NuSTAR detection of a broad absorption line in IGR J06074+2205

TL;DR

This study uses NuSTAR data to analyze the X-ray pulsar IGR J06074+2205, revealing a cyclotron line, pulse profile evolution, and spin-down behavior, contributing new insights into its magnetic field and accretion regime.

Contribution

First broadband X-ray analysis of IGR J06074+2205 detecting a cyclotron line and detailed pulse profile evolution, providing new information on its magnetic field and accretion state.

Findings

Detection of a ~55 keV cyclotron line indicating a magnetic field of ~4.74×10^12 G.

Observation of dual-peaked pulse profiles with energy-dependent amplitude changes.

The source is spinning down at 0.0202(2) s per day and likely in a sub-critical accretion regime.

Abstract

We present the broadband X-ray study of the BeXRB pulsar IGR J06074+2205 using NuSTAR observations. The temporal and spectral characteristics of the source are investigated. We detect coherent X-ray pulsations of the source and determine the spin period evolution. Using the current spin period data of the source, we show that the source is spinning down at 0.0202(2)\; s\; $day^{-1}$. The pulse profiles are found to evolve with energy and luminosity. Another interesting feature of the source is that the pulse profiles are dual peaked. The dual-peaked pulse profile is characterized by a decreasing secondary peak amplitude with increasing energy. We also observed a proportionate increase in the primary peak amplitude as the energy increases. The pulse fraction exhibits an overall increasing trend with the energy. The X-ray continuum of the source indicates the existence of a characteristic absorption feature with a centroid energy $\sim 55$ keV, which may be interpreted as a cyclotron line. We estimate the corresponding magnetic field strength to be $\sim4.74\times10^{12}$ G. A peculiar `10 keV' absorption feature is observed in the X-ray spectra of the second observation.The luminosity measurements predict that the source may be accreting in the sub-critical regime.