HD 77191 is a spectroscopic binary composed of a Sun-like variable star and a probable red dwarf,[4] located in the zodiac constellation of Cancer. It has the variable-star designation HL Cancri (abbreviated to HL Cnc). With an apparent magnitude of 8.88, it is too faint to be seen by the naked eye but observable using binoculars[10] as a yellow-hued dot of light. It is located at a distance of 198.5 light-years (60.9 parsecs) according to Gaia EDR3 parallax measurements, and is receding farther away from the Sun at a heliocentric radial velocity of 7.10 km/s.

The star is part of the Castor stream,[11] a moving group of young stars that includes some of the brightest stars in the night sky, such as Castor, Fomalhaut, and Vega.[12]

Stellar properties

A light curve for HL Cancri, plotted from TESS data.[13] The 10 day rotation period is marked in red.

The primary star is a G-type main-sequence star with the spectral type G0V, almost identical to the Sun in mass, effective temperature, and metallicity, but approximately 7% smaller in radius. Its spectrum shows clear signs of high stellar activity and a strong lithium doublet spectral line at wavelength 6707.8 Å, indicative of its youth,[6] with an estimated age of 1.46±1.26 Gyr. Accordingly, the star displays large starspots, which are responsible for slight variations in its brightness, first discovered in 2000[3] with a mean amplitude of about 0.025 mag and a period of 10.0±0.2 d (which is also the star's rotation period).[4] Hence, the star is classified as a BY Draconis variable.[6]

Data collected by Hipparcos suggested that the star was single,[3] but radial velocity observations via the Coravel spectrograph at the University of Cambridge yielded a 44-day period orbit for a binary companion. By matching the primary's rotational velocities measured through Doppler broadening and its photometric period, the mass of the unseen secondary star is placed at roughly 0.38 M☉, making it likely a red dwarf.[4]

References

  1. ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ^ a b Høg, E.; et al. (February 2000). "The Tycho-2 Catalogue of the 2.5 Million Brightest Stars". Astronomy and Astrophysics. 355 (1): L27 – L30. Bibcode:2000A&A...355L..27H.
  3. ^ a b c Lebzelter, T. (5 September 2000). "HD 77191: Another Variable Solar Twin". Information Bulletin on Variable Stars. 4949 (1). Konkoly Observatory, Budapest: International Astronomical Union. Bibcode:2000IBVS.4949....1L.
  4. ^ a b c d e f g h i Griffin, R. F. (October 2005). "The BY Dra Star HD 77191 Is a Spectroscopic Binary, but GQ Leo May Not Be". The Observatory. 125: 323–325. Bibcode:2005Obs...125..323G.
  5. ^ a b Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  6. ^ a b c Dall, T. H. (9 December 2004). "Spectroscopic Confirmation of Three Suspected BY Dra Variables". Information Bulletin on Variable Stars. 5581 (1). Konkoly Observatory, Budapest: International Astronomical Union. Bibcode:2004IBVS.5581....1D.
  7. ^ López-Santiago, J.; Montes, D.; Gálvez-Ortiz, M. C.; Crespo-Chacón, I.; Martínez-Arnáiz, R. M.; Fernández-Figueroa, M. J.; de Castro, E.; Cornide, M. (2010). "A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age" (PDF). Astronomy and Astrophysics. 514: A97. arXiv:1002.1663. Bibcode:2010A&A...514A..97L. doi:10.1051/0004-6361/200913437. ISSN 0004-6361. Retrieved 22 December 2024.
  8. ^ Adibekyan, V.; de Laverny, P.; Recio-Blanco, A.; Sousa, S. G.; Delgado-Mena, E.; Kordopatis, G.; Ferreira, A. C. S.; Santos, N. C.; Hakobyan, A. A.; Tsantaki, M. (2018). "The AMBRE project: searching for the closest solar siblings" (PDF). Astronomy & Astrophysics. 619: A130. arXiv:1810.01813. Bibcode:2018A&A...619A.130A. doi:10.1051/0004-6361/201834285. ISSN 0004-6361. Retrieved 22 December 2024.
  9. ^ "HD 77191". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 22 December 2024.
  10. ^ Zarenski, Ed (2004). "Limiting Magnitude in Binoculars" (PDF). Cloudy Nights. Archived (PDF) from the original on 21 July 2011. Retrieved 6 May 2011.
  11. ^ Vereshchagin, S. V.; Chupina, N. V. (1 January 2015). "Details of the Spatial Structure and Kinematics of the Castor and Ursa Major Streams". Open Astronomy. 24 (4): 421. arXiv:1603.03159. Bibcode:2015BaltA..24..421V. doi:10.1515/astro-2017-0244. ISSN 2543-6376. Record for this source at VizieR.
  12. ^ Mamajek, Eric E.; Bartlett, Jennifer L.; Seifahrt, Andreas (2013). "The Solar Neighborhood XXX: Fomalhaut C". The Astronomical Journal. 146 (6): 154. arXiv:1310.0764. Bibcode:2013AJ....146..154M. doi:10.1088/0004-6256/146/6/154.
  13. ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
Allikas: http://en.wikipedia.org/wiki/HD_77191
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