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A luminous red nova (abbr. LRN, pl. luminous red novae, pl.abbr. LRNe) is a stellar explosion thought to be caused by the merging of two stars. They are characterised by a distinct red colour, and a light curve that fades slowly with resurgent brightness in the infrared. Luminous red novae are not related to standard novae, which are explosions that occur on the surface of white dwarf stars.

Discovery

A small number of objects exhibiting the characteristics of luminous red novae have been observed over the last 30 years or so. The red star M31 RV in the Andromeda Galaxy flared brightly during 1988 and may have been a luminous red nova. In 1994, V4332 Sagittarii, a star in the Milky Way galaxy, flared similarly, and in 2002, V838 Monocerotis followed suit and was studied quite closely.

The first confirmed luminous red nova was the object M85 OT2006-1, in the galaxy Messier 85. It was first observed during the Lick Observatory Supernova Search, and subsequently investigated by a team of astronomers from both U.C. Berkeley and Caltech. They confirmed its difference from known explosions such as novae and thermal pulses, and announced luminous red novae as a new class of stellar explosion.[1]

V1309 Scorpii is a luminous red nova that followed the merger of a contact binary in 2008.[2] In January 2015, a luminous red nova was observed in the Andromeda Galaxy.[3] On February 10, 2015, a luminous red nova, known as M101 OT2015-1 was discovered in the Pinwheel Galaxy.[4][5]
Characteristics

The luminosity of the explosion occurring in luminous red novae is between that of a supernova (which is brighter) and a nova (dimmer). The visible light lasts for weeks or months, and is distinctively red in colour, becoming dimmer and redder over time. As the visible light dims, the infrared light grows and also lasts for an extended period of time, usually dimming and brightening a number of times.

Infrared observations of M85 OT2006-1 have shown that temperature of this star is slightly less than 1000 K, a rather low temperature. It is not clear if this characteristic is shared by other luminous red novae.
Evolution

The team investigating M85 OT2006-1 believe it to have formed when two main sequence stars merged. (See the article on V838 Mon for further information on mergebursts and alternative possibilities.)

At the time the mergeburst occurs, the LRN appears to expand extremely rapidly, reaching thousands to tens of thousands of solar radii in only a few months. This would cause the object to cool, explaining the intriguing co-existence of a bright flash with a cool post-flash object.
Other viewpoints

Some astronomers believe it to be premature to declare a new class of stellar explosions based on such a limited number of observations. For instance, they may be due to a type II-p supernova;[6] alternatively, supernovae undergoing a high level of extinction will naturally be both red and of low luminosity.[7]
Prediction

In 2017 KIC 9832227, a binary star system, was predicted to merge and produce a red nova by early 2022.[8][9] In September 2018, a typo was discovered in data used for the initial prediction, and it was determined that the merger would likely not take place at the predicted time.[10]
See also

Binary star
Cataclysmic variable star
Dwarf nova
Hypernova
Nova
Supernova

References

Kulkarni, S. R.; Ofek, E. O.; Rau, A.; Cenko, S. B.; Soderberg, A. M.; Fox, D. B.; Gal-Yam, A.; Capak, P. L.; Moon, D. S.; Li, W.; Filippenko, A. V.; Egami, E.; Kartaltepe, J.; Sanders, D. B. (2007). "An unusually brilliant transient in the galaxy M85". Nature. 447 (7143): 458–460.arXiv:0705.3668. Bibcode:2007Natur.447..458K. doi:10.1038/nature05822. PMID 17522679. S2CID 4300285.
Tylenda, R.; Hajduk, M.; Kamiński, T.; Udalski, A.; Soszyński, I.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Poleski, R.; Wyrzykowski, Ł.; Ulaczyk, K. (2011). "V1309 Scorpii: Merger of a contact binary". Astronomy and Astrophysics. 528: 114.arXiv:1012.0163. Bibcode:2011A&A...528A.114T. doi:10.1051/0004-6361/201016221. S2CID 119234303.
"M31N 2015-01a - A Luminous Red Nova". The Astronomer's Telegram. Retrieved 2015-03-18.
"PSN J14021678+5426205 in M 101". The Astronomer's Telegram.
"List of supernovae sorted by name for 2015". Bright Supernova.
Pastorello, A.; Della Valle, M.; Smartt, S. J.; Zampieri, L.; Benetti, S.; Cappellaro, E.; Mazzali, P. A.; Patat, F.; Spiro, S.; Turatto, M.; Valenti, S. (2007). "A very faint core-collapse supernova in M85". Nature. 449 (7164): E1–E2.arXiv:0710.3753. Bibcode:2007Natur.449E...1P. doi:10.1038/nature06282. PMID 17943088. S2CID 4310528.
Thompson, Todd A.; Prieto, José L.; Stanek, K. Z.; Kistler, Matthew D.; Beacom, John F.; Kochanek, Christopher S. (2009). "A New Class of Luminous Transients and a First Census of their Massive Stellar Progenitors". The Astrophysical Journal. 705 (2): 1364–1384.arXiv:0809.0510. Bibcode:2009ApJ...705.1364T. doi:10.1088/0004-637X/705/2/1364. S2CID 17581579.
Molnar, Lawrence A. (2017), "KIC 9832227: a red nova precursor", American Astronomical Society Meeting Abstracts #229, American Astronomical Society, 229: 417.04, Bibcode:2017AAS...22941704M
Wenz, John. "Two stars will merge in 2022 and explode into red fury". Astronomy Magazine. Retrieved 9 January 2017.

