Quasi-periodic Oscillations in GX 339-4 during the 2021 Outburst Observed with Insight-HXMT
Abstract
A new outburst of GX 339-4 in 2021 was monitored by the Hard X-ray Modulation Telescope (Insight-HXMT). By using the data of Insight-HXMT from 2021 February to March, we make an X-ray timing analysis of this new outburst. Based on the results of the count rates, hardness-intensity diagram, and power density spectrum (PDS), we confirm that the source exhibits spectral transitions from the low-hard state (LHS) to the hard-intermediate state (HIMS). During the transition from the LHS to the HIMS, low-frequency quasi-periodic oscillations (QPOs) are detected in the PDS. We found that these QPOs are all type C QPOs with centroid frequencies evolving from 0.1 to 0.6 Hz in the LHS and in the 1-3 Hz frequency range in HIMS. The QPO features above 50 keV are reported for the first time in this black hole by Insight-HXMT. The QPO rms stays stable with time but decreases with energy at a higher energy above ~10 keV. We also find that the phase lag of the type C QPO is close to zero in the early outburst stage but becomes positive as the outburst evolves, with a hard lag of ~0.6-1.2 rad in 50-100 keV. The implications of the phase lag in high energy bands and the possible physical mechanisms to explain those observations are also discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2023
- DOI:
- 10.3847/1538-4357/ace168
- arXiv:
- arXiv:2306.13994
- Bibcode:
- 2023ApJ...953...33J
- Keywords:
-
- Black hole physics;
- X-ray binary stars;
- Stellar accretion disks;
- 159;
- 1811;
- 1579;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 15 pages, ApJ in press