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. (°) h m O ‘ Var. Sun

Jun.29 23:15 Rho Per 03 05 +38 50 3.5 3 +10 -10 Jly 31 01:55 NSV 2537 Aur 05 41 +31 22 6.1 2 +13 -13

Leek, Staffs. (53°06 N, 02°03' W)

Sep.07 20:15 TV UMa 1146 +35 54 7.4 3 + 17 -13

Leven, E. Yorks. (53°53' N, 0°18’W)

Jan.05 06:00 Chi Oph 16 27 -18 27 4.2 2 +4 -19 22 05:55 V I294 Aql 19 34 +03 46 6.7 2 +6 -14 05:55 U Del 20 46 +18 05 7.3 3 +7 -14 05:55 R Set 18 48 -05 42 6.2 2 +5 -14 Feb. 16 18:35 GO Peg 22 55 +19 33 7.8 2 +20 -13 18:35 TX Psc 23 46 +03 29 5.9 2 + 15 -13 Mar. 10 19:10 TV Psc 00 28 +17 54 5.3 3 + 15 -12 Apr.23 21:05 X Per 03 55 +31 03 6.4 3 + 14 -14 21:05 BU Tau 03 49 +24 08 5.4 3 +8 -14 May 06 21:20 S Mon 06 41 +09 54 4.7 3 + 10 -12 21:20 CE Tau 05 32 + 18 36 5.2 3 +8 -12 Aug.08 02:05 BU Gem 06 12 +22 54 6.9 3 + 10 -15 02:05 TV Gem 06 12 +21 52 7.0 3 +9 -15 Sep.04 19:50 Chi Oph 16 27 -18 27 4.1 3 + 12 -10 Dec. 18 06:35 AC Her 18 30 +21 52 8.1 2 + 15 -13 06:45 V2048Oph 1800 +04 22 4.7 3 +7 -12 20 17:10 R Set 18 48 -05 42 5.6 2 + 10 -14 17:15 RCrB 15 49 +28 09 6.2 2 + 10 -14 24 17:05 V2048Oph 18 00 +04 22 4.7 3 + 11 -13 25 17:20 RCrB 15 49 +28 09 6.2 2 +8 -13 31 06:45 Chi Oph 16 27 -18 27 4.5 3 +7 -12

Wallingford, Oxon. (51 °36' N, 0 Γ 0 8 W)

May 29 21:55 UU Aur 06 37 +38 27 5.6 3 + 15 -11 21:55 IS Gem 06 50 +32 26 5.7 3 + 12 -11

Can anything be «included from the above results? There is clearly considerable scatter in the altitudes of the variables, but there is less scatter in the altitudes of the Sun. The situation is «implicated by the fact that most of these observations will actually have been made noton the limiting dates of the apparition, but several days from such dates. In addition, although most of these observations will have been made at times of good

4 atmospheric transparency, it might be the case that some of the observations were only possible due to conditions of exceptional atmospheric transparency. There is a tendency, however, for observation of brighter variables to have been made when they were lower in the sky and the Sun was less far below the horizon than was the case for fainter variables. Thus, very provisionally, combinations of limiting altitudes might be:

Magnitude of variable 8.0 7.0 6.0 5.0 4.0 Lim. alt. of variable +17° +13° +11° +10° +9° Lim. alt. of Sun -13° -12° -11° -10° -9° More data would obviously allow more accurate limiting altitudes to be determined. Such limiting values will only apply when a variable is at the start or end of its apparition. It is, of course, possible to observe variables on intervening dates at a lower altitude, when the Sun is less far below the horizon. For example, the observations of V465 Cas from Edinburgh were made with the Sun only 10° below the horizon. Despite being well above the horizon, V465 Cas was a difficult binocular object around the time of the summer solstice due to the all-night twilight glow. Even R Set, though in the southern part of the sky was ‘lost’ during deep minima during June and early July. This analysis has so far considered two factors: the altitude of the variable and the altitude of the Sun. Other factors which may affect the visibility include: 1 Elongation from the Sun This will affect the position of the variable relative to the twilight glow. 2 Atmospheric transparency Quite often variables will not be visible on their limiting dates due to cloud. Even many ‘clear’ nights will be affected by haze or mist, thus preventing the observation of variables that are low in the sky. 3 Local factors These may affect the ability to observe variables that are low in the sky. such factors include trees, hills, buildings and light pollution. 4 Ease of location Most of the variables in the analysis were successfully located due to their proximity to bright stars or distinctive asterisms. 5 Instrumentation All of the observations used in the analysis were made using hand­ held 10 x 50 binoculars. Larger instruments may allow a faint object to be visible at an altitude at which it is not visible in 10 x 50 binoculars, and thus extend the limits of the apparition. In addition, the use of setting circles will make the field of the variable easier to locate.

Even if these additional factors are taken into account, two questions must be asked before determining limiting dates for other variables: 1 Are observations possible? Even if the variable can be seen, it will not always be possible to make a magnitude estimate. Typically, the comparison stars may be at a significantly different altitude from that of the variable and thus will be affected differently by atmospheric absorption. Variables affected in this way include W Boo and R CrB in the morning sky and Epsilon Peg in the evening sky.

5 2 Are observations useful? Any observations made when a variable is at a low altitude will be of limited accuracy. If the variable involved only has a small magnitude range, then the uncertainty in the derived magnitude may exceed this amplitude and thus the observation will be of little use. In the case of larger-amplitude variables, such as U Gem, AC Her, R Set and SU Tau, for which the dates of maxima and minima cannot accurately be predicted, however, it should be possible to differentiate between maxima and minima even when the variable is at a low altitude and estimates close to the apparition limits will therefore be useful. In summary, the observational data were only able to give an indication of what the limiting altitude criteria might be. A determination of more accurate values will require more observations. Once it is believed that accurate limiting altitude criteria have been determined, these could be used to make predictions for other variables, which could then be tested. If such predictions were to lead to observers making ‘useful’ observations of variables closer to their apparition limits, then the exercise of establishing criteria and making predictions would be worthwhile.

