COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3792 Konkoly Observatory Budapest 22 October 1992 HU ISSN 0374 - 0676 A PHOTOMETRIC SURVEY OF SMALL-AMPLITUDE RED VARIABLES Introduction. Small-amplitude red variables (SARVs) are M giants which are pulsating with small amplitudes and with period of 20 to 200 days (but typically 50 to 100 days). They are red giant or asymptotic giant branch stars. A detailed study of a typical SARV (EU Del) has been reported by Percy et al. (1989). As a long-term project, one of us (JRP) is accumulating and analyzing observations of SARVs using a variety of techniques and sources, in order to clarify the status of the hundreds of suspected or poorly documented SARVs in the Yale Catalogue of Bright Stars, as well as to understand the systematics, evolutionary status, pulsation properties, and other processes in these stars. In 1990 and 1991, observations of SARVs were made using the 0.4m "teaching telescope" on the main campus of the University of Toronto. The 1990 results were. reported by Percy and Fleming (1992) and the 1991 results are reported here. The variables which have been discovered or confirmed in 1990 and 1991 will be followed up by the American Association of Variable Star Observers (AAVSO) photoelectric photometry program, or with the Automatic Photometric Telescope (APT) Service in Arizona. Observations and Results. The observational procedures are the same as described by Percy and Fleming (1992). Tables of individual observations will be deposited in the IAU Commission 27 Archives of Unpublished Photoelectric Photometry (Breger 1988). The results are summarized in Table 1. The "remarks" column refers mainly to information from the General Catalogue of Variable Stars (GCVS: Kholopov 1985) and the New Catalogue of Suspected Variables (NSV: Kholopov 1982). Because our data are not as extensive or precise as those obtained by Percy and Fleming (1992), we have not shown individual light curves. Copies of these can be obtained from JRP, or from the archival data. HR 5590. The amplitude is <0.10 and the period, if any, is about 30 days. Unfortunately, the comparison stars show large scatter. HR 5594. This star appears constant, but one of the comparison stars may be slightly variable. HR 5654 (FL Ser). There is scatter in the comparison stars, so we cannot confirm the GCVS classification (Lc) or amplitude (0.23). HR 5879 (NSV 7269). The range appears less than 0.05. The check star 5 Her (G8III) appears to be variable. HR HD V SpT Result Remarks Pgm 5590 132833 5.52 M0III var? VAR? Co 5573 132132 5.53 K1III var? Ch 5536 130970 6.18 K3III var? Pgm 5594 132933 5.71 M0.5IIb const? VAR? Co 5601 133165 4.40 K0.5III const? Ch 5631 134047 6.16 K0III const? Pgm 5654 134943 5.89 M4III var? FL Ser, Lb, Delta V=0.23 Co 5692 136138 5.70 G8III var? Ch 5740 137510 6.27 G0IV-V var? Pgm 5879 140477 4.09 M4III const? VAR? 35 kappa Ser Co 5924 142574 5.44 M0III const? Ch 5966 143666 5.12 G8III var 5 Her Pgm 5932 142780 5.37 M3III const? VAR? 2 Her Co 5950 143209 6.31 K0 const? Ch 5957 143435 5.62 gK5 const? Pgm 6010 145002 5.73 M3.5III var? FS Ser, Delta V=0.04 Co 6014 145148 5.97 K0IV const? Ch 6011 145085 5.91 gK5 const? Pgm 6056 146051 2.74 M0.5III const VAR? delta Oph Co 6075 146791 3.24 G9.5III const 2 epsilon Oph Ch 6016 145206 5.37 K4III var? Pgm 6107 147749 5.20 M2III const? VAR? 20 nu^1 CrB Co 6108 147767 5.39 K5III const? 21 nu^1 CrB Ch 6043 145802 6.29 K2III const? Pgm 6128 148349 5.23 M2.5III var? V2105 Oph, Delta V=0.06 Co - 145894 6.84 K0 var? Ch - 144892 6.70 F6V+F8V var? Pgm 6200 150450 4.90 M2.5III const VAR? 42 Her Co 6183 150030 5.79 G8 const Ch - 149105 7.00 G0V var? Pgm 6346 154356 6.69 M4III var VAR? 61 Her Co 6336 154126 6.36 K0 const Ch 6328 153897 6.55 F5V const Pgm 6495 157967 5.98 M4III var V640 Her, Lb, Delta V=0.17 Co 6542 159353 5.69 gK0 const? Ch 6541 159332 5.64 F6V const? HR HD V SpT Result Remarks Pgm 6765 165625 5.06 M3III const? VAR? 98 Her Co 6820 167193 6.12 K4III const Ch - 166842 6.67 K1III const Pgm 6834 167654 6.01 M4III const VAR? Delta V=0.10 Co 6866 168656 4.86 G8III const 74 Oph Ch 6857 168387 5.39 K2III const? Pgm 7405 183439 4.44 M0III const? VAR? 6 alpha Vul Co 7406 183491 5.81 K0III const? 