HD 77191

HD 77191

Location of HD 77191 (circled)
Observation data Epoch J2000[1]      Equinox J2000[1]
Constellation	Cetus
Right ascension	09^h 01^m 22.77660^s
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)×10^6 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
HL Cancri, AG+10°1163, BD+11°1961, Gaia DR3 603701328976020864, HD 77191, HIP 44303, SAO 98298, PPM 126017, TIC 323492976, TYC 815-2116-1, GSC 00815-02116, 2MASS J09012277+1043585[9]
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

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. 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. 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. 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. 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. 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. 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.