38 Cancri

38 Cancri is a variable star in the zodiac constellation Cancer, located around 607 light years from the Sun. This object has the variable star designation BT Cancri; 38 Cancri is the Flamsteed designation. It is a member of the Praesepe cluster[9] but is a challenge to view with the naked eye, having an apparent visual magnitude of 6.65.[2] The star is moving closer to the Earth with a heliocentric radial velocity of +32 km/s.[5]

38 Cancri
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cancer
Right ascension 08h 39m 42.65445s[1]
Declination +19° 46′ 42.4386″[1]
Apparent magnitude (V) 6.65[2]
Characteristics
Evolutionary stage subgiant
Spectral type F0 IV[3]
B−V color index 0.248±0.010[2]
Variable type δ Sct[4]
Astrometry
Radial velocity (Rv)+32.0±2.0[5] km/s
Proper motion (μ) RA: −36.879[1] mas/yr
Dec.: −13.103[1] mas/yr
Parallax (π)5.3700 ± 0.0705[1] mas
Distance607 ± 8 ly
(186 ± 2 pc)
Absolute magnitude (MV)0.36[2]
Details
Mass1.786[6] M☉
Radius1.834[6] R☉
Luminosity59.31[2] L☉
Surface gravity (log g)2.92±0.20[7] cgs
Temperature7300±200[7] K
Metallicity [Fe/H]−0.16±0.10[7] dex
Rotation0.670 d[6]
Rotational velocity (v sin i)138.5[6] km/s
Other designations
38 Cnc, BT Cancri, BD+20°2149, HD 73575, HIP 42485, SAO 98006[8]
Database references
SIMBADdata

This is an evolving subgiant star with a stellar classification of F0 IV.[3] It was found to be a pulsating variable by Michel Breger in 1970[10] and is classed as a Delta Scuti variable. The star displays a pattern of variation showing up to 22 different frequencies, with three being dominant.[11] The brightness varies by up to 0.07 in magnitude.[4] The star has a magnetic field with a computed longitudinal field strength of −215±149 G.[7] It has 1.8[6] times the mass of the Sun and 1.8[6] times the Sun's radius. The star is radiating 59[2] times the Sun's luminosity from its photosphere at an effective temperature of around 7,300 K.[7]

References
  1. 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. Gaia DR2 record for this source at VizieR.
  2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  3. Gray, R. O.; et al. (April 2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars", The Astronomical Journal, 121 (4): 2148–2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
  4. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  6. van Saders, Jennifer L.; Pinsonneault, Marc H. (October 2013), "Fast Star, Slow Star; Old Star, Young Star: Subgiant Rotation as a Population and Stellar Physics Diagnostic", The Astrophysical Journal, 776 (2): 20, arXiv:1306.3701, Bibcode:2013ApJ...776...67V, doi:10.1088/0004-637X/776/2/67, S2CID 119097746, 67.
  7. Fossati, L.; et al. (December 2007), "Late stages of the evolution of A-type stars on the main sequence: comparison between observed chemical abundances and diffusion models for 8 Am stars of the Praesepe cluster", Astronomy and Astrophysics, 476 (2): 911–925, arXiv:0710.0579, Bibcode:2007A&A...476..911F, doi:10.1051/0004-6361:20078320, S2CID 16152096.
  8. "38 Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-01.
  9. Michel, E.; et al. (February 1999), "Seismology of delta Scuti stars in the Praesepe cluster. I. Ranges of unstable modes as predicted by linear analysis versus observations", Astronomy and Astrophysics, 342: 153–166, Bibcode:1999A&A...342..153M.
  10. Breger, Michel (November 1970), "Metallic-Line a Stars and Pulsation", Astrophysical Journal, 162: 597, Bibcode:1970ApJ...162..597B, doi:10.1086/150691
  11. Breger, M.; et al. (February 2012), "Delta Scuti stars in the Praesepe cluster observed by the MOST satellite", Astronomische Nachrichten, 333 (2): 131, arXiv:1201.0892, Bibcode:2012AN....333..131B, doi:10.1002/asna.201111640, S2CID 118458884.
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