Discovery of spin-up in the X-ray pulsar companion of the hot subdwarf HD 49798

The hot subdwarf HD 49798 has an X-ray emitting compact companion with a spin-period of 13.2 s and a dynamically measured mass of 1.28+/-0.05 M_sun, consistent with either a neutron star or a white dwarf. Using all the available XMM-Newton and Swift observations of this source, we could perform a ph...

Full description

Saved in:
Bibliographic Details
Published in:arXiv.org 2016-03
Main Authors: Mereghetti, Sandro, Pintore, Fabio, Esposito, Paolo, Nicola La Palombara, Tiengo, Andrea, Israel, Gian Luca, Stella, Luigi
Format: Article
Language:English
Subjects:
Accretion disks
Astronomical models
Neutron stars
Neutrons
Pulsars
Stellar winds
Subdwarf stars
White dwarf stars
XMM (spacecraft)
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The hot subdwarf HD 49798 has an X-ray emitting compact companion with a spin-period of 13.2 s and a dynamically measured mass of 1.28+/-0.05 M_sun, consistent with either a neutron star or a white dwarf. Using all the available XMM-Newton and Swift observations of this source, we could perform a phase-connected timing analysis extending back to the ROSAT data obtained in 1992. We found that the pulsar is spinning up at a rate of (2.15+/-0.05)x10^{-15} s/s. This result is best interpreted in terms of a neutron star accreting from the wind of its subdwarf companion, although the remarkably steady period derivative over more than 20 years is unusual in wind-accreting neutron stars. The possibility that the compact object is a massive white dwarf accreting through a disk cannot be excluded, but it requires a larger distance and/or properties of the stellar wind of HD 49798 different from those derived from the modelling of its optical/UV spectra.
ISSN:2331-8422
DOI:10.48550/arxiv.1603.01505