IRC +10420

IRC+10420, also known as V1302 Aql, is a yellow hypergiant star located in the constellation of Aquila at a distance of 4-6 kiloparsecs of the Sun.

IRC+10420

MERLIN and e-VLBI observations of the OH masers in IRC+10420
Credit: Joint Institute for VLBI in Europe (JIVE)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension 19h 26m 48.098s[1]
Declination +11° 21′ 16.76″[1]
Apparent magnitude (V) 11.66 (variable)[2]
Characteristics
Evolutionary stage Post-red supergiant yellow hypergiant
Spectral type F8Ia+[3]–A2I[4][5][6]
B−V color index 2.32[2]
Variable type Unique[7]
Astrometry
Proper motion (μ) RA: −1.858[1] mas/yr
Dec.: −7.531[1] mas/yr
Parallax (π)0.2040 ± 0.0585 mas[1]
Distanceapprox. 16,000 ly
(approx. 5,000 pc)
Absolute magnitude (MV)−9.5[5]
Details
Mass~10[4][8] M☉
Radius380[9] R☉
Luminosity (bolometric)513,000[10] L☉
Surface gravity (log g)0.01[4] cgs
Temperature7,930±140 (6,000-8,000)[4] K
Metallicity [Fe/H]−0.18[4] dex
Other designations
IRC+10420, V1302 Aql, IRAS 19244+1115, AAVSO 1922+11
Database references
SIMBADdata

Discovery
A blue band light curve for IRC+10420, adapted from Gottlieb & Liller (1978)[11]

IRC+10420 was first identified in the 1969 Infrared Catalogue of 2.2 micron sources.[12] It was quickly noted as a very unusual object after being detected at 20 microns as one of the brightest sources in the sky with a large infrared excess, and was compared to Eta Carinae during one of its outbursts.[3] It was also discovered to be a strong source of OH maser emission.[13]

It was formally catalogued as variable star V1302 Aquilae.[14] Identification on historical photographic plates showed possible irregular variations of about a magnitude before 1925, followed by a smooth gradual increase in brightness from magnitude 15 to brighter than magnitude 14 by 1976.[11]

Some authors had grouped IRC+10420 with the proto-planetary nebulae because of the surrounding nebulosity, but it was widely recognised as a highly luminous supergiant.[15]

Physical properties
IRC+10420 and its circumstellar material

Despite being one of the most luminous stars known, 513,000 times brighter than the Sun,[6] IRC+10420 cannot be seen with the naked eye and needs a telescope to be observed.

IRC+10420's spectrum has changed from late F to early A in recent decades without experiencing changes in its luminosity. This suggests IRC+10420 is a former red supergiant that is evolving blueward on the Hertzsprung-Russell diagram to become a luminous blue variable, or Wolf–Rayet star. Models suggest it started its life as a 40-50 solar masses star that lost most of its mass due to strong stellar winds leaving it with just 10 solar masses and that the star - which actually has a high surface temperature - is totally enshrouded in the matter it has expelled appearing as a fake photosphere, so IRC+10420 appears with a later spectral type as humans see just the expelled dust and gas it has blown out during its life and not the star itself.

Surrounding nebula

IRC+10420 is surrounded by a reflection nebula with a mass of 30-40 solar masses that has been made by the material expelled by the strong stellar winds of its central star. This nebula has been studied with the help of the Hubble Space Telescope, showing a complex structure that includes arcs, rays, and condensations and that has been compared to the one surrounding the red hypergiant VY Canis Majoris. The star and its surrounding material have been compared to IRAS 17163-3907.[16]

