HR 4138

This article is about K Carinae. For k Carinae, see HD 81101.

HR 4138 is a single^[10] star in the constellation Carina. It has the Bayer designation K Carinae,^[11] abbreviated K Car, while HR 4138 is the star's designation in the Bright Star Catalogue. It has a white hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.72.^[2] This star is located at a distance of approximately 261 light years from the Sun based on parallax measurements,^[1] and it is drifting further away with a radial velocity of +7.5 km/s.^[2] Judging from its motion through space, it is a candidate member of the Sirius supercluster.^[12]

HR 4138

Observation data Epoch J2000      Equinox J2000
Constellation	Carina
Right ascension	10h 30m 20.12710s[1]
Declination	−71° 59′ 34.0602″[1]
Apparent magnitude (V)	+4.72[2]
Characteristics
Spectral type	A2IV[3][4] or A1V[5] or A2III[6]
B−V color index	+0.042±0.007[2]
Astrometry
Radial velocity (Rv)	+7.5±0.4[2] km/s
Proper motion (μ)	RA: +27.59[1] mas/yr Dec.: −30.73[1] mas/yr
Parallax (π)	12.52 ± 0.17 mas[1]
Distance	261 ± 4 ly (80 ± 1 pc)
Absolute magnitude (MV)	0.21[2]
Details
Mass	2.10[7] M☉
Radius	3.45[8] R☉
Luminosity	75.06[2] L☉
Surface gravity (log g)	3.71[7] cgs
Temperature	9,169±312[7] K
Metallicity [Fe/H]	+0.06[2] dex
Rotational velocity (v sin i)	12[7] km/s
Age	403[7] Myr
Other designations
K Car, CD−71°1034, FK5 2842, GC 14457, HD 91375, HIP 51438, HR 4138, SAO 256722[9]
Database references
SIMBAD	data

This object is a superficially normal^[4] A-type star. However, there is some disagreement over the evolutionary state of the star, as it has received luminosity classifications of a subgiant,^[4] main sequence,^[5] and a giant star.^[6] Unexpectedly for an A-type star, a magnetic field has been detected.^[4] It is around 400 million years old and has a low projected rotational velocity of 12 km/s.^[7] The star displays an infrared excess,^[10] indicating the presence of an orbiting debris disk with a black body temperature of 45 K at a separation of 314.2 AU from the host star.^[8]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
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.; Garrison, R. F. (1987), "The Early A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation", The Astrophysical Journal Supplement Series, 65: 581, Bibcode:1987ApJS...65..581G, doi:10.1086/191237.
4. Mathys, G.; Hubrig, S. (July 2006), "The diagnosis of the mean quadratic magnetic field of Ap stars", Astronomy and Astrophysics, 453 (2): 699–715, Bibcode:2006A&A...453..699M, doi:10.1051/0004-6361:20054353.
5. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1975mcts.book.....H.
6. Levato, O. H. (August 1972), "Rotational Velocities and Spectral Types of Some A-Type Stars", Publications of the Astronomical Society of the Pacific, 84 (500): 584, Bibcode:1972PASP...84..584L, doi:10.1086/129336.
7. 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, S2CID 33401607.
8. Cotten, Tara H.; Song, Inseok (July 2016), "A Comprehensive Census of Nearby Infrared Excess Stars", The Astrophysical Journal Supplement Series, 225 (1): 24, arXiv:1606.01134, Bibcode:2016ApJS..225...15C, doi:10.3847/0067-0049/225/1/15, S2CID 118438871, 15.
9. "HD 91375". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-12-06.
10. Rodriguez, David R.; Zuckerman, B. (February 2012), "Binaries among Debris Disk Stars", The Astrophysical Journal, 745 (2): 147, arXiv:1111.5618, Bibcode:2012ApJ...745..147R, doi:10.1088/0004-637X/745/2/147, S2CID 73681879.
11. Kostjuk, N. D. (2004), "VizieR Online Data Catalog: HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index (Kostjuk, 2002)", VizieR On-line Data Catalog: IV/27A. Originally Published in: Institute of Astronomy of Russian Academy of Sciences (2002), 4027, Bibcode:2004yCat.4027....0K.
12. Palous, J.; Hauck, B. (July 1986), "The Sirius supercluster", Astronomy and Astrophysics, 162: 54–61, Bibcode:1986A&A...162...54P.