The orbital period of Swift J1816.7-1613 revealed by the Swift-BAT telescope

TL;DR

This paper identifies the orbital period of Swift J1816.7-1613 as approximately 118.5 days through timing analysis of Swift-BAT data, suggesting it is a Be X-ray binary with characteristic outbursts.

Contribution

The study reveals the orbital period and spectral properties of Swift J1816.7-1613, providing evidence for its classification as a Be binary system based on timing and spectral analysis.

Findings

Orbital period of 118.5 days determined.

Behavior consistent with Be binary systems.

Spectral analysis shows a flat photon index and high absorption.

Abstract

We have analyzed the Swift data relevant to the high mass X-ray binary Swift J1816.7-1613. The timing analysis of the BAT survey data unveiled a modulation at a period of P_0=118.5+/-0.8 days that we interpret as the orbital period of the X-ray binary system. The modulation is due to a sequence of bright flares, lasting ~30 d, separated by long quiescence intervals. This behavior is suggestive of a Be binary system, where periodic or quasi-periodic outbursts are the consequence of an enhancement of the accretion flow from the companion star at the periastron passage. The position of Swift J1816.7-1613 on the Corbet diagram strengthens this hypothesis. The broad band 0.2-150 keV spectrum is well modeled with a strongly absorbed power-law with a flat photon index Gamma~ 0.2 and a cut-off at ~ 10 keV.