* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Stars -> AR Scorpii
Post Info TOPIC: AR Scorpii
Blobrana


L

Posts: 131433
Date:
RE: AR Scorpii
Permalink  
 

Title: AR Scorpii is a new white dwarf in the ejector state
Author: N.G. Beskrovnaya, N.R. Ikhsanov

Marsh et al. (2016) have recently reported the discovery of a radio-pulsing white dwarf in the cataclysmic variable AR Sco. The period of pulsations which are also seen in the optical and UV is about 117 seconds. High intensity of pulsing radiation and non-thermal character of its spectrum leave little room for doubt that the white dwarf in AR Sco operates as a spin-powered pulsar and, therefore, is in the ejector state. We show that this system is very much resembling a well-known object AE Aqr. In both systems the compact components are spin-powered and have relatively strong surface magnetic field of order of 100-500 MG. They originated due to accretion spin-up in the previous epoch during which the magnetic field of the white dwarf had substantially evolved being initially buried by the accreted matter and recovered to its initial value after the spin-up phase had ended.

Read more (17kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: AR Sco: A White Dwarf Synchronar
Author: J. I. Katz

The emission of the white dwarf-M dwarf binary AR Sco is driven by the rapid synchronization of its white dwarf, rather than by accretion. This requires a comparatively large magnetic field ~100 gauss at the M dwarf and ~10^8 gauss on the white dwarf, larger than the fields of most intermediate polars but within the range of fields of known magnetic white dwarfs. The spindown power is dissipated in the atmosphere of the M dwarf by magnetic reconnection, accelerating particles that produce the observed synchrotron radiation. The displacement of the optical maximum from conjunction may be explained either by dissipation in a bow wave as the white dwarf's magnetic field sweeps past the M dwarf or by a misaligned white dwarf's rotation axis and oblique magnetic moment. In the latter case the rotation axis precesses with a period of decades, predicting a drift in the orbital phase of maximum. Binaries whose emission is powered by synchronization may be termed synchronars, in analogy to magnetars.

Read more (55kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: A Model of White Dwarf Pulsar AR Scorpii.
Author: Jin-Jun Geng, Bing Zhang, Yong-Feng Huang

A 3.56-hour white dwarf (WD) - M dwarf (MD) close binary system, AR Scorpii, was recently reported to show pulsating emission in radio, IR, optical, and UV, with a 1.97-minute period, which suggests the existence of a WD with a rotation period of 1.95 minutes. We propose a model to explain the temporal and spectral characteristics of the system. The WD is a nearly perpendicular rotator, with both open field line beams sweeping the MD stellar wind periodically. A bow shock propagating into the stellar wind accelerates electrons in the wind. Synchrotron radiation of these shocked electrons can naturally account for the broad-band (from radio to X-rays) spectral energy distribution of the system.

Read more (67kb, PDF)



__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Stars -> AR Scorpii


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard