Multiwavelength spectral and high time resolution observations of SWIFT J1753.5-0127: new activity?

TL;DR

This study presents multiwavelength observations of SWIFT J1753.5-0127 during a period of renewed activity, revealing spectral and timing features indicative of complex accretion processes.

Contribution

It provides a comprehensive multi-band observational analysis of SWIFT J1753.5-0127, highlighting new activity signatures and timing phenomena.

Findings

Optical and X-ray spectra show increased activity and a blue continuum.

Detection of quasi-periodic oscillations at 0.08 Hz in optical data.

Power spectra indicate flickering behavior up to 0.1 Hz.

Abstract

We have conducted an extensive observational campaign of SWIFT J1753.5-0127 during June 2007 after its bright outburst episode in 2005. We have performed multi-band optical photometry, optical spectroscopy, X-ray spectroscopy and timing and ULTRACAM optical photometry simultaneously in three bands. Both the optical spectrum and the X-ray spectrum, along with enhanced brightness in broad-band photometry point to recent increased activity. We analyze the different spectral regions, finding a smooth optical continuum with a remarkable lack of lines and a very blue component modulated with a period of 3.2hr and a hard power-law X-ray spectrum. Both the X-ray and optical power spectra are flat at low frequencies up to the 0.1 Hz (10 s) range, then decreasing roughly as a power law consistent with flickering. Furthermore, the optical data show quasi-periodic oscillations (QPOs) near 0.08 Hz (13 s). Together with a dynamical and auto-correlation analysis of the light curves we attempt to construct a complete physical picture of this intriguing system.