15-20 March 2020
Garching
Europe/Berlin timezone

Low level accretion activity in X-ray binaries

19 Mar 2020, 17:45
15m
Garching

Garching

Speaker

David Russell (New York University Abu Dhabi)

Description

Low-mass X-ray binaries can lay dormant, remaining undetected for decades, until they are usually detected by X-ray monitoring satellites when they undergo bright outbursts. However, during these periods of quiescence between outbursts, low level accretion does occur but usually cannot be studied at X-ray energies due to their extremely low fluxes. We have been monitoring ~40-50 X-ray binaries with the Faulkes Telescopes / Las Cumbres Observatory (LCO) global robotic network for more than a decade. We find evidence for low level, variable accretion activity, long-term trends and jets being launched at 10^-6 - 10^-8 times the Eddington luminosity in some systems. Different activity states exist in quiescence. The X-ray spectra of quiescent X-ray binaries are described by a power law; different sources have slightly different spectra. eROSITA on SRG will achieve high S/N soft X-ray spectra of Galactic quiescent low-mass X-ray binaries. We wish to test if accretion activity (identified by our optical monitoring) correlates with the X-ray properties uncovered by eROSITA. I will also introduce our new real-time optical monitoring 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. We are now detecting the early stages of these outbursts with our optical telescopes, before they become bright enough for X-ray detection. This allows us to trigger X-ray and multi-wavelength campaigns during the very early stages of outbursts, to constrain the outburst triggering mechanism.

Primary author

David Russell (New York University Abu Dhabi)

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