PKS 2052−474
Blazar in the constellation of Indus
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PKS 2052−474 is a blazar[1] located in the southern constellation of Indus. The redshift of the object is (z) 1.491[2] and was discovered as a radio source during observations conducted at Parkes Observatory located in New South Wales, in September 1964.[3] It was later identified as a galaxy by Keith Tritton,[4] with its radio spectrum described as flat, thus making it a flat-spectrum radio quasar.[5][6]
| PKS 2052−474 | |
|---|---|
| Observation data (J2000.0 epoch) | |
| Constellation | Indus |
| Right ascension | 20h 56m 16.35s |
| Declination | −47° 14′ 47.62″ |
| Redshift | 1.491500 |
| Heliocentric radial velocity | 447,140 km/s |
| Distance | 9.335 Gly |
| Apparent magnitude (V) | 19.1 |
| Apparent magnitude (B) | 18.29 |
| Characteristics | |
| Type | FSRQ; LPQ blazar |
| Other designations | |
| PKS 2052−47, 2MASS J20561636−4714475, PMN J2056−4714, SUMSS J205616−471448, LEDA 2830665, Cul 2052−474, WMAP 208, G4Jy 1665, RX J2056.2−4714 | |
Description
PKS 2052−474 is very variable on the electromagnetic spectrum. It is noted for its increasing gamma-ray activity as indicated on 9 August 2009, where it reach a high state with a gamma-ray flux measurement of 8.7 ± 1.6 × 10−7 photons cm−2 s−1, detected by Fermi Gamma-ray space Telescope, which was more than a factor of 4.[1] It also underwent two minor flares between June and July 2009, with its flux increasing upwards to 15.6 magnitude in R-bands by 21 July, followed by an outburst in August.[7][8] On 2 March 2020, it was found in an elevated gamma-ray emission state with its flux measured as 1.2 ± −0.2 × 10−6 photons cm−2 s−1 making this the highest daily flux detected in this source.[9] Data from a light curve, have showed PKS 2052−474 has two flaring periods, occurring in February and June 2009, but absence of significant emission line variability.[10][11][12]
The source of PKS 2052−474 is compact. Very Long Baseline Interferometry imaging at 8.4 GHz, have shown the object has a prominent radio core measuring 0.38 Jansky and a jet component located at a distance of 0.7 milliarcseconds with a position angle of -66°.[13][14] At 4.8 GHz, imaging showed the source has the same core with the weakest feature interpreted as a secondary component appearing 8 milliarcseconds to the east, likely interpreted as an imaging artifact.[14] A two-sided jet is seen emerging from the core region on arcsecond scales while first-epoch imaging results showed there is a weak jet towards west direction.[15][16]
PKS 2052−474 has been used as a Molonglo calibrator. When observed by the Molonglo Observatory Synthesis Telescope, the source is found to have a steep radio spectrum at a low frequency. However, it then flattens when reaching high frequencies prompting astronomers to classify it as variable on a time scale amongst 17 other sources. This is suggested by scintillation in interstellar medium rather caused by intrinsic effects on the source.[17] A lower limit has also been calculated for the object with a brightness temperature of 2 × 1011 K, based on an upper limit of the source's angular size.[11] There is evidence PKS 2052−474 has quasi-periodic periodicity of 637 days, making it a candidate quasar with a binary supermassive black hole.[18][19] An accretion disk temperature of 1.23 (± 0.33) × 104 K and disk luminosity of 1.29 (± 1.68) × 1046 erg s−1 has been calculated for PKS 2052−474.[20]