Coordinates: Sky map 05h 09m 25.96370s, +05° 41′ 35.3279″

TXS 0506+056

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TXS 0506+056
Observation data (J2000 epoch)
Right ascension05h 09m 25.9645434784s[1]
Declination+05° 41′ 35.333636817″[1]
Redshift0.3365 ± 0.0010
Apparent magnitude (V)14.78
Apparent magnitude (B)14.95
TypeBlazar of BL Lac-type
Other designations
QSO J0509+0541, EGR J0509+0550, 2MASS J05092597+054135, VSOP J0509+0541
References: [2][3]

TXS 0506+056 is a very high energy blazar – a quasar with a relativistic jet pointing directly towards Earth – of BL Lac-type.[3] With a redshift of 0.3365 ± 0.0010,[3] it is about 1.75 gigaparsecs (5.7 billion light-years) from Earth.[4] Its approximate location on the sky is off the left shoulder of the constellation Orion.[5] Discovered as a radio source in 1983, the blazar has since been observed across the entire electromagnetic spectrum.

TXS 0506+056 is the first known source of high energy astrophysical neutrinos,[6] identified following the IceCube-170922A neutrino event[7] in an early example of multi-messenger astronomy.[12] The only astronomical sources previously observed by neutrino detectors were the Sun and supernova 1987A, which were detected decades earlier at much lower neutrino energies.[6]

Observational history[edit]

The object has been detected by numerous astronomical surveys, so has numerous valid source designations. The most commonly used, TXS 0506+056, comes from its inclusion in the Texas Survey of radio sources (standard abbreviation TXS) and its approximate equatorial coordinates in the B1950 equinox used by that survey.[13][14]

Location of TXS 0506+056 as observed in gamma rays (energies greater than 1 GeV) by the Fermi Space Telescope[15]

TXS 0506+056 was first discovered as a radio source in 1983.[16] It was identified as an active galaxy in the 1990s, and a possible blazar in the early 2000s.[17] By 2009 it was regarded as a confirmed blazar and catalogued as a BL Lac object.[18] Gamma rays from TXS 0506+056 were detected by the EGRET and Fermi Space Telescope missions.[17][19][20]

Radio observations using very-long-baseline interferometry have shown apparent superluminal motion in the blazar's jet.[21] TXS 0506+056 is one of the blazars regularly monitored by the OVRO 40 meter Telescope, so has an almost-continuous radio light curve recorded from 2008 onwards.[22]

The gamma-ray flux from TXS 0506+056 is highly variable, by at least a factor of a thousand, but on average it is in the top 4% of brightest gamma-ray sources on the sky.[6][23] It is also very bright in radio waves, in the top 1% of sources.[6] Given its distance, this makes TXS 0506+056 one of the most intrinsically powerful BL Lac objects known, particularly in high-energy gamma rays.[6][23]

Neutrino emission[edit]

On September 22, 2017, the IceCube Neutrino Observatory detected a high energy muon neutrino, dubbed IceCube-170922A.[7] The neutrino carried an energy of ~290 tera–electronvolts (TeV); for comparison, the Large Hadron Collider can generate a maximum energy of 13 TeV.[24] Within one minute of the neutrino detection, IceCube sent an automated alert to astronomers around the world with coordinates to search for a possible source.[7]

A search of this region in the sky, 1.33 degrees across, yielded only one likely source: TXS 0506+056, a previously-known blazar, which was found to be in a flaring state of high gamma ray emission.[7][6] It was subsequently observed at other wavelengths of light across the electromagnetic spectrum, including radio, infrared, optical, X-rays and gamma-rays.[7][25] The detection of both neutrinos and light from the same object was an early example of multi-messenger astronomy.[11]

A search of archived neutrino data from IceCube found evidence for an earlier flare of lower-energy neutrinos in 2014-2015 (a form of precovery), which supports identification of the blazar as a source of neutrinos.[23] An independent analysis found no gamma-ray flare during this earlier period of neutrino emission, but supported its association with the blazar.[6] The neutrinos emitted by TXS 0506+056 are six orders of magnitude higher in energy than those from any previously-identified astrophysical neutrino source.[6]

The observations of high energy neutrinos and gamma-rays from this source imply that it is also a source of cosmic rays, because all three should be produced by the same physical processes,[26] though no cosmic rays from TXS 0506+056 have been directly observed.[11] In the blazar, a charged pion was produced by the interaction of a high-energy proton or nucleus (i.e. a cosmic ray) with the radiation field or with matter.[7] The pion then decayed into a lepton and the neutrino. The neutrino interacts only weakly with matter, so it escaped the blazar.[7] Upon reaching Earth, the neutrino interacted with the Antarctic ice to produce a muon, which was observed by the Cherenkov radiation it generated as it moved through the IceCube detector.[7]

Analysis of 16 very long baseline radio array 15-GHz observations between 2009 and 2018 of TXS 0506+056 revealed the presence of a curved jet or potentially a collision of two jets, which could explain the 2014-2015 neutrino generation at the time of a low gamma-ray flux and indicate that TXS 0506+056 might be an atypical blazar.[27]

In 2020, a study using MASTER global telescope network found that TXS 0506+056 was in an 'off' state in the optical spectrum 1 minute after the alert for IceCube-170922A event and switched back on 2 hours later. This would indicate that the blazar was in a state of neutrino efficiency.[28]

