RR Lyrae Bulletin, Number 5

Number 5	December 2002

Chairman's Notes

The more the field of amateur astronomy changes the more it stays the same. As technology would seem to be displacing the visual observer from his/her role on some of the well known variables, it simultaneously opens new territory that needs to be investigated by the visual observer.

The photographic sky surveys taken early in the last century resulted in the discovery of thousands of variable stars. Professional astronomers had time to investigate only a portion of these stars and it fell to the amateur visual astronomer to fill the gap. With the advent of the modern CCD camera, the more technically astute amateurs are replacing the visual observer's work with better quality data and some visual observers lament that they no longer have a useful function. But, today, many thousands of more variables are being discovered by sky surveys such as the Robotic Optical Transient Search Experiment (ROTSE) and the limited number of CCD observers have no chance of keeping up with all of these newly discovered variables. Admittedly, most of the new discoveries are variables of low amplitude, i.e., a preponderance of RR Lyrae type stars. This opens a whole new arena for the visual observer to determine periods and establish ephemerides for these variables. I toss this out as food for thought with the expectation that future issues of this Bulletin will be dealing with some of these stars.

Meanwhile, this issue of the Bulletin deals mostly with unfinished business left over from the old photographic surveys of many decades ago. Currently we turn our attention to two stars which were generally neglected for decades, but finally began to give up some of their secrets when brought under intense scrutiny by visual observation.

Until a few years ago, the period of KZ Puppis was unknown. The period was found visually with considerable difficulty. The difficulty resulted from a combination of reasons as noted in the article on that star.

In the case of the other star, DG Hydrae, early investigators were able to determine a period, but it was not well studied. We now find that both of these stars have a marked Blazhko effect and we encourage an intense observing campaign this season in an attempt to unravel more of these stars' secrets.

Marvin E. Baldwin

RR Lyrae Bulletin will be on-line

Thanks to the assistance of AAVSO Webmaster, Kate Davis, this issue of the RR Lyrae Bulletin will be posted shortly on the AAVSO website at:

Archived copies of the previous four issues will be available at this site also.

Editor's Corner

Happy Anniversary RR Lyrae Bulletin!
It's been one year since the first copy of the Bulletin was published, during which the main objective has been largely met with quarterly issues that report on unusual activities of certain RR Lyrae type stars, highlight observer's work on these stars, and pass on general information about RR Lyrae stars. It appears to have also spurred the RR Lyrae Committee to increased accomplishments, including working with Mike Simonsen in revising the charts for all of the program stars, both in standard and revised formats, initiating observing campaigns of particularly active stars, and using observer's data to update the AAVSO ephemeris for 2003 to a higher level of accuracy than that attained in any previous year. Thoughts and insights of professionals were featured in articles by Janet Mattei and Horace Smith. A few new observers have tried their hand with RR Lyrae stars as a result of this publication.

For the coming year, we plan to increase concentrated studies of a few selected stars (see the article on SZ Hya, DG Hya and KZ Pup in this issue - there will be more). Interested observers will be kept informed in Bulletin articles and possibly through an email list. Visual observers are needed to help identify period deviations, phase changes and amplitude variations. The precision of CCD observers will then refine the activity and if enough data can be obtained, we may eventually get a few answers as to what these stars are up to. For the more casual observers, visual and CCD alike, the overall group of AAVSO program stars needs to be simply monitored for any changes in light elements and/or activity.

RR Lyrae stars are some of the most fascinating objects in the galaxy, with enough activity in an evening to interest and frequently surprise you. Come join us in the quest during 2003!

- Ray Berg

Chart Revisions

DL Herculis - When it was noted in the last issue of this Bulletin that two visual observers not only missed two predicted ToMx's of DL Herculis, but failed to even see the star at minimum (magnitude 12.4) with 8-inch telescopes, the RR Lyrae Committee promised to investigate.

Starting with a literature search, Marv Baldwin found a study by Patrick Wils in IBVS 5134 which in part compared positions of variable stars in the ROTSE1 survey with those in the General Catalog of Variable Stars (GCVS). In a number of instances, the positions differed by as much as 5'. DL Herculis was included in the study, with a listed ROTSE1 position of R.A. 17:20:22.29 Dec +14:30:40.6. This position matches with the star GSC 0990 0684 which is located 2.5' northwest of the GCVS position, an amount significant enough to create an identity miss. Marv emailed the ROTSE1 position on to other interested observers and Rik Hill was the first to catch a ToMx at the new location. Rik's observation was confirmed shortly after with four additional ToMx timings by Baldwin, Gerry Samolyk and the Editor before the field of the variable was lost in the sun. It was noted by all that the star was reaching maximum about an hour later than the predicted time in the ephemeris.

Mike Simonsen has corrected the variable's position on the AAVSO chart and Headquarters has posted the revised chart on the AAVSO website. However, please note that the chart for DL Herculis on the AAVSO CD-ROM 2 is incorrect. Since this star has been hard to locate previously, data for it in the AAVSO archives is sparse to non-existent. Therefore, with the corrected position and adjusted light elements, observers are encouraged to add this star to their program in 2003. Be sure to download the new chart and to send your data directly to the Chairman, Marv Baldwin.

Three "hyperactive" RR Lyrae type stars are coming into good placement for observation now and are selected here for a concentrated observing campaign. The three stars, SZ Hya, DG Hya and KZ Pup, have all been observed in the last season and discussed in recent issues of the Bulletin. Different questions continue to be unanswered for each star, all of which will require LOTS of data to resolve! Your active participation is encouraged. Read on ........

Figure 1 - Phase plots of SZ Hydrae in 2002 - CCD(V) data by G. Samolyk
Please click image to enlarge.

