Astronomy:15 Cancri

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Short description: Star in the constellation Cancer
15 Cancri
Location of 15 Cancri (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Cancer
Right ascension  08h 13m 08.86806s[1]
Declination +29° 39′ 23.5368″[1]
Apparent magnitude (V) 5.53 - 5.65[2]
Characteristics
Evolutionary stage main sequence[3]
Spectral type A0:V:spSiSr[4]
B−V color index −0.073±0.002[5]
Variable type α2 CVn[2]
Astrometry
Radial velocity (Rv)25.0±0.8[6] km/s
Proper motion (μ) RA: −11.265[1] mas/yr
Dec.: −19.506[1] mas/yr
Parallax (π)4.6720 ± 0.2238[1] mas
Distance700 ± 30 ly
(210 ± 10 pc)
Absolute magnitude (MV)−0.97[5]
Orbit[6]
Primary15 Cancri A
Companion15 Cancri B
Period (P)635.73±0.53 days[note 1]
Eccentricity (e)0.55±0.08
Periastron epoch (T)2422045±18
Argument of periapsis (ω)
(primary)		196±13°
Semi-amplitude (K1)
(primary)		9.6±1.1 km/s
Details
15 Cnc A
Mass2.4[3] M☉
Radius3.4[3] R☉
Luminosity131[3] L☉
Surface gravity (log g)3.68[3] cgs
Temperature10,400[3] K
Rotation6.563 days[7]
Rotational velocity (v sin i)25[4] km/s
Age358[8] Gyr
Other designations
15 Cnc, BM Cnc, BD+30°1664, HD 68351, HIP 40240, HR 3215, GSC 01939-01462[9]
Database references
SIMBADdata
A light curve for BM Cancri, plotted from TESS data[10]

15 Cancri is an α2 CVn-type variable star in the zodiac constellation of Cancer, located around 700 light years away.[1] It has the variable star designation BM Cancri (BM Cnc); 15 Cancri (15 Cnc) is the Flamsteed designation. This system is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of about 5.6. It is moving away from the Earth with a heliocentric radial velocity of 25 km/s.[6]

Radial velocity measurements taken at the Dominion Astrophysical Observatory in Victoria, British Columbia Canada in 1918 and 1919 led to the determination that 15 Cancri is a single-lined spectroscopic binary system.[11] The first orbit was calculated in 1973 by Helmut Abt and Michael Snowden with a period of 585 days[12] however later measurements showed that the orbital period was 635 days.[6][note 1]

15 Cancri A, the visible component, is an Ap star, a chemically peculiar star with an over-abundance of iron peak elements, particularly silicon, chromium, and strontium, in its spectrum.[13][4]

Like all Ap stars, 15 Cancri has a strong magnetic field. This magnetic field varies as it rotates and in 1968 the visual brightness of the star was shown to vary regularly over about four days.[14] 15 Cancri was given the variable star designation BM Cancri in 1972 as a member of the α2 CVn class of variable stars.[15] The period has since been measured more accurately at 3.3095 d, believed to be the rotational period of the star.[16]

In Johann Bayer’s Uranometria, this star was designated as Psi Geminorum. When the constellation borders were set in 1930, it was moved to Cancer, so the designation has been dropped.[17]

Notes

  1. ↑ 1.0 1.1 An alternate period of 475 days is possible but less likely.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 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. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Glagolevskij, Yu. V. (2019). "On Properties of Main Sequence Magnetic Stars". Astrophysical Bulletin 74 (1): 66. doi:10.1134/S1990341319010073. Bibcode: 2019AstBu..74...66G. 
  4. ↑ 4.0 4.1 4.2 Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement 99: 135. doi:10.1086/192182. Bibcode: 1995ApJS...99..135A. 
  5. ↑ 5.0 5.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 6.2 6.3 Stickland, D. J.; Weatherby, J. (1984). "Radial velocities of northern Mercury stars". Astronomy and Astrophysics Supplement Series 57: 55–67. Bibcode: 1984A&AS...57...55S. 
  7. ↑ Balona, L. A. (2022). "Rapidly oscillating TESS A-F main-sequence stars: Are the roAp stars a distinct class?". Monthly Notices of the Royal Astronomical Society 510 (4): 5743. doi:10.1093/mnras/stac011. Bibcode: 2022MNRAS.510.5743B. 
  8. ↑ Kordopatis, G.; Schultheis, M.; McMillan, P. J.; Palicio, P. A.; De Laverny, P.; Recio-Blanco, A.; Creevey, O.; Álvarez, M. A. et al. (2023). "Stellar ages, masses, extinctions, and orbital parameters based on spectroscopic parameters of Gaia DR3". Astronomy and Astrophysics 669: A104. doi:10.1051/0004-6361/202244283. Bibcode: 2023A&A...669A.104K. 
  9. ↑ "15 Cancri". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=15+Cancri. 
  10. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  11. ↑ Plaskett, J. S. et al. (1919). "Fourth list of spectroscopic binaries". Journal of the Royal Astronomical Society of Canada 13: 372–378. Bibcode: 1919JRASC..13..372P. 
  12. ↑ Abt, Helmut A.; Snowden, Michael S. (1973). "The Binary Frequency for AP Stars". Astrophysical Journal Supplement 25: 137–162. doi:10.1086/190265. Bibcode: 1973ApJS...25..137A. 
  13. ↑ Renson, P.; Manfroid, J. (2009). "Catalogue of Ap, Hg Mn and Am stars". Astronomy & Astrophysics 498 (3): 961–966. doi:10.1051/0004-6361/200810788. Bibcode: 2009A&A...498..961R. 
  14. ↑ Stepien, K. (1968). "Photometric behavior of magnetic stars". The Astrophysical Journal 154: 945. doi:10.1086/149815. Bibcode: 1968ApJ...154..945S. 
  15. ↑ Martins, D. H. (1972). "New Southern Variable Stars". Information Bulletin on Variable Stars 705: 1. Bibcode: 1972IBVS..705....1M. 
  16. ↑ Wraight, K. T.; Fossati, L.; Netopil, M.; Paunzen, E.; Rode-Paunzen, M.; Bewsher, D.; Norton, A. J.; White, Glenn J. (2012). "A photometric study of chemically peculiar stars with the STEREO satellites - I. Magnetic chemically peculiar stars★". Monthly Notices of the Royal Astronomical Society 420 (1): 757–772. doi:10.1111/j.1365-2966.2011.20090.x. Bibcode: 2012MNRAS.420..757W. 
  17. ↑ Ian Ridpath. "Bayer's Uranometria and Bayer letters". http://www.ianridpath.com/startales/bayer.htm. 



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