Swift observations of black hole candidate XTE J1752-223 during outburst

TL;DR

This study presents Swift broadband observations of the black hole candidate XTE J1752-223 during its outburst, analyzing spectral states, optical variability, and timing properties to understand its behavior and support its classification as a black hole.

Contribution

First comprehensive broadband analysis of XTE J1752-223 during outburst, revealing spectral state behaviors, optical variability, and jet contributions.

Findings

Confirmed canonical spectral states during outburst

Detected optical variability correlated with X-ray emission

Observed hysteretical behavior suggesting jet contribution

Abstract

Here we summarise the Swift broadband observations of the recently discovered X-ray transient and black hole candidate, XTE J1752-223,obtained over the period of outburst from October 2009 to June 2010. We offer a phenomenological treatment of the spectra as an indication of the canonical spectral state of the source during different periods of the outburst. We find that the high energy hardness-intensity diagrams over two separate bands follows the canonical behavior, confirming the spectral states. From Swift-UVOT data we confirm the presence of an optical counterpart which displays variability correlated, in the soft state, to the X-ray emission observed by Swift-XRT. The optical counterpart also displays hysteretical behaviour between the states not normally observed in the optical bands, suggesting a possible contribution from a synchrotron emitting jet to the optical emission in the rising hard state. Our XRT timing analysis shows that in the hard state there is significant variability below 10Hz which is more pronounced at low energies, while during the soft state the level of variability is consistent with being minimal.These properties of XTE J1752-223 support its candidacy as a black hole in the Galactic centre region.