The evolutionary status of the RCB stars Don Pollacco

Why observe RCB stars? Well, apart from the purely esoteric satisfaction of observing large amplitude irregular variable stars, there’s also the fact that you may well be helping professionals in their quest to understand these enigmatic objects. Fundamental questions remain to be answered - some we still can only guess their solutions: * Where do RCB stars come from, and where are they going? * How did the atmospheres of these objects arrive at such a peculiar composition? * What causes their dramatic minima? Until recently little progress had been made on the first and second of these problems, while we have been making steady progress in understanding the third. It is likely that any theory developed to understand the RCB evolutionary status must also attempt to explain their atmospheric abundances (little or no hydrogen and a massive over-abundance of carbon). In a universe where 50% of stars are members of binary systems it is perhaps not surprising that classical single star evolution is completely incapable of understanding RCB stars: atmospheric mixing models have failed to relate the observed atmospheric abundances to those found in ordinary stars. Recently two rather exotic models have emerged that address this problem:

* The last thermal pulse model. Calculations have shown that if a white dwarf suffers a thermal pulse (a kind of slightly controlled explosion) it may be intense enough to re-ignite thermonuclear reactions within the star. Subsequently, the re-bom star is expected to rapidly evolve (a few hundred years) towards the red supergiant (RCB) phase. This process is likely to be accompanied by large scale mixing of the

6 atmosphere. Further evolution is expected to follow that of planetary nebular (PN) central stars back to the white dwarf phase. * The merged white dwarf model. It is thought possible that a white dwarf binary may lose sufficient angular momentum by various mechanisms to allow the orbital period to decrease sufficiently that the system may merge, producing a single star. It is expected that the resultant object would have atmospheric abundsance patterns similar to those observed in RCB stars.

The first clues to the evolutionary status of the RCB stars may have been found by George Herbig who, while observing R CrB in deep minima found evidence of a PN like spectrum. These lines only occur in low temperature and density material and suggest that R CrB may be surrounded by a low-surface brightness nebula. Infrared observations of R CrB have revealed the presence of a huge fossil dust shell some 8pc in diameter. Further clues have been found from studies of the ‘hot’ RCB star(l) V348 Sge which is surrounded by a faint nebula. It seems that in order to understand the spectrum and size of the nebula, the central star has to have been significantly hotter in the recent past (120- 2000 yr). It is likely then that this object is rapidly evolving towards the cool RCB phase. In order to test this model we have used ESO’s NTT to search for faint nebullae around other RCB stars. Multiple images were obtained of UW Cen in a very deep minima that clearly show the star to be surrounded by afaint (and small) nebula of unusual physical appearance (see Fig. 1). The morphology consists of a fainter outer envelope of a circular appearance while the central parts are dominated by a pair of reasonably collimated and diagonally opposed “jets”. Narrow band imaging and spectra obtained with the NTT sugest that the nebular spectrum is similar to that in reflection nebular and not PN. The nebular structure has proved difficult to understand within the context of the evolutionary models set out above and is more likely related to the characteristic minima observed in these objects. The classical model of RCB minima requires the star to eject a puff of material which if in our line of sight will condense causing an effect analogous to a solar eclipse. As the stellar wind pushes the cloud to greater distances it disperses allowing the star to regain its former brightness. If the UW Cen nebular is connected to this model it would suggest that material is not ejected randomly but instead along a preferred path. Judging by the gas velocities observed in RCB stars during their declines the UW Cen nebula could have been produced within the last 2500 yr -a value not in contradiction with the suspected lenght of the RCB phase. Further observations of other RCB stars in deep minima will allow us to confirm or reject this model and may shed light on the physics occuring within the jets. Furthermore, the detection or non-detection of PN like spectra (which is still not ruled out) will help us decide which of (or indeed if) the evolutionary models apply. There is still work for all of us to do!.

1 Hot RCB stars are thought similar to the RCB stars but have much higher atmospheric temperatures.

7 discussion see text. Figure Contour 1: plotof theNTT image ofthe RCB starUW Cen indeep minima. For

8 Light-curves from our computerized records

The following light-curves represent some of the series of data that have now been computerized. The remarks made by Dave McAdam (VSSC 73, p.9) apply. Essentially, these are ‘quick-look’ plots at various scales and in various forms. They are included here to give observers some feedback, and to show observers and potential users how our data- processing is progressing and the general behaviour of the stars in which they may be interested. For research purposes, more detailed, larger plots (or raw data plots) are available on specific request. The light-curves given here include error bars showing the standard deviation of each mean, with the exception of V Boo, where a duplicate light-curve without error bars is given, and Z Cam, where just the means are shown. Comments on the various forms of presentation here and in VSSC 73 are invited. We are aware that the necessity for the light-curves to be reduced means that there are ce rtain problems with legibility, but we believe that the information will serve its purpose, and be generally welcomed.

9 10 R And, R 1981-87 W And, W 1985-87 RW And, RW 1977-87 K. T.G. J.D. K. Robinson, Saville, D. Toone, WheelerJ. Shanklin, P.J. Stott, R.A .H. R.APaterson, G. Poyner, Ramsay, Wheeler J. G. D. Stott, Toone, .H. P.J. R.A.H. R.A.H. G. Poyner, Paterson, Pickard, R.D. Rock, D.R.B. J. Wheeler, D. P.B. P.J. Stott, Withers Saw, Observers: Observers: C. R.H. S.W. G.A.V. Brookman, Albrighton, Chambers, J.W. Coady, Dryden, R.C. Fraser, Ells, Feijth, R.B.I. H. J. Lashley, J. Lubbock, T. Markham, S.J. Middlemist, C.R. I.A. Nicholls, Munford, R.A.H. M.J. Pickard, Paterson, R.D. Observers: Observers: Albrighton, S.W. M.A. Brookes, Chambers, R.H. J.W. Cole, D.J. Dryden, R.C. Ells, R.B.I. Fraser, M.J. Gainsford, H. H. Feijth, Gainsford, R.J. M.J. Godden, Hoste, G. Hirst, M.B. Howarth, J. Houchen, S. J.E. S.J. Isles, N.F.H. Kay, Knight, M.J. Gainsford, Gough, M.J. T. Hoste, Hollis, S. Howarth, D. A.J. Howarth, J. I J.E. Kay, Isles, Lubbock, R. S.J. S.J. McNaught, M.B. Houchen, M.B. Howarth, J.E. J. A. Lubbock, T. Kimber, Markham, Isles, S.J. C.R. I.A. Middlemist, Munford, M.J. Nicholls, Observers: Observers: C.M. S.W. Albrighton, Allen, S.J. Anderson, R.H. A.T. Chambers, G.A.V. Coady, R.C. Bueno, Dryden, J.W. Ells,

