Skip to main content

Science to be done on SR's?

4 posts / 0 new
Last post
HTY's picture
Science to be done on SR's?

Since my CCD camera is sick, I've been looking at other projects to do until it comes back online.  I was looking at many of the brighter stars in the AID and I notice that many of the brighter ones are semi-regulars with fairly small amplitudes.  Some of these show good definition in their lightcurves via visual observations but some are very red and have very small amplitudes which makes it difficult to see anything other than a seasonal blob in their long term lightcurves.

I would think that these targets, given the brightness of many of them, would be pretty much perfect for suitably transformed DSLR photometry or a BSM type scope.  But my question is:  Is there any real science to be done with these stars?  I watch the daily releases in arXiv > astro-ph and I don't recall seeing a paper about these types of stars.  As a matter of fact I don't recall EVER seeing a paper about these types of stars specifically.  Is there anything to be gained by monitoring these stars electronically?

....Tim (HTY)

Matthew Templeton


It's difficult to gauge which long-period stars are going to produce interesting results, and by their nature, they don't do exciting things quickly.  Interesting behavior may only manifest itself after several years.  That's an unsatisfying answer even for me, and I study these stars more than most.

One way to search for potentially interesting targets is simply to look at the data that we have and see what you find striking.  As an example, I pulled a list of the SRA variables having more than 2500 observations in the AID and then went to Simbad to look at the publication histories.  Most of the best-observed stars don't have recent deep astrophysical papers, they're more like updates or broad surveys. 

However, even the publication records don't tell you everything.  As an example, one of the stars on the list was SW Gem.  The publication record is very poor, but when I went to the light curve, I see that the pulsation behavior has fundamentally changed since the mid-20th century.  It used to be a pretty decent pulsator, but for the past few decades it's hardly budged.  Why?  What happened?  Is it still pulsating with the 680 day period?  Did the colors change?  There's an observing project right there.

By the way, that list of SRAs with more than 2500 observations is as follows, for those interested: V Boo, RS Cyg, RY UMa, V CVn, eta Gem, RU Cyg, S Aql, SS Vir, S Cam, X Mon, RS Aur, S Pav, T CVn, ST And, SW Gem, V Hya, RW Sgr, VX And, RV And, RU And, RZ Cyg, U LMi, SZ Lyr, RR Cam, AU Cam, TX Tau, TV Tau, RS CrB, SV Cas, V0380 Sco, V0393 Cas, and RS And.


HTY's picture
I was expecting that

Hi Matt,

Thanks for your answer.  I was kind of expecting that.  It looks like only LONG term monitoring on these stars is what is necessary.  I looked at the last 1,000 days of SW Gem and there seem to be some shorter periods that can be seen at small amplitudes in the Tri-G data.  I haven't done a literature search to see if these have already been studied.

V Boo looks like its amplitude has decreased also since the early 20th century and again there are hints of shorter low amplitude periods in the V and Tri-G data.  I suppose that more precise observations and data could tease some of these shorter periods out but what does the fact that the star is flashing multiple periods tell us astrophysically about that star?


dquig's picture
Yes! Escpecialy usefull are B

Yes! Escpecialy usefull are B and V readings so corretions can be applied, theres a paper by Zissel and another by Stanton outlining the process. Any corrections can then be compared to readings taken in the V band. There are quite a few papers, I've attached one Muliperiodicities of semi-regular variables where they make use of CCD readings to first improve the dataset.

Log in to post comments
AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484