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A magnetar is a type of neutron star believed to have an extremely powerful magnetic field (∼109 to 1011 T, ∼1013 to 1015 G). The magnetic-field decay powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays. A theory regarding these objects was proposed in 1992 by Robert Duncan and Christopher Thompson. The theory was subsequently developed by Bohdan Paczyński and by its proposers. The theory served to explain a burst of gamma rays from the Large Magellanic Cloud that had been detected on March 5, 1979, and other less bright bursts from within our galaxy. During the following decade, the magnetar hypothesis became widely accepted as a likely explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). In 2020, a fast radio burst (FRB) was detected from a magnetar.
Stellar radio sources, radio source stars or radio stars are stellar objects that produce copious emissions of various radio frequencies, whether constant or pulsed. Radio emissions from stars can be produced in many varied ways.
X-ray pulsars or accretion-powered pulsars are a class of astronomical objects that are X-ray sources displaying strict periodic variations in X-ray intensity. The X-ray periods range from as little as a fraction of a second to as much as several minutes.
An astronomical radio source is an object in outer space that emits strong radio waves. Radio emission comes from a wide variety of sources. Such objects are among the most extreme and energetic physical processes in the universe.
A pulsar is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward Earth, and is responsible for the pulsed appearance of emission. Neutron stars are very dense and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays.
PSR J2144−3933 is a pulsar about 0.002 parsec]]s from Earth. It is the coldest known neutron star with a surface temperature less than 42000 Kelvin as measured by the Hubble Space Telescope. It was previously thought to have a period of 2.84 seconds but is now known to have a period of 8.51 seconds, which is among the longest-known radio pulsar.
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.
PSR J0737−3039 is the only known double pulsar. It consists of two neutron stars emitting electromagnetic waves in the radio wavelength in a relativistic binary system. The two pulsars are known as PSR J0737−3039A and PSR J0737−3039B. It was discovered in 2003 at Australia's Parkes Observatory by an international team led by the Italian radio astronomer Marta Burgay during a high-latitude pulsar survey.
Astropulse is a distributed computing project that uses volunteers around the globe to lend their unused computing power to search for primordial black holes, pulsars, and extraterrestrial intelligence (ETI). Volunteer resources are harnessed through Berkeley Open Infrastructure for Network Computing (BOINC) platform. In 1999, the Space Sciences Laboratory launched SETI@home, which would rely on massively parallel computation on desktop computers scattered around the world. SETI@home utilizes recorded data from the Arecibo radio telescope and searches for narrow-bandwidth radio signals from space, signifying the presence of extraterrestrial technology. It was soon recognized that this same data might be scoured for other signals of value to the astronomy and physics community.
A binary pulsar is a pulsar with a binary companion, often a white dwarf or neutron star. Binary pulsars are one of the few objects which allow physicists to test general relativity because of the strong gravitational fields in their vicinities. Although the binary companion to the pulsar is usually difficult or impossible to observe directly, its presence can be deduced from the timing of the pulses from the pulsar itself, which can be measured with extraordinary accuracy by radio telescopes.
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 pulse-to-pulse variability than the bulk of the known pulsars. The working definition of what a RRAT is, is a pulsar which is more easily discoverable in a search for bright single pulses, as opposed to in Fourier domain searches so that 'RRAT' is little more than a label and does not represent a distinct class of objects from pulsars. As of March 2015 over 100 have been reported.
A radio-quiet neutron star is a neutron star that does not seem to emit radio emissions, but is still visible to Earth through electromagnetic radiation at other parts of the spectrum, particularly X-rays and gamma rays.
The Magnificent Seven is the informal name of a group of isolated young cooling neutron stars at a distance of 120 to 500 parsecs from Earth. These objects are also known under the names XDINS or simply XINS.
PSR B1937+21 is a pulsar located in the constellation Vulpecula a few degrees in the sky away from the first discovered pulsar, PSR B1919+21. The name PSR B1937+21 is derived from the word "pulsar" and the declination and right ascension at which it is located, with the "B" indicating that the coordinates are for the 1950.0 epoch. PSR B1937+21 was discovered in 1982 by Don Backer, Shri Kulkarni, Carl Heiles, Michael Davis, and Miller Goss.
Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays.
