Photometric Surveys of Suspected Small-Amplitude Red Variables. III. An AAVSO Photometric Photometry Survey

Publications of the Astronomical Society of the Pacific 106: 611-615, 1994 June Photometric Surveys of Suspected Small-Amplitude Red Variables. III. An AAVSO Photometric Photometry Survey John R. Percy and Nancy Wong Erindale Campus, University of Toronoto, Mississauga, Ontario L5L 1C6, Canada Electronic mail: percy@astro.utoronto.ca Dietmar Bohme Nr. 11, PSF 93, Nessa 04851, Germany David R. Curott Lioncrest Observatory, Department of Physics and Earth Science, University of North Alabama, Florence, Alabama 35630 Frank Dempsey 1152 Tänzer Court, Pickering, Ontario L1W 3S6, Canada George L. Fortier 63 Devon Road, Baie d Urfe, Quebec H9X 2W7, Canada Matt Ganis and Stephanie Parello Pace Observatory, 861 Bedford Road, Pleasantville, New York 10570 Howard J. Landis Landis Observatory, 303 Saddle Creek Drive, McDonough, Georgia 30253 Kenneth D. 9624 Giddings Avenue NE, Albuquerque, New Mexico 87109 Donald Furnace Hill Observatory, 40 Hillcrest Drive, Cranston, Rhode Island 02921 Michael S. 6715 North Table Mountain Road, Tucson, Arizona 85718 Leroy F. MacLean Observatory, P. O. Box 3964, Incline Village, Nevada 89450 Raymond R. 7 Welton Street, Maple, Ontario L6A 1R8, Canada Rick Wasson Sunset Hills Observatory, 15870 Del Prado Drive, Hacienda Heights, California 91745 Harold O. Williams and William S. G. Walker Williams Observatory, 71 Milton Road, Mt. Eden, Auckland 4, New Zealand James E. Faun Lane Observatory, 11732 Faun Lane, Garden Grove, California 92641 (Received 1993 September 23; accepted 1994 March 9) ABSTRACT. We have carried out a survey of the photometric (V) variability of 61 known or suspected small-amplitude red variables, mostly M giants. Approximately two-thirds appear to be variable; several suspected variable comparison stars have also been identified. The incidence and average amplitude of variability increase rapidly from spectral type M0 III to M6 III. 611 1994. Astronomical Society of the Pacific

612 PERCY ET AL. 1. INTRODUCTION Small-amplitude red variables (SARVs) are M giants that are pulsating with small amplitudes and with periods of up to 200 days. Most of the known SARVs are bright stars. There are 164 known and 136 suspected variables among the approximately 500 M giants in the Yale Catalogue of Bright Stars (YCBS). There are also 16 known and 215 suspected variables among the approximately 1600 K giants in that catalog. Very few of these are actually variable; those which are appear to be RS Canum Venaticorum stars (Percy 1993). SARVs are red-giant or asymptotic-giant-branch stars. Their properties have been reviewed by Querci (1986) and Percy (1985). A detailed study of a typical SARV (EU Delphini) has been reported by Percy et al. (1989). As a long-term project, one of us (J. R. P.) is accumulating and analyzing observations of SARVs using a variety of techniques and sources. The goal is to clarify the status of the many hundred suspected or poorly documented SARVs in the YCBS, as well as to understand the systematics, evolutionary status, pulsation properties, and processes in these stars. Part of the survey has been carried out with the 0.4-m teaching telescope on the main campus of the University of Toronto (Percy and Fleming 1991; Percy and Shepherd 1992). Another part (reported here) has been carried out through the photoelectric photometry program of the American Association of Variable Star Observers (AAVSO). 