Properties of the transient X-ray pulsar Swift J1816.7–1613 and its optical companion

¹ Department of Physics and Astronomy, University of Turku, 20014, Finland
e-mail: armin.nabizadeh@utu.fi
² Space Research Institute, Russian Academy of Sciences, Profsoyuznaya str. 84/32, Moscow 117997, Russia
³ Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden
⁴ Sobolev Astronomical Institute, Saint Petersburg State University, Staryj Peterhof, Saint Petersburg 198504, Russia

Received: 13 November 2018
Accepted: 8 January 2019

Abstract

We present results of investigation of the poorly studied X-ray pulsar Swift J1816.7–1613 during its transition from the type I outburst to the quiescent state. Our studies are based on the data obtained from X-ray observatories Swift, NuSTAR, and Chandra alongside with the latest IR data from UKIDSS/GPS and Spitzer/GLIMPSE surveys. The aim of the work is to determine the parameters of the system, namely the strength of the neutron star magnetic field and the distance to the source, which are required for the interpretation of the source behaviour in the framework of physically motivated models. No cyclotron absorption line was detected in the broad-band energy spectrum. However, the timing analysis hints at the typical for the X-ray pulsars magnetic field from a few ×10¹¹ to a few ×10¹² G. We also estimated the type of the IR-companion as a B0-2e star located at a distance of 7–13 kpc.