[vsnet-chat 7622] NSV 10028 an interesting project

[Sebastián Otero]

This is an interesting project.

NSV 10028 is an orange star that seems to undergo 0.8-0.9 mag. fadings (extreme range is V= 11.55 - 12.43)
2MASS J-K is 0.61 and the ASAS light curve shows an event in mid-Sept. 2008 and another possible one at the end of 2003.
http://www.astrouw.edu.pl/cgi-asas/asas_variable/180156+0422.3,asas3,690,1870.610000,400,200

Two possibilites come to mind:
1) A long period eclipsing binary, which agrees with Hoffmeister's 1967 discovery and interpretation.
2) An RCB star.

If 1), then the light curve reminds me of a symbiotic system. There are variations at maximum that may come from the red giant and the long period is typical of these systems.

If 2), the variability at maximum could be the typical pulsations in RCB-stars.

Colors are okay for the two possibilities. 
Amplitude seems a little small for RCB.
But NSVS data seem to compromise the eclipse interpretation with a 690 d. period.

if it is an eclipser, then we should look for a new fading according to the following ephemeris:

HJD 2454727 + 690 x E

It takes more than 40 days for the star to recover (if the behaviour is periodic) 
An eclipser should have taken place on HJD 2455417 or so, 31 days ago (I found it a little late!)

A brightening trend should still be apparent if we hurry up and get some observations right now.

Cheers,
Sebastian.


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