Kucinski, Matt. "Team Of Researchers Challenge Bold Astronomical Prediction". Calvin College. Retrieved 5 November 2018.

External links

Caltech Press Release "Caltech and Berkeley Astronomers Identify a New Class of Cosmic Explosions"
Smithsonian/NASA ADS Astronomy Abstract Service "Spitzer Observations of the New Luminous Red Nova M85 OT2006-1"
Cosmos Online "Stars merge in new cosmic explosion"

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Stars
Formation

Accretion Molecular cloud Bok globule Young stellar object
Protostar Pre-main-sequence Herbig Ae/Be T Tauri FU Orionis Herbig–Haro object Hayashi track Henyey track

Evolution

Main sequence Red-giant branch Horizontal branch
Red clump Asymptotic giant branch
super-AGB Blue loop Protoplanetary nebula Planetary nebula PG1159 Dredge-up OH/IR Instability strip Luminous blue variable Blue straggler Stellar population Supernova Superluminous supernova / Hypernova

Spectral classification

Early Late Main sequence
O B A F G K M Brown dwarf WR OB Subdwarf
O B Subgiant Giant
Blue Red Yellow Bright giant Supergiant
Blue Red Yellow Hypergiant
Yellow Carbon
S CN CH White dwarf Chemically peculiar
Am Ap/Bp HgMn Helium-weak Barium Extreme helium Lambda Boötis Lead Technetium Be
Shell B[e]

Remnants

White dwarf
Helium planet Black dwarf Neutron
Radio-quiet Pulsar
Binary X-ray Magnetar Stellar black hole X-ray binary
Burster

Hypothetical

Blue dwarf Green Black dwarf Exotic
Boson Electroweak Strange Preon Planck Dark Dark-energy Quark Q Black Gravastar Frozen Quasi-star Thorne–Żytkow object Iron Blitzar

Stellar nucleosynthesis

Deuterium burning Lithium burning Proton–proton chain CNO cycle Helium flash Triple-alpha process Alpha process Carbon burning Neon burning Oxygen burning Silicon burning S-process R-process Fusor Nova
Symbiotic Remnant Luminous red nova

Structure

Core Convection zone
Microturbulence Oscillations Radiation zone Atmosphere
Photosphere Starspot Chromosphere Stellar corona Stellar wind
Bubble Bipolar outflow Accretion disk Asteroseismology
Helioseismology Eddington luminosity Kelvin–Helmholtz mechanism

Properties

Designation Dynamics Effective temperature Luminosity Kinematics Magnetic field Absolute magnitude Mass Metallicity Rotation Starlight Variable Photometric system Color index Hertzsprung–Russell diagram Color–color diagram

Star systems

Binary
Contact Common envelope Eclipsing Symbiotic Multiple Cluster
Open Globular Super Planetary system

Earth-centric
observations

Sun
Solar System Sunlight Pole star Circumpolar Constellation Asterism Magnitude
Apparent Extinction Photographic Radial velocity Proper motion Parallax Photometric-standard

Lists

Proper names
Arabic Chinese Extremes Most massive Highest temperature Lowest temperature Largest volume Smallest volume Brightest
Historical Most luminous Nearest
Nearest bright With exoplanets Brown dwarfs White dwarfs Milky Way novae Supernovae
Candidates Remnants Planetary nebulae Timeline of stellar astronomy

Related articles

Substellar object
Brown dwarf Sub-brown dwarf Planet Galactic year Galaxy Guest Gravity Intergalactic Planet-hosting stars Tidal disruption event

vte

Variable stars
Pulsating
Cepheids and
cepheid-like

Type I (Classical cepheids, Delta Scuti) Type II (BL Herculis, W Virginis, RV Tauri) RR Lyrae Rapidly oscillating Ap SX Phoenicis

Blue-white with
early spectra

Alpha Cygni Beta Cephei Slowly pulsating B-type PV Telescopii Blue large-amplitude pulsator

Long-period

Mira Semiregular Slow irregular

Other

Gamma Doradus Solar-like oscillations White dwarf

Eruptive
Protostar and PMS

Herbig Ae/Be Orion
FU Orionis T Tauri

Giants and
supergiants

Luminous blue variable R Coronae Borealis (DY Persei) Yellow hypergiant

Eruptive binary

Double periodic FS Canis Majoris RS Canum Venaticorum

Other

Flare Gamma Cassiopeiae Lambda Eridani Wolf–Rayet

Cataclysmic

AM Canum Venaticorum Dwarf nova Luminous red nova Nova Polar Intermediate polar Supernova
Hypernova SW Sextantis Symbiotic
Symbiotic nova Z Andromedae

Rotating
Non-spherical

Rotating ellipsoidal

Stellar spots

BY Draconis FK Comae Berenices

Magnetic fields

Alpha² Canum Venaticorum Pulsar SX Arietis

Eclipsing

Algol Beta Lyrae Planetary transit W Ursae Majoris

Physics Encyclopedia

World

Index

Hellenica World - Scientific Library

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