11 12 DZ And, DZ 1984-87 RX RX And, 1986-87 S.J. Lubbock, S.J. R.A.H. Paterson, I.A. Middlemist, Poyner, J. Toone G. P. P. C.R. R.A.H. Paterson, R.D. Mettam, G. Munford, Poyner, L.R. Pickard, Toone J. Stevens, Observers: Observers: R.H. L.K. Chambers, E.H. Collinson, Albrighton, S.W. Brundle, M.J. Gainsford, J.E. Isles, Observers: Observers: J.W. Albrighton, S.W. M.J. Chambers, Cole, R.H. J.W. Ells, J.E. Gainsford, A. Kimber, Isles,

13 14 U Boo, U 1983-87 R Aql, R 1983-87 V603 Aql, 1981-87 Observers: J.E. Observers: N.S. Hurst, A.T. Isles, G.M. Kieman Bueno, D.Stott, D.M. D.Stott, Tanti, Taylor, J. Toone, T. R.J. E.J.W. West, Stuart, M.D. Swain, P.J. Wheeler Observers: Observers: Ells, Chambers, R.H. Gainsford, Houchen, Albrighton, D.J. Dryden, S.W. R.B.I. Fraser, Hoste, R.C. M.J. S. M.B. J.F.. Kieman,N.S. Isles, P. Lubbock, R.J. T. J.W. Kimber, Mettam, S.J. A. Macvey, Middlemist, McKim, Markham, I.A. J.F.. J.E. Isles, N.S. Kieman, T. Markham, I. A. Middlemist, C.R. Munford, R.D. Pickard, G. Poyner, J.D. Shanklin, H.W.S. Smith, R.D. C.R. G. Poyner, J.D. Middlemist, Pickard, H.W.S. Munford, A. Smith, Shanklin, J.E. Kieman, Isles, N.S. T. Markham, I. R.W R.W C.R. G. Pickard, Poyner, D. R.D. R.J. Nicholls, Munford, M.J. Middleton, Stuart, Stott, Withers Toone, J. P.J. Wheeler, P.B. Observers: Observers: P.C. Ells, R.H. J Brookes, J.W. S.W. Gainsford, Chambers, I. Albrighton, Howarth, Burgess, M.J. Howard-Duff, M.A. .

15 16 V Boo, 1983-87 V V Cam, 1983-87 Observers: Observers: Albrighton, S.W. R.H. M.A. Brookes, Chambers, J.W. Gainsford, Ells, R.J. Godden, Currie, M.J. .J. J.E. I sles, S.J. P. J.E. Lubbock, sles, S.J. R.A.H. I Paterson, G. Pickard, Mettam, R.D. L.R. P.J. WheelerRamsay, D. Stott, Stevens, J.E. J.E. N.S. Kieman, Isles, J.W. A. Kimber, Lubbock, S.J. R.J. P. McKim, T. Markham, Mettam, Macvey, l.A. Middlemist, R.W. R.W. C.R. Pickard, Munford, Middleton, Poyner, D. Nicholls, R.D. M.J. R.J. G. Stuart, Stott, J. Toone, Wheeler, P.B. Withers P.J. Observers: Observers: P.C. J.W. Ells, R.H. Brookes, Albrighton, S.W. Burgess, M.A. Chambers, J Howarth, M.J. Gainsford, Howard-Duff, I. .

17 18 Z Cam, 1986-87 Observers: S.W. Albrighton, L.K. Brundle, E.H. Collinson, M.J. Gainsford, I. Howard-Duff, S.J. Lubbock, R.A.H. Paterson, G. Poyner, D. Stott, J. Toone

AH Dra, 1987-89 Observers: S.W. Albrighton, R.W. Fleet, R.B.I. Fraser, M.J. A. Hutchings, J.E. Isles, R.A. Kendall, T. Markham, I. A. Middlemist, G. Ramsay, A. Smeaton, J.S. Smith, D.M. Swain, M.D. Taylor, J. Toone, K. West 20 21 PRO-AM LIASON COMMITTEE (PALC) NEWSLETTER NO.5

PRO-AM EXCHANGES REPORT 6 Covering period 1991 January 1 to June 30

Date Subject Professional 001 910102 UV Persei Brian Marsden, CBAT Outburst detected by S. Korth Jan 1.779 UT, 13.9 relayed.

002 910105 EG And Dr Vogel, Zurich Special observing run for Jan to monitor UV during eclipse whilst we maintain visual coverage. Project set up.

003 910121 Cepheids C. Bernardino, Lisbon General enquiry re these stars answered by our team.

004 910126 Comets 1991a,b Brian Marsden, CBAT Astrometry by H. Ridley Jan 13-17 relayed.

005 910126 Cataclysmic Binaries H. Ritter, Garching Astrometric programme to be undertaken on variables with lack of precise positions.

006 910211 RCrB Stars DonPollacco Pros have overrides on several telescopes for declining R CrBs and we agree semi-permanent monitoring with e-mail alerts.

