The red giant star SU Lyn is listed in Simbad as a semi-regular pulsating variable. It has recently been identified in a paper by Mukai et al.
http://arxiv.org/abs/1604.08483v1 as a new symbiotic star. They say “The X-ray spectrum, the optical to UV spectrum, and the rapid UV variability of SU Lyn are all consistent with our interpretation that it is a symbiotic star containing an accreting white dwarf.” It is powered by accretion onto the white dwarf rather than shell-burning resulting in weak optical emission lines and the previous failure to identify it as a symbiotic variable. They suggest that the weak emission line signature of accretion-powered symbiotic variables may mean there are many more similar to SU Lyn yet to be discovered.
I recorded the following flux calibrated spectrum of SU Lyn on 2nd May and concurrently measured its V magnitude as 8.62 and B-V colour index as 1.97. With no correction for reddening the spectral type is close to M6III, consistent with M5.8III assigned in the paper. It has a weak H-alpha emission line and just detectable H-beta and H-gamma emission.
David
- _sulyn_20160502_872_D.Boyd_flux.png (40.28 KiB) Viewed 3531 times