Kilonova

Source: Wikipedia, the free encyclopedia.
Artist's impression of neutron stars merging, producing gravitational waves and resulting in a kilonova
Kilonova illustration

A kilonova (also called a macronova) is a

isotropically during the merger process.[2]
The measured high sphericity of the kilonova
AT2017gfo at early epochs was deduced from the blackbody nature of its spectrum.[3][4]

History

Animation showing two small, very dense neutron stars merge via gravitational wave radiation and explode as a kilonova

The existence of thermal transient events from neutron star mergers was first introduced by Li & Paczyński in 1998.[1] The radioactive glow arising from the merger ejecta was originally called mini-supernova, as it is 1⁄10 to 1⁄100 the brightness of a typical supernova, the self-detonation of a massive star.[5] The term kilonova was later introduced by Metzger et al. in 2010[6] to characterize the peak brightness, which they showed reaches 1000 times that of a classical nova.

The first candidate kilonova to be found was detected as a short

KONUS/WIND spacecraft and then observed using the Hubble Space Telescope 9 and 30 days after burst.[7]

This artist's impression shows a kilonova produced by two colliding neutron stars.

On October 16, 2017, the

standard candle to measure cosmic expansion. Since kilonovae explosions are spherical, astronomers could compare the apparent size of a supernova explosion with its actual size as seen by the gas motion, and thus measure the rate of cosmic expansion at different distances."[15]

Theory

The

compact objects are a strong source of gravitational waves (GW).[6] The basic model for thermal transients from neutron star mergers was introduced by Li-Xin Li and Bohdan Paczyński in 1998.[1] In their work, they suggested that the radioactive ejecta from a neutron star merger is a source for powering thermal transient emission, later dubbed kilonova.[16]

Observations

First kilonova observations by the Hubble Space Telescope[17]

A first observational suggestion of a kilonova came in 2008 following the gamma-ray burst GRB 080503,[18] where a faint object appeared in optical light after one day and rapidly faded. However, other factors such as the lack of a galaxy and the detection of X-rays were not in agreement with the hypothesis of a kilonova. Another kilonova was suggested in 2013, in association with the short-duration gamma-ray burst GRB 130603B, where the faint infrared emission from the distant kilonova was detected using the Hubble Space Telescope.[7]

In October 2017, astronomers reported that observations of

AT 2017gfo showed that it was the first secure case of a kilonova following a merger of two neutron stars.[11]

Fading kilonova in GRB160821B seen by the Hubble Space Telescope.

In October 2018, astronomers reported that

optical and x-ray emissions, as well as to the nature of the associated host galaxies, are considered "striking", and this remarkable resemblance suggests the two separate and independent events may both be the result of the merger of neutron stars, and both may be a hitherto-unknown class of kilonova transients. Kilonova events, therefore, may be more diverse and common in the universe than previously understood, according to the researchers.[19][20][21][22] In retrospect, GRB 160821B, a gamma-ray burst detected in August 2016, is now believed to also have been due to a kilonova, by its resemblance of its data to AT2017gfo.[23]

A kilonova was also thought to have caused the long gamma-ray burst GRB 211211A, discovered in December 2021 by Swift’s Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM).[24][25] These discoveries challenge the formerly prevailing theory that long GRBs exclusively come from supernovae, the end-of-life explosions of massive stars.[26] GRB 211211A lasted 51s;[27][28] GRB 191019A (2019)[29] and GRB 230307A (2023),[30][31] with durations of around 64s and 35s respectively, have been also argued to belong to this class of long GBRs from neutron star mergers.[32]

In 2023,

lanthanides.[33]

See also

References

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  21. ^ Mohon, Lee (16 October 2018). "GRB 150101B: A Distant Cousin to GW170817". NASA. Retrieved 17 October 2018.
  22. ^ Wall, Mike (17 October 2018). "Powerful Cosmic Flash Is Likely Another Neutron-Star Merger". Space.com. Retrieved 17 October 2018.
  23. ^ Strickland, Ashley (2019-08-27). "This is what it looks like when an explosion creates gold in space". CNN. Retrieved 2022-12-11.
  24. ^ Reddy, Francis (2022-10-13). "NASA's Swift, Fermi Missions Detect Exceptional Cosmic Blast". NASA. Retrieved 2022-12-11.
  25. ^ "Kilonova Discovery Challenges our Understanding of Gamma-Ray Bursts". Gemini Observatory. 2022-12-07. Retrieved 2022-12-11.
  26. ^ Troja, Eleonora; Dichiara, Simone (21 December 2022). "Unusual, long-lasting gamma-ray burst challenges theories about these powerful cosmic explosions that make gold, uranium and other heavy metals". The Conversation. Retrieved 2022-12-27.
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