007 910212 UV Per Ian Howarth, UCL Sequence analysis with CCD shows originally published comparisons accurate and we relay to contacts in Japan.

008 910213 GSC Data Elaine Sadler, Australia Requests download of data from GSC. Duly e-mailed. After Elaine told her boss they sent half­ way around the world for the data, it was agreed to buy a CD Reader!

009 910215 SU UMa, YZ Cnc, IP Peg, U Gem, TY Psc, RX And, AF Cam, IR Gem Derek Jones, La Palma Requested visual data to correlate with campaign late 1988. Duly transmitted.

010 910227 R CrB Stars Don Pollacco, St Andrews Existing programme extended to Northern R CrBs as well.

011 910227 Comet (1991d) Brian Marsden, CBAT Astrometry by M. Mobberley Feb 16 relayed.

012 910309 EG And Franz Agerer, Germany Photoelectric B,V of minimum Jan 16.8 observed and relayed to professionals.

1 013 910310 V854Cen Don Pollaco, St Andrews Fade detected of this R-CrB type and relayed to Don.

014 910311 3C 345 Mark Kidger, Tenerife Monitoring of this quasar set up in response to request from Mark as currently in outburst. H. Mikuz and A. Dolzan, Yugoslavia, responded with CCD. Mag V=15.8 Mar 13.07.

015 910314 TAV 0033+59 Don Pollacco, St Andrews Observation by Hurst Mar 13 of a ‘recovery’ relayed.

016 910316 Comet Shoemaker Ted Bowell, USA Confirmation of new comet requested. Results by H. Mikuz, Yugoslavia, duly confirmed discovery and relayed.

017 910320 RS Oph Nye Evans, Keele Data on RS Oph 1958, and 1960-1987 supplied to Keele.

018 910325 Nova Her 1991 Brian Marsden, CBAT Discovery of nova by G. Alcock Mar 25.19 UT relayed to CBAT. Confirmation by D. Buczynski. Announced on IAUC. Precise position by Buczynski later also relayed.

019 910329 DX And Brian Marsden, CBAT Janet Drew, Oxford Outburst detected by T. Kinnunen, Finland Mar 25 11.5 relayed. IUE sun-constrained. Updates of observations Mar 26,29 later relayed.

020 910331 Nova Her 1991 B. Fried, Flagstaff We e-mail GSC sequence at their request.

021 910404 SVSge Brian Marsden, CBAT Don Pollacco, St Andrews Fade found by G. Poyner Apr 3 12.7, relayed. DP requests advice when star below mag 14.

022 910406 GSC download R. McNaught, Australia GSC download of 1991 GA field supplied to Rob.

023 910415 SN 1991T Brian Marsden, CBAT and others. First supernova discovery by UK Nova/Supernova Patrol. Found by Mirko Villi, Italy who telexed details to us which were relayed to the Central Bureau and announced on IAU Circular 5239.

024 910422 V635 Cas D. Roussell-Dupre, Los Alamos Observations by G. Poyner Jan 2-Apr 7 (14.8-15.2) supplied to Diane. Diane responds that bright in X-rays 1991 Mar which may correlate with our visual observations.

025 910423 SVSge Don Pollacco, St Andrews Fade has reached 14.0 (1991 Apr 23) and Don notified.

11 026 910424 V3795 Sgr Don Pollacco, St Andrews Fade (1 mag below usual) Apr 23 found by A. Pearce, Australia and relayed.

027 910428 EX Hydrae A. Jones, New Zealand Brian Marsden advises US that A. Jones detected an outburst Apr 28 at 10.1

028 910505 Nova Her 1991 M. Kidger, Tenerife General background discovery story supplied to Mark.

029 910512 SS Cygni S. Duck, ROSAT Data on SS Cyg for 1990 Nov supplied to ROSAT team to help correlation with their results.

030 910530 GS 2000+25= QZ Vul P. Charles, La Palma We ask for comparison star data to help analysis of photos taken by amateurs in Sweden. Duly received.

031 910531 Nova Her 1991 M. Bode, Lancshire Polytechnic Telescopic chart and sequence faxed to La Palma for their observing run.

032 910601 3C345 M. Kidger, Tenerife Negative results by G. Poyner for 1991 Apr ([15.2) relayed.

033 910601 SV Sge D. Pollacco, St Andrews Apr data by Poyner showing fade to 13.9 (Apr 23) supplied.

034 910609 Comet (1990c) B. Marsden, CBAT Photometry by H. Ridley Apr 3 relayed.

035 910611 TZ Per J.Drew, Oxford Outburst found by G. Poyner June 10, 12.8 relayed.

036 910624 IUE Program J. Drew June results on all UGs (66 stars covered!) supplied as part of IUE joint program.

037 910624 SV Sge D. Pollacco, St Andrews Fade to 14.2 by June 24 (Poyner) relayed.

038 910627 AH Her J. Drew, Oxford Outburst of AH Her relayed re IUE. IUE used on this star June 28/29.

039 910628 B D +5 4290 B. Marsden, CB AT Star missing from AAVSO Atlas found by A. Pereira. We investigate for CBAT but find it is merely a normal omission.

040 910629 IUE J. Drew, Oxford AB Dra rising (13.0 by June 28) relayed.

iii PRO-AM EXCHANGES REPORT 7 Covering period 1991 July 1 - 1991 December 31

Date Subject Professional 001 910701 AH Herculis Janet Drew, Oxford We are advised that during IUE campaign (see 910624) both rises to maxima of AH Herculis were first detected and alerted by our group. This led to valuable monitoring of UV spectra.

002 910704 DODraconis Robert Smith, Sussex Enquiry received as to observations of this star in 1987 Mar-Jun. Data was extracted from ‘TA’ records showing it had been at minimum near mag 14.5 during 1987 March.

003 910707 Possible Nova Brian Marsden, CBAT CBAT had received a report of a possible nova at: RA 20h31m DEC +15.5deg (1950?) magnitude 8. Subsequent visual checks by Guy Hurst failed to confirm.

