[vsnet-newvar 1493] (fwd) [vsnet-chat 5359] Re: Probable new faint variable star in Scorpius

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

(fwd) [vsnet-chat 5359] Re:  Probable new faint variable star in Scorpius

From: aah@nofs.navy.mil
Date: Sun, 7 Jul 2002 12:32:40 -0700

On June 16, Mati Morel mentioned a possible faint variable,
along with a proposed identification for EF Sco:

>One star which caused a problem was EF Sco, range 13.3-14.4p. The Guide8
>display puts it way off the nearest 13mag star, which happens to be GSC
>6821-01679, at 16h51m40.36s -29 41'25.5".  The notes in HB857 state that
>HV4231 = EF Sco
>was observed 30 times in 1926, sufficient to derive a period of 0.6056d.
>So, while the Harvard position is poor, I surmise that the nearby star GSC
>6821-01679 is EF Sco. It appears to have a close companion to the east.

I have now observed this field on three nights, and find that EF Sco
can be identified with the star with coordinates:
16:51:42.25  -29:42:26.2 (J2000, errors <100mas)
This star is about 39arcsec from the GCVS position, but has a much more
RRLyr-like color (B-V=0.5) than the GSC star Mati selected.  The candidate
is bluer at maximum, and shows 0.8mag variation over the three nights. 
The Bmag at maximum is about 15.2 so the GCVS magnitude range is in error.
This variable is too far south for me to observe, but it would be a nice
star for southern amateurs to follow and derive a better light curve and
improved period.  Towards that end, I have posted a two-night field photometry
file at
http://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/efsco.dat
Be careful to find uncrowded comparison stars.
Arne

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp