[vsnet-alert 18661] V704 And (alias LD 317)

[roberto nesci]

vsnet-alert 18657 (V0704 And) refers to a star located at 23:44:57.51 
+43:31:22.30. The star is known by SIMBAD as LD 317.

At these coordinates there is a blue star, detected in the First Byurakan Survey 
Its spectrum is visibile at the Digitized FBS archive
(http://www.ia2-byurakan.oats.inaf.it). At the epoch of the observation 
1974-09-14 the stars was B=13.70, R=13.70 in the scale of the USNO-A2 catalog.
It was classified as an sdO by Mickaelian et 2008 AJ 136, 946 (CDS Catalog III/258).
The star was first indicated as variable by Dahlmark 1991, IBVS 4734, and later 
studied by Papadaki et al 2006 A&A 456, 599 who found a periodicity of 3.6 hours 
but different in different nights with small amplitude, and with substantially 
different average value at different epochs.
On the Catalina Real Time Survey at this sky location there are formally two 
objects, with the same coordinates, so they are actually the same object. Both 
have a variable light curve: the classification of this star is NL,SY 
(nova-like, SY Scl) which means that the star stays normally at maximum light 
with irregular drops: these drops are likely due to a decrease of mass transfer 
from the normal to the compact member. The magnitude at maximum of V704 And is 
about V=13 in CRTS data.
Also the NSVS reports a variable star very near to LD 317, ID 3621797, with mean 
mag 13.47, rms amplitude variability 0.185 mag.

No further publications relative to the light curve of this star are reported in 
SIMBAD, nor in ADS, after 2006, so surely it deserves a more detailed study. 
Unfortunately now it can be seen only shortly before sunrise, but a campaign for 
intranight variability could be prepared for next autumn.

Also the AAVSO light curve shows this star to be stable at V=13.5 for several 
years, with small variability, followed by a fainter state with larger variations.
The star is therefore recovering from a long phase of low luminosity and will 
likely reach it previous value around V=13 mag.

-- 
prof. Roberto Nesci,  associated to Istituto Nazionale di Astrofisica,
(National Institute of Astrophysics) INAF-IAPS, via Fosso del Cavaliere 100, 
00133 Roma, Italia