[vsnet-alert 8794] ALERT: Possibly double variable acting up = NSV 19448

[Sebastian Otero]

NSV 19448 = HD 109962 = GSC 8232 1689 at 12h 39m 07.89s -45º 33'
44.2" (2000.0) is brightening again.

A background mira on the line of sight of an EB-type eclipsing binary?
http://www.astrouw.edu.pl/cgi-asas/asas_lc/123908-4533.7

-HIGH RESOLUTION IMAGES NEEDED to solve the mira companion if it exists.
-VISUAL OBSERVATIONS AT HIGH POWER to resolve the 9.7-mag eclipser and the 
(currently) 10.5-mag mira if it exists.
-COLOUR PHOTOMETRY NEEDED to detect a reddening.
-IF IT IS A DOUBLE VARIABLE STAR, separation and PA measures of this new 
visual binary (Francisco, someone in the South?)
-SPECTROSCOPY

I copy below info I sent last year when the star made another display.

It was classified as a MISC variable with a period of 360.475 d. in the ASAS 
catalogue.

I have found it to be an eclipsing binary of the EB-type with elements: Min
I= HJD 2452491.552 + 0.893025 d. x E. Spectral type is F2V and the range in
V= 9.54 - 9.84 (secondary minimum= 9.74) according to ASAS-3 data.
The lightcurve is here:
http://ar.geocities.com/varsao/NSV_19448.htm

The object underwent four brightenings lasting ~40 days on April-May 2001,
March-May 2003, March-April 2004 and April-May,2005. There is a gap in ASAS 
data so another
"event" might have taken place on April-May 2002. During brightenings the
star reaches V= 9.1-9.3.
On December 26, 2005, the star has started the current brightening, detected 
by Patrick Wils in ASAS data.

Although 2MASS quick look images and POSS archival plates reveal no other
candidate capable of being responsible for any coincidental line of sight
behaviour down to roughly within two arcseconds of HD 109962, I can't help
thinking of a background mira possibility. The lightcurve seems to show a
very regular pattern and maxima look like a mix between the EB variations
and a mira star maximum. Also the amplitude seems to be somewhat larger in
unfiltered magnitudes (reported by Vello Tabur, Australia), so this might be 
a clue of a reddening.
BUT it's not clear what it is. A mira that can get as bright as 10th
magnitude should stand out in 2MASS data.
Multiband photometry and especially spectroscopic analysis during
brightenings is essential to unveil the true nature of this object(s).

It would be interesting even visually to detect a companion or a color
change when this "thing" brightens!
I have made a chart for visual and photometry use (there is a nearby star
with UBVRI) and it's available at:
http://ar.geocities.com/varsao/Carta_NSV_19448.htm

Thanks John Greaves and Patrick Wils for their interest in this star.

Cheers,
Sebastian.