First simultaneous multi-wavelength observations of the black hole candidate IGR J17091-3624: ATCA, INTEGRAL, Swift, and RXTE views of the 2011 outburst

TL;DR

This study reports the first simultaneous multi-wavelength observations of the black hole candidate IGR J17091-3624 during its 2011 outburst, revealing state transitions, jet behaviour, and distance estimates.

Contribution

It provides the first correlated radio, X-ray, and gamma-ray observations of IGR J17091-3624, demonstrating jet evolution and state transition effects in a black hole candidate.

Findings

Radio emission detected in all observations, with spectral changes indicating jet evolution.

Source transitioned from hard to soft intermediate state, with associated jet quenching.

Distance estimated between 11 and 17 kpc based on spectral transition luminosity.

Abstract

We present the results of the first four (quasi-)simultaneous radio (ATCA), X-ray (Swift, RXTE), and Gamma-ray (INTEGRAL) observations of the black hole candidate IGR J17091-3624, performed in February and March 2011. The X-ray analysis shows that the source was in the hard state, and then it transited to a soft intermediate state. We study the correlated radio/X-ray behaviour of this source for the first time. The radio counterpart to IGR J17091-3624 was detected during all four observations with the ATCA. In the hard state, the radio spectrum is typical of optically thick synchrotron emission from a self-absorbed compact jet. In the soft intermediate state, the detection of optically thin synchrotron emission is probably due to a discrete ejection event associated with the state transition. The position of IGR J17091-3624 in the radio versus X-ray luminosity diagram (aka fundamental plane) is compatible with that of the other black hole sources for distances greater than 11 kpc. IGR J17091-3624 also appears as a new member of the few sources that show a strong quenching of radio emission after the state transition. Using the estimated luminosity at the spectral transition from the hard state, and for a typical mass of 10 M_sun, we estimate a distance to the source between ~11 and ~17 kpc, compatible with the radio behaviour of the source.