HD 77191
  | |
| Observation data Epoch J2000[1] Equinox J2000[1] | |
|---|---|
| Constellation | Cetus |
| Right ascension | 09h 01m 22.77660s |
| Declination | +10° 43′ 58.5175″ |
| Apparent magnitude (V) | 8.88[2] |
| Characteristics | |
| Spectral type | G0V[3] + M[4] |
| B−V color index | +0.63[2] |
| J−H color index | +0.294[5] |
| J−K color index | +0.390[5] |
| Variable type | BY Draconis variable[6] |
| Astrometry | |
| Radial velocity (Rv) | 7.10±0.1[7] km/s |
| Proper motion (μ) | RA: −12.524[1] mas/yr Dec.: 4.156[1] mas/yr |
| Parallax (π) | 16.4293 ± 0.0623 mas[1] |
| Distance | 198.5 ± 0.8 ly (60.9 ± 0.2 pc) |
| Absolute magnitude (MV) | 4.83±0.16[4] |
| Orbit[4] | |
| Primary | HD 77191 A |
| Companion | HD 77191 B |
| Period (P) | 44.32±0.29 d |
| Semi-major axis (a) | (9.87±0.10)×106 km (minimum) |
| Eccentricity (e) | 0.315±0.008 |
| Inclination (i) | 105.1±3.5° |
| Periastron epoch (T) | 53494.80±0.19 |
| Argument of periastron (ω) (secondary) | 297.5±2.2° |
| Details[8] | |
| HD 77191 A | |
| Mass | 1.01±0.02 M☉ |
| Radius | 0.93±0.02 R☉ |
| Surface gravity (log g) | 4.51±0.02 cgs |
| Temperature | 5785±40 K |
| Metallicity [Fe/H] | −0.02±0.03 dex |
| Rotation | 10.0±0.2 d[4] |
| Rotational velocity (v sin i) | 4.5±0.5[4] km/s |
| Age | 1.46±1.26 Gyr |
| HD 77191 B | |
| Mass | ~0.38[4] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | HD 77191 |
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
[edit]
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
[edit]- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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. doi:10.1051/0004-6361/200913437. ISSN 0004-6361. Retrieved 22 December 2024.
- ^ 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. doi:10.1051/0004-6361/201834285. ISSN 0004-6361. Retrieved 22 December 2024.
- ^ "HD 77191". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 22 December 2024.
- ^ Zarenski, Ed (2004). "Limiting Magnitude in Binoculars" (PDF). Cloudy Nights. Archived (PDF) from the original on 21 July 2011. Retrieved 6 May 2011.
- ^ 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). doi:10.1515/astro-2017-0244. ISSN 2543-6376. Retrieved 22 December 2024. Record for this source at VizieR.
- ^ Mamajek, Eric E.; Bartlett, Jennifer L.; Seifahrt, Andreas (2013). "The Solar Neighborhood XXX: Fomalhaut C". The Astronomical Journal. 146: 154. arXiv:1310.0764. Bibcode:2013AJ....146..154M. doi:10.1088/0004-6256/146/6/154.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
