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.
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]
^ abcdKehrig, 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.
^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. S2CID17490296.
^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. S2CID211572824.
