PHL 293B
Galaxy in the constellation Aquarius
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PHL 293B, also known as Kinman's dwarf, is a low-metallicity blue compact dwarf galaxy about 23.15 megaparsecs (75.51 million light-years) from the Earth in the constellation Aquarius.[9]
| PHL 293B | |
|---|---|
 Hubble Space Telescope image of PHL 293B; the purported luminous blue variable is located near the core of the galaxy | |
| Observation data (J2000 epoch) | |
| Constellation | Aquarius |
| Right ascension | 22h 30m 36.8s[1] |
| Declination | −00° 06′ 37″[1] |
| Redshift | 0.0051[1] |
| Heliocentric radial velocity | 1,606 km/s[2] |
| Galactocentric velocity | 1,723±10 km/s[3] |
| Distance | 75.51 ± 8.072 Mly (23.150 ± 2.475 Mpc)[3] |
| Apparent magnitude (V) | 16.87[4] |
| Apparent magnitude (B) | 17.35[4] |
| Characteristics | |
| Type | compact Im?[1][3] HII[3] |
| Size | 5,450 ly × 4,960 ly (1.67 kpc × 1.52 kpc) (diameter; 25.0 B-mag arcsec−2)[3][a] |
| Apparent size (V) | 0.24′ × 0.20′[3] |
| Other designations | |
| Kinman's Dwarf, PGC 69018[4] | |
| Observation data Epoch J1950 Equinox J1950 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 28.1m [5] |
| Declination | −0° 22′[5] |
| Characteristics | |
| Evolutionary stage | Luminous blue variable? |
| Astrometry | |
| Radial velocity (Rv) | (of galaxy) 1,606[2] km/s |
| Distance | 23,150,000±2,475,000[3] pc |
| Details | |
| Radius | 1,348–1,463[6] R☉ |
| Luminosity | 2,500,000–3,500,000[6] L☉ |
| Temperature | 6,000–6,800[6] K |
| Other designations | |
| SDSS J2230–0006,[7] SDSS J223036.79-000636.9, A2228-00[8] | |
| Database references | |
| SIMBAD | PHL 293B |
| PHL 293 (Simbad mistakenly showing results for PHL 293B) | |
It had a very likely associated, notable, blue-light, long-lived star with constant outbursts or a large supernova observed to have faded and which then disappeared. Although this bright visible jet-producing object responsible for broad hydrogen emission lines with P Cygni profiles was widely considered to be a luminous blue variable ejecting matter, other studies posited the mentioned, competing, explanations for the bright light source within.
Observation history
PHL 293 was first listed as entry 293 in a catalogue of faint blue stars published by Guillermo Haro and Willem Jacob Luyten in 1962.[10] In 1965, Thomas Kinman observed two faint possible companions to it, about 1′ away, which he dubbed A and B. HL 293B, sometimes called Kinman's Dwarf, was noted to be an extragalactic, nonstellar object, with a jet, approximately 22.6 Mpc away from Earth.[9][8] The acronym PHL has since been applied to distinguish it from other HL catalogues; it is most commonly referred to by astronomers as PHL 293B.[5] The galaxy was identified as a blue compact dwarf, a type of small irregular galaxy undergoing a strong burst of star formation.[7]
The spectrum of PHL 293B is unusual both for its low metallicity and for broad hydrogen emission lines with P Cygni profiles. These are interpreted as being from a large luminous blue variable star in the galaxy. The star is believed to have been undergoing an outburst during previous observations,[7] an interpretation is disputed by some publications.[citation needed] An alternative explanation would be a long-lived type IIn supernova, similar to the transient event of SDSS1133.[11] These emission features in the spectrum of the galaxy faded during 2019 and by the end of the year had disappeared (at least visibly), likely due to the disappearance of a bright star of the galaxy.[6]
See also
Notes
- The quick-look major axis physical diameter given by NED were based on a distance estimate of 23.150 ± 2.475 Mpc (75.51×106 ± 8.072×106 ly) using a scale of 112.2 parsec/arcsec multiplied with given angular diameters.