SPA Variable Star Section

SPA VSS Newsletter: April 1997

Annual Totals for 1996

Cepheids                Eclipsing               Miscellaneous

Delta Cep     333       Beta Lyr      247       Gamma Cas    160
Eta Aql       213       u Her         144       R Sct         79
Zeta Gem      117       RZ Cas         70     
                        Algol          49
                        Lambda Tau     20

1. Michael Clarke       1. Michael Clarke       1. Michael Clarke
2. John Coates          2. Kevin Barnwell       2. Shelagh Godwin
3. Melvyn Taylor        3. Tony Markham         3. Tony Markham
4. Kevin Barnwell       4. Shelagh Godwin       4. Kevin Barnwell
5. Shelagh Godwin       5. Matthew Barrett      5. Eric Horsley

Semi Reg & Irreg        Miras                   Overall

Mu Cep        180       R UMa          70       1. Michael Clarke
Alpha Her     121       T Cep          52       2. Shelagh Godwin
R Lyr         110       Chi Cyg        49       3. Kevin Barnwell
Rho Per        90       U Ori          40       4. Tony Markham
Eta Gem        79       R Tri          36       5. Eric Horsley
Alpha Ori      77       Mira           24       6. Matthew Barrett
Beta Peg       73       R Ser          21       7. Melvyn Taylor
                                                8. John Coates
1. Michael Clarke       1. Michael Clarke       9. Simon Jenner
2. Shelagh Godwin       2. Tony Markham        10. Graham Pointer
3. Kevin Barnwell       3. Eric Horsley        11. Keith Darbyshire
4. Eric Horsley         4. Shelagh Godwin      12. Neil Bone
5. Tony Markham         5. John Coates

Congratulations to Michael Clarke who as well as being the most prolific observer overall also managed to be the most active in every category. Currently the section is dependant on Michael who alone follows the Mira type variables down to minimum. Is anyone else with a telescope able to make similar observations ? (charts are available).

Introduction

Two significant changes have been made since this time last year:

the removal of the need to work out the Julian Date when completing report forms and the redesign of the report forms to reflect this.
the VSS section of the SPA Web Pages. This now includes light curves for all variables on the sections programme. Other features include predictions for eclipses of RZ Cas (more detailed than on the list issued annually) and news of recent variable star activity. The address of the page is:

http://www.u-net.com/ph/spa/sections/vs.htm

Summary of results for each variable

There now follows a summary of the results for each variable, based on the observations that were received for 1996 by late March. Light curves for the variables are linked to this newsletter.

Eta Aquilae

The 1996 light curve shows the mean magnitudes ranged from mag 3.56 at phase 0 to mag 4.33 near phase 0.7. [Light Curve]

RZ Cassiopeiae

Results from previous years had shown the primary eclipse to be centred on around phase 0.014-0.016 (rather than phase 0 which would be the case if eclipses were occuring on schedule). The 1996 light curve shows that the primary eclipse is now centred on around phase 0.02 (30-35 mins late), suggesting that the discrepancy is increasing. [Light Curve]

Gamma Cassiopeiae

Once again, this star has shown little variation. Monthly means (after making small adjustments for systematic differences between observers) ranged from mag 2.16 to mag 2.25. [Light Curve]

T Cephei

This variable rose from mag 7.6 at the start of 1996 to reach maximum at around mag 5.7 in mid February - brighter than the 1995 maximum. It then faded, reaching mag 8.0 by early June and mag 10.0 by mid August. From mag 10.2 in mid October, it stayed at ninth magnitude throughout most of November and December, reaching mag 8.9 by the end of the year. Following its March 1997 maximum, T Cephei should remain visible in binoculars until the early summer and will be approaching binocular brightness again by the end of the year, on the way to its spring 1998 maximum. [Light Curve]

Delta Cephei

The mean magnitudes ranged from mag 3.45 at phase 0 to mag 4.08 near phase 0.7. [Light Curve]

