[vsnet-alert 11209] re NSV 18024 and ASAS 150946-2147.7 and V1129 Cen

[eruptors at Safe-mail.net]

In case peeps are missing this similarity :-

NSV 18024

<http://www.astrouw.edu.pl/cgi-asas/asas_variable/084434-3757.9,asas3,0,0,1000,0>

ASAS  150946-2147.7

<http://www.astrouw.edu.pl/cgi-asas/asas_variable/150946-2147.8,asas3,0,0,1000,0>

V1129 Cen (= NSV 19448 = HD 109962)

<http://www.astrouw.edu.pl/cgi-asas/asas_variable/123907-4533.8,asas3,0,0,1000,0>

The first two show a commonality of symmetry in their outburst and decline profiles, the last one not so certainly so.

NSV 18024 memory advises was first noted as to its nature by Sebastian Otero, circa some time ago, during his studies of ASAS3 data.  I don't seem to remember any spectroscopic followup on that one.

The star is late G with cyanogen bands, thus the bright ROSAT xray source could as readily be a signature of chromospheric activity for the main sequence star.

The new ASAS variable object in Libra, noted by Pojmanski himself, circa now, is noted in CBET 1774 as having a "late A" background, likely for the main sequence star.

The final one, since denoted V1129 Centauri, is not so certainly equivalent in outburst profile, but is somewhat symmetric at least, and again was first noted by Sebastian Otero using ASAS3 data circa quite somet time ago.  This one is superposed upon what looks to be a contact binary which may lead to the fact that it's outbursts are actually periodic

http://ar.geocities.com/varsao/NSV_19448.htm

and Bond et al did some spectroscopic work on the object, eg, 

http://www.cfa.harvard.edu/iauc/08600/08663.html#Item1

from which can readily be seen comments regarding HeII emission for comparision with similar statements in CBET 1774 for the new object in Libra.  Despite neither main sequence star being anything to do with spectral types WR, O or B.

Here are outbursts of very similar kind, associated with normal but distinct main sequence stars, two likely in convective states (well, one at least is a contact binary with possible chromospheric activity as shown by xray) and one possibly in a radiative state.  The "parent" star almost seems irrelevant to the outburst, nor having any commonality that could be given to explain the outbursts are upon them themselves.

So, three stars with common outbursts, one predictably so, two currently being kind enough to be in outburst at the same time, thus ideal for comparative xray and spectroscopic monitoring.


All of this shows the beauty and utility of surveys like ASAS3 which can avoid a plethora of traditional selection effects and discover novel and truly interest variable objects which would be completely missed otherwise.

I see a lot on arxivs of late re decadal white papers.  I've not seen anything yet that comments on the fact that follow up of such objects is still very hit and miss, personal preference, and fashion dictated, with no real infrastructural support.  Increasingly in depth optical photometry doesn't cut it nor add anything extra, multiwavelength data and goodly dispersion multiepoch spectroscopy are needed, yet rarely available.

Let's be hoped the Swift teams can manage to find ToO time for NSV 18024 as much as ASAS 150946-2147.7, as it too is unpredictable re outburst occurrence.  V1129 Cen is more a GI target, being predictable.

Anyway, whatever I do and do not think, there are now three of these objects in somewhat diverse character parent systems, albeit not markedly diverse, but not overly similar either.

All pretty much in the South again, too.

Cheers

John

John Greaves