[vsnet-alert 11254] Re: re New flare star candidates

[kstars at Safe-mail.net]

Last revision on this :-

The Calcium Hydride issue seems to indicate that it isn't stictly a main sequence star after all, but a "subdwarf" M star, so the absolute magnitude info likely won't apply.

That's low metallicity stuff.

And this might well explain the apparent B-V to J-Ks discrepancy, as these stars appear redder in B-V than in other colours, see this in general re spectral discernment of these objects (note high proper motion has been a strong selection criterion for red subdwarfs too), and the bottom paragraph in particular re colours.

http://www-int.stsci.edu/~inr/ldwarf.html

Reading the Mv for the red subdwarfs off of the bottom graph at the above url against the measured B-V of 1.6 and the distance shrinks to m-M ~ 0 ~ 10 parsecs distance.

The endpoint being, it doesn't necessarily need it it's spectrum measuring.  Unless someone wants to know if it's sdM, esdM or usdM, eg

http://www.iop.org/EJ/abstract/0004-637X/669/2/1235

I got there in the end...

Interesting star still (possibly nearby star possibly missed out of the standard catalogues, some low metallicity ancient Halo probably fully convective thing that's still chromospherically active, still with a magnetic dynamo, and "superflares" if the 3 mag amplitude is valid), and it makes a change don't it.  Likelihood of seeing another flare any time soon?  Bloody low.

Cheers

John

-------- Original Message --------
From: kstars at Safe-mail.net
Apparently from: vsnet-alert-bounces at ooruri.kusastro.kyoto-u.ac.jp
To: vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp, skiyota at nias.affrc.go.jp
Subject: [vsnet-alert 11253]  re New flare star candidates
Date: Thu, 21 May 2009 11:45:59 -0400

> The CMC14 r' and 2MASS J-Ks colours, r'-J = 3.00 and J-Ks = 0.85, are in fact just about fine for an M0 main sequence star.
> 
> I can't add up it seems, I originally got 11.24 - 8.24 = 2....
> 
> Sorry about that.
> 
> Absolute magnitude then would be about 9.8 ish, so with the ASAS3 V ~ 11.8 is that gives a distance modulus of about ~ 2, which gives about 25 parcsecs distance (_if_ I've added that one up properly).
> 
> And whilst looking to see if SIMBAD had any V measures I suddenly find I missed looking at one of the only three references coz I thought it was to another edition of Stephenson's S star catalogue but on checking find that it's actually a reference to a paper by another guy we likely couldn't have done without re objective prism spectra, MacConnell.
> 
> And the contradiction suddenly all melts away coz it isn't an S star, it's a red dwarf with a CaH line at the very adjacent wavelength of 639 nm (CaH = Calcium Hydride) as noted here specifically for CSS 1237 :-
> 
> http://cdsads.u-strasbg.fr/full/gif/1997BaltA...6..105M/0000108.000.html
> 
> in a paper that actually asks where are all the main sequence C and S stars are!  (And finds there aren't any of the latter, at least none found so far in 1997).
> 
> It's all there if ya just look a lot of the time.
> 
> Cheers
> 
> John