SZ HYDRAE - Bulletin No.1, issued a year ago, pointed out that the light curve of the RRab type star SZ Hydrae can significantly change shape and amplitude as well as phase, indicating a strong Blazhko effect. This is illustrated in some of last year's measurements plotted in Figure 1. The AAVSO receives just enough timings of SZ Hydrae each year to keep track of the primary period, but insufficient to probe any further into the star's activity. The aim of the campaign for 2003 is to establish a current epoch for the Blazhko effect and then use the scattered maxima collected over the past few years to either verify or modify the Blazhko period of 25.8 days published by S. Kanyo (IBVS 490). The campaign was started last season to provide increased coverage and needs to be greatly intensified this year in order to make a decent determination of the Blazhko period. The brightness and phase shifts of this star are easily recorded by visual observers to supplement the work of the CCD observers. The AAVSO ephemeris times are stable and well established but the very real possibility of the star reaching maximum an hour early should be considered when selecting an observing start time.

Visual observers should use the chart for SZ Hydrae posted on the AAVSO web site. CCD observers should use GSC 5462 0077 as the comparison star.

Figure 2 - Phase plots of DG Hydrae in 2002 - CCD(V) data by G. Samolyk
Please click image to enlarge.

DG HYDRAE - Last season, a brief but very intense series of observations conducted by three observers showed this star to exhibit widely variable phase shifts in the times of maxima as indicated in Figure 2. These phase shifts were found to be of the order of up to two hours. Amplitude variation was not noted at that time, but more data is needed to confirm this. It was also noted that the star has had a relatively stable period for the past 17 years, although a minor adjustment was required last year to improve the accuracy of the ephemeris.

For this season, more data is needed to determine how the shape and possibly the amplitude can vary. If these phase shifts are a continuing phenomena, are they cyclic in nature? If they can be found to occur in a predictable way, can they then be zeroed out in a search for short term changes in the primary period? And finally, the light elements adjusted last year may need further refinement. Data, data, data! A lot of it is needed to continue this study and we invite all observers to assist in this season's campaign. While the 2003 AAVSO ephemeris values should be considered close, remember that the phase shifts may cause maximum to be an hour early or an hour late.

Visual observers should use the chart for DG Hydrae posted on the AAVSO web site. CCD observers should use GSC 4873 1232 as the comparison star.

Figure 3 - Phase plots of KZ Puppis in 2002 - CCD(V) data by G. Samolyk
Please click image to enlarge.

KZ PUPPIS - This star is perhaps the greatest challenge of the three. It is deeply shrouded in unknowns. The GCVS lists it as an RR Lyrae type variable, but cannot identify the subtype. The star's position listed in that source is inaccurate. Until a few years ago, the period of KZ Puppis was unknown. The period was finally found visually by Marv Baldwin with considerable difficulty. The difficulty arose from a combination of reasons:
1. The star is far south for northern observers.
2. It often rides through a scheduled maximum with hardly a blip on the visual scale.
3. The period turned out to be almost exactly 2/3 day which meant that for some years the northern observer has little or no chance to catch a maximum.

It was with great satisfaction that the star was finally forced to give up it's secret after making 700 visual observations in seven years.

The evidence, as well as can be surmised at this point, is that this star has wild changes in the shape of the light curve and may have sudden large changes of period. Gerry Samolyk made CCD measurements on three nights in February 2002. The data is plotted to phase in Figure 3, which shows some of the light curve variation.

Obviously, a lot of questions need to be answered here. We expect the maximum to be well positioned for observers in the western hemisphere in the upcoming season. Reasonable data can be obtained by the careful visual observer. Charts for this purpose will be found on the following pages which also provide an accurate location of the variable. CCD observers should use GSC 5986 0155 as the comparison star. Predicted maximum can be calculated from:

KZ Pup Charts:

• KZPUP-E.GIF
• KZPUP-ER.GIF (reversed chart)

Observers in 2002 -

The Chairman has forwarded the following list of observers who provided data in 2002 on individual stars in sufficient quantity and properly spaced so that it may be useful for determining times of maxima.

Gerry Samolyk - Wisconsin
Gil Lubcke - Wisconsin
Marv Baldwin - Indiana
Mike Nicholis - Arizona
Neal Simmons - Wisconsin
Chris Hesseltine - Wisconsin
Rik Hill - Arizona
Ray Berg - Indiana
Loucas Michalis - Greece
Andrej Markiewicz - Poland
Bill Wilson - England

Thanks to all and keep looking up!

More Observing Aids On Line -

The Milwaukee Astronomical Society (MAS) will be posting, by January 2003, an expanded ephemeris of RR Lyrae stars, prepared by Gerry Samolyk, on their website at: http://www.milwaukeeastro.org/observing.htm

This will supplement the AAVSO ephemeris by including a number of other RR Lyrae stars of interest, Delta Scuti stars and SX Phe stars. Some of these non-program stars will be reviewed in future issues of this Bulletin.

Recommended Comp Stars -

To properly evaluate amplitude variation and other aspects of the Blazhko effect in RR Lyrae type stars, it is important that all observers use the same comparison stars. Visual observers should use the charts available on the AAVSO web site except for the special charts published in this Bulletin (such as RR Lyrae and KZ Puppis). In recent years, we have started to receive increasing amounts of CCD observations and as with the visual requirements, standardized comparison stars are required to make all CCD data comparable. The table below lists a number of RR Lyrae stars that CCD observers have been covering and comp stars (by GSC number) recommended by the RR Lyrae Committee based on (B-V) values and proximity to the variable. Use a V filter. Additional variables and comp stars will be covered in future issues.