HV 2112

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Star
HV 2112
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Toucan
Right ascension 01 h 10 m 3.85 s
declination −72 ° 36 ′ 52.6 ″
Apparent brightness (16.6) mag
Typing
B − V color index (1.80) 
U − B color index (0.33) 
R − I index (4.74) 
Spectral class M5 II to III
Variable star type Yes 
Astrometry
Radial velocity (150) km / s
Visual absolute brightness M vis (−5.2) mag
Proper movement 
Rec. Share: (1.11 ± 0.07)  mas / a
Dec. portion: (−1.29 ± 0.07)  mas / a
Physical Properties
radius (900)  R ☉
Luminosity

(50000 to 100000)  L ☉

Effective temperature (3450)  K.
Other names
and catalog entries
2MASS catalog 2MASS J01100385-7236526 [1]
Other names HV 2112

HV 2112 is a star in the Small Magellanic Cloud that was identified as a variable star by Henrietta Leavitt in 1908 . According to its spectral class, it is a red giant . Its magnitude fluctuates between 12.7 and 16.7. However, since the luminosity may exceed the expected maximum of 60000 L ☉ at the assumed distance , the star could also be a so-called Thorne-Żytkow object (TŻO).

Distance of the star

The distance to the star was unknown for a long time and it was therefore unclear whether the star was located within the Small Magellanic Cloud or just in front of it, but within the Milky Way .

If the star belonged to the Milky Way and just happened to have a similar direction of movement as the Small Magellanic Cloud, it could be regarded as a normal AGB star and would accordingly no longer have a prominent luminosity.

However, current data from Gaia DR2 support the assumption that the star belongs to the Small Magellanic Cloud. So the star should definitely be very luminous.

Type of object

Even if the latest data locate the star within the Small Magellanic Cloud, the nature of the star cannot yet be clearly determined.

While Levesque's work in 2014 classifies the star as the first possible Thorne-Żytkow object, a work by Beasor from 2018 comes in at half the luminosity despite its location within the Small Magellanic Cloud and therefore doubts the exotic nature of the star. Due to the lower luminosity, the object could be a red supergiant . As an argument for this assumption, the study cites spectroscopic studies which do not show the expected abnormal spectrum of a TŻO. This work suggests the star HV 11417 as a candidate for a TŻO.

Web links

Individual evidence

  1. ↑ a b c d e f g HV 2112. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed September 16, 2018 .
  2. ^ A b C. S. Kochanek, BJ Shappee, KZ Stanek, TW-S. Holoien, Todd A. Thompson, J.-L. Prieto, Subo Dong, JV Shields, D. Will, C. Britt, D. Perzanowski, G. Pojmanski: The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0 . In: arXiv . 1706, 2017, p. ArXiv: 1706.07060. arxiv : 1706.07060 . bibcode : 2017arXiv170607060K .
  3. ↑ a b BJ Shappee, JL Prieto, D. Grupe, CS Kochanek, KZ Stanek, G. De Rosa, S. Mathur, Y. Zu, BM Peterson, RW Pogge, S. Komossa, M. Im, J. Jencson, TW-S. Holoien, U. Basu, JF Beacom, DM Szczygieł, J. Brimacombe, S. Adams, A. Campillay, C. Choi, C. Contreras, M. Dietrich, M. Dubberley, M. Elphick, S. Foale, M. Giustini, C. Gonzalez, E. Hawkins, DA Howell: The Man behind the Curtain: X-Rays Drive the UV through NIR Variability in the 2013 Active Galactic Nucleus Outburst in NGC 2617 . In: The Astrophysical Journal . 788, 2014, p. 48. arxiv : 1310.2241 . bibcode : 2014ApJ ... 788 ... 48S . doi : 10.1088 / 0004-637X / 788/1/48 .
  4. ↑ a b c d e f Emily Levesque: Discovery of a Thorne-̇Żytkow object candidate in the Small Magellanic Cloud . In: Monthly Notices of the Royal Astronomical Society: Letters . 443, September 1, 2014, p. L94. arxiv : 1406.0001 . bibcode : 2014MNRAS.443L..94L . doi : 10.1093 / mnrasl / slu080 .
  5. ↑ a b Emma Beasor, Ben Davies, Ivan Cabrera Ziri, Georgia Hurst: A critical re-evaluation of the Thorne-Żytkow object candidate HV 2112 . In: Monthly Notices of the Royal Astronomical Society . 479, No. 3, July 2, 2018, p. 3101. arxiv : 1806.07399 . bibcode : 2018MNRAS.479.3101B . doi : 10.1093 / mnras / sty1744 .
  6. ^ Henrietta S. Leavitt: 1777 variables in the Magellanic Clouds . In: Annals of Harvard College Observatory . 60, 1908, p. 87. bibcode : 1908AnHar..60 ... 87L .
  7. ^ PR Wood, MS Bessell, MW Fox: Long-period variables in the Magellanic Clouds - Supergiants, AGB stars, supernova precursors, planetary nebula precursors, and enrichment of the interstellar medium . In: Astrophysical Journal . 272, 1983, p. 99. bibcode : 1983ApJ ... 272 ​​... 99W . doi : 10.1086 / 161265 .
  8. ^ Paul J McMillan, Ross P Church: Gaia DR2 confirms that candidate Thorne-Żytkow object HV 2112 is in the SMC . In: Research Notes of the AAS . 2018. arxiv : 1804.10192 . bibcode : 2018RNAAS ... 2b..18M . doi : 10.3847 / 2515-5172 / aac0fb .