2. OBSERVATIONS Program stars were observed in the V band, relative to comparison and check stars of mostly G and K type (since other M giants would be likely to be variable). The differential observations were corrected for extinction, and transformed to the standard UBV system, either by a standard procedure at AAVSO HQ or by individual observers using a similar procedure. The accuracy of the observations varies with both the individual observer, and with the differential brightness, color, and air mass of the stars involved. Typical accuracies are given in square brackets below. Note that, since each star was observed by one observer only, there were no errors due to systematic differences between observers. The observers equipment was as follows. Böhme [0.010]: Hopkins Observatory photometer on a 25 cm Cassegrain; Curott [0.010]: OPTEC SSP-5 on a 25 cm Meade cassegrain; Dempsey [0.012]: SSP-3 on a 15 cm Newtonian; Fortier [0.010]: OPTEC SSP-3 on a 32 cm Newtonian; Ganis/Parello [0.012]: Starlight-1 on a 28 cm (11") Celestron; Landis [0.008]: homebuilt photometer (1P21 PMT) on a 20 cm Newtonian; [0.012]: SSP-3 on a 20 cm (8") Celestron; [0.010]: SSP-3 on a 25 cm Meade cassegrain; [0.012]: SSP-3 on a 20 cm (8") Celestron; [0.008]: SSP-3 on a 56 cm (22") cassegrain; [0.010]: SSP-3 on either an 11 cm polar axis refractor or a 25 cm Schmidt-cassegrain; Wasson [0.012]: SSP-3 A on a 36 cm Newtonian; [0.010]: homebuilt photometer (EMI 9924A PMT) on a 53 cm cassegrain; [0.012]: SSP-3 on a 25 cm Schmidt-cassegrain. 3. RESULTS The results are summarized in Table 1, which gives the basic information on the program, comparison, and check stars; for the program and check stars, it gives the mean AV relative to the comparison star, the standard deviation, number of observations, and an assessment of the variability. Generally, stars were considered to be variable if <x>0.020; probably constant if 0.015^ct<0.020, and constant otherwise. GCVS4 refers to the Fourth Edition of the General Catalogue of Variable Stars (Kholopov 1985). NSV refers to the New Catalogue of Suspected Variable Star (Kholopov 1982). Notes on individual stars are given below, and a few representative light curves are shown in Figs. 1-4. 4. NOTES ON INDIVIDUAL STARS HR 105. 77 Scl; Lb variable, range 4.80 to 4.90 in V (GCVS4). We find 4.79 to 4.96 and a time scale of a month or two; the observations are sparse. HR 257. BQ Tue; Lb? variable, range 5.60 to 5.80 (GCVS4). We find 5.62 to 5.82 and a time scale of a month or two; the observations are sparse. HR 304. CC Tue; range 0.10 in V (GCVS4). We find 6.24 to 6.34 and a time scale of 25 days. HR 689. VAR? (YCBS). We find 5.23 to 5.30; the time scale may be about 20 days. HR 2717. BQ Gem; SRb variable, range 6.63 to 7.02 in B, time scale about 50 days (GCVS4). We find 4.84 to 5.26 in V and periods of 52 days and possibly a year or more (Fig. 1). HR 2967. NZ Gem; SR variable with a range of 5.52 to 5.72 in V (GCVS4). We find 5.50 to 5.61 and a rather irregular light curve with time scales of 40 and >200 days. HR 3061. BC CMi; SRb variable, range 6.14 to 6.42 in V, time scale about 35 days (GCVS4). We find 6.16 to 6.40 and a similar time scale. HR 3169. BL Cnc; Lb variable, range 5.97 to 6.04 (GCVS4). We find 5.87 to 6.07 and a rather irregular light curve with time scales of 20 and >100 days (Fig. 2). HR 3319. BP Cnc; SRb variable, range 5.41 to 5.75, period about 40 days. (GCVS4). We find 5.43 to 5.75 and a period of 40 days (Fig. 3). HR 3577. NSV 04332 (variability doubtful). We find a range of 6.30 to 6.39; the time scale is uncertain. HR 3773. NSV 04514; range 4.28 to 4.34 in V. There is one discordant observation; otherwise the range is ^0.02. HR 3993. NSV 04764; variable in K magnitude. We find a range of 5.79 to 5.88 and a time scale of 30 days. HR 4008. U UMa, range 6.20 to 6.25 in V (GCVS4); constant? (YCBS). We find a range of 6.13 to 6.19 and a time scale of a month or two. HR 4184. RX LMi; SRb variable, range 5.98 to 6.16, period 150: days (GCVS4). We find 5.99 to 6.08 and a possible short time scale as well as a longer (>100 days) one. HR 4267. VY Leo; Lb? variable; range 5.69 to 6.03 (GCVS4). We find 5.77 to 6.14, and time scales ranging from 40 days to a year or more. HR 4483. o) Vir; Lb variable, range 5.23 to 5.50 (GCVS4). We find 5.23 to 5.37, with time scales of 30 to >100 days.

AAVSO PHOTOELECTRIC PHOTOMETRY SURVEY 613 Table 1 Results of a Survey of the Photometric Variability of a Sample of Suspected Small-Amplitude Red Variables Program Star HR V B-V SpT AV N R 45 80 +1.,57 M2III -0.773 0.016 35 c? 105 81 +1.,64 M4III -0.398 0.065 6 257,56 M4III -0.291 0.068 304.64 M2III 0.839 0.036 5 689,65 M2III -0.321 0.023 16 v 877 11 +1,.77 M4III -0.167 0.053 3 v 1155 47 +1..88 M2II -0.362 0.016 6 c? 2717 00 +1..66 M4III -0.696 0.110 30 v 2725 82 +1..56 M1III 0.791 0.010 6 2738,63 M1III 0.688 0.011 5 c 2795,52 MOIII -0.162 0.015 30 c? 2905 06 +1,54 MOIII 0.457 0.007 8 c 2967 56 +1,64 M3II-III -0.673 0.028 28 3061 31 +1,59 M4III 0.122 0.088 11 3169 99 +1,66 M3III 0.667 0.055 15 v 3319 50 +1,60 M3III -0.709 0.109 13 v 3576 76 +1 53 M3III -0.386 0.013 17 c 3577 38 +1.55 M4III 0.186 0.026 10 v 3705 13 +1.55 K7III -1.430 0.014 23 3769,53 MIHI -0.485 0.012 23 c 3773 31 +1..54 K5III -0.134 0.021 13 3866 35 +1.,63 M2III -0.307 0.018 13 3993 85 +1,,29 gk3-0.479 0.025 23 4008 25 +1..60 MOOOO 0.165 0.021 10 v 4178 12 +1,,20 K2III -0.625 0.005 15 c 4184 02 +1.,62 M2III 1.014 0.027 11 4267 81 +1,.45 M5.5III -0.405 0.094 30 v 4336 89 +1.,57 M2III -0.157 0.008 6 c 4483 36 +1,.57 M4III -0.255 0.042 16 v 4517 03 +1..51 M1III -1.552 0.017 17 c? 4807 71 +1..60 M3III 0.331 0.012 c 4858 41 +1,.60 M3III 0.392 0.016 6 c? 4920 78 +1..56 M1III -1.242 0.010 11 c 5589 60 +1..59 M5III -0.548 0.092 19 6055 44 +1,.73 M2III -0.326 0.059 6 v 6146 04 +1.52 M6III 0.721 0.204 85 v 6200 90 +1.55 M2.5III -1.067 0.018 6 c? 6429 88 +1.67 M3III -0.502 0.052 7 6543.48 +1.60 M4III 0.721 0.068 31 6815.97 +1.65 M3III -0.766 0.032 41 v 6861.25 +1.84 M5III -0.339 0.082 7 v 6872.33 +1.17 K2III 2.083 0.006 8 c 7023.35 +1.75 M4III 1.107 0.114 7045.42 +1.65 M4III 1.001 0.058 5 7537.94 +1.70 M1III -0.297 0.025 7 v 7566.12 +1.69 M2III -0.906 0.053 67 7728.39 +1.54 M4III 1.004 0.084 17 7951.42 +1.65 M3III -0.625 0.082 24 v 8011.17 +1.12 K0III -0.829 0.009 21 8015.51 +1.47 gk5-0.797 0.014 13 c 8224.10 +1.75 M3III 0.005 0.028 12 v 8284.11 +1.60 M1III -0.145 0.014 10 c 8556.97 +1.03 G6-8III -0.899 0.004 6c 8560.11 +1.57 M4.5III -0.744 0.016 8 c? 8582.81 +1.61 M4III -0.512 0.048 6 v 8889.09 +1.60 M3III -0.057 0.030 8 8940.32 +1.60 M5III -1.062 0.047 8978.60 +1.57 M1III 0.389 0.024 8991.06 +1.68 M2III 0.541 0.024 9030.79 +1.66 M3III 1.237 0.045 