GCRT J1745−3009
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GCRT J1745−3009 is a Galactic Center radio transient (GCRT), or bursting low-frequency radio source which lies in the direction of the
Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...
.A Faint, Steep Spectrum Burst from the Radio Transient GCRT J1745-3009, Scott D. Hyman, Subhashis Roy, Sabyasachi Pal, T. Joseph W. Lazio, Paul S. Ray, Namir E. Kassim, and Sanjay Bhatnagar
arXiv:astro-ph/0701098


Discovery

A group of astronomers from
Sweet Briar College Sweet Briar College is a Private college, private Women's colleges in the United States, women's liberal arts college in Sweet Briar, Amherst County, Virginia, Amherst County, Virginia. It was established in 1901 by Indiana Fletcher Williams in ...
and the
Naval Research Laboratory The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. Located in Washington, DC, it was founded in 1923 and conducts basic scientific research, appl ...
detected transient emission from two sources in 1998 while studying the
Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...
. They then began monitoring the region specifically looking for transient sources and detected five bursts of
radio waves Radio waves (formerly called Hertzian waves) are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies below 300 gigahertz (GHz) and wavelengths ...
about 1 meter in wavelength (frequency 330 MHz) during a seven-hour period from September 30 to October 1, 2002. The five bursts were of equal brightness, with each lasting about 10 minutes, and occurring every 77 minutes.Text at ''Nature''.
/ref> Like an earlier low-frequency transient discovered by the same group, it was given the designation ''GCRT'', an abbreviation for ''Galactic Center Radio Transient''. The source was also nicknamed a ''burper''.
/ref> The group found no X-ray or γ-ray counterpart to the object. Another burst from the source was later found in data recorded September 28, 2003, and a weaker burst was found in data recorded March 20, 2004. As of January 2007, no other bursts have been found.


Structure

The discoverers argue that if the source is further than 70
parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...
s away, its high
brightness temperature Brightness temperature or radiance temperature is a measure of the intensity of electromagnetic energy coming from a source. In particular, it is the temperature at which a black body would have to be in order to duplicate the observed intensity ...
would require it to be powered by a
coherent Coherence is, in general, a state or situation in which all the parts or ideas fit together well so that they form a united whole. More specifically, coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics ...
emission process. (If within 70 parsecs, the source could be either coherent or incoherent.) They also claim that most known coherent emission processes are unlikely explanations for the source. Models proposed by others include a nulling pulsar, a pair of orbiting neutron stars, a radio-emitting white dwarf, and a pulsar precessing with a period of 77 minutes.GCRT J1745-3009: a precessing radio pulsar?, W. W. Zhu and R. X. Xu, ''
Monthly Notices of the Royal Astronomical Society ''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal in astronomy, astrophysics and related fields. It publishes original research in two formats: papers (of any length) and letters (limited to ...
'' 365, #1 (pp. L16–L20)
Paper at ADSABS
also
arXiv:astro-ph/0504251


See also

*
GLEAM-X J162759.5−523504.3 GLEAM-X J162759.5-523504.3 is a transient astronomical radio source, found in 2020, in archival data recorded in 2018 by the Murchison Widefield Array. The source was active in radio for about 1 minute every 18 minutes, from January to Ma ...
*
Rotating radio transients Rotating radio transients (RRATs) are sources of short, moderately bright, radio pulses, which were first discovered in 2006. RRATs are thought to be pulsars, i.e. rotating magnetised neutron stars which emit more sporadically and/or with higher pu ...


References


External links


BBC Radio interview with Scott Hyman
(MPEG)


Mysterious Radio Bursts
{{DEFAULTSORT:GCRT J1745-3009 Pulsars Scorpius