Affiliation
American Association of Variable Star Observers (AAVSO)
Sat, 05/21/2016 - 16:05
I am in the process of running vstar charts on the stars in this PMS/YSO program that I have been monitoring with this group. It is turning out that some of the stars that are listing as "I" somethings are often actually SR types of one sort or the other. v0682 Aql, DU Cep are examples and I have two more submitted for review on the vsx now. I am pretty sure there will be more. My inclination is, once such stars are turned up and reclassified, that I should drop them from my list, which is focused on PMS objects. I am wondering if anyone has any idea why so many stars located in young star fields would turn out to be red giants? Are these just field stars? Are there so many red giants?
Yes, I think some of these are field stars, and you should drop them from your programme if you are interested in them as YSOs. Nothing of course to stop you observing them as 'normal' variables! I think a lot of these stars may have been classified in the past on scanty information (lightcurve or position in an OB association etc). V751 Cyg is one such, in the Cygnus T1 association but in fact not a YSO at all. One of my 'favourites' is EY Ori, which by all accounts should be one of those 'classed as algol but really UXOR' stars. Nope - it actually is an algol, even though it's in M42!
I think I said on the original YSO home page that some of the stars on the programme (I'll take DU Cep off) would turn out to be non-YSOs, and that's what we are finding.
Another star I am wondering about is v0347 Aur. Typed as INT. At first I thought it might be another SR but that seems highly unlikely, being as it is in a nebula. I suppose that could be coincidental. But on further examination, it looks like it could be an EXOR. I think I am the only one observing it and my data remains too thin to get a solid look at the LC. I am going to add some color. Not sure if color has any diagnostic value for an EXOR but will provide some addition data points, if nothing else.
Hi Bruce,
it is not a red giant because B-V is 1.2 according to APASS. And there are also spectra in the literature showing it as a M2Ve(T) star.
The ups and downs look too frequent compared to the typical EXOrs though.
See ASAS-3 EX Lupi light curve as an example.
Cheers,
Sebastian
Sebastian, not contending that it is a red giant, but I wonder about your statement that it could not be a red giant with a B-V of 1.2? I accept that is a bit warm for an M-class star, more like say and K6 or so right? Would the spectrum not be a more reliable indicator of the star's class though? In this regard, I note that all the APASS data is taken at the very peak magnitude shown in the AAVSO data, could it be that accounts for the incongruity between the stated spectrum and the color index?
I see what you mean about the frequency, but the little bit of data I have looks like some type of eruption process more than a pulsation - novice eyes granted. That and the amplitude discouraged me from thinking it was some type of red giant.
Do you think it currently looks like a typical INT? I have not looked at that many yet, but I picture something far more scattered and random. I note also that the VSX actually gives a period for it. Can you have a period for an "I" anything? Lots to learn, sorry to burden you with so many questions. Any illumination is welcome. Thanks