A Unique X-ray Binary with a Hot Subdwarf Companion Reveals New Insights on Compact Object Accretion

Paper Title:

New X-ray observations of the hot subdwarf binary HD49798 / RXJ0648.0-4418

Published on:

8 April 2021

Primary Category:

Solar and Stellar Astrophysics

Paper Authors:

S. Mereghetti,

F. Pintore,

T. Rauch,

N. La Palombara,

P. Esposito,

S. Geier,

I. Pelisoli,

M. Rigoselli,

V. Schaffenroth,

A. Tiengo

Bullets

Key Details

•

HD 49798/RX J0648.0-4418 contains a white dwarf spinning at 13.2 s orbiting a hot subdwarf star

•

The white dwarf spin period is steadily decreasing at a constant rate for 30 years

•

Hard X-ray emission shows ~70% variability, indicating clumping in the subdwarf's stellar wind

•

A white dwarf atmosphere model fits the soft X-ray component better and predicts more optical emission

•

Future searches for optical pulsations are warranted based on the atmosphere model prediction

Explore the topics in this paper

accretion

spin period

subdwarf stars

white dwarfs

x-ray binaries

AI generated summary

A Unique X-ray Binary with a Hot Subdwarf Companion Reveals New Insights on Compact Object Accretion

This paper reports on new X-ray observations of the peculiar binary HD 49798/RX J0648.0-4418, the only known X-ray binary with a hot subdwarf companion. The observations confirm the compact object is a rapidly spinning white dwarf and show its spin period is steadily decreasing over time. Variability in the hard X-ray emission suggests the subdwarf's stellar wind has time-dependent inhomogeneities. Fits with a white dwarf atmosphere model imply the thermal X-rays likely originate from most of the surface. The model also predicts much more optical emission than a blackbody fit, so future searches for optical pulsations are promising.