Mu Cephei

The linked light curve shows the activity of Mu Cephei in recent years. Whereas it is often the case that the periodic rises and falls in brightness of many semi regular variables can be hard to see in their light curves, the variations of Mu Cephei can easily be seen. After fading during 1995, it brightened by 0.3-0.4 mag between January and the summer of 1996 before fading slightly by the end of the year. Previous maxima had occured during the second halves of 1991 and 1994, indicating that the period of Mu Cephei is probably about 2-3 years. [Light Curve]

Omicron Ceti (Mira)

Poor weather in early 1996 severely limited observations as Mira approached its March 1996 maximum. It wasnt observed at all in January. Two observations by Michael Clarke in late February before it disappeared into the evening twilight placed it at mag 5.0. Observations during the autumn indicate a fairly flat maximum at about mag 8.9, with it starting to brighten during November and reaching mag 4.5 by year end. Early reports from 1997 indicate a brighter than usual maximum during February. When further observations from early 1997 have been received, an updated version of the linked light curve will be included in the early autumn SPA News Circular.

The next maximum is predicted for January 1998. **** Please make sure that you have the latest sequence (dated 961117, A=Alpha Ari=2.19, B=Beta Cet=2.39, etc). [Light Curve]

Chi Cygni

Observations show Chi Cygni rising from mag 11.0 in mid May 1996 to mag 8.8 by late June and reaching maximum at mag 5.5/5.9 in mid August - making it a fainter maximum than usual. It then faded, reaching mag 8.0 by late September and mag 11.3 by the end of the year. The next maximum is predicted for late September 1997, so it is likely to be approaching binocular brightness by July. [Light Curve]

Zeta Geminorum

The weather significantly affected the quality of the 1996 mean light curve. When the dates/times were converted into phases, it was found that whereas some phases were very well covered, there were others (e.g. phases 0.1, 0.3-0.4, 0.6, 0.8) which, by chance, were very sparsely covered. Nevertheless, mean magnitudes do show a fairly symmetrical light curve with a range of 3.70-4.15. [Light Curve]

Eta Geminorum

Monthly means indicate a rise of 0.1-0.2 mag between January and the autumn. The last pre-conjunction (May 5) and first post-conjunction (Aug 20) observations could indicate a fade associated with the eclipse predicted for June, but in the absence of other observations it is not possible to be sure whether the fade was genuine or was a consequence of the difficult observing conditions. Observations on May 3 and Sep 12 showed it to be at around its normal brightness. [Light Curve]

Alpha Herculis

Following a fade in the second half of 1995, observations in 1996 show it brightening again from March onwards. However, there is considerable scatter and there are times when some observers see it brightening while others see it fading ! The light curve for 1992-96 does hint at a period of around 2 years, but the scatter makes it difficult to be certain. [Light Curve]

u Herculis

Observations showed that both primary and secondary eclipses were occuring on schedule. Whereas the catalogued range is 0.7 mag, the dips seen in the mean light curve are somewhat smaller - 0.3 mag at primary eclipse and 0.2 mag at secondary eclipse. [Light Curve]

R Lyrae

The linked light curve shows monthly means for the most active observers during the years 1992-96. As for other semi-regular variables, it has been necessary to make adjustments to allow for the fact that some observers always see red variables systematically brighter than do other observers. Hence a light curve of your own observations might be shifted upwards (or downwards) by several tenths of a magnitude relative to this light curve. There are several maxima - in early 1994, early 1995 and early 1996. [Light Curve]

Beta Lyrae

Primary eclipse in 1996 appears to be have been centred near phase 0.15, continuing the trend seen in previous years whereby the observed eclipses are getting progressively later relative to the times predicted by the General Catalogue of Variable Stars. [Light Curve]

U Orionis

In early 1996, U Orionis was fading from its Nov 1995 maximum. Observations show it fading from mag 8.9 in late January to mag 10.8 by late March. Observations later in the year show it rising from mag 8.9 in late September to maximum in early November - there is considerable scatter in the maximum brightness between observers. Most observers saw a peak brightness of around 7.1/7.5, although some saw it brighter. By the end of the year it had faded to mag 8.4.

