This is just a welcome to those interested in exploring the nature of short period pulsating variable stars. Historically this has primarily been Cepheids and RR Lyr. Since my research interest is delta Scuti I hope to add a lot more targets of this type. I also plan to add gamma Doradus, roAp stars, and perhaps information on white dwarf objects. Some of these might be very challenging target. Finally, there is a chance to explore a potential new class of pulsating variable stars from their Fourier parameters.
I'm working to update the SPP pages with more information and new targets. This might be a slow process, but hopefully you will see new items at regular intervals.
If you have questions, or idea, you can use the forum, or you can contact me directly.
I look forward to working with everyone.
Eric Hintz (Brigham Young University, Orson Pratt Observatory)
Looking forward to the updates!
I'm in the process of trying to figure out which type of variables I want to "specialize" in and SPP's are definitely on the short list.
Really can't wait to see the new targets and how we may be able to contribute to a potential new class of variable! :)
Have a good one!
Eric and Bert,
Thanks for starting the new forum! These should be some interesting targets - with much to learn. I'll be adding some of your targets to my observing list and look forward to reading more about them!
I have been getting some RR Lyrae and Cepheid lightcurves in the last couple of years in two or three colors. Attached is the last two nights on X LMi. Luckily the time-of-max ephemeris prediction in VSX was off by about 3 hours, so I was able to capture successive maxima at the end of the first night, and at the beginning of the second night, getting complete phase coverage in the process (two 9 to 10-hour runs). The plot simply has the three lightcurves stacked up with B,V,I from bottom to top. This from the Lowell 0.7-m robotic telescope on two 'photometric' (cloud-free) nights.
Great to see this. I've been observing SPPs (almost exclusively RRLs but a few HADS and, recently, a couple of dozen Cepheids) for many years. I've been hoping for over a couple of years now to get involved in supporting the Section (including starting up a forum) but have (and may always be?) involved with too many projects to make the time available. However, this new forum re-energizes me and I hope I can contribute.
I've been observing Cepheids and RR Lyr stars almost exclusively in my DSLR program, because they are about the only bright variables that aren't either too red or have strong emission lines. But I am concerned that the accuracy achievable in measuring magnitudes with a DSLR may be insufficient to improve the Cepheid/RR Lyr rung of the cosmological distance scale. Could you comment on the requirements for measurement accuracy to support that research?
A lot of the work requires accurate periods from the data. With that in mind every data point helps. While errors in individual points might be higher, when they are averaged with data from other observers they work great. I've been working on a Cepheid variable spectroscopically and while the photometric data in the archive has a significant error range, the average let we see a phase jump in the light curve that was predicted from the spectroscopy. While any data helps it is good to get into at least a few hundreths range in terms of error. If you can push to lower errors so much the better.
Actually, upon researching further I've come to the conclusion that amateur observations of the visual or DSLR type are pretty useless. For either of the two areas of real interest for Cepheids and RR Lyr, those being recalibration of the cosmic distance ladder and helioseismology, it appears that sub-millimagnitude estimates of magnitude are required. I don't think DSLR photometry can come within 2 orders of magnitude of the accuracy required, and don't see how aggregation of realistic numbers of measurements can drive the variance down to the necessary level. That's why I don't do DSLR photometry any more.
SPP stars are on my very interest list!
@SFS: with a 4 inch achromat Skyw. & a 8 inch Newton and a Canon 200 D, i can obtain 3 - 10 mmag accuracy with Muniwin & the ensemble option. Depending on the magnitude of the star & if the seeing is good. Of course if one is looking for smaller changes, or multi-pulsations around 0.1 mmag or 0.01 mmag? than every SOA (small observatory astronomer) is out.
Maybe, this section can define SPP-stars for some classes of inch (6,8,9,10,..), magnitude, or mmag accuracy?
If by accuracy you mean that which is reported in the AAVSO report format, I think you are confused. All that is is the standard deviation of the measurements, and is not to be confused with accuracy.
There are a number of factors that are discounted by the AAVSO in ascribing accuracy to DSLR measurements (perhaps also to CCD measurements, I don't know). For one thing, there is the mismatch between the spectral bandpasses of commercial cameras and those of standard filters,, a mismatch that cannot be compensated to the required accuracy using the simple assumed linear relation between the two. This leads to differences in the estimates for a given star as a function of the spread in B-V among ensembles of comparison stars. Next there is the inaccuracy of knowledge of the actual magnitudes of the comparison stars among members of the ensembles. It is very rare to find even a single comparison star having B and B-V known with a 1-sigma accuracy of 1 mmag; typically the errors are over 5 mmag. Next there are the effects of noise, both internal and external. When all of these errors are added together in quadrature, one is forced to the conclusion that even 10 mmag accuracy is very rarely achievable.
If you wish to convince yourself of this, simply do a set of measurements on a suitably bringt Landolt standard star for which the uncertainty is but a few mmag, using a comparison star sequence from the AAVSO. Be sure to accumulate an ensemble of at least 30 measurements, each comprising at least 10 exposures, and run the statistics. To make things more interesting, reprocess the data using subsets of the comparison star ensemble, with varying spreads on ensemble B-V. I have done this, and that is why I posted what I did.
Yes I know, we are not living in an ideal world, even at variable star astronomy.
I believe observations of pulsating stars, especially cepheids & RR Lyrs by CCD & DSLR, less so by visual, allows monitoring of the stability or variability of the period of variation. By generating nightly long time-series for shorter period variables or phase-folded light curves for the longer period variables one can get times of maximum that are perfectly good. It doesn't require milli-magnitude photometry to do this type of work. These variables are slowly moving thru the instability strip and over time will change and monitoring the pulsation period is a good thing to do to understand them as they slowly evolve. Brian Skiff's previous comment is one example. The AAVSO J. and the astronomical literature are full of papers analyzing the periods of these types of stars.
Jim DeYoung (DEY)
I agree wholeheartedly. Time series DSLR photometry is precise enough to do good, publishable work on the timing of the maxima of SPP.