CH Cygni

CH Cygni (CH Cyg / HIP 95413 / BD +49 2999) is a red giant, variable, symbiotic binary in the constellation Cygnus. It is the nearest symbiotic star to Earth, and one of the brightest, making it an ideal candidate for study.

CH Cygni
Location of CH Cygni (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension  19h 24m 33.06773s[1]
Declination +50° 14′ 29.1263″[1]
Apparent magnitude (V) 5.60 – 8.49[2]
Characteristics
Spectral type M7IIIab + Be[3]
Variable type Z And and SR[2]
Astrometry
Radial velocity (Rv)-59.74[4] km/s
Proper motion (μ) RA: -7.09[1] mas/yr
Dec.: -59.74[1] mas/yr
Parallax (π)5.4642 ± 0.2172[5] mas
Distance600 ± 20 ly
(183 ± 7 pc)
Orbit[6]
Period (P)15.58±0.13 yr
Semi-major axis (a)8.5 AU
Eccentricity (e)0.122±0.024
Inclination (i)84°
Semi-amplitude (K1)
(primary)		4.45±0.12 km/s
Details[6]
Red giant
Mass2 M☉
Radius280 R☉
Luminosity5012 L☉
Temperature3,100 K
White dwarf
Mass0.7 M☉
Luminosity0.25 L☉
Other designations
HD 182917, BD+49°2999, HIP 95413, SAO 31632
Database references
SIMBADdata

Properties

CH Cygni has a mass of 2 M☉ and a radius of 280 R☉. Its white-dwarf companion has a mass of 0.75 M☉, and the orbital period of the two stars is 5689 days.[6] CH Cygni is classified as M7IIIab + Be.[3]

Observation history

The earliest observations of CH Cygni were made in 1890 by Pickering and Wendel using wedge photometer, and was classified as a M6III variable star in 1924.[7] In 1963 strong H I emissions were observed, indicating CH Cygni was likely in a symbiotic relationship with a white dwarf. Similar emissions were observed in 1965, 1967, 1977, 1992, and 1998.[8] The system was briefly thought to contain a third star[9] but this was later disproved.[6]

In 1984 bipolar jets were detected coming from CH Cygni, which were suspected to be due to accretion from its companion star.[8][7] The luminosity of the system decreased significantly in 1986, likely owing to dust thrown out of the system by the jets or a concurrent helium flash. This dust had dissipated by 2002, with subsequent luminosities returning to pre-1985 levels.[3]

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References
  1. van Leeuwen, F. (13 August 2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. 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.
  3. Shenavrin, V. I; Taranova, O. G; Nadzhip, A. E (2011). "Search for and study of hot circumstellar dust envelopes". Astronomy Reports. 55: 31. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070.
  4. Famaey, B.; Pourbaix, D.; Frankowski, A.; Van Eck, S.; Mayor, M.; Udry, S.; Jorissen, A. (18 February 2009). "Spectroscopic binaries among Hipparcos M giants". Astronomy & Astrophysics. 498 (2): 627–640. arXiv:0901.0934. Bibcode:2009A&A...498..627F. doi:10.1051/0004-6361/200810698.
  5. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  6. Hinkle, Kenneth H; Fekel, Francis C; Joyce, Richard R (2009). "Infrared Spectroscopy of Symbiotic Stars. Vii. Binary Orbit and Long Secondary Period Variability of Ch Cygni". The Astrophysical Journal. 692 (2): 1360. arXiv:0811.0631. Bibcode:2009ApJ...692.1360H. doi:10.1088/0004-637X/692/2/1360.
  7. Mikołajewski, M.; Mikołajewska, J.; Khudiakova, T.N. (August 1990). "A long-period symbiotic binary CH Cygni. I - A hundred years' history of variability". Astronomy and Astrophysics. 235 (1–2): 219–233. Bibcode:1990A&A...235..219M. ISSN 0004-6361.
  8. Burmeister, M.; Leedjärv, L. (9 July 2009). "Spectroscopy of the symbiotic binary CH Cygni from 1996 to 2007". Astronomy & Astrophysics. 504 (1): 171–180. arXiv:0907.2017. Bibcode:2009A&A...504..171B. doi:10.1051/0004-6361/200911686.
  9. Hinkle, Kenneth H.; Fekel, Francis C.; Johnson, Diana S.; Scharlach, Werner W. G. (March 1993). "The triple symbiotic system CH Cygni". The Astronomical Journal. 105: 1074. Bibcode:1993AJ....105.1074H. doi:10.1086/116494.
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