Timing and Spectral Study of IGR J19294+1816 with RXTE: Discovery of Cyclotron Feature

TL;DR

This study analyzes RXTE observations of IGR J19294+1816 during two outbursts, discovering a cyclotron resonance feature at 35.5 keV indicating a strong magnetic field, along with spectral and timing evolution.

Contribution

First detection of a cyclotron resonance scattering feature in IGR J19294+1816, revealing its magnetic field strength and spectral behavior during outbursts.

Findings

Detection of a 35.5 keV cyclotron feature indicating B = 4.13×10^12 Gauss

Fe line emission at 6.4 keV during high flux periods

X-ray pulsations observed in 9 out of 10 observations

Abstract

Rossi X-ray Timing Explorer (RXTE)/Proportional Counter Array (PCA) observations of IGR J19294+1816 covering two outburst episodes are reported. The first outburst happened during MJD 54921-54925 (2009 C.E.) and the second one happened during MJD 55499-55507 (2010 C.E.). In both the cases the PCA observations were made during the decay phase of the outburst, with the source exhibiting temporal and spectral evolution with the change in flux. At the bright flux level an absorption feature at 35.5 keV is detected in the spectra which may be attributed to Cyclotron Resonance Scattering Feature corresponding to a magnetic field of B = 4.13*10^12 Gauss. This is also detected at a lower significance in two other observations. In addition an Fe line emission at 6.4 keV is prominently detected during the highest flux. X-ray pulsations are detected in 9 out of 10 observations; no pulsations were found in the observation with the lowest flux level. During this observation with the lowest flux the pulsation phenomenon becomes detectable only at the soft X-ray bands.