8 Vul Ch 7421 184010 5.87 K0III-IV const? Pgm 7414 185630 5.03 M1III const 36 Aql Co 7404 183387 6.25 K2 const Ch 7438 184663 6.38 F6IV const? Pgm 7442 184786 5.96 M4.5III var VAR? Delta V=0.10 Co 7427 184293 5.53 gK1 const? Ch 7451 184960 5.73 F7V const? Pgm 7635 189319 3.47 M0III const VAR? 12 gamma Sge Co 7667 190211 5.96 K3II-III const Ch 7679 190608 5.10 K2III const? 16 eta Sge HR 5932 (NSV 7335). The variability, if any, appears small; there is larger-than-average scatter in all three stars. HR 6010 (FS Ser). This star appears to be slightly variable. The GCVS amplitude is very small (0.04 in V), and we cannot confirm or refute it. HR 6056 (NSV 7556). This star appears constant, but the NSV amplitude is small (0.03 in V) and not inconsistent with our result. The check star HR 6016 (K4III) may be slightly variable. HR 6107 (NSV 7676). The variability, if any, is small. The NSV amplitude is 0.08 in V. HR 6128 (V2105 Oph). The amplitude is at least 0.2 in V, and the time scale appears to be 30 days or more. The range, according to the GCVS, is 5.0 to 5.38 in V, which is consistent with our result. HR 6200 (NSV 7896). Our five observations do not indicate any variability, but they are insufficient to rule out the small range (0.05 in V) given in the NSV. HR 6346 (NSV 8159). This star is definitely variable. Our results are consistent with the NSV range of 0.2 in V. The time scale is not well-defined, but appears to be 30 days or more. HR 6495 (V640 Her). The range is consistent with that given in the GCVS (0.17 in V). The time scale (based on our limited data) is about 100 days. HR 6765 (NSV 10208). Our six observations do not indicate any variability. The NSV range is 0.13 in V. HR 6834 (NSV 10466). Our five observations do not indicate any variability. The NSV range is 0.14 in V. HR 7405 (NSV 12069). Our six observations are consistent with the NSV amplitude (0.07 in V), and a time scale of 50 days, but there is larger-than-average scatter in the comparison stars. HR 7414. This star appears to be constant. HR 7635 (NSV 12638). This star appears to be constant, though the time distribution of our six observations may have been such that the NSV amplitude of 0.09 in V was missed. Discussions and Conclusions. The data which we obtained in 1991 were not as extensive and precise as the data obtained in 1990 (Percy and Fleming 1992), so our conclusions about the variability of individual stars are not as secure. The proportions of non-variable, possibly variable, and definite variable stars were about the same. The general correlations between spectral type, amplitude and time scale of variability (Percy and Fleming 1992, figure 3) remain the same. We thank the Natural Sciences and Engineering Research Council of Canada for a research grant (JRP) and an Undergraduate Summer Research Award (CS). John R. Percy Erindale Campus University of Toronto Mississauga, Ontario Canada L5L 1C6 Charles W. Shepherd Department of Astronomy University of Toronto Toronto, Ontario Canada M5S 1A1 References: Breger, M. 1988. PASP, 100, 751. [BIBCODE 1988PASP..100..751B ] Kholopov, P.N. (editor-in-chief) 1985, General Catalogue of Variable Stars, fourth edition (Moscow: Nauka). Kholopov, P.N. (editor-in-chief) 1982, New Catalogue of Suspected Variable Stars (Moscow: Nauka). [BIBCODE 1982ncss.book.....K ] Percy, J.R. and Fleming, D.E.B. 1992, PASP, 104, 96 [BIBCODE 1992PASP..104...96P ] Percy, J.R., Landis, H.J. and Milton, R.E. 1989, PASP, 101, 893. [BIBCODE 1989PASP..101..893P ]