**** Please make sure that you are using the latest sequence (dated 960525, G=8.00, etc). [Light Curve]

Alpha Orionis (Betelgeuse)

The linked light curve shows monthly means for the years 1988-96. Poor weather in late 1995 / early 1996 restricted the number of estimates made and contributed to the scatter, but it seems that Betelgeuse stayed near maximum during 1996 and possibly brightened slightly. [Light Curve]

Beta Pegasi

There is some evidence that Beta Pegasi may have been slightly brighter than usual during the first half of 1996 - but this is based on only a few observations. Monthly means for the second half of 1996 show little variation. [Light Curve]

Beta Persei (Algol)

The linked light curve shows the primary eclipse according to the 1996 observations. Although there are only a few estimates prior to mid eclipse, the observations do confirm the 1995 results which showed that mid eclipse is centred on about phase 0.01 - about 40 mins later than the GCVS elements predict. [Light Curve]

Rho Persei

Poor weather restricted observations early in the year, but monthly means indicate a fade of about 0.2 mag during 1996 [Light Curve].

R Scuti

The 1996 light curve appears at the end of this newsletter. Deep minima, to 8th magnitude occured in April and September, with a shallow minimum occuring during July. The most favourable deep minimum in 1997 is likely to occur during the early summer, with another in mid autumn. [Light Curve]

R Serpentis

Poor weather restricted observations but available observations show a rise from mag 8.5 in late January 1996 to a maximum of around mag 6.0 in late February, and a fade to mag 8.4 by late April and mag 11.8 by late July. The next maximum is predicted for February 1998. [Light Curve]

Lambda Tauri

Although there is scatter between different observers, the linked light curve does show that primary eclipse is occuring close to phase 0 and is about 0.5 magnitudes deep. In 1997, the most favourable series of eclipses will run from early November to mid December. [Light Curve]

R Trianguli

As the linked light curve shows, the 1996 maximum was again bright. Opportunities for binocular observation of R Trianguli will be limited in 1997 - the late April maximum occurs when R Trianguli is not observable (did you manage to catch it rising towards maximum in late March ?), but during December it should become visible in binoculars as it rises towards its January 1998 maximum. [Light Curve]

R Ursae Majoris

Two maxima of R Ursae Majoris occured during 1996. As the linked light curve shows, the January maximum was fainter than the average peak of mag 7.5, but the November peak was brighter than average. The light curve also shows how the rise to maximum is much steeper than the fade from maximum. The next maximum is predicted for early September 1997. [Light Curve]

News of other variables

Nova Cas 1995

This faded slowly, from mag 8.4 in February 1996 to mag 10.2 in June and mag 13.9 by February 1997. There were, however, several short-lived outbursts superimposed on this decline. For example, it brightened to mag 8.5 twice in August.

R Coronae Borealis

This variable brightened from mag 13.3 in February to mag 8.6 by late May and by November was at mag 6.3, close to its normal brightness.

CH Cygni

This former binocular variable faded from mag 9.1 in February to mag 10.3 in June - its faintest ever. Late in the year it started to brighten again, reaching mag 9.6 by February 1997. It is suspected that some of the fades of CH Cygni that have been seen over the years may actually have been eclipses. [Light Curve]

FG Sagittae

This peculiar variable, which was at 9th magnitude just a few years ago, was recorded at 16th mag in April 1996 - its faintest since 1894. By November it had brightened to mag 12.2

SN 1997bo

This type Ia supernova in galaxy NGC 673 was discovered at mag 16.5 on Oct 18 by amateur Mark Armstrong, making it the first ever discovery of an extragalactic supernova from the UK.

Spurious Supernovae

Mark Armstrong imaged another possible supernova at mag 17 close to NGC 3041 on 1997 Feb 26. However, subsequent observations showed it to be moving and thus presumably a previously undiscovered asteroid.

Another spurious supernova was reported in IAU Circular 6516. Recent investigations indicate that the supernova previously given the designation 1956C was in fact an asteroid passing close to a galaxy. The asteroid, now known as 1988XB5, wasnt discovered until the 1980s.

Finally ....

Many thanks for all of the observations received for 1996. Do visit the SPA VSS Web Pages if you get the chance. Any comments on the content would be welcome.

Tony Markham April 1997.

Maintained by Michael Oates Email: mike@ph.u-net.com
Last modified 26th Aug 1997