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Variable Star Section Circular

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Variable Star Section Circular The British Astronomical Association VARIABLE STAR SECTION DECEMBER CIRCULAR 74 1992 ISSN 0267-9272 Office: Burlington House, Piccadilly, London, W1V 9AG SECTION OFFICERS Director Tristram Brelstaff, 3 Malvern Court, Addington Road, Reading, Berks. RG1 5PL Tel: Reading (0734) 268981 Assistant Director S.R. Dunlop, 140 Stocks Lane, East Wittering, Chichester, West Sussex PO20 8NT Tel: Bracklesham Bay (0243) 670354 Fax: Bracklesham Bay (0243) 670400 Email: CompuServe 100015,1610 JANET: SDUNLOP @ UK.AC.SUSSEX.STARLINK INTERNET: SDUNLOP @ STARLINK.SUSSEX.AC.UK Secretary M.D. Taylor, 17 Cross Lane, Wakefield, West Yorkshire WF2 8DA Tel: Wakefield (0924) 374651 Chart Secretary J. Toone, Hillside View, 17 Ashdale Road, Cressage, Shrewsbury SY5 6DT Tel: (0952)510794 Nova/Supemova G.M Hurst, 16 Westminster Close, Kempshott Rise, Basingstoke, Hants. Secretary RG22 4PP Tel. & Fax: Basingstoke (0256) 471074 Telex: 9312111261 (TA G) Email: Telecom Gold 10074:MIK2885 JANET: GMH @ UK. AC.CAM. AST-STAR INTERNET: GMH @ STARLINK.CAMBRIDGE.AC.UK Prof./Am. Liaison R.D. Pickard, 28 Appletons, Hadlow, Kent TN11 0DT Comm. Secretary Tel: Tonbridge (0732) 850663 Email: Telecom Gold 10074:MIK3229 Computer D. McAdam, 33 Wrekin View, Madeley, Telford, Shropshire TF7 5HZ Secretary Tel: Telford (0952) 432048 Email: Telecom Gold 10087:YQQ587 Telephone Alert Numbers The following numbers may be called at any time up to 23:00 UT (or BST when in operation) to report variable-star activity, or at any time during the night for possible novae and supemovae only: Guy Hurst 0256 471074 Gary Poyner 021 350 4312 Denis Buczynski 0524 68530 Graham Keitch 0934 862924 Martin Mobberley 0245 252975 weekdays - 0284 828431 weekends Notes on some suspected variables Chris Lloyd While following up the papers dealing with the Spearman Rank Correlation test, I came across a number of suspected variables and wondered what the professional literature had to say about them. In some cases it was very little but others had commanded more attention. The following notes are not exhaustive, but I hope they will help anyone who is interested in pursuing these stars. BS 551 = HD 11613 = SAO 37607 (And) A light curve and finding chart are given by Ian Middlemist ( VSSC67,26) and brief notes are also given by other observers (VSSC 61,9; 65,2). An analysis of the light curve in my paper on the statistical tests (VSSC 73,38) strongly suggests that the star is variable. However the two published photoelectric measurements are similar (V= 6.24). The star is a late type giant (Κ2ΠΙ) in a low amplitude spectroscopic binary, with a period of 838 days. The orbit is most probably circular (Griffin; Observatory 101,175 (1981)). In the light curve several fades are visible and the phasing of some of these is almost correct for eclipses but the others are clearly not. There is no obvious periodicity but all things considered this star must be a good candidate for variability and deserves to be put on someones photoelectric programme. NSV 13150 = HD 196036 = SAO 106259 = BD+19 4450 (Del) Magnitudes are given by John Isles (VSSC 67,12) and it receives a brief mention in VSSC 61,9. The literature has practically nothing to say about it. The spectral type is Μ, M7 in the NSV. If it is a main sequence dwarf then from the magnitudes it should be a very nearby star, and have a reliable parallax. It does not, nor does have a high proper motion, so in all probability it is a giant. From the application of the suite of statistical tests it is probably variable and what has been seen is consistent with a late type giant. HD 11907 = SAO 37652 (And) This star is given as a suspected variable by Tony Markham (VSSC 72,13). It seems to be a nearby F5 field dwarf, but very little else is known about it. The limited photometry does not suggest variability and no radial velocities appear to have to published. If this star is variable then it may be an eclipsing binary but intrinsic variations seem unlikely. NSV 02859 = HD 42379 = SAO 78074 (Gem) Another observed by Tony Markham. In the NSV the spectral type is given as Be but it is more generally given as B1II/B 11a. It has been observed as a suspected {greek capital beta} Cephei variable but this was not confirmed. It is variable by several hundredths and is probably an irregular luminous blue variable. One for PEP. NSV 03597 = HD 58640 = SAO 41795 (Lyn) The main claim to fame is a suggestion of micro-variability. The spectral type is M3 and it is probably a giant, so it must stand a good chance of being variable. 