GCRT J1745-3009

From Wikipedia, the free encyclopedia

GCRT J1745-3009
Observation data
Epoch J2000.0
Constellation
(pronunciation)		 Scorpius
Right ascension 17h 45m 5.1s
Declination -30° 09′ 56″
Data sources:
[1]

GCRT J1745-3009 is a newly-discovered transient, bursting low-frequency radio source which lies in the direction of the galactic center.

Contents

[edit] Discovery

An image of the new source located below a large expanding ring of debris from a supernova remnant. The plot below is a radio light curve of the five detected bursts occurring every 77 minutes.
An image of the new source located below a large expanding ring of debris from a supernova remnant. The plot below is a radio light curve of the five detected bursts occurring every 77 minutes.
A radio image of the central region of the Milky Way galaxy. The arrow indicates the same supernova remnant seen in the previous image.
A radio image of the central region of the Milky Way galaxy. The arrow indicates the same supernova remnant seen in the previous image.

A group of astronomers from Sweet Briar College and the Naval Research Laboratory detected transient emission from two sources in 1998 while studying the Galactic Center. They then began monitoring the region specifically looking for transient sources and detected five bursts of radio waves 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.[2] Like an earlier low-frequency transient discovered by the same group[3], it was given the designation GCRT, an abbreviation for Galactic Center Radio Transient. The source was also nicknamed a burper.[4] The group found no X-ray or γ-ray counterpart to the object.[2]

Another burst from the source was later found in data recorded September 28, 2003[5], and a weaker burst was found in data recorded March 20, 2004.[1] As of January 2007, no other bursts have been found.

[edit] Structure

The discoverers argue that if the source is further than 70 parsecs away, its high brightness temperature would require it to be powered by a coherent 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.[2] Models proposed by others include a nulling pulsar[4], a pair of orbiting neutron stars[6], a radio-emitting white dwarf[7], and a pulsar precessing with a period of 77 minutes.[8]

[edit] References

  1. ^ a b 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.
  2. ^ a b c Scott D. Hyman, T. Joseph W. Lazio, Namir E. Kassim, Paul S. Ray, Craig B. Markwardt and Farhad Yusef-Zadeh (2005). "A powerful bursting radio source towards the Galactic Centre". Nature 434 (7029): 50–52. doi:10.1038/nature03400. PMID 15744294.  Text at Nature.
  3. ^ Low-Frequency Radio Transients in the Galactic Center, Scott D. Hyman, T. Joseph W. Lazio, Namier E. Kassim, and Ashlee L. Bartleson, Astronomical Journal 123, #3 (March 2002), pp. 1497–1501. Paper at ADSABS
  4. ^ a b S. R. Kulkarni and E. Sterl Phinney (2005). "Astronomy: blasts from the radio heavens". Nature 434 (7029): 28–29. doi:10.1038/434028a. PMID 15744281.  Text at Nature.
  5. ^ A New Radio Detection of the Transient Bursting Source GCRT J1745-3009, Scott D. Hyman, T. Joseph W. Lazio, Subhashis Roy, Paul S. Ray, Namir E. Kassim, and Jennifer L. Neureuther, Astrophysical Journal 639, #1 (March 2006), pp. 348–353. Paper at ADSABS; also arXiv:astro-ph/0508264.
  6. ^ Is the Bursting Radio Source GCRT J1745-3009 a Double Neutron Star Binary?, R. Turolla, A. Possenti and A. Treves, Astrophysical Journal 628, #1 (July 2005), pp. L49–L52. Paper at ADSABS; also, arXiv:astro-ph/0506199.
  7. ^ GCRT J1745-3009 as a Transient White Dwarf Pulsar, Bing Zhang and Janusz Gil, Astrophysical Journal 631, #2 (October 2005), pp. L143–L146. Paper at ADSABS; also, arXiv:astro-ph/0508213.
  8. ^ GCRT J1745-3009: a precessing radio pulsar?, W. W. Zhu and R. X. Xu, Monthly Notices of the Royal Astronomical Society 365, #1 (pp. L16–L20). Paper at ADSABS; also, arXiv:astro-ph/0504251.

[edit] External links