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.
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.
Most detected neutron stars are pulsars, and emit radio-frequency electromagnetic radiation. About 700 radio pulsars are listed in the Princeton catalog, and all but one emit radio waves at the 400 MHz and 1400 MHz frequencies. [1] That exception is Geminga, which is radio quiet at frequencies above 100 MHz, [2] but is a strong emitter of X-rays and gamma rays. [1]
In all, ten bodies have been proposed as rotation-powered neutron stars that are not visible as radio sources, but are visible as X-ray and gamma ray sources. [1] Indicators that they are indeed neutron stars include them having a high X-ray to lower frequencies emission ratio, a constant X-ray emission profile, and coincidence with a gamma ray source. [1]
Quark stars, hypothetical neutron star-like objects composed of quark matter, have been proposed to be radio-quiet.[ citation needed ]
More plausibly, however, radio-quiet neutron stars may simply be pulsars which do not pulse in our direction. As pulsars spin, it is hypothesized that they emit radiation from their magnetic poles. When the magnetic poles do not lie on the axis of rotation, and cross the line of sight of the observer, one can detect radio emission emitted near the star's magnetic poles. Due to the star's rotation this radiation appears to pulse, colloquially called the "lighthouse effect". Radio-quiet neutron stars may be neutron stars whose magnetic poles do not point towards the Earth during their rotation. [1]
The group of radio-quiet neutrons stars informally known as the Magnificent Seven are thought to emit mainly thermal radiation. [3]
Possibly some powerful neutron star radio emissions are caused by a positron-electron jet emanating from the star blasting through outer material such as a cloud or accretion material. [4] Note some radio quiet neutron stars listed in this article do not have accretion material.
Magnetars, the most widely accepted explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs), are often characterized as being radio-quiet. [5] However, magnetars can produce radio emissions, but the radio spectrums tend to be flat, with only intermittent broad pulses of variable length. [6]
Can be classified as XDINS (X-ray Dim Isolated Neutron Stars), [7] [8] [9] XTINS (X-ray Thermal Isolated Neutron Stars), XINS (X-ray Isolated Neutron Stars), [7] TEINS (Thermally Emitting Neutron Star), [7] INS (Isolated Neutron Stars). [10] [lower-alpha 1]
Defined as thermally emitting neutron stars of high magnetic fields, although lower than that of magnetars. [7] Identified in thermal X-rays, and thought to be radio-quiet. [11]
Compact Central Objects in Supernova remnants (CCOs in SNRs) are identified as being radio-quiet compact X-ray sources surrounded by supernova remnants. [1] [9] They have thermal emission spectra, [12] and lower magnetic fields than XDINSs and magnetars. [7]
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses (M☉), possibly more if the star was especially metal-rich. Except for black holes, neutron stars are the smallest and densest known class of stellar objects. Neutron stars have a radius on the order of 10 kilometers (6 mi) and a mass of about 1.4 M☉. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei.
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus. The common name comes from a drawing that somewhat resembled a crab with arms produced by William Parsons, 3rd Earl of Rosse, in 1842 or 1843 using a 36-inch (91 cm) telescope. The nebula was discovered by English astronomer John Bevis in 1731. It corresponds with a bright supernova recorded by Chinese astronomers in 1054 as a guest star. The nebula was the first astronomical object identified that corresponds with a historically-observed supernova explosion.
A magnetar is a type of neutron star with 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 soft gamma repeater (SGR) is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them.
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.
A pulsar wind nebula, sometimes called a plerion, is a type of nebula sometimes found inside the shell of a supernova remnant (SNR), powered by winds generated by a central pulsar. These nebulae were proposed as a class in 1976 as enhancements at radio wavelengths inside supernova remnants. They have since been found to be infrared, optical, millimetre, X-ray and gamma ray sources.
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.
Geminga is a gamma ray and x-ray pulsar source thought to be a neutron star approximately 250 parsecs from the Sun in the constellation Gemini.
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.
IC 443 is a galactic supernova remnant (SNR) in the constellation Gemini. On the plane of the sky, it is located near the star Eta Geminorum. Its distance is roughly 5,000 light years from Earth.
Gamma-ray burst progenitors are the types of celestial objects that can emit gamma-ray bursts (GRBs). GRBs show an extraordinary degree of diversity. They can last anywhere from a fraction of a second to many minutes. Bursts could have a single profile or oscillate wildly up and down in intensity, and their spectra are highly variable unlike other objects in space. The near complete lack of observational constraint led to a profusion of theories, including evaporating black holes, magnetic flares on white dwarfs, accretion of matter onto neutron stars, antimatter accretion, supernovae, hypernovae, and rapid extraction of rotational energy from supermassive black holes, among others.
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.
RRAT J1819-1458 is a Milky Way neutron star and the best studied of the class of rotating radio transients (RRATs) first discovered in 2006.
PSR J1614–2230 is a pulsar in a binary system with a white dwarf in the constellation Scorpius. 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.
Imaging X-ray Polarimetry Explorer, commonly known as IXPE or SMEX-14, is a space observatory with three identical telescopes designed to measure the polarization of cosmic X-rays of black holes, neutron stars, and pulsars. The observatory, which was launched on 9 December 2021, is an international collaboration between NASA and the Italian Space Agency (ASI). It is part of NASA's Explorers program, which designs low-cost spacecraft to study heliophysics and astrophysics.
A central compact object (CCO) is an x-ray source found near the center of a young, nearby supernova remnant (SNR). Given the observed x-ray flux and spectra observed from these objects, the almost certain conclusion is that CCOs are the remnant neutron stars which resulted from the recent supernova. Unlike most pulsars, CCOs generally lack pulsed radio emission or variation in the observed x-rays due to such phenomena being either nonexistent or difficult to detect. The weaker magnetic fields than most other detected neutron stars means that most of the detected x-rays are due to blackbody radiation. Confirmation that the CCO is associated with the past supernova can be done using the kinematics of the objects and matching them to the age and kinematics of the host SNR.
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