004 910709 Nova Set 1981 Taichi Kato, Japan Recent amateur report suggested a further outburst of this possible 1981 nova had been detected. Taichi Kato obtained CCD photometry of the field at Ouda Observatory and found no new object to magnitude V=17 on 1991 July 9.62 UT.

005 910711 Possible Comet Brian Marsden, CBAT & T. Kryacho, Majdanak Three precise positions supplied for 1991 July 7-10 by CBAT of a possible comet found by T. Kryacho at Majdanak. David Moore, Ireland, suggested this may be a recovery of P/ Comet Hartley. This was independently suggested by S. Nakano and announced on IAUC 5304.

006 910712 Possible Asteroid Peter Andrews, RGO Details relayed by Peter Andrews of a mag 12 object recorded on three CCD frames of Messier 51. Subsequent computer search of all known asteroids using newly developed software by a member of our group, Nick James failed to show a candidate.

007 910717 VSS Centenary Janet Drew, Oxford In view of recent valuable successes with IUE, Janet Drew asked if she could present a paper at the forthcoming VSS meeting of professionals and amateurs and kindly agreed.

008 910718 V667 Cas=NSV 01098 J.S. Chauhan, India Request from Physical Research Laboratory, Navrangpura, Ahmedabad, India for data on above star relayed by Hans Bengtsson, Sweden. The star was ‘re-discovered’ by Mike Collins during nova patrols and data supplied. Professionals in India obtained photopolarimetric observations with a 2.34-m telescope.

009 910719 WW Ceti Robert Smith, Sussex We supply data on this star obtained by Patrick Schmeer, Germany from 1990 July to date from TA Records.

IV 010 910720 Asteroidal Occultations Ian Griffin, Armagh Charts of events involving 191 Kolga, 702 Alauda and 3 Juno sent to Armagh as requested.

011 910725 HN Cygni I.L. Andronov, USSR Observations by member of our group, Gary Poyner submitted. Although star no longer considered a dwarf nova, the new classification as a mira by Munnari (IBVS 3496) is not supported by our observations.

012 910808 Novae Hilmar Duerbeck, Germany Data on DQ Her, V533 Her, CP Lac, GK Per, CT Ser and FH Ser supplied to Hilmar Duerbeck in connection with his research into the hibernation hypothesis.

013 910808 R Scuti Mervyn Shenton, Keele Visual data of 1980, 1981 and 1985-1990 supplied to correlate with UV and IR results.

014 910808 EUVE Koji Mukai, USA Center for EUV Astrophysics, Berkeley, California supply initial details of EUVE project planned to start 1992. We arrange to go on e-mail list for bulletins.

015 910831 STARLINK Review Alan Penny, RLSAC We supply details of use of STARLINK for PALC activities providing highlights of recent successful exchanges and publication sources of relevant results.

016 910901 Nova Scuti 1991 Brian Marsden, CBAT Confirmation of this possible nova obtained by Martin Mobberley (photographically) and Gary Poyner (visually) supplied to CBAT. Published on IAUC 5334.

017 910906 FN And Brian Marsden, CBAT Taichi Kato, Japan Report of rare visually-detected outburst of this star by Patrick Schmeer, Germany relayed.

018 910909 Saturn Brian Marsden, CBAT Mark Kidger, Tenerife Splitting of Saturn’s North Equatorial Belt detected by members of Agrupacion Astronomica de Tenerife (amateurs) submitted and published on IAUC 5341.

019 910909 Nova Set 1991 Mark Kidger on behalf of La Palma Group Photo by Martin Mobberley showing exact location of nova faxed to La Palma to assist with their observing run that night. They successfully obtained a spectrum, infrared data and approx V measure.

020 910912 XXOph Nye Evans, Keele Data on XX Oph from 1990 onwards extracted from TA database supplied. Feedback from Keele is that they found data in a Harvard Circular (1926) covering 1890-1925 but nothing held for period 1926-1981!

V 021 910913 TT Crateris Bruce Margon, USA Following earlier confirmation by Bruce Margon of this star as a dwarf nova following original discovery by Richard Fleet he now supplies a preprint of the proposed paper as feedback.

022 910917 V635 Cas Diane Roussel-Dupre, Los Alamos, USA; & Ginga Team Gary Poyner visually detects a rise from 15.2 (1991 Aug 4) to 14.8 (1991 Sept 17) and ‘outburst’ news is relayed. Diane also relays to Ginga team to see if they can detect x-rays.

023 910921 XX Oph Nye Evans, Keele Data extracted from TA for 1985 Feb to date and relayed, (see also 910912). Nye responds that Dr J. Albinson, who has last 20 years copies of TA will extend data search back!

024 -----910930 EUVE ------Koji Mukai, USA Following initial contact (910808 entry) we offer to co-ordinate European effort on program stars.

025 911005 HN Cygni Bruce Margon, USA G. Wallerstein, USA Details of the peculiar activity of this star monitored by Gary Poyner (see also 910725) relayed to Bruce Margon for comment. He relays response from G. Wallerstein who provides detailed answer suggesting it may be a semi-regular M star.

026 911015 EF Pegasi Brian Marsden, CBAT; Yoshiro Yamada, Japan; & Alan Gilmore, N.Z. Rare outburst of this star detected by P. Schmeer 1991 Oct 15 at 10.9. Confirmed by G. Poyner 10.7 on same date. Relayed to CBAT. Published on LAUC 5369. News also posted on Bulletin Board of Yokohama Science Center in Japan and relayed to Alan Gilmore at Mount John Observatory, New Zealand.

027 911021 LD 22 Lennart Dahlmark, France Mike Collins discovers another variable during his nova patrol work which is found to be the same as LD 22 listed in IBVS 2157. We approach Dahlmark providing our data.

028 911022 Nova Set & Nova Her 91 Hilmar Duerbeck,Germany Light curves and charts supplied to Hilmar Duerbeck.

