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2 The Strömgren photometric survey


   
Table 1: List of the targets of the Strömgren uvby program. CMP means a comparison star for a Primary Target which reason to be selected in our program is given as follows: variable (VR), spectroscopic variable (SV), infrared excess (IR), with known circumstellar gas (CG). Campaign 1 refers to the austral summer 1995-1996, 2 to 1996-1997, 3 to 1997-1998. Data from CDS and the Bright Star Catalog (Hoffleit & Warren 1991)
  star * $\alpha_{2000}$ $\delta_{2000}$ mV Spectral type $v \sin i$ Campaigns
  HD 203 CMP 00h 06m 50.0s -23$^\circ$06' 27'' 6.18 F2IV 155 3
HR 10 HD 256 VR,SV,CG 00h 07m 18.3s -17$^\circ$23' 13'' 6.23 A2IV/V 220 1,2,3
  HD 693 CMP 00h 11m 15.8s -15$^\circ$28' 04'' 4.89 F5V 8 2,3
                 
  HD 16417 CMP 02h 36m 58.6s -34$^\circ$34' 41'' 5.78 G5IV   2,3
$\alpha$ Fornacis HD 20010A IR 03h 12m 04.4s -28$^\circ$59' 14'' 3.85 F8IV 0 2,3
  HD 17729 CMP 02h 49m 54.1s -27$^\circ$56' 31'' 5.36 A0V 135 2,3
                 
  HD 21790 CMP 03h 30m 37.0s -05$^\circ$04' 31'' 4.74 B9Vs 72 3
$\epsilon$ Eridani HD 22049 IR 03h 32m 55.9s -09$^\circ$27' 30'' 3.73 K2V 8 1,2,3
  HD 22243 CMP 03h 34m 37.4s -09$^\circ$52' 05'' 6.25 A2V 160 1,2,3
                 
  HD 22713 CMP 03h 39m 01.1s -05$^\circ$37' 34'' 5.96 K1V   3
o 2 Eridani HD 26965A VR 04h 15m 16.3s -07$^\circ$39' 09'' 4.41 K1V   2,3
  HD 25069 CMP 03h 58m 52.4s -05$^\circ$28' 12'' 5.83 G9V   3
                 
  HD 26703 CMP 04h 13m 49.8s +12$^\circ$45' 12'' 6.25 K0   3
HR 1307 HD 26676 IR 04h 13m 34.5s +10$^\circ$12' 45'' 6.23 B8Vn 300 1,2,3
  HD 26793 CMP 04h 14m 36.1s +10$^\circ$00' 41'' 5.22 B9Vn 350 1,2,3
                 
  HD 32743 CMP 05h 02m 48.7s -49$^\circ$09' 04'' 5.38 F2V 0 3
$\zeta$ Dorado HD 33262 IR 05h 05m 30.6s -57$^\circ$28' 21'' 4.72 F7V 0 2,3
  HD 35072 CMP 05h 19m 22.1s -50$^\circ$36' 21'' 5.45 F7III-IV   3
                 
  HD 38382 CMP 05h 44m 28.3s -20$^\circ$07' 35'' 6.34 F8/G0V   3
$\gamma$ Leporis B HD 38392B VR 05h 44m 26.5s -22$^\circ$25' 18'' 6.15 K2V   2,3
$\gamma$ Leporis A HD 38393A IR 05h 44m 27.7s -22$^\circ$26' 27'' 3.60 F7V 15 2,3
  HD 35386 CMP 05h 23m 12.0s -26$^\circ$42' 19'' 6.49 F6V   3
                 
$\zeta$ Leporis HD 38678 IR 05h 46m 57.3s -14$^\circ$49' 19'' 3.60 A2Vann 245 1,2
                 
  HD 37935 CMP 05h 36m 55.1s -66$^\circ$33' 36'' 6.30 B9.5Ve   3
$\delta$ Dorado HD 39014 IR 05h 44m 46.4s -65$^\circ$44' 08'' 4.35 A7V 206 1,2,3
  HD 39963 CMP 05h 51m 23.1s -64$^\circ$02' 01'' 6.36 G8III   3
                 
  HD 35580 CMP 05h 22m 22.1s -56$^\circ$08' 04'' 6.08 B8.5V   1,2,3
$\beta$ Pictoris HD 39060 VR,SV,IR,CG 05h 47m 17.1s -51$^\circ$04' 00'' 3.80 A5V 104 1,2,3
  HD 40200 CMP 05h 54m 41.1s -49$^\circ$37' 37'' 6.10 B3V   1,2,3
                 
  HD 41692 CMP 06h 06m 38.7s -04$^\circ$11' 38'' 5.39 B5IV 20 3
HR 2174 HD 42111A CG 06h 08m 57.8s +02$^\circ$29' 58'' 5.73 A3V 120 3
  HD 42824 CMP 06h 12m 44.4s -02$^\circ$30' 16'' 6.63 A2V   3
                 
  HD 155450 CMP 17h 12m 58.6s -32$^\circ$26' 19'' 6.01 B1II 114  
51 Ophiuchi HD 158643 IR,CG 17h 31m 24.8s -23$^\circ$57' 46'' 4.81 A0V 210 3
  HD 160915 CMP 17h 43m 25.7s -21$^\circ$41' 00'' 4.87 F6/F7V 0 3

To compensate for the relatively small number of measurements obtained with our previous survey using the Geneva system between 1989 and 1997, a denser and long lasting photometric survey of $\beta$ Pictoris and of some other suspected $\beta$ Pictoris-like star candidates was needed. In October 1995 we began a circumstellar disk survey with the accurate Strömgren uvby photometric system being used almost permanently by the SAT group of the Copenhagen University Observatory. On behalf of a collaboration between Copenhagen Observatory and Institut d'Astrophysique de Paris through INSU (CNRS), we have performed three successive observational campaigns from 1995 to 1998, each season from October to April, using the SAT automatic 50 cm Danish telescope atop La Silla Observatory (Florentin Nielsen et al. 1987; Florentin Nielsen 1993).

We report here the result of 3 years of observations of the stars listed in Table 1. This circumstellar program was conducted from 1995 to 1998. As it could be noted only a small amount of stars were selected within our program, the reason being that only about a dozen of stars could be surveyed in a dense enough manner to be compatible with both the overall SAT observing program and the fact that at least two comparison stars should be observed simultaneously for each program star. The star list being extremely short, the program stars have to be selected in an extremely biased manner. They are in fact partly from our previous Geneva survey and partly as being "probably" good candidates, either because some variability is already suspected, or because they present some IR excess with known high $v \sin i$ value to favour the probability of extinction by dust within the disc.

Finally, during these three years as studies of dusty disks around A stars were made by several teams, some new stars were added to the program or suppressed from it during the chain of campaigns. Note that particularly $\beta$ Pictoris, HD 35580 (comparison, hereafter CMP), HD 40200 (CMP), HR 10, HD 22049, HD 22243 (CMP), HD 26676, HD 26793 (CMP) and HD 39014 were observed during all three years, whereas some other stars were observed during only one or two of our campaigns.


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