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  3. Humphreys, Roberta M.; Strecker, D. W.; Murdock, T. L.; Low, F. J. (1973). "IRC+10420-ANOTHER Eta Carinae?". Astrophysical Journal. 179: L49. Bibcode:1973ApJ...179L..49H. doi:10.1086/181114.
  4. Nieuwenhuijzen, H.; De Jager, C. (2000). "Checking the yellow evolutionary void. Three evolutionary critical Hypergiants: HD 33579, HR 8752 & IRC +10420". Astronomy and Astrophysics. 353: 163. Bibcode:2000A&A...353..163N.
  5. Klochkova, V. G.; Yushkin, M. V.; Chentsov, E. L.; Panchuk, V. E. (2002). "Evolutionary Changes in the Optical Spectrum of the Peculiar Supergiant IRC+10420". Astronomy Reports. 46 (2): 139. Bibcode:2002ARep...46..139K. doi:10.1134/1.1451927. S2CID 84835394.
  6. Tiffany, C.; Humphreys, R. M.; Jones, T. J.; Davidson, K. (2010). "THE MORPHOLOGY OF IRC+10420's CIRCUMSTELLAR EJECTA". The Astronomical Journal. 140 (2): 339. arXiv:1006.0501. Bibcode:2010AJ....140..339T. doi:10.1088/0004-6256/140/2/339. S2CID 119107151.
  7. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  8. Dinh-V.-Trung; Muller, Sébastien; Lim, Jeremy; Kwok, Sun; Muthu, C. (2009). "Probing the Mass-Loss History of the Yellow Hypergiant IRC+10420". The Astrophysical Journal. 697 (1): 409–419. arXiv:0903.3714v1. Bibcode:2009ApJ...697..409D. doi:10.1088/0004-637X/697/1/409. S2CID 16971892.
  9. Wong, K. T.; Menten, K. M.; Kamiński, T.; Wyrowski, F.; Lacy, J. H.; Greathouse, T. K. (2018). "Circumstellar ammonia in oxygen-rich evolved stars". Astronomy & Astrophysics. 612: A48. arXiv:1710.01027. Bibcode:2018A&A...612A..48W. doi:10.1051/0004-6361/201731873. S2CID 55019902.
  10. Klochkova, V. G. (2019). "Unity and Diversity of Yellow Hypergiants Family". Astrophysical Bulletin. 74 (4): 475–489. arXiv:1911.09387. Bibcode:2019AstBu..74..475K. doi:10.1134/S1990341319040138. S2CID 208202411.
  11. Gottlieb, E. W.; Liller, W. (1978). "Photometric histories of six infrared objects and three highly reddened blue supergiants". Astrophysical Journal. 225: 488. Bibcode:1978ApJ...225..488G. doi:10.1086/156509.
  12. Neugebauer, G.; Leighton, R. B. (1969). "Two-micron sky survey. A preliminary catalogue". NASA Sp. Bibcode:1969tmss.book.....N.
  13. Giguere, P. T.; Woolf, N. J.; Webber, J. C. (1976). "IRC +10 420 - A hot supergiant maser". Astrophysical Journal. 207: L195. Bibcode:1976ApJ...207L.195G. doi:10.1086/182211.
  14. Kukarkin, B. V.; Kholopov, P. N.; Kukarkina, N. P. (1975). "61st Name-List of Variable Stars". Information Bulletin on Variable Stars. 1068: 1. Bibcode:1975IBVS.1068....1K.
  15. Jones, Terry Jay; Humphreys, Roberta M.; Gehrz, Robert D.; Lawrence, Geoffrey F.; Zickgraf, Franz-Josef; Moseley, Harvey; Casey, Sean; Glaccum, William J.; Koch, Carol J.; Pina, Robert; Jones, Barbara; Venn, Kim; Stahl, Otmar; Starrfield, Sumner G. (1993). "IRC +10420 - A cool hypergiant near the top of the H-R diagram". Astrophysical Journal. 411: 323. Bibcode:1993ApJ...411..323J. doi:10.1086/172832.
  16. Lagadec, E.; Zijlstra, A. A.; Oudmaijer, R. D.; Verhoelst, T.; Cox, N. L. J.; Szczerba, R.; Mékarnia, D.; Van Winckel, H. (2011). "A double detached shell around a post-red supergiant: IRAS 17163-3907, the Fried Egg nebula". Astronomy & Astrophysics. 534: L10. arXiv:1109.5947. Bibcode:2011A&A...534L..10L. doi:10.1051/0004-6361/201117521. S2CID 55754316.

Further reading
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