HD 49976

HD 49976 is a variable star in the constellation of Monoceros (the Unicorn). It has the variable star designation V592 Monocerotis, while HD 49976 is the identifier from the Henry Draper Catalogue.[10] It has a white hue and is near the lower limit of visibility to the naked eye, having an apparent visual magnitude that fluctuates from 6.16 down to 6.32 with a 2.976 day period.[2] Based upon parallax measurements, it is located at a distance of approximately 337 light years from the Sun.[1] The star is drifting further away with a radial velocity of +19 km/s.[6]

HD 49976
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Monoceros
Right ascension  06h 50m 42.30314s[1]
Declination –08° 02′ 27.5937″[1]
Apparent magnitude (V) 6.16 to 6.32[2]
Characteristics
Spectral type A2p Sr Cr Eu[3] or B9V[4]
U−B color index +0.02[5]
B−V color index +0.00[5]
Variable type α2 CVn[2]
Astrometry
Radial velocity (Rv)+19.2±2.4[6] km/s
Proper motion (μ) RA: –9.794[1] mas/yr
Dec.: +2.720[1] mas/yr
Parallax (π)9.6666 ± 0.0529[1] mas
Distance337 ± 2 ly
(103.4 ± 0.6 pc)
Absolute magnitude (MV)+1.13[7]
Details[7]
Mass2.21±0.11 M☉
Radius2.3±0.3 R☉
Luminosity32 L☉
Surface gravity (log g)4.04±0.13 cgs
Temperature9,016 K
Rotation2.976 days
Rotational velocity (v sin i)31[8] km/s
Age209[9] Myr
Other designations
V592 Monocerotis, BD−07°1592, HD 49976, HIP 32838, HR 2534, SAO 133761[10]
Database references
SIMBADdata

This is a magnetic chemically peculiar star with a stellar classification of A2p Sr Cr Eu,[3] showing excesses in strontium and the rare earth elements in the photosphere, among others. Houk and Swift (1999) assigned it a class of B9V, matching a B-type main sequence star.[4] It is an Alpha2 Canum Venaticorum variable;[2] the magnetic field is complex; not corresponding to a simple dipole.[11]

HD 49976 is an estimated 209[9] million years old and is spinning with a period of 2.976 days.[7] The star has 2.2 times the mass of the Sun and 2.3 times the Sun's radius. It is radiating 32 times the luminosity of the Sun from its photosphere at an effective temperature of 9,016 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. 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.
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819
  4. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
  5. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J
  6. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  7. North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics, 334: 181–187, arXiv:astro-ph/9802286, Bibcode:1998A&A...334..181N
  8. Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943
  9. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  10. "V592 Mon". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-06-06.
  11. Glagolevskij, Yu. V.; et al. (October 2013), "Features of calcium and strontium distribution on the surface of CP star HD49976", Astrophysical Bulletin, 68 (4): 454–460, Bibcode:2013AstBu..68..454G, doi:10.1134/S1990341313040068
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