029 911022 X Persei Paul Roche, Southampton. Phase change announced at BAAVSS meeting. Recent visual data requested and supplied showing star currendy near 6.6.

030 911026 X Persei Mark Kidger, Tenerife Infrared observing planned at Tenerife. Chart supplied at their request.

vi 031 911028 EF Peg Bob Fried, Flagstaff Reports successful photometry (see 911015) of current outburst.

032 911028 V I251 Cygni Brian Marsden, CB AT & Taichi Kato, Japan Rare outburst of this star apparently detected for first time since 1963 (IBVS 123) found by Moriyama, Japan (1991 Oct 25, 12.4) and Patrick Schmeer, Germany (Oct 26, 12.7). Relayed to CBAT and Japan. Published IAUC 5377.

033 911106 V1251 Cygni Taichi Kato, Japan In response to 911028 entry, Kato reports superhumps detected on Nov 3.448, 3.524 and 3.600, amplitude 0.25-0.35 in V. IAUC 5379.

034 911106 HN Cygni I. Andronov, USSR See 910725. Response received indicating agreement that star is not UG or M but probably semi-regular with maser emission as in the case of RX Boo. They plan to publish a paper from Odessa State University.

035 911111 Various Stars Endre Zsoldos, Hungary Data supplied on: TW Cam 74-75; rho Cas 64-86; DF Cyg 35-36; 74-75; SS Gem 74-75; SU Gem 74-75; AC Her 83-87; U Mon 64-87; CT Ori 74-75; R Sge 74-75; RV Tau 50-87; V Vul 74-81; 83-87.

036 911120 X Per Paul Roche, Southampton Updated received from Paul Roche indicating IR mags are unchanged even though shell emission at H-alpha strengthening. We report that little change in mv.

037 911125 Nova Her 1991 Mark Kidger, Tenerife Entire raw data file of our visual estimates e-mailed to Mark Kidger for proposed paper.

038 911218 DY Persei A. Alksnis, Latvia We contact Dr Alksnis at Radioastrophysical Observatory, Latvian Academy of Sciences who has announced on IAUC 5400 that this star is of possible R CrB type requesting further details which are duly received by fax and post!

039 911220 X Per Paul Roche, Southampton We receive message that a brightening is inferred from their monitoring at other wave­ lengths. We report still no evidence of this in visual.

040 911222 V635 Cas Diane Roussel-Dupre, USA At request of Los Alamos, we supply 20 visual estimates covering 1991 Aug 4 to Nov 24 obtained by G. Poyner and G. Johnstone from our group.

041 911221 SN 1991bg Brian Marsden, CBAT Observation by W. Worraker on 1991 Dec 18.26 UT, 14.2v supplied.

Vll 042 911224 UV Persei Brian Marsden, CB AT Details of outburst found by M. Gainsford (1991 Dec 22.80, 13.0v) with follow-up confirmation by G. Hurst supplied to CBAT and published on IAUC 5421.

043 911224 Possible Comet Brian Marsden, CBAT Telex received of possible comet discovery by Mauro Zanotta, Italy. Confirmed visually by Martin Mobberley Dec 24.719 UT at mag 9 and relayed to CBAT.

PRO-AM Exchanges Summary Updated

Half year ending Number of exchanges Report Nos

1988 Dec 31 42 1 1989 Jun 30 51 2,3 1989 Dec 31 45 3 1990 Jun 30 69 4 1990 Dec 31 23 5 1991 June 30 40 6 1991 Dec 31 43 7

To Date 313

viii AH AH Her, 1983-87 S.J. Lubbock, S.J. C.R. Paterson, Nicholls, Munford, M.J. R.A.H. Poyner, Pickard, Toone R.D. J. G. J.D. D. Shanklin, Stott, Observers: Observers: L.K. Chambers, Gainsford, R.H. J.W. Ells, Albrighton, S.W. Brundle, M.J. Howard-Duff, J.E. Hoste, S. I. Isles,

22 RS Oph, RS 1985-89 Observers: Observers: S.W. L.K. Chambers, Albrighton, R.H. G.M. Hurst, J.E. Brundle, Isles, Lubbock, S.J. R.W. Middleton, C.R Pointer, G. Poyner, G. Muuford, J.D. D. . Shanklin, Toone, Worraker, J, Stott, Xylaris, W.J. K. E.J.D. Youngs

23 Light-curves of RV Tauri stars

Althoughinrecentyears many professional astronomers haveconcentratedoninvestigating cataclysmic variables, a small number continue to study the pulsating stars that have been followed by the Section for many years - in some cases literally for 100 years. Recently there has been increased interest in the RV Tauri stars, with Professor John Percy, of Toronto University, and Dr Mervyn Shenton, of Keele University, two researchers who may be mentioned. The Section recently supplied Dr Shenton with data for R Set, AC Her, and U Mon. The data for R Set included that used for the various light-curves shown in VSSC 73, pp.32-5. Light-curves for AC Her an d U Mon are reproduced here, together with a plot of the raw data for U Mon for the period 1982-91. The latter plot clearly shows the secondary period (P2 = 2000 days) in U Mon. Although such secondary periods are present in all stars of the RVB sub-class, the amplitude of approximately 2 magnitudes in this case is exceptional. The primary and secondary maxima (and minima) associated with the primary period (PI = 90 days) are more clearly seen on the plots for individual pairs of years. In recent correspondence with Dave McAdam, Dr Shenton says that the cause of such secondary periods in RV Tauri stars remains unexplained. It is possible that it is some complicated modulation of the short-term variation. As with many other stars, long-term, visual coverage is of great significance, because, as Dr Shenton points out, it is then possible to determine the precise phase - of both the primary and secondary periods - of other, individual observations made at various wavelengths. In the case of U Mon, Dr Shenton expects to be able to correlate the visual observations with recent optical-IR data, extending to 20 pm; with an earlier IRAS observation; and with some 20 IUE high-resolution spectra. The infrared flux comes predominantly from a circumstellar dust shell, and appears at first glance not to be related to the underlying stellar variation, although, in fact, it is highly unlikely that heating of the shell is independent of the radiation flux from the central star. Although AC Her is an RVA star - i.e., it has no secondary fluctuation - it should be possible to correlate the visual data with various unpublished high- and low-resolution spectra obtained by IUE.