See also[edit]


  1. ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. ^ "TXS 0506+056". SIMBAD. Centre de données astronomiques de Strasbourg.
  3. ^ a b c Paiano, Simona; Falomo, Renato; Treves, Aldo; Scarpa, Riccardo (2018). "The Redshift of the BL Lac Object TXS 0506+056". The Astrophysical Journal. 854 (2): L32. arXiv:1802.01939. Bibcode:2018ApJ...854L..32P. doi:10.3847/2041-8213/aaad5e. S2CID 118950365.
  4. ^ Keivani, A.; Murase, K.; Petropoulou, M.; Fox, D. B.; Cenko, S. B.; Chaty, S.; Coleiro, A.; Delaunay, J. J.; Dimitrakoudis, S.; Evans, P. A.; Kennea, J. A.; Marshall, F. E.; Mastichiadis, A.; Osborne, J. P.; Santander, M.; Tohuvavohu, A.; Turley, C. F. (2018). "A Multimessenger Picture of the Flaring Blazar TXS 0506+056: Implications for High-energy Neutrino Emission and Cosmic-Ray Acceleration". The Astrophysical Journal. 864 (1): 84. arXiv:1807.04537. Bibcode:2018ApJ...864...84K. doi:10.3847/1538-4357/aad59a. S2CID 62828464. given its redshift z = 0.3365 (Paiano et al. 2018) and a consensus cosmology, the luminosity distance of TXS 0506+056 is dL ≈ 1750Mpc.
  5. ^ Cowen, Doug; Keivani, Azadeh; Fox, Derek (12 July 2018). "The IceCube observatory detects neutrino and discovers a blazar as its source". The Conversation. Retrieved 21 July 2018.
  6. ^ a b c d e f g h Padovani, P.; Giommi, P.; Resconi, E.; Glauch, T.; Arsioli, B.; Sahakyan, N.; Huber, M. (2018). "Dissecting the region around IceCube-170922A: the blazar TXS 0506+056 as the first cosmic neutrino source". Monthly Notices of the Royal Astronomical Society. 480 (1): 192. arXiv:1807.04461. Bibcode:2018MNRAS.480..192P. doi:10.1093/mnras/sty1852.
  7. ^ a b c d e f g h Aartsen; et al. (The IceCube Collaboration, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S., INTEGRAL, Kanata, Kiso, Kapteyn, Liverpool Telescope, Subaru, Swift/NuSTAR, VERITAS, VLA/17B-403 teams) (12 July 2018). "Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A". Science. 361 (6398): eaat1378. arXiv:1807.08816. Bibcode:2018Sci...361.1378I. doi:10.1126/science.aat1378. PMID 30002226. S2CID 204803450.
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  16. ^ Lawrence, C. R; Bennett, C. L; Garcia-Barreto, J. A; Greenfield, P. E; Burke, B. F (1983). "5 GHz observations of sources in the Arecibo 611 MHz survey". The Astrophysical Journal Supplement Series. 51: 67. Bibcode:1983ApJS...51...67L. doi:10.1086/190840.
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  18. ^ Massaro, E; Giommi, P; Leto, C; Marchegiani, P; Maselli, A; Perri, M; Piranomonte, S; Sclavi, S (2009). "Roma-BZCAT: A multifrequency catalogue of blazars". Astronomy & Astrophysics. 495 (2): 691. arXiv:0810.2206. Bibcode:2009A&A...495..691M. doi:10.1051/0004-6361:200810161. S2CID 18206181.
  19. ^ Lamb, R. C; MacOmb, D. J (1997). "Point Sources of GeV Gamma Rays". The Astrophysical Journal. 488 (2): 872. Bibcode:1997ApJ...488..872L. CiteSeerX doi:10.1086/304736.
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  26. ^ De Angelis, Alessandro; Pimenta, Mario (2018). Introduction to particle and astroparticle physics (multimessenger astronomy and its particle physics foundations). Springer. doi:10.1007/978-3-319-78181-5. ISBN 978-3-319-78181-5.
  27. ^ Britzen, S.; Fendt, C.; Böttcher, M.; Zajaček, M.; Jaron, F.; Pashchenko, I. N.; Araudo, A.; Karas, V.; Kurtanidze, O. (2 October 2019). "A cosmic collider: Was the IceCube neutrino generated in a precessing jet-jet interaction in TXS 0506+056?". Astronomy & Astrophysics. 630: A103. Bibcode:2019A&A...630A.103B. doi:10.1051/0004-6361/201935422.
  28. ^ Lipunov, V. M.; Kornilov, V. G.; Zhirkov, K.; Gorbovskoy, E.; Budnev, N. M.; Buckley, D. A. H.; Rebolo, R.; Serra-Ricart, M.; Podesta, R.; Tyurina, N .; Gress, O. (2020-06-15). "Optical Observations Reveal Strong Evidence for High-energy Neutrino Progenitor". The Astrophysical Journal. 896 (2): L19. arXiv:2006.04918. Bibcode:2020ApJ...896L..19L. doi:10.3847/2041-8213/ab96ba. ISSN 2041-8213. S2CID 219558330.

External links[edit]