Swift Observations of the High-mass X-ray Binary IGR J16283-4838 unveil a 288-day Orbital Period

TL;DR

This study identifies a 288-day orbital period in the high-mass X-ray binary IGR J16283-4838 using Swift BAT data, revealing periodic outbursts and spectral characteristics indicative of a Be star system.

Contribution

First detection of a long-term orbital period and detailed spectral analysis of IGR J16283-4838, suggesting its classification as a Be high-mass X-ray binary.

Findings

Detected a 287.6-day orbital period with >4σ significance.

Observed sharp peaks and a 300-day outburst consistent with Be X-ray binary behavior.

Broadband spectrum fits an absorbed power-law with spectral steepening.

Abstract

We report on the temporal and spectral properties of the HMXB IGR J16283-4838 in the hard X-ray band. We searched the first 88 months of Swift BAT survey data for long-term periodic modulations. We also investigated the broad band (0.2--150 keV) spectral properties of IGR J16283--4838 complementing the BAT dataset with the soft X-ray data from the available Swift-XRT pointed observations. The BAT light curve of IGR J16283-4838 revealed a periodic modulation at P_o=287.6+7-1.7 days (with a significance higher than 4 standard deviations). The profile of the light curve folded at P_o shows a sharp peak lasting ~ 12 d, over a flat plateau. The long-term light curve shows also a ~300 d interval of prolonged enhanced emission. The observed phenomenology is suggestive of a Be nature of IGR J16283-4838, where the narrow periodic peaks and the ~300 d outburst can be interpreted as Type I and Type II outbursts, respectively. The broad band 0.2-150 keV spectrum can be described with an absorbed power-law and a steepening in the BAT energy range.