PSR J1614–2230 is a pulsar in a binary system with a white dwarf. It was discovered in 2006 with the Parkes telescope in a survey of unidentified gamma ray sources in the Energetic Gamma Ray Experiment Telescope catalog. PSR J1614–2230 is a millisecond pulsar, a type of neutron star, that spins on its axis roughly 317 times per second, corresponding to a period of 3.15 milliseconds. Like all pulsars, it emits radiation in a beam, similar to a lighthouse. Emission from PSR J1614–2230 is observed as pulses at the spin period of PSR J1614–2230. The pulsed nature of its emission allows for the arrival of individual pulses to be timed. By measuring the arrival time of pulses, astronomers observed the delay of pulse arrivals from PSR J1614–2230 when it was passing behind its companion from the vantage point of Earth. By measuring this delay, known as the Shapiro delay, astronomers determined the mass of PSR J1614–2230 and its companion. The team performing the observations found that the mass of PSR J1614–2230 is 1.97 ± 0.04 M☉. This mass made PSR J1614–2230 the most massive known neutron star at the time of discovery, and rules out many neutron star equations of state that include exotic matter such as hyperons and kaon condensates.
PALFA is a large-scale survey for radio pulsars at 1.4 GHz using the Arecibo 305-meter telescope and the ALFA multibeam receivers. It is the largest and most sensitive survey of the Galactic plane to date.
PSR J0348+0432 is a pulsar–white dwarf binary system. It was discovered in 2007 with the National Radio Astronomy Observatory's Robert C. Byrd Green Bank Telescope in a drift-scan survey.
In radio astronomy, a fast radio burst (FRB) is a transient radio pulse of length ranging from a fraction of a millisecond to a few milliseconds, caused by some high-energy astrophysical process not yet understood. Astronomers estimate the average FRB releases as much energy in a millisecond as the Sun puts out in 3 days. While extremely energetic at their source, the strength of the signal reaching Earth has been described as 1,000 times less than from a mobile phone on the Moon. The first FRB was discovered by Duncan Lorimer and his student David Narkevic in 2007 when they were looking through archival pulsar survey data, and it is therefore commonly referred to as the Lorimer Burst. Many FRBs have since been recorded, including several that have been detected to repeat in seemingly irregular ways. Nonetheless, one FRB has been detected to repeat in a regular way: particularly, FRB 180916 seems to pulse every 16.35 days. Most FRBs are extragalactic, but the first Milky Way FRB was detected by the CHIME radio telescope in April 2020. In June 2021, astronomers reported over 500 FRBs from outer space detected.
References
- ↑ McLaughlin, M. A.; et al. (2006). "Transient radio bursts from rotating neutron stars". Nature. 439 (7078): 817–820. arXiv: astro-ph/0511587 . Bibcode:2006Natur.439..817M. doi:10.1038/nature04440. PMID 16482150.
- ↑ Hu, H.-D.; Esamdin, A; Yuan, J.-P.; Liu, Z.-Y.; Xu, R.-X.; Li, J.; Tao, G.-C.; Wang, N. (2011). "Strong pulses detected from a rotating radio transient J1819-1458". Astronomy and Astrophysics . 530: A67. arXiv: 1104.3256 . Bibcode:2011A&A...530A..67H. doi:10.1051/0004-6361/201015953.
- ↑ N. Rea; M. A. McLaughlin; B. M. Gaensler; P. O. Slane; L. Stella; S. P. Reynolds; M. Burgay; G. L. Israel; A. Possenti; S. Chatterjee (2009). "DISCOVERY OF EXTENDED X-RAY EMISSION AROUND THE HIGHLY MAGNETIC RRAT J1819-1458". The Astrophysical Journal Letters . 703 (1): L41–L45. arXiv: 0906.1394 . Bibcode:2009ApJ...703L..41R. doi:10.1088/0004-637X/703/1/L41.
- ↑ N. Rea; G. Lo Curto; V. Testa; G. L. Israel; A. Possenti; M. McLaughlin; F. Camilo; B. M. Gaensler; M. Burgay (2010). "Near-infrared observations of rotating radio transients". Monthly Notices of the Royal Astronomical Society . 407 (3): 1887–1894. arXiv: 1003.2085 . Bibcode:2010MNRAS.407.1887R. doi:10.1111/j.1365-2966.2010.17032.x.
- ↑ Gaensler, B. M.; et al. (2007). "Chandra smells a RRAT: X-ray Detection of a Rotating Radio Transient". Astrophysics and Space Science. 308 (1–4): 95–99. arXiv: astro-ph/0608311 . Bibcode:2007Ap&SS.308...95G. doi:10.1007/s10509-007-9352-8.
- ↑ Lyne, A. G.; McLaughlin, M. A.; Keane, E. F.; Kramer, M.; et al. (2006). "Unusual glitch activity in the RRAT J1819-1458: an exhausted magnetar?". Monthly Notices of the Royal Astronomical Society . 400 (3): 1439–1444. arXiv: 0909.1165 . Bibcode:2009MNRAS.400.1439L. doi:10.1111/j.1365-2966.2009.15668.x.