The Evolution of the Orbital Lightcurve of Hercules X-1 with 35 Day Phase
Abstract
Hercules X-1/HZ Hercules (Her X-1/HZ Her) is an X-ray binary monitored by multiple X-ray missions since the last century. With the abundance of long-term observations, we present a complete set of orbital lightcurves of Her X-1/HZ Her during the six states of the 35 day cycle in multiple energy bands. These illustrate in detail the changing lightcurve caused by the rotating twisted-tilted accretion disk surrounding the neutron star. The orbital lightcurves during the main high state are analyzed in 0.05 35 day phase intervals. These show the regular occurrence of pre-eclipse dips that march to earlier orbital phases as the 35 day phases increase. From the multiband lightcurves, we derive the time-average orbital phase dependence of column density for photoelectric absorption and energy-independent transmission as a function of 35 day phase. The X-ray lightcurves during low states are similar in shape to the optical low-state lightcurve, but X-ray leads optical by ≃0.04-0.08 in orbital phase.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2022
- DOI:
- 10.3847/1538-4357/ac496f
- arXiv:
- arXiv:2201.04074
- Bibcode:
- 2022ApJ...927..143W
- Keywords:
-
- X-ray binary stars;
- Light curves;
- Accretion;
- Neutron stars;
- 1811;
- 918;
- 14;
- 1108;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 19 pages, 6 figures