COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2376 Konkoly Observatory Budapest 1 August 1983 HU ISSN 0374-0676 AN INVESTIGATION OF SHORT TIMESCALE VARIABILITY IN 6 EARLY B STARS Six early B stars suspected of short period variability on timescales of about a day or less were investigated photometrically in September 1992 at the University of Toronto. Observations were made in the B band with the Department of Astronomy 0.4 m telescope relative to nearby comparison stars. The standard deviation in each measurement was typically 0.01 magnitudes or more. A transformation equation of the form deltaB=deltaB(observed)+0.050 delta(B-V) (Percy, 1982) was used. (B-V) values were taken from published data or were estimated from the spectral type. A differential extinction coefficient of the form deltaB = -k_B delta(sec z) was assumed, with kB = 0.40 magnitudes. (Eight determinations in July and August give k_B = 0.41 +- 0.06 (Percy, 1983)). Of the six stars variability was confirmed in three cases: V358 Per, 2 Vul, and V819 Cyg. In no case could a convincing fit be made to previous periods. In addition, two of the check stars, HD13970 and HR7577, were observed to have relatively large amplitude, short timescale variations. Notes on Individual Stars 1 Cam A companion 10.3" away with V magnitude 6.9 gives a combined magnitude V=5.45 and colour (B-V)=0.18. Jerzykiewicz and Sterken (1982) report possible variability on a timescale of hours with range 0.01 magnitude in b. No significant variation of 1 Cam (V) relative to 2 Cam (C1) was detected in this study, but the data are clearly insufficient to rule out variability. 2 Cam A double star with separation 0.3". Combined photometry and spectral type are given. No significant variation of 2 Cam (C1) relative to HR1314 (C2) was detected. HR8105 There is a companion star 21.5" away with V magnitude 12.2. All photometry is of HR8105 alone. Jerzykiewicz and Sterken (1982) report variation, possibly on a timescale of hours, with range 0.02 magnitudes in y. No significant variation of HR8105 (V) relative to HD202126 (C1) was detected in this study. HD202126 A B magnitude of 6.82 was obtained by comparison with HR8120. The spectral type is from the SAO catalogue, and (B-V) is estimated from the spectral type. No significant variation of HD202126 (C1) relative to HR8120 (C2) was detected. V358 Per Listed as a Be star in Jaschek and Egret (1981). Hill (1967b) reports an amplitude of 0.09 magnitudes and a period of 1.241 days. Variability has been confirmed, but the observations do not fit Hill's light curve. Errors are large because the stars are faint and in a crowded field. HD13831 Listed as a Be star in Jaschek and Egret (1981). It has been checked for constancy by Hill (1967a). HD13970 There appear to be hour-to-hour variations relative to HD13831 (which does not exhibit such rapid changes relative to V358 Per). The observed range of HD13970 (C2) relative to HD13831 (C1) is about 0.07 magnitudes in B. V558 Cyg A suspected beta Cephei star (Bolton, 1992). Listed as a Be star in Jaschek and Egret (1981). No significant variation of V568 Cyg (V) relative to HD196120 (C1) was detected. HD196120 The spectral type is from the SAO Catalogue. No significant variation of HD195120 (C1) relative to HD195102 (C2) was detected. HD195102 The spectral type is from the SAO Catalogue. Table I: A list of the stars observed -------------------------------------------------------- Name HR HD V B-V Sp -------------------------------------------------------- V 1 Cam 1417 28446 5.77 0.18 B0III C1 2 Cam 1466 29316 5.35 0.07 A8V C2 HR1314 1314 26764 5.19 0.05 A2Vn V HR8105 8105 201819 6.54 -0.14 B1Vp C1 HD202126 -- 202126 6.76: 0.06: A2 C2 HR8120 8120 202240 6.05 0.21 F0III V V358 Per -- 13890 8.51 0.19 B1III C1 HD13831 -- 13831 8.27 0.10 B0IIIp C2 HD13970 -- 13970 8.30 0.14 B5Ib V V568 Cyg 7927 197419 6.66 -0.16 B2IV-Ve C1 HD195120 -- 196120 6.67 -0.12 B9 C2 HD195102 -- 195102 7.00 -0.06 B9 V 2(ES)Vul 7318 180968 5.43 0.02 B0.5IV C1 HD181751 -- 181751 6.6: -0.06: B8 C2 1 Vul 7306 180554 4.77 -0.05 B4IV V V819 Cyg 7600 188439 6.29 -0.11 B0.5IIIn C1 HR7591 7591 188252 5.91 -0.18 B2III C2 HR7577 7577 188074 6.20 0.36 F2V --------------------------------------------------------- For