Be X-ray binaries
Encyclopedia
Be X-ray binaries are a class of high-mass X-ray binaries that consist of a Be star
and a neutron star
. The neutron star is usually in a wide highly elliptical orbit around the Be star. The Be stellar wind
forms a disk confined to a plane often different from the orbital plane of the neutron star. When the neutron star passes through the Be disk, it accretes plenty of gas in a short time. As the gas falls onto the neutron star, a bright flare in hard X-ray
s is seen.
is a periodic, radio-emitting binary system that is also the gamma-ray source, CG135+01. Using the ROSAT
and VLA
observatories, an X-ray outburst with an ~10 d duration was detected. LSI+61°303 is a variable radio source characterized by periodic, non-thermal radio outbursts with a period of 26.496 d. The 26.5 d period has been attributed to the eccentric orbital motion of a compact object, probably a neutron star, around a rapidly rotating B0 Ve star, with a Teff ~26,000 K and luminosity of 1031 watt
s (1038 erg s-1). Photometric observations at optical and infrared wavelengths also show a 26.5 d modulation.
Of the 20 or so members of the Be X-ray binary systems, as of 1996, only X Per and LSI+61°303 have X-ray outbursts of much higher luminosity and harder spectrum (kT
≈ 10–20 keV) vs. (kT ≤ 1 keV); however, LSI+61°303 further distinguishes itself by its strong, outbursting radio emission. "The radio properties of LSI+61°303 are similar to those of the "standard" high-mass X-ray binaries such as SS 433
, Cyg X-3
and Cir X-1
."
Be star
A Be star is a B-type star with prominent emission lines of hydrogen in its spectrum. The designation is combined by the spectral class, B, and the lowercase e denoting emission in the spectral classification system. Line emission from other atomic ions might be present as well, but is typically...
and a neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
. The neutron star is usually in a wide highly elliptical orbit around the Be star. The Be stellar wind
Stellar wind
A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.Different types of stars have...
forms a disk confined to a plane often different from the orbital plane of the neutron star. When the neutron star passes through the Be disk, it accretes plenty of gas in a short time. As the gas falls onto the neutron star, a bright flare in hard X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s is seen.
LSI+61°303
LSI+61°303LS I +61 303
LS I +61 303 is a binary system harboring a compact object and a massive star that emits HE and VHE gamma rays. It is only one of three known star systems that produce such energetic rays...
is a periodic, radio-emitting binary system that is also the gamma-ray source, CG135+01. Using the ROSAT
ROSAT
ROSAT was a German Aerospace Center-led satellite X-ray telescope, with instruments built by Germany, the UK and the US...
and VLA
VLA
VLA may refer to:Transport* RUM-139 VL-ASROC, a vertically-launched anti-submarine rocket* Very Light Aircraft, a category of aircraft, per the European EASA CS-VLA specificationsGovernment Agencies...
observatories, an X-ray outburst with an ~10 d duration was detected. LSI+61°303 is a variable radio source characterized by periodic, non-thermal radio outbursts with a period of 26.496 d. The 26.5 d period has been attributed to the eccentric orbital motion of a compact object, probably a neutron star, around a rapidly rotating B0 Ve star, with a Teff ~26,000 K and luminosity of 1031 watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
s (1038 erg s-1). Photometric observations at optical and infrared wavelengths also show a 26.5 d modulation.
Of the 20 or so members of the Be X-ray binary systems, as of 1996, only X Per and LSI+61°303 have X-ray outbursts of much higher luminosity and harder spectrum (kT
KT (energy)
kT is the product of the Boltzmann constant, k, and the temperature, T. This product is used in physics as a scaling factor for energy values in molecular-scale systems , as the rates and frequencies of many processes and phenomena depend not on their energy alone, but on the ratio of that energy...
≈ 10–20 keV) vs. (kT ≤ 1 keV); however, LSI+61°303 further distinguishes itself by its strong, outbursting radio emission. "The radio properties of LSI+61°303 are similar to those of the "standard" high-mass X-ray binaries such as SS 433
SS 433
SS 433 is one of the most exotic star systems observed. It is an eclipsing X-ray binary system, with the primary most likely a black hole, or possibly a neutron star., pp. 23–24. The spectrum of the secondary companion star suggests that it is a late A-type star...
, Cyg X-3
Cygnus x-3
Cygnus X-3 is one of the stronger binary X-ray sources in the sky.Classified as a microquasar, it is believed to be a compact object in a binary system which is pulling in a stream of gas from an ordinary star companion....
and Cir X-1
Circinus X-1
Circinus X-1 is an X-ray binary star system that includes a neutron star. Observation of Circinus X-1 in July 2007 revealed the presence of X-ray jets normally found in black hole systems; it is the first of the sort to be discovered that displays this similarity to black holes.-Location:On June...
."