6 9036.08 +1.60 M2.5III -1.107 0.027 5 v Check Star HR V B-V SpT AV N R 131 5.38 +1.08 K0III -0.199 0.019 35 c? 13 5.68 +1.12 K1III 0.456 0.064 v 176 5.89 +0.55 G1V -0.087 0.012 c. 420 5.93 +1.56 K5III 0.453 0.011 5 c 739 5.35 +1.02 gg3-0.218 0.023 16 v 926 6.05 +1.04 K0III -0.186 0.010 3c 1205 5.00'+1.45 K3I-II 0.200 0.014 4 c 2684 5.44 +1.03 G8III -0.301 0.017 28 v 2643 5.93 +0.60 G4V 0.833 0.014 6 c 2643 5.93 +0.60 G4V 0.862 0.023 3 v 2692 6.43 +0.89 G9V 1.206 0.051 27 v 2808 5.03 +0.90 G8III 1.447 0.016 7 c? 3030 6.04 +1.38 K0-0.143 0.022 24 v 3050 6.18 +1.12 K1III 0.034 0.011 11 3127 6.34 +1.1: K1III-IV 1.043 0.013 14 c 3231 6. 38 +0. 9: G8III 0.145 0.029 12 v 3531 5, 58 +0. 86 G6III 0.401 0.010 17 c 3510 6, 38 +0. 64 G1V 0.203 0.015 9 c? 3815 5, 41 +0. 77 G8III 3815 5. 41 +0. 77 G8III -0.481 0.011 21 c 3627 5, 14 +0. 97 KOIII 0.725 0.029 12 v 3896 6. 46 +1. 5: MOIII 0.781 0.013 13 c 3928 5. 14 +0. 46 F6V -1.230 0.056 21 v 4051 6, 45 +0. 54 F9V 0.428 0.014 10 c 4181 5. 00 +1. 38 K3III -0.739 1 4256 72 +1. 01 gg7 0.709 0.011 11 4201 28 +1. 21 K4III -0.083 0.013 11 4280 47 +1. 47 K5III -0.568 0.011 6 4515 85 +0. 18 A4V -0.731 0.013 16 4515 85 +0. 18 A4V -0.723 0.013 16 c 4805 33 -K). 01 A1V 0.275 0.013 4805 33 +0. 01 A1V 0.276 0.014 3 4962 91 +1. 45 K5III -0.039 0.014 11 c 5714 02 +1. 37 K4III -0.117 0.024 19 6024 94 +1. 04 G8III -0.848 0.029 6 v 6183 5.79 +1.04 G8III 6163 4.24 +1.06 KOIII 6577 6.12 +0.56 F6III 6775 5.04 +0.52 F7V 6801 4.98 +1.05 KOIII 6807 5.58 +0.91 G8III 7038 6.36 +0.45 F5V 7038 6.36 +0.45 F5V 7521 6.25 +1.13 K1III 7729 6.53 +0.37 F2V 7873 4.89 +1.60 K5II. 8057 6.31 +1.67 M1III 7994 6.38 +0.67 G1V 8312 6.08 +1.34 K1III 8208 5.60 +0.32 F0V 8488 5.10 +0.92 G8III 8488 5.10 +0.92 G8III 8620 5.97 +1.46 K4III 8843 5.66 +0.51 F7V 8953 6.43 +1.6: M1III 8883 5.64 40.82 G4V 8893 5.08 +1.31 K3III 8893 5.08 +1.31 K3III 9035 6.11 +1.59 M2III -0.122 0.021 6-2.106 0.071 5 v 0.454 0.010 31 c 0.676 0.018 40 c? -1.572 0.037 7 v 0.012 0.012 8 c 0.975 0.020 0.975 0.020 5 v 0.083 0.009 7 c 0 1.247 0.025 14 0.006 0.038 23 0.344 0.030 21 0.142 0.024 10 v 0.031 0.015 12 c? 0.357 0.010 10 0.272 0.009 5-3.216 0.005 8 c 0.641 0.006 6 c? -0.504 0.016 8 v? 0.011 0.024-0.536 0.022 v 0.567 0.013 6 0.568 0.014 c -0.039 0.018 5 v Comparison Star HR V B-V SpT 22,53 +1.04 G9III 35,25 +0.44 F4V 186,98 +1.32 K5III 270,45 +1.09 K2III 672.58 +0.60 GO.5IV 908.25 +1.05 K0 1129,80 +0.80 G0III 2632.74 +1.1: ggl 2808.03 +0.90 G8III 2808.03 +0.90 G8III 2846.22 +0.39 F5V 2985,57 +0.93 G8III 2953.24 +1.1: K0 3093,17 +0.98 G8III 3176.30 +0.63 GiV 3376,28 +1.17 KOIII 3609,14 +1.51 K5III 3558.17 +1.00 K1III 3800.55 +0.92 G8.5III 3764.85 +1.05 gg8 2731 4,,46 +1.23 K2III 3877 5.,63 +1.49 gk4 3987 6,.32 +1.25 gk3 4052 6,,00 +1.13 gk3 4176 5..75 +1.30 gk3 4258 5,.03 +1.10 K1III 4207 6,.37 +1.12 gkl 4264 6..03 +1.13 K2III 4559 5..58 +0.94 gko 4559 5,.58 +0.94 gko 4878.02 +1.29 gk4 4878.02 +1.29 gk4 4929.96 +0.96 KOIII 5691.03 +0.53 F9IV 6073.77 +0.97 KOIII 6023 4.26-0.07 B9 6090 5.91 +1.37 gk6 6646 6.35 +1.50 K3-4III 6542 5.69 +1.01 gko 6768 5.71 +1.16 KOIII 6846 6.51 +1.34 gkl 6901 6.36 +1.3: K2 7046 5.37 +1,64 K4III 7046 5.37 +1.64 K4III 7621 6.17 +1.06 KOIII 7555 6.11 +0.90 G5-8III 7703 5.32 +0.87 K3V 7831 4.91 +1.15 K2III 7973 5.98 +0.43 F5V 8096 6.27 +1.16 KOIII 8179 6.11 +1.00 G5III 8228 5.24 +0.97 KOIII 8644 4.85 +1.03 KOIII 8644 4.85 +1.03 KOIII 8531 5.32 +0.67 G3IV 8829 6.12 +0.79 G8V 8922 6.35 +1.0: G9III 8999 6.17 +0.50 F4V 8923 4.55 +0.94 G7III 8923 4.55 +0.94 G7III 9055 6.15 +1.60 M2III Observer Curott Fortier Wasson Landis Fortier Curott Wasson Dempsey Bohme Dempsey Ganis Kuedeke HR 5589. RR UMi; SRb variable, range 4.53 to 4.73 in V, period 43.3 days (GCVS4). We find 4.33 to 4.68 in V, and a time scale ranging from 30 to 50 days. HR 6055. NSV 07574, range 4.9 to 5.47 in V. We find 5.38 to 5.54; the time scale is uncertain. HR 6146. g Her; SRb, range 4.3 to 6.3 in V, period 89.2 days (GCVS4). We find 4.57 to 5.46, and a time scale of 80 to 90 days. The light curve is semiregular. HR 6429. VAR? (YCBS). We find a range of 5.79 to 5.91; the time scale is uncertain. HR 6543. V642 Her; SRb variable, range 6.41 to 6.56, time scale about 12 days (GCVS4). We find 6.32 to 6.55, and a time scale of 25 days (Fig. 4). HR 6815. V669 Her; range 0.14 (GCVS4). We find 4.88 to 5.00 in V; the time scale is uncertain, but may be about 20 days. HR 6861. V4028 Sgr, SR: variable, range 6.10 to 6.38 in V; time scale 35: days (GCVS4). We find a range of 6.06 to 6.30, and a time scale of >50 days. HR 7023. V3879 Sgr; SRb variable, range 6.05 to 6.58, time scale about 50 days (GCVS4). We find 6.30 to 6.57 and a time scale 50 days from sparse data.

