V Sge - VLT monitoring campaign

Thu, 06/01/2023 - 09:12

The remarkable long-term variable V Sge is now being observed by VLT (under poor conditions due to its brightness) so as to obtain wide wavelength (optical-NIR) spectra of the star over a period of several weeks.  The aim is to follow the spectroscopic evolution that occurs between high (V~10) and low (V~13) states, when it changes from a faint hard X-ray source to a bright supersoft X-ray source.  It also eclipses on its 12.3 hr orbital period.

V Sge is regularly monitored already, but it would be particularly valuable to obtain more extensive, higher time-resolution (10s of secs to a few minutes) light curves in the V-band.  We expect substantial evolution of the orbital light curve between its high and low states, and having these around the time of our spectra would be potentially very useful.  Note that we cannot predict when the spectra will be taken as they are mostly done at times of poorer conditions at ESO when bright targets can be observed.

ESO began our program on May 28, so light-curves capable of being combined for full orbital cycles over the next 2 months would be ideal.