24 25 26 27 28 29

31

U Mon, 1982-91 Observers: S.W. Albrighton, N.M. Bone, T. Brelstaff, R.H. Chambers, E.H. Collinson, R.C. Dryden, R.B.I. Fraser, M.J . Gainsford, S. Hoste, M B. Houchen, D. Hufton, J.E. Isles, J. Kelly, N.S. Kieman, G.J. Kirby, N.F.H. Knight, R. Livingstone, T. Ma rkham, P. Mettam, I.A. Middlemist, R.W. Middleton, B.R.M. Munden, I.P. Nartowicz, R.A.H. Paterson, R.D. Pickard, G. Pointer, G. Poyn er, T.G. Saville, D.R.B. Saw, J.D. Shanklin, S.R. Srinivasan D. Stott, D.M. Swain, T. Tanti, M.D. Taylor, J. Thorpe, J. Toone, F. V entura, E.J.W. West, W.J. Worraker Please check your address

We would appreciate it if all recipients would take a moment to check that their addresses and postcodes are correctly shown on the address label that accompanied this mailing. Certain addresses remain uncertain, primarily because of poorly legible hand-written details when the subscription was initially entered. A number of addresses in the United Kingdom were without postcodes - despite these having been introduced 20 years ago! These have now been added from the official directory. Please check that your code is correct. Similarly, to our German readers, we shall be grateful if you will inform us as soon as possible if your postcode (Postleitzahl) is altered at the beginning of 1993 July. Please try to remember to inform us when you move. Although we sometimes note changes by chance in BAA or RAS membership lists, all too often material is returned to us, sometimes after many months and from half-way round the world.

A note on the numbering of Circulars

Recipients will know that Circulars 73-76 have been issued out of order for various reasons. To prevent confusion, however, the numbering and dates have been shown so that they fall in a chronological sequence.

A valedictory editorial

In these hard times we have become all too accustomed to seeing people around us out lose their jobs. It nevertheless still comes as a shock to be unexpectedly rendered redundant oneself. Finding that I was no longer to edit these Circulars, I have had occasion to look back to see when I did first become involved in their production. I discovered, somewhat to my surprise, that this was as long ago as 1972, with Circular 13. After 21 years, 61 issues, and miscellaneous special publications, a ‘retrospective’ may perhaps be permitted. When reintroduced in 1972, after a 27-year break, the Circular was initially quarto in size, and amounted to 5 pages. The size soon changed to A4, and the page-count climbed steadily over the years. Yellow covers were introduced with No.20 (actually when it became inconvenient to list the Section Officers' addresses in the body of the text). The deeper ‘old gold’ colour, which has become the instantly recognizable ‘trademark’ of the VSS, came later. The first of the A5-sized issues was No.53, published in 1983 March, with 16 pages. As members will know, the page-count has increased ever since. Production methods have evolved over the years, beginning with wax stencils cut on a typewriter, and diagrams painstakingly scribed by hand, all printed on a very messy hand-operated ink duplicator, through certain photocopied sheets, to the provision of camera-ready copy and the introduction of professional printing. A switch to desktop publishing, with copy being prepared on a PC-compatible computer and passed to a

34 Macintosh-based system for final layout became inevitable. Various improvements have been introduced to the typefaces and design to provide greater legibility. Although a few individual items have been produced using a more sophisticated TeX/LaTeX system, allowing even greater control of complex setting, the intended switch to this method for the preparation of the whole Circular will not, of course, now be implemented. One thing that has not changed over the time that I have been preparing Circulars is the extreme difficulty in obtaining material. Complaints of late or missing issues arrive promptly enough, but how I have wished that the same could be said for contributions! One puzzling aspect that has never changed is the lack of understanding that people show for the limitations of the reproduction process. Even now, after all these years, contributors still submit diagrams drawn in black or blue ink on dark grey graph paper. The human eye may be able to distinguish between the points and background lines easily enough, but the same does not apply to the plates used for reproduction. Countless diagrams have had to be completely redrawn for this single reason. The advent of diagrams produced by computer printers has not solved the problem, because only laser or ink-jet printers produce an acceptably dark image. Even then, extreme care needs to be taken to obtain clear plots where all the data points will be visible individually after the reduction process. I should perhaps finish by thanking those who have helped over the years. Despite the problems sometimes involved, I do thank all the contributors, especially those who have sometimes gone to considerable trouble to send in carefully prepared material, including, in later years, text copy on disk. It is, perhaps regrettably, extremely easy to thank those who have helped directly, because over all those years - and apart from some initial help turning the handle of the ink duplicator - only two persons have ever volunteered any help with the Circulars. (The late Doug Saw did once distribute one, when I was unable to do so, but vowed he never wanted to do so again.) Peter Wheeler has been deservedly thanked for the onerous task of compiling the cumulative index to issues 12-70. My thanks particularly go to Melvyn Taylor, however, who over the years has frequently helped with redrawing diagrams and light-curves and in other ways. Thank you, Melvyn.

35 CHANGES OF ADDRESS T. Cragg 19 Belar Street, Coonabarabran, NSW 2357, Australia P. Craven Kivipellonpolku 2.C.15, 03100 Nummela, Finland Brian Espey Faculty of Arts & Sciences, University of Pittsburgh, Pittsburgh, PA 15260 U.S.A. J.C. Fairweather 12 Bardon Walk, Goldworth Park, Woking, Surrey GU21 3DA R. Fleet ‘Romaron’, Bunces Lane, Burghfield Common, Reading, Berks. RG7 3DG Colin Henshaw Maunatlala, Junior Secondary School, Private Bag 1, Maunatlala (via Palapye), BOTSWANA John Isles 1S21 Golfview Drive, Kalamazoo, MI 49001-5224, U.S.A. R. M MacLeod 48 Worsley Road, Andsell, Lytham St Annes, Lancs. FY8 4AW Roy Mitchell 5 Pelham Road, Knightsbridge (site 492), Waterside, Londonderry BT47 IFF Gavin Ramsay Mullard Space Science Lab., Holmbury St. Mary, Dorking, Surrey RH5 6NT Martin Ratcliffe 310 Cliffside Drive #34, Pittsburgh, PA 15202 U.S.A. Dr J.H. Shears Allee des Grillons 4, B-1410 Waterloo, BELGIUM S. R. Srinivasan c/o S.K. Ranganathan, ‘Swastika’, Site 6, Gokulam III Stage, 7th Main Road, Mysore 570002, INDIA J.Toone Hillside View, 17 Ashdale Road, Cressage, Shrewsbury, SY5 6DT W.J. Worraker 65 Wantage Road, Didcot, Oxon. ΟΧΙ 1 0ΑΕ

ADDRESS CORRECTION A.A. Smeaton Hochdorfer StraBe 7 D-7012 FELLBACH 5 GERMANY

U Ori, 1982-87 See p. 23 Observers: S.W. Albrighton, C.M. Allen, S.J. Anderson, N.M. Bone, M.A. Brookes, I..K. Brundle, A T. Bueno, R.H. Chambers, G.A.V. Coady, J.W. Cole, D. Conner, H.J. Davis, R.C. Dryden, D.J. Ells, J.W. Ells, H. Feijth, R.W. Fleet, J. Fraser, R.B.I. Fraser, M.J. Gainsford, D. Gavine, R.J. Godden, G. Hirst, S. Hoste, M B. Houchen, J. Howarth, G.M. Hurst, A. Hutchings, J.E. Isles, C. P. Jones, S.J. Kay, R.A. Kendall, I.H. Kennedy, N.S. Kieman, A. Kimber, S. Koushiappas, N.F.H. Knight, J. Eashley, P.C. Leyland, S. J. Lubbock, R.J. McKim, J.W. Macvey, T. Markham, P. Mettam, I.A. Middlemist, R.W. Middleton, C.R. Munford, M.J. Nicholls, R.A.H. Paterson, R.D. Pickard, G. Pointer, G. Poyner, G. Ramsay, K. Robinson, T.G. Saville, J.D. Shanklin, A. Smeaton, H.W.S. Smith, J.S. Smith, L.R. Stevens, D. Stott, R.J. Stuart, D.M. Swain, T. Tanti, M.D. Taylor, J. Toone, E.J.W. West, K. West, P.J. Wheeler, W.J. Worraker, K. Xylaris, E.J.D. Youngs

36 NEW MEMBERS N. Britton 15 Auburn Close, Clonmel, Co. Tipperary, EIRE H.G. Duncan The Swamp, Les Hauts Plans, 83440 Seillans, FRANCE R. Livingstone Rat 4, 37 South Parade, Pensam, Abergele, Clwyd LL22 7RH T. Lubek Upper Knaven, Maud, Aberdeenshire AB42 8ST A. Mark 5 Gisland Close, Acklam, Middlesborough, Cleveland T55 8RU R. Minty Gellyhill Cottage, Banff, Aberdeenshire AB45 3LB Rev. G. Thompson Throssel Hole Priory, Carrshield, Hexham, Northumberland NE47 8AL

WELCOME BACK Geoff Chaplin 19 Longdown Road, Lower Bourne, Farnham, Surrey GU10 3JU Greg Coady Falcon Cottage, Grays Close, Haslemere, Surrey GU27 2LJ Mrs J.D. Kirk 7 Cromwell Avenue, Findern, Derby DE6 6AY Tony Markham 20 Hillside Drive, Leek, Staffs. ST13 8JQ

CIRCULARS

Charges: U.K. & Eire - £6.00 for Circulars and light-curves (4 issues) Other countries - £7.00

Payments (made out to the BAA) and material fa- inclusion should be sent to Storm Dunlop.

CHARTS Eclipsing - Order from Tristram Brelstaff All others - John Toone

Charges: Telescopic - SAE plus 30p per star Eclipsing - SAE plus 6p per star (1 sheet) Binocular - SAE plus 8p per star (1 sheet)

NB: SAEs should preferably be A4 size

BOOKLETS

Direct sale prices apply if collected from the Office at Burlington House or purchased at BAA Meetings.

Binocular Variable Star Charts: Vol.l

£1.25 (U.K) or £1.50 (Overseas) each, including postage (Direct sale price £1.00)

Eclipsing Binary Programme Handbook: 1988 (still contains much relevant material)

£1.25 (U.K.) or £1.50 (Overseas) each, including postage (Direct sale price £1.00)

Available from Storm Dunlop or BAA Office at Burlington House VARIABLE STAR SECTION

CIRCULAR 74

CONTENTS

Notes on some suspected variables 1 Chris Lloyd When is a variable visible? 3 Tony Markham The evolutionary status of RCB stars 6 Don Pollacco Light-curves from our computerized records 9 R And, 1981-87 10 W And, 1985-87 10 RW And, 1977-1987 11 RX And, 1986-87 12 DZ And, 1984-87 13 R Aql, 1983-87 14 V603 Aql, 1981-87 14 U Boo, 1983-87 15 V Boo, 1983-87 16 V Cam, 1983-87 17 Z Cam, 1986-87 18 AH Dra, 1987-89 19 AH Her, 1983-87 20-22 RS Oph, 1985-89 23 U Ori, 1982-87 23 Light-curves of RV Tauri stars 24 AC Her, 1982-91 25-29 UMon, 1982-91 30-33 Please check your address 34 A note on the numbering of Circulars 34 A valedictory editorial 34

Pro-Am Liason Committee Newsletter No.5 centre pages