Astronomy & Astrophysics Seminar: An Algorithm to Search for Dormant Compact Objects in Short-Period Binaries

Zoom: https://us02web.zoom.us/j/84211520648?pwd=dllEbUhBU1VRUDZPL2lWRnhjWEdzZz09

Abstract:

Only a few tens of stellar black holes (BH) in short-period binaries (BHB) are known in the Galaxy. All known BHB were found by their X-ray emission, generated by mass transfer from the optical companion onto the compact object. However, most of the short-period BHB are not known because they do not emit X-rays, either because the optical star does not fill its Roche-lobe or the accretion disc is in a quiescent phase. We suggest an algorithm to detect dormant BHB (and dormant binaries with neutron stars) by identifying optical stars that display large ellipsoidal periodic modulations, induced by tidal interaction with their compact companions. The proposed algorithm can survey very large samples of photometric light curves, and therefore has the potential to enlarge the number of known short-period binaries with compact objects. Finally, we consider 10,956 OGLE short-period variables towards the Galactic Bulge, identified by the OGLE team as ellipsoidals. We re-analyze their modulation and identify 136 main-sequence systems as candidates for having compact-object secondaries, assuming their observed periodic modulations reflect indeed the ellipsoidal effect. Obviously, one needs follow-up observations to find out the true nature of these companions.

Seminar Organizer: Dr. Iair Arcavi