Hyper-Luminous X-ray source 1, commonly known as HLX-1, is an

intermediate-mass black hole An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range 102–105 solar masses: significantly more than stellar black holes but less than the 105–109 solar mass supermassive black holes. Several IMBH candidate obje ...

candidate located in the lenticular galaxy ESO 243-49 about 290 million light-years from Earth. The source was discovered at the Institut de Recherche en Astrophysique et Planétologie (IRAP, formerly the CESR), Toulouse, France and gained interest from the scientific community because of strong evidence supporting it as an intermediate-mass black hole. HLX-1 is possibly the remnant of a dwarf galaxy that may have been in a galactic collision with ESO 243-49.

Discovery

The object was first observed in November 2004, in which it was seen as a source emitting X-rays in the outskirts of the spiral galaxy ESO 243-49 and was catalogued as 2XMM J011028.1-460421, but nicknamed "HLX-1". In 2008, a team of astronomers led by Natalie Webb at the Institut de Recherche en Astrophysique et Planétologie in

Toulouse Toulouse ( , ; oc, Tolosa ) is the prefecture of the French department of Haute-Garonne and of the larger region of Occitania. The city is on the banks of the River Garonne, from the Mediterranean Sea, from the Atlantic Ocean and from Pa ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

, discovered HLX-1 and from the very high X-ray luminosity (~1 x 10⁴² erg s⁻¹, 0.2-10.0 keV), as well as its X-ray characteristics, proposed that it was an intermediate mass black hole candidate. Follow up analysis using further X-ray, optical and radio observations support the intermediate-mass black hole nature. In 2012, further work showed that there was a small cluster of stars amassed around HLX-1, leading Sean Farrell and collaborators to conclude that the black hole was once the galactic center of a dwarf galaxy, which was consumed by ESO 243-49. Farrell remarked, "The fact that there's a very young cluster of stars indicates that the intermediate-mass black hole may have originated as the central black hole in a very low-mass dwarf galaxy. The dwarf galaxy was then swallowed by the more massive galaxy.".

References

{{DEFAULTSORT:HLX-1 Phoenix (constellation) Intermediate-mass black holes