ASASSN-15lh
SLSNe (Type Ic), SNSLSN-I | |
Right ascension | 22h 2m 15.45s[2] |
---|---|
Declination | −61° 39′ 34.64″[2] |
Distance | 1,171 megaparsecs 3.82 gigalight-years |
Redshift | 0.2326 |
Host | APMUKS(BJ) B215839.70−615403.9[3] |
Peak apparent magnitude | 16.9 |
Other designations | SN 2015L |
ASASSN-15lh (
The nature of ASASSN-15lh is disputed. The most popular explanations are that it is the
Discovery
A possible supernova was first noticed during an observation in June 2015 by ASAS-SN's twin 14-cm telescopes in Chile; the team gave it the designation ASASSN-15lh.
Later, other images were found to have been made of ASASSN-15lh as early as May 8, 2015. At this stage the
Properties
Based on its redshift and location projected on the nucleus of a large galaxy, the distance of ASASSN-15lh is calculated at 1,171 Mpc, in a large luminous galaxy.[3]
At its peak, the
The spectrum of ASASSN-15lh was relatively featureless, with no hydrogen or helium lines, but two very broad absorption bands. Ionised magnesium absorption doublets were detected and used to confirm the redshift at 0.2326.[3]
The temperature of ASASSN-15lh at the time of maximum luminosity was 20,000 K, although it was hotter earlier in the outburst. By 50 days after the peak, the temperature had declined to 11,000 K and then remained relatively constant. The radius of ASASSN-15lh at peak brightness was over 70,000 R☉.[3]
Host galaxy
The host galaxy for ASASSN-15lh is APMUKS(BJ) B215839.70−615403.9, much larger and more luminous than the Milky Way. The host galaxy has visual magnitude 18.5 and is red in color with a low rate of star formation. It maintained a steady brightness until the supernova lit up. The strongest parts of the galaxy's spectrum have wavelengths around 1 μm in the near infrared.[3]
Suggested mechanisms
The precise mechanism underlying the very large ASASSN-15lh explosion is still unknown, with speculation ranging from the presence of very large quantities of decaying nickel-56 to the amplifying effects of a magnetar. Its unusual location in a relatively quiescent galaxy may offer clues for scientists to discover and observe similar events.[12]
Superluminous supernova
The initial hypothesis was that ASASSN-15lh was the most extreme superluminous supernova (SLSN) so far seen, but it was recognized as being unusual in several respects. The spectrum did not closely match other type I SLSNe and previous SLSNe have been discovered in relatively small active star-producing galaxies, not in the central regions of large galaxies.[12] The double-peaked light curve is not expected from a SLSN and the total energy output approaches theoretical limits.[3]
The lack of hydrogen and helium features in the spectrum suggest an explosion originating in an object lacking both hydrogen and helium, which would imply a highly stripped star such as a massive Wolf–Rayet star. The energetics of the explosion would require a massive star.
Magnetar
One model for unusually luminous supernovae involves the conversion of rotational energy from a rapidly-spinning neutron star into polar jets that heat surrounding material. Again, the energy produced by ASASSN-15lh strains the theoretical limits of this type of explosion and the detailed properties are difficult to reproduce with a magnetar model.[3]
Quark nova
One unusual explanation for ASASSN-15lh is a quark-nova within the supernova explosion from a WO-type Wolf-Rayet star. The quark nova is produced by the neutron star remnant of the supernova and occurs a few days after the core collapse of the Wolf-Rayet star. This can reproduce many of the unusual features of the observed event but is somewhat speculative and not widely accepted.[13]
Tidal disruption event (TDE)
One known method for producing extremely large amounts of energy is the tidal disruption of objects such as stars by a supermassive black hole. ASASSN-15lh occurred in the nucleus of a large passive galaxy where a supermassive black hole is likely. A black hole of the mass expected in the host galaxy of ASASSN-15lh would normally swallow stars without a visible flare. The conditions for the production of a highly luminous flare from a TDE around a black hole of the expected mass are unusual, but a rapidly-spinning
Gravitational lensing
Unexpectedly bright visible objects can be produced by
References
- ^ S2CID 119253925.
- ^ a b Young, Monica (July 12, 2015). "The Most Luminous Supernova". Sky & Telescope. Retrieved January 16, 2016.
- ^ S2CID 31444274.
- ^ a b Jessica Orwig (January 14, 2016). "Astronomers are baffled by a newly discovered cosmic explosion that shines 570 billion times brighter than the sun". Business Insider. Retrieved March 22, 2016.
- ^ a b c Billings, Lee (January 14, 2016). "Found: The Most Powerful Supernova Ever Seen". Scientific American. Retrieved January 16, 2016.
- Bibcode:2015CBET.4120....1D.
- ^ Young, Monica (January 15, 2016). "Brightest Supernova Baffles Astronomers". Sky & Telescope. Retrieved January 16, 2016.
- ^ Carnegie Institution for Science (January 14, 2016). "Most-luminous supernova ever discovered". phys.org. Retrieved January 15, 2016.
- S2CID 182077393.
- ^ Bhanoo, Sindya N. (January 15, 2016). "Supernova Has Energy of Hundreds of Billions of Suns". The New York Times. Retrieved January 16, 2016.
- ^ Boyle, Rebecca (January 14, 2016). "We've found the brightest ever supernova but can't explain it". New Scientist. Retrieved January 15, 2016.
- ^ a b Thomson, Jason (January 14, 2016). "Astronomers spot brightest supernova in history". The Christian Science Monitor. Retrieved January 15, 2016.
- arXiv:1611.03657 [astro-ph.HE].
- S2CID 73645264.
Further reading
- Gilkis, Avishai; Soker, Noam; Papish, Oded (November 4, 2015). "Explaining the most luminous supernovae with an inefficient jet-feedback mechanism". The Astrophysical Journal. 826 (2): 178. S2CID 119159928.
External links
- Brightest supernova ever seen pushes theoretical models to the edge Astronomy
- 'Brightest Supernova Ever' Was Actually Monster Black Hole's Violent Star Slashing Space.com
- Kerr Black Hole Eating Sun-like Star Explains Superluminous Explosion ASASSN-15lh Breaking Science News | Sci-News.com
- Superluminous Supernova Is The Brightest Ever Seen Forbes