stars with HR numbers the source for photometry and spectral types is Hoffleit (1982). Otherwise, unless noted, Nicolet (1978) was used for photometry and Jaschek (1978) for spectral type. [FIGURE 1] Figure 1. Photoelectric observations of V358 Per (V) relative to HD13831 (C1). The typical error in each measurement is shown. Table II Summary of observations ------------------------------------------------------------------------ V C1 C2 Nights Obs'ns sigma(V-C1) sigma(C1-C2) ------------------------------------------------------------------------ 1 Cam 2 Cam HR1314 2 3 0.012 0.009 HR8105 HD202126 HR8120 3 12 0.009 0.010 V358 Per HD13831 HD13970 3 10 0.019 0.016 V568 Cyg HD196120 HD195102 4 12 0.008 0.010 2 Vul HD181751 1 Vul 3 9 0.017 0.017 V819 Cyg HR7591 HR7577 5 15 0.008 0.011 ------------------------------------------------------------------------ Each measurement sigmaB_i has standard deviation sigma_i. The mean of the sigma_i is sigma, and the mean of the sigmaB_i is sigmaB with standard deviation sigma_deltaB. The variation is significant only if sigma_deltaB > sigma. [FIGURE 2] Figure 2. Photoelectric observations of HD13970 (C2) relative to HD13831 (C1). The typical error in each measurement is shown. [FIGURE 3] Figure 3. Photoelectric observations of 2 Vul (V) relative to HD181751 (C1). The typical error in each measurement is shown. [FIGURE 4] Figure 4. Photoelectric observations of V819 Cyg (V) relative to HR7591 (C1). The typical error in each measurement is shown. [FIGURE 5] Figure 5. Photoelectric observations of HR7577 (C2) relative to HR7591 (C1), plotted with a period of 0.485 days. The typical error in each measurement is shown. 2 Vul Short period variability is confirmed, with amplitude about 0.04 magnitudes in B. Data do not fit Lynds' (1959) period of 0.6046 days. HD 181751 Spectral type and V magnitude are from the SAO Catalogue. (B-V) is estimated from the spectral type. 1 Vul Listed as a suspected variable in Kukarkin et al (1955). No significant variation of 1 Vul relative to HD181751 (C1) was detected in this study. V819 Cyg The light curve of V819 Cygni (V) relative to H97591 (C1) clearly indicates short period variation with an amplitude of 0.03 magnitudes in B. The data do not fit Lynds' (1959) period of 0.3775 day. HR7591 Listed as a suspected variable in Kukarkin et al.(1965). Because both V819 Cyg (V) and HR7577 (C2) appear to be varying also, it was not possible to confirm this. HR7577 HR7577 displays changes in brightness of up to 0.03 magnitudes in only two hours, relative to both V819 Cyg and HR 7591. The variation of HR7577 (C2) - HR 7591 (C1) can be fitted to a 0.485 day period with amplitude 0.05 magnitudes in B. The observations described in this paper have been deposited in the IAU Archives. The author wishes to thank Dr. John R. Percy for discussions and much helpful advice. Financial support in the form of a Mary H. Beattie Fellowship is also gratefully acknowledged. CHRISTOPHER STAGG Department of Astronomy University of Toronto Toronto, Canada M5S 1A7 References: Bolton, C.T. 1982, private communication. Hill, G. 1967a, Astrophys. J. Suppl. 14, 263. [BIBCODE 1967ApJS...14..263H ] Hill, G. 1967b, Astrophys. J. Suppl. 14, 301. [BIBCODE 1967ApJS...14..301H ] Hoffleit, D. 1982, The Bright Star Catalogue, Yale University Observatory. Jaschek, M. 1978, Catalog of Selected Spectral Types in the MK System, Observatoire de Strasbourg. [BIBCODE 1978csst.book.....J ] Jaschek, M. and Egret, D. 1981, A Catalogue of Be Stars on Microfiche, Observatoire de Strasbourg. Jerzykiewicz, M. and Sterken, C. 1982, Be Stars (ed. by M. Jaschek and H.-G. Groth), p. 49. [BIBCODE 1982IAUS...98...49J ] Kukarkin, B.V., Kholopov, P.N., Efremov, Yu.N., Kurochkin, N.E. 1965, The Second Catalogue of Suspected Variable Stars, Astronomical Council of the Academy of Sciences of the USSR and the Sternberg State Astronomical Institute. [BIBCODE 1965CSV...C......0K ] Lynds, C.R. 1959, Astrophys. J. 130, 577. [BIBCODE 1959ApJ...130..577L ] Nicolet, B. 1978, Catalogue of Homogeneous Data in UBV Photoelectric Photometry, Observatoire de Strasbourg. [BIBCODE 1978ppch.book.....N ] Percy, J.R. 1982, private communication. Percy, J.R. 1983, private communication. [DATAFILE 3]