PKS 2155−152
BL Lacertae object located in the constellation Capricornus
From Wikipedia, the free encyclopedia
PKS 2155−152 is an optically violent variable[2] BL Lacertae object located in the southern constellation of Capricornus. It has a redshift of (z) 0.672[1][3] and it was first discovered as an astronomical radio source in 1970 by astronomers whom they designated it as OX −192.[4]
| PKS 2155−152 | |
|---|---|
PKS 2155−152 imaged by DESI Legacy Surveys | |
| Observation data (J2000.0 epoch) | |
| Constellation | Capricornus |
| Right ascension | 21h 58m 06.28s[1] |
| Declination | −15° 01′ 09.32″[1] |
| Redshift | 0.672000[1] |
| Heliocentric radial velocity | 201,461 km/s[1] |
| Distance | 6.358 Gly |
| Apparent magnitude (V) | 18.30 |
| Apparent magnitude (B) | 18.63 |
| Characteristics | |
| Type | Opt.var.; HPQ BLLAC[1] |
| Other designations | |
| 6dF J2158063−150109, 2MASSI J2158062−150109, 2MASS J21580628−1501093, LEDA 2831143, PMN J2158−1501, OX −192, NVSS J215806−150109, VLSS J2158.1−1501, WMAP 018, 1H 2158−150, RX J2158.1−1500[1] | |
Description
PKS 2155−152 is radio-loud quasar with a steep radio spectrum with a bolometric luminosity of 45.67 erg s−1 and a supermassive black hole mass of 7.59 M☉.[5][6] It is classified as a blazar due to its variability on the electromagnetic spectrum, showing a 3.5 magnitude outburst detected towards the end of the 19th century in 1899. Between the years 1933, 1941 and in 1948, the object had several outbursts of around 3 magnitudes.[2] When observed in 1995, it showed a variability timescale of approximately 15.5 days.[5]
The radio structure of PKS 2155−152 is compact. An observation with Very Long Baseline Interferometry (VLBI) conducted in May 1993, found the source has a core-jet morphology, consisting of an unresolved radio core whose brightness temperature is estimated to be more than 6.7 × 1011 Kelvins.[7] When detected with Very Long Baseline Array (VLA) it has a bright core with a jet pointing towards the southern direction.[8] Further investigations suggested the jet may be extending south-west instead which was confirmed by Pushkarev.[9] An X-ray jet counterpart was found in 2011 by Chandra X-ray Observatory with its X-ray emission terminating at 8 arcseconds from the core.[10]
It is confirmed that PKS 2155−152 is highly polarized.[11] Based on results, it has polarization in both its core and inside a second jet component south-west. VLBI observations showed the core polarization was shown varying while the jet component polarization remained constant.[12] A study involving calculating the vector sum of the two polarized components in the object via model fitting and with VLA, found a sharp drastic decrease in flux density suggesting most of the variations occurred inside the core.[9] In January 2025, Yongyun Chen found the host galaxy of PKS 2155−152 has a logarithm star formation of 3.386 and a stellar mass of 11.97.[13]