Optical precursors to X‐ray binary outbursts

• DOI: 10.1002/asna.201913610
• Publication Date: 2019-04-04T06:34:38Z
• Authors: David M. Russell; Daniel M. Bramich; Fraser Lewis; Aisha AlMannaei; Thabet Al Qaissieh; Ahlam Al Qasim; Aisha Al Yazeedi; Maria Cristina Ba...; Federico Bernardini; Nour Elgalad; Aldrin Gabuya; Jean‐Pierre Lasota; Alejandro Palado; Paul Roche; Hinna Shivkumar; Silviu‐Marian Udr...; Guobao Zhang
• Keywords: High Energy Astrophysical Phenomena (astro-ph.HE); accretion disks; X‐rays: binaries; black hole physics; FOS: Physical sciences; 01 natural sciences; stars: neutron; accretion; 0103 physical sciences; [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph]; [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]; Astrophysics - High Energy Astrophysical Phenomena

Disc instability models predict that for X‐ray binaries in quiescence, there should be a brightening of the optical flux prior to an X‐ray outburst. Tracking the X‐ray variations of X‐ray binaries in quiescence is generally not possible, so optical monitoring provides the best means to measure the mass accretion rate variability between outbursts, and to identify the beginning stages of new outbursts. With our regular Faulkes Telescope/Las Cumbres Observatory (LCO) monitoring we are routinely detecting the optical rise of new X‐ray binary outbursts before they are detected by X‐ray all‐sky monitors. We present examples of detections of an optical rise in X‐ray binaries prior to X‐ray detection. We also present initial optical monitoring of the new black hole transient MAXI J1820+070 (ASASSN‐18ey) with the Faulkes, LCO telescopes, and Al Sadeem Observatory in Abu Dhabi, UAE. Finally, we introduce our new real‐time data analysis pipeline, the “X‐ray Binary New Early Warning System (XB‐NEWS)” which aims to detect and announce new X‐ray binary outbursts within a day of first optical detection. This will allow us to trigger X‐ray and multiwavelength campaigns during the very early stages of outbursts, to constrain the outburst triggering mechanism.