations of anger on the part of the people when they believe that the public theatre of domination and injustice must stop. Generally, the public expression of the feeling of injustice occurs when, on a specific subject, here land evictions, all remedies have been exhausted and when the taboo must be broken publicly in order to engage the public responsibility of the authorities. But, in Việt am, as in other authoritarian regimes, the possibility of free popular expression is severely limited.

Figure 3, 4 and 5: Demonstration and resistance in peripheries of Hanoi

The expression of this anger, riot or even revolt is not in fact economically determined. These violent demonstrations are moments of expression of dignity that reflect a general and increasingly obvious disavowal by the population towards its management structures. In addition to the riots in Thaí Bình in April 1997 and those in the highlands in 2001, a series of events must now be added to the riots in the highlands which agree in the sense of an ever-increasing defiance of the population towards their management structures. Thus, the case Đoàn Văn Vưon in 2012 at Haỉ Phòng, the clashes and hostage-taking at Đồng Tâm (district of Mỹ Đức, Hà ội, 2018) or the tensions surrounding the Ecopark project (Hà ội) add to the population's long list of outbursts of anger against its administration.

If, according to press reports, popular protest rallies are, for the authorities, the work of "scum" or "extremists", it must be noted that these events are multiplying, intensifying and that citizens are diversifying their modes of action, in particular by broadening the base of their demands. Indeed, like E. Harms, we argue that "the agitation over land use rights and civility [...] operate as a surrogate for the kind of political life citizens in other countries normally enjoy"[E. Harms, 2016, introduction]. Land claims are political claims in the sense that they point to the connections and corruption between the administration and the private sector, the authoritarian nature of evictions and the relationship between the VCP and the CCP. The events of June 2018 began with opposition to a proposed SEZ (Special Economic Zone) project in which Chinese investors are benefiting from 99-year leases 23 . The risk feared by the demonstrators is that these areas will be managed autonomously by Chinese nationals, so it is a question of sovereignty that is obviously part of a historical conflict between China and Việt. Nam. However, beyond the land claims and national momentum observed during these events, other messages, less relegated by the Vietnamese press, were conveyed. If in the processions one could read "No land rental to China, even for a day" or "China, out of Vietnam! ", other slogans openly criticized the cyber-security law adopted on June 12, 2018 or, and this is rare enough to mention, the Vietnamese Communist Party itself.

Conclusion

23 From 23 to 28 may 2018, the Vietnamese Parliament met to discuss a draft law on the creation of three special economic and administrative zones "called the Law on Administrative and Economic Units" to be granted for 99 years to foreign companies, located in three strategic coastal areas of the country: in northern Việt. Nam Đồn (2.200 km 2 , of which 551.33 km 2 on land and 1620 km 2 on sea, Quảng inh province) in the bay of Hạ Long near the Chinese border, in the centre in Vân Phong Nord (11,000 ha of which 56,000 ha on land and 55,000 km on sea, Khánh Hòa province) 30 km from Nha Trang, facing the Spratly, and in the south Phú Quốc island (58,923 ha, Kiên Giang) off Hà Tiên in the Gulf of Thailand.

With a growth rate of 6.88 % in 2018, a GDP per capita of USD 2343 24 and an urban transition already well under way, Việt am is undoubtedly working on its development and integration into the networks of globalization. The urban and civilizational ambition of the Party-State contributes to its legitimacy but does not protect it from the increase in inequalities and, above all, from the growing sense of injustice among populations that do not all benefit from urbanization. To address the threats facing it, the VCP monitoring and trying to anticipate the possibility of an overflow from the population. Through iterative governance, arrangements and compromises, authorities till manages to convince within its administration but faces greater difficulties with regard to a part of the population that does not benefit from the economic spin-offs of growth.

Those left behind in development policy and urbanization, through their everyday speeches and resistance strategies, point to the failure of the authorities to build consent in the field of urbanization. It is also noted that, unlike a commonplace frequently mentioned, manifestations of anger or revolt are not only the consequence of economic situations but also have much to do with dignity and respect for the social contract that binds, in principle, the population to its management structures. Like Leon Trotsky, we believe that "if the cause of revolutions were poverty, there would be revolutions every day".

Figure 1 :Figure 2 :

 12 Figure 1: Enlargement of the province of Hà Nội (August 2008) Figure 2: Planning project of the new Hanoi city

Faced

  with social unrest due to land issues (between 2008 and 2011, the number of complaints and charges about land issues increased from 187,037 to 236,466) 10 -the State and its agencies try to participate as actively as possible in local life, whether or associative. It is also, of course, a way to continue the work of persuasion and thus to participate actively in the making of "common sense". Rites, feasts and other celebrations, some of which were banned during the communist period, are central in Vietnamese villages and are reactivated from Đổi Mới. As Benoit[START_REF] Tréglodé | Héros et révolution au Viet-Nam [Heros and revolution in Vietnam[END_REF] reminds us, the cult of national heroes pursues a political objective since this type of cult is most often organized by the local party and proposes to unite around the tradition of the centralizing state.While during the communist period, population management structures were most often used to contain and organize village activities, the post-Đổi Mới period is characterized by the emergence of new associative actors (NGOs, clubs, "volunteer associations") 11 that are sources of social innovations. These new village organizations are in addition to the mass associations organized under the aegis of the Vietnamese Fatherland Front, which they do not compete with.Presented as independent of the public authorities, these new social structures are in fact often placed under the supervision of a ministry. Created at different levels around the defence of heritage, the promotion of crafts or the practice of a sport, art or religion, these associations are regularly invited to participate in meetings at 10 Based on report 304/BC-CP dated 26 October 2012. According to the same report, 70% of complaints and other administrative appeals filed with various public institutions related to land issues. 11 According to Wischermann and guyễn Quang Vinh[Wischermann and guyễn Quang Vinh, 2003, 4], more than 700 civic organizations were created between 1986 and 2005 at Hà ội and Hồ Chí Minh city.

  22 Author's translation Đục nước béo cò nên cố bám In troubled waters, storks hold Bầu không trúng c vẫn không thôi Even unelected they continue Thật là đau lắm ơn Đồ ơn ơn ơi! Đồ ơn, it's painful! Since the 1990s, the Vietnamese Party-State as demonstrated a renewed pragmatism and rethought in the light of the challenges posed by economic and social development. Exchanges, negotiations, compromises and other consultations

  //data.worldbank.org/indicator/SP.URB.TOTL.IN.ZS?locations=VN, consulted on 01/15/19)

	3	14,7	%	in	1960,	20,2	%	in	1990,	33 %	in	2014
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3

attest to the progress of urban transition, which is accompanied by powerful metropolitan dynamics, particularly at Hồ Chí Minh city (economic capital), Hà ội (political capital) and

Foreign direct investments in real estate increased from 0.3% in[START_REF] Guyễn Duy | Impact of urbanization on poverty and social stratification : a case study in the Hanoi suburban area[END_REF] to 23.6% in 2008 [World Bank, 2015, 23].