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

## TL;DR

This study investigates the properties of the X-ray pulsar Swift J1816.7--1613 and its optical companion, estimating magnetic field strength, distance, and companion type through multi-wavelength observations during its transition from outburst to quiescence.

## Contribution

The paper provides new estimates of the neutron star's magnetic field and the system's distance, and identifies the IR companion type using combined X-ray and IR data.

## Key findings

- Magnetic field estimated between 10^{11} and 10^{12} G.
- IR companion identified as B0-2e star.
- Distance to the system estimated at 7-13 kpc.

## 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 \textit{Swift}, \textit{NuSTAR} and \textit{Chandra} alongside with the latest IR data from UKIDSS/GPS and \textit{Spitzer}/GLIMPSE surveys. The aim of the work is to determine parameters of the system: 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 $\times 10^{11}$ to a few $\times 10^{12}$ G. We also estimated type of the IR-companion as a B0-2e star located at distance of 7--13~kpc.