PHL 293B

PHL 293B star
Observation data; Epoch J1950 Equinox J1950
Constellation	Aquarius
Right ascension	22h 28.1m
Declination	−0° 22′
Characteristics
Evolutionary stage	Luminous blue variable?
Astrometry
Radial velocity (Rv)	(of galaxy) 1,606 km/s
Distance	22,600,000 pc
Details
Radius	1,348–1,463 R☉
Luminosity	2,500,000–3,500,000 L☉
Temperature	6,000–6,800 K
Other designations
	SDSS J2230–0006, SDSS J223036.79-000636.9, A2228-00
Database references
SIMBAD	PHL 293B
	PHL 293 (Simbad mistakenly showing results for PHL 293B)

PHL 293B
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
Declination	−00° 06′ 37″
Redshift	0.0051
Distance	74 Mly (22.6 Mpc)
Apparent magnitude (V)	16.87
Apparent magnitude (B)	17.35
Characteristics
Type	Im?
Other designations
	Kinman's Dwarf, PGC 69018

PHL 293B, also known as Kinman's dwarf, is a low-metallicity blue compact dwarf galaxy about 22.6 Mpc from the Earth in the constellation Aquarius.^[2]

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.^[9] 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.^[2]^[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.^[4] 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.^[10] 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]

References

^ ^a ^b ^c ^d Kehrig, C.; Iglesias-Páramo, J.; Vílchez, J. M.; Gil De Paz, A.; Duarte Puertas, S.; Pérez-Montero, E.; Díaz, A. I.; Gallego, J.; Carrasco, E.; Cardiel, N.; García-Vargas, M. L.; Castillo-Morales, A.; Cedazo, R.; Gómez-Álvarez, P.; Martínez-Delgado, I.; Pascual, S.; Pérez-Calpena, A. (2020). "Mapping the ionized gas of the metal-poor H II galaxy PHL 293B with MEGARA" (PDF). Monthly Notices of the Royal Astronomical Society. 498 (2): 1638–1650. arXiv:2009.11600. doi:10.1093/mnras/staa2299.
^ ^a ^b ^c ^d Kinman, T. D. (1965). "The Nature of the Fainter Haro-Luyten Objects". The Astrophysical Journal. 142: 1241. Bibcode:1965ApJ...142.1241K. doi:10.1086/148392.
^ ^a ^b ^c "PHL 293B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 30 August 2021.
^ ^a ^b ^c French, H. B. (1980). "Galaxies with the spectra of giant H II regions". The Astrophysical Journal. 240: 41. Bibcode:1980ApJ...240...41F. doi:10.1086/158205.
^ Guseva, N. G.; Papaderos, P.; Meyer, H. T.; Izotov, Y. I.; Fricke, K. J. (2009). "An investigation of the luminosity-metallicity relation for a large sample of low-metallicity emission-line galaxies". Astronomy & Astrophysics. 505 (1): 63–72. arXiv:0908.2539. Bibcode:2009A&A...505...63G. doi:10.1051/0004-6361/200912414. S2CID 17490296.
^ ^a ^b ^c ^d Allan, Andrew P.; Groh, Jose H.; Mehner, Andrea; Smith, Nathan; Boian, Ioana; Farrell, Eoin J.; Andrews, Jennifer E. (2020). "The possible disappearance of a massive star in the low-metallicity galaxy PHL 293B". Monthly Notices of the Royal Astronomical Society. 496 (2): 1902. arXiv:2003.02242. Bibcode:2020MNRAS.496.1902A. doi:10.1093/mnras/staa1629. S2CID 220302328.
^ ^a ^b ^c Izotov, Yuri I.; Thuan, Trinh X. (2009). "Luminous Blue Variable Stars in the two Extremely Metal-Deficient Blue Compact Dwarf Galaxies DDO 68 and PHL 293B". The Astrophysical Journal. 690 (2): 1797–1806. arXiv:0809.3077. Bibcode:2009ApJ...690.1797I. doi:10.1088/0004-637X/690/2/1797. S2CID 14150936.
^ ^a ^b Terlevich, Roberto; Terlevich, Elena; Bosch, Guillermo; Díaz, Ángeles; Hägele, Guillermo; Cardaci, Mónica; Firpo, Verónica (2014). "High-velocity blueshifted Fe ii absorption in the dwarf star-forming galaxy PHL 293B: Evidence for a wind driven supershell?". Monthly Notices of the Royal Astronomical Society. 445 (2): 1449–1461. arXiv:1409.1189. Bibcode:2014MNRAS.445.1449T. doi:10.1093/mnras/stu1806. S2CID 118457805.
^ Haro, G.; Luyten, W. J. (1962). "Faint Blue Stars in the Region near the South Galactic Pole". Boletín de los Observatorios de Tonantzintla y Tacubaya. 3: 37. Bibcode:1962BOTT....3...37H.
^ Burke, Colin J.; Baldassare, Vivienne F.; Liu, Xin; Foley, Ryan J.; Shen, Yue; Palmese, Antonella; Guo, Hengxiao; Herner, Kenneth; Abbott, Tim M. C.; Aguena, Michel; Allam, Sahar; Avila, Santiago; Bertin, Emmanuel; Brooks, David; Carnero Rosell, Aurelio; Carrasco Kind, Matias; Carretero, Jorge; Da Costa, Luiz N.; De Vicente, Juan; Desai, Shantanu; Doel, Peter; Eifler, Tim F.; Everett, Spencer; Frieman, Josh; García-Bellido, Juan; Gaztanaga, Enrique; Gruen, Daniel; Gruendl, Robert A.; Gschwend, Julia; et al. (2020). "The Curious Case of PHL 293B: A Long-lived Transient in a Metal-poor Blue Compact Dwarf Galaxy". The Astrophysical Journal. 894 (1): L5. arXiv:2002.12369. Bibcode:2020ApJ...894L...5B. doi:10.3847/2041-8213/ab88de. S2CID 211572824.