1 NSV 02357 = HD 37519 = SAO 58319 = BS 1938 = BD+311048 (Aur) Observed by Tony Markham (VSSC 61,9) and others (VSSC 65,2). This is an evolved early type star and a possible weak Hg-Mn star (B9.5III-IVp). The published photometry shows a range of a few hundredths but no real evidence of variability. There is some suggestion of radial velocity variations. Its main claim to fame is the flash (flare implies dMe stars) of some 1-2 magnitudes. Reports of flashes in otherwise normal stars have been collected by Schaefer(ApJ 337,927; 1989). NSV 13784 = HD 205349 = SAO 51027 = BS 8248 = BD+45 3584 (Cyg) The spectral type is given generally as K llab( var) and so is almost certainly photometrically variable. The published photometry shows a range of a few hundredths but no real evidence of variability. Marginal activity is reported visually (VSSC 61,9). The spectral type is rather late for a Cepheid but it may be one of the ill defined, irregular, low amplitude variables that inhabit this part of the HR diagram. One for PEP?. 70 UMa = HD 107465 = SAO 28346 = BS 4701 = BDt-58 1371 The spectral type is Κ5ΠΙ so it may be a low amplitude, long period variable of some description. There is no evidence of radial velocity or photometric variations and only marginal visual activity (VSSC 61,9). NSV 00021 = HD 37 = BD+49 4329 (Cas) The spectral type of G9III is perhaps a little early for a giant variable but there are no hard and fast rules. Very little else is know about the star. The NSV suggests a range of 1 magnitude. Observations are reported in VSSC 65,2. ε Peg = HD 206778 = SAO 127029= BS 8308 The spectral type of K2Ib(var), slight radial velocity variations and arange of 0. lm in the photometric measurements all suggest that this is a low amplitude irregular supergiant variable. Interestingly it shows variations of a few tens of metres per second during anight and 2 -5 km/s on longer time scales. This star is also one of Schaefer’s flashers and apparently brightened to 0.7 on one night in 1972. Little visual activity is reported (VSSC 53, 11; 61,9). Chris Lloyd Astrophysics Division Rutherford Appleton Laboratory Chilton, Didcot Oxon, OX 11 0QX 2 When is a variable visible? Tony Markham When light-curves are generated for variable stars, there are often gaps in the coverage. Gaps due to bad weather, neglect by observers or the variable being too faint are difficult to predict. Annual gaps resulting from the variable being unfavourably positioned relative to the Sun ought, however, to be predictable. Unfortunately, these annual gaps are often larger than they need be. For example, observers might be slow to recommence observations as the variable emerges from the morning twilight, and may prematurely stop observing the variable before it has been lost in the evening twilight. Observations close to the limits of the apparition obviously require good sky conditions. Observers would also benefit from knowing the earliest and latest dates on which the variable might be visible given these good sky conditions. How easily can the limiting dates of the apparition be estimated? In order to predict such dates, it is necessary to establish criteria which define the circumstances under which the variable is visible on the first and last days of its apparition, given good, but not exceptional, sky conditions. The following results are based on my observations in the period 1980-91 of variables close to the limits of their apparitions. The observations were made using 10 x 50 binoculars. Times were recorded to the nearest 5 minutes. The results have been analysed to calculate the altitudes of the variable and the Sun at the time of each observation. Cholsey, Oxon. (51°35' N, 01°09' W) Date Time (UT) Variable RA Dec Mag Class Alt. (°) h m O ‘ Var. Sun Apr. 18 20:30 C K O ri 05 30 +04 12 6.6 3 + 14 -12 22 20:55 X P er 03 55 +31 03 6.2 3 + 15 -14 20:55 BUTau 03 49 +24 08 5.5 3 +9 -14 May 15 21:25 BQ Gem 07 13 + 16 10 5.6 2 + 14 -12 21:45 BN Gem 07 37 +16 54 6.6 3 + 16 -13 JlyO l 01:30 X P er 03 55 +31 03 6.2 3 +7 -15 21 01:35 NSV 2537 Aur 05 41 +31 22 6.5 3 +7 -15 Aug.04 02:45 BU Gem 06 12 +22 54 6.9 2 + 12 -14 02:45 TV Gem 06 12 +21 52 7.0 3 + 11 -14 Edinburgh (55°56' N, 03' °12' W) May 05 21:50 TV Gem 06 12 +21 52 7.1 3 +15 -12 14 21:35 BQ G em 07 13 + 16 10 5.5 2 +16 -9 21:35 Rho Per 03 05 +38 50 3.6 3 +9 -9 Jun.21 23:40 V465 Cas 01 18 +57 48 6.9 2 +35 -10 29 23:15 V465 Cas 01 18 +57 48 6.9 2 +36 -10 3 Date Time (UT) Variable RA Dec Mag Class Alt.
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