614 PERCY ET AL. HR 3319 JULIAN DATE (2448000+) Fig. 1 The V light curve of BQ Gem (HR2717), relative to the comparison star HR 2632. The line segments have been added to delineate the variations, which have a time scale of 52 days. There is some evidence for longer-term variations. The error bar is shown in the upper left comer. Fig. 3 The V light curve of BP Cnc (HR 3319), relative to the comparison star HR 3376. The line segments have been added to delineate the variations, which have a time scale of 40 days. The error bar is shown in the upper left comer. HR 7045. VAR? No NSV number; range 0.15 in V (YCBS). We find 6.30 to 6.45 and a time scale of 50 days, from sparse data. HR 7537. NSV 12432, range 0.12 in V. We find 5.85 to 5.91; the time scale is uncertain. HR 7566. V1509 Cyg; Lb variable, range 5.08 to 5.4 in V (GCVS4). We find 5.15 to 5.31, and a time scale of 30 days. The observer did not use a check star. HR 7728. NSV 12949 (but variability doubtful). We find a range of 6.18 to 6.42, and a time scale of 50 days. HR 7951. EN Aqr; Lb variable, range 4.41 to 4.45 (GCVS4). We find 4.14 to 4.49, with a time scale of about 30 days. HR 8057. This variable Ml III check star is presumably a HR 8224. NSV 13729, range 6.09 to 6.5 in V. We find a range of 6.08 to 6.16, and a time scale of about 25 days. HR 3169 HR 8582. v Tue. Lb: variable, range 4.75 to 4.93 (GCVS4). We find a range of 4.77 to 4.88; the time scale is uncertain. HR 8889. NSV 14529, range 0.14 in V. We find 6.03 to 6.11; the time scale is uncertain. HR 8953. This variable Ml III check star is presumably a HR 9035. This variable M2 III check star is presumably a 5. DISCUSSION AND CONCLUSIONS Our results confirm the variability of many known or suspected SARVs, and identify several new variables. These will be followed up on a long-term basis as part of the AAVSO photoelectric photometry program. Such a program HR 6543 Fig. 2 The V light curve of BL Cnc (HR 3169), relative to the comparison star HR 3176. The line segments have been added to delineate the variations, which appear to have time scales of about 20 and >100 days. The error bar is shown in the upper left comer. Fig. A (a) and (b) The V light curve of V642 Her (HR 6543), relative to the comparison star HR 6542, over two seasons. The line segments have been added to delineate the variations, which have a time scale of 25 days; there is some evidence for longer-term variations. The error bar is shown in the upper left comer.

AAVSO PHOTOELECTRIC PHOTOMETRY SURVEY 615 Fig. 5 The amplitude of variation in V, as a function of the published spectral type. Since the data are sparse, and the amplitude may be variable with time, this graph shows a general trend only. has proven to be effective in discovering or confirming the variability of these stars, and in following them up. Figure 5 summarizes the results: the incidence of amplitude of variability become noticeable at about Ml III spectral type, and tend to increase with advancing spectral type. The trend, however, is not an exact one. Several of the stars show some evidence of variability on both short time scales (weeks) and long time scales of a year or more. This is a characteristic of many SARVs (Percy et al. 1993). Many years of observations will be required in order to identify the periods. The long-term variability is of particular interest, because its cause is not known. We thank Howard J. Landis for his many contributions to the AAVSO photoelectric photometry program, and Janet A. Mattei for her interest and cooperation. J. R. P. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada in the form of a research grant. REFERENCES Kholopov, P. N. (editor-in-chief) 1982, New Catalogue of Suspected Variable Stars (Moscow, Nauka) Kholopov, P. N. (editor-in-chief) 1985, General Catalogue of Variable Stars, Fourth ed. (Moscow, Nauka) Percy, J. R. 1985, IAPPP Commun., 19, 14 Percy, J. R. 1993, PASP, 105, 1422 Percy, J. R., Landis, H. J., and Milton, R. E. 1989, PASP, 101, 893 Percy, J. R., and Fleming, D. E. B. 1991, PASP, 104, 96 Percy, J. R, and Shepherd, C. W. 1992, IAU Inf. Bull. Var. Stars, No. 3792 Percy, J. R., Ralli, J. A., and Sen, L. V. 1993, PASP, 105, 287 Querci, F. R. 1986, in The M-Type Stars, ed. H. R. Johnson and F. R. Querci (Washington, NASA SP-492)