Astronomy:S Monocerotis

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Short description: Star in the constellation Monoceros
S Monocerotis
Monoceros constellation map.svg
S Monocereotis lies in NGC 2264 at the very northern edge of Monoceros.
Observation data
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
Constellation Monoceros
A
Right ascension  06h 40m 58.656s[1]
Declination +09° 53′ 44.71″[1]
Apparent magnitude (V) 4.66[2] (4.62 - 4.68[3]) + 5.90[2]
B
Right ascension  06h 40m 58.566s[1]
Declination +09° 53′ 42.20″[1]
Apparent magnitude (V) 7.830[1]
Characteristics
U−B color index −1.034[4]
B−V color index −0.261[4]
Variable type Ia[3]
Astrometry
A
Radial velocity (Rv)22.00[5] km/s
Proper motion (μ) RA: −2.61[6] mas/yr
Dec.: −1.61[6] mas/yr
Parallax (π)3.55 ± 0.50[6] mas
Distance720[7] pc
Absolute magnitude (MV)−5.21[8]
B
Proper motion (μ) RA: −1.971[9] mas/yr
Dec.: −4.225[9] mas/yr
Parallax (π)1.4019 ± 0.0984[9] mas
Distance2,300 ± 200 ly
(710 ± 50 pc)
C
Proper motion (μ) RA: −1.464[10] mas/yr
Dec.: −2.746[10] mas/yr
Parallax (π)1.5438 ± 0.0394[10] mas
Distance2,110 ± 50 ly
(650 ± 20 pc)
Orbit[11]
PrimaryAa
CompanionAb
Period (P)108±12 yr
Semi-major axis (a)112.5±6 mas
Eccentricity (e)0.770+0.023
−0.030
Inclination (i)47±2°
Longitude of the node (Ω)60±3°
Periastron epoch (T)B 1996.05+0.15
−0.10
Argument of periastron (ω)
(secondary)		63±4°
Details
Aa
Mass29.1[2] M☉
Radius9.9[12] R☉
Luminosity214,000[12] L☉
Surface gravity (log g)4.5[13] cgs
Temperature38,500[12] K
Rotational velocity (v sin i)120[14] km/s
Ab
Mass21.3[2] M☉
Age3.1[15] Myr
Other designations
15 Monocerotis, HD 47839, HIP 31978, HR 2456, SAO 114258, BD+10°1220
Database references
SIMBADdata
ARICNSdata
NGC 2264 including the Cone Nebula and the Christmas Tree Cluster (upside down in this image) with S Monocerotis at the very top of the image (and the base of the Christmas tree)

S Monocerotis, also known as 15 Monocerotis, is a massive multiple and variable star system located in the constellation Monoceros. It is the brightest star in the Christmas Tree open cluster in the area catalogued as NGC 2264.

S Monocerotis is found within an open cluster and the Washington Double Star Catalog lists many companion stars.[16] The closest and brightest is S Mon B, magnitude 7.8 and 3 arcseconds away. It is classified as B2 main sequence star with a mass of 7.31 M☉. Designated component C is an 11th-magnitude B8V star.[17] The cluster contains another dozen or so 9th and 10th magnitude stars and many fainter stars.

S Monocerotis A is a spectroscopic binary system with an eccentric orbit of about 112 years.[11] Since 1943, the spectrum of this star has served as the MK standard for O7 by which other stars are classified.[18] It is also an irregular variable star with a range of less than a tenth of a magnitude. The orbital parameters can be used to derive the masses of the two stars, giving 31 M☉ and 11 M☉.[17]

The distance to S Monocerotis and NGC 2264 has been derived in various ways, including dynamical parallax and isochrone fitting. These consistently give estimates of 700 - 900 parsecs, although this is double the likely distance derived from the Hipparcos parallax measurements.[6] Gaia Early Data Release 3 contains parallaxes for the companions components B and C of 1.4 mas and 1.5 mas respectively, consistent with the expected distance to the cluster.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27. doi:10.1888/0333750888/2862. ISBN 0333750888. Bibcode: 2000A&A...355L..27H. 
  2. ↑ 2.0 2.1 2.2 2.3 Cvetkovc, Zorica; Vince, Istvan; Ninkovic, Slobodan (2008). "Orbit of Binary 15 Monocerotis". arXiv:0804.0698 [astro-ph].
  3. ↑ 3.0 3.1 Samus, N. N. 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. 
  4. ↑ 4.0 4.1 Oja, T. (August 1985). "Photoelectric photometry of stars near the north Galactic pole. II". Astronomy and Astrophysics Supplement Series 61: 331–339. Bibcode: 1985A&AS...61..331O. 
  5. ↑ Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; Levato, H.; Morrell, N. I.; Torres, G. et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics 424 (2): 727–732. doi:10.1051/0004-6361:20041213. Bibcode: 2004A&A...424..727P. 
  6. ↑ 6.0 6.1 6.2 6.3 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V. 
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named orbit2010
  8. ↑ Feinstein, A.; Vazquez, R. A.; Benvenuto, O. G. (1986). "Of-stars in young open clusters". Astronomy and Astrophysics 159: 223. Bibcode: 1986A&A...159..223F. 
  9. ↑ 9.0 9.1 9.2 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  10. ↑ 10.0 10.1 10.2 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  11. ↑ 11.0 11.1 Maíz Apellániz, J. (2019). "Gaia DR2 distances to Collinder 419 and NGC 2264 and new astrometric orbits for HD 193 322 Aa,Ab and 15 Mon Aa,Ab". Astronomy and Astrophysics 630: A119. doi:10.1051/0004-6361/201935885. Bibcode: 2019A&A...630A.119M. 
  12. ↑ 12.0 12.1 12.2 Herrero, A.; Kudritzki, R. P.; Vilchez, J. M.; Kunze, D.; Butler, K.; Haser, S. (1992). "Intrinsic parameters of galactic luminous OB stars". Astronomy and Astrophysics 261: 209. Bibcode: 1992A&A...261..209H. 
  13. ↑ Sung, Hwankyung; Stauffer, John R.; Bessell, Michael S. (2009). "A Spitzer View of the Young Open Cluster NGC 2264". The Astronomical Journal 138 (4): 1116–1136. doi:10.1088/0004-6256/138/4/1116. Bibcode: 2009AJ....138.1116S. 
  14. ↑ Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago 239 (1): 1. Bibcode: 1970CoAsi.239....1B. 
  15. ↑ Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (2010). "Masses and luminosities of O- and B-type stars and red supergiants". Astronomische Nachrichten 331 (4): 349–360. doi:10.1002/asna.200911355. Bibcode: 2010AN....331..349H. 
  16. ↑ Worley, C. E.; Douglass, G. G. (1997). "The Washington Double Star Catalog (WDS, 1996.0)". Astronomy and Astrophysics Supplement Series 125 (3): 523. doi:10.1051/aas:1997239. Bibcode: 1997A&AS..125..523W. 
  17. ↑ 17.0 17.1 Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy and Astrophysics Supplement Series 124: 75–84. doi:10.1051/aas:1997181. Bibcode: 1997A&AS..124...75T. 
  18. ↑ Garrison, R. F. (December 1993). "Anchor Points for the MK System of Spectral Classification". Bulletin of the American Astronomical Society 25: 1319. Bibcode: 1993AAS...183.1710G. http://www.astro.utoronto.ca/~garrison/mkstds.html. Retrieved 2012-02-04. 

External links



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