Discovery and Monitoring of a new Black Hole Candidate XTE J1752-223 with RXTE: RMS spectrum evolution, BH mass and the source distance

TL;DR

This study reports the discovery and detailed monitoring of a new black hole candidate XTE J1752-223, analyzing its spectral and variability evolution to estimate its mass and distance, and exploring accretion physics during state transitions.

Contribution

It provides the first comprehensive spectral-timing analysis of XTE J1752-223, including mass and distance estimates using a novel scaling technique during state transitions.

Findings

Black hole mass estimated between 8 and 11 solar masses.

Distance to the source approximately 3.5 kiloparsecs.

Strong correlation between variability and spectral hardness.

Abstract

We report on the discovery and monitoring observations of a new galactic black hole candidate XTE J1752-223 by Rossi X-ray Timing Explorer (RXTE). The new source appeared on the X-ray sky on October 21 2009 and was active for almost 8 months. Phenomenologically, the source exhibited the low-hard/high-soft spectral state bi-modality and the variability evolution during the state transition that matches standard behavior expected from a stellar mass black hole binary. We model the energy spectrum throughout the outburst using a generic Comptonization model assuming that part of the input soft radiation in the form of a black body spectrum gets reprocessed in the Comptonizing medium. We follow the evolution of fractional root-mean-square (RMS) variability in the RXTE/PCA energy band with the source spectral state and conclude that broad band variability is strongly correlated with the source hardness (or Comptonized fraction). We follow changes in the energy distribution of rms variability during the low-hard state and the state transition and find further evidence that variable emission is strongly concentrated in the power-law spectral component. We discuss the implication of our results to the Comptonization regimes during different spectral states. Correlations of spectral and variability properties provide measurements of the BH mass and distance to the source. The spectral-timing correlation scaling technique applied to the RXTE observation during the hard-to-soft state transition indicates a mass of the BH in XTE J1752-223 between 8 and 11 solar masses and a distance to the source about 3.5 kiloparsec.