Omicron Gruis

ο Gruis, Latinised as Omicron Gruis, is a binary or triple star[4] system in the southern constellation of Grus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.52.[2] Based upon an annual parallax shift of 32.50 mas as seen from the Earth,[1] the system is located 100 light years from the Sun.

Omicron Gruis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Grus
Right ascension 23h 26m 36.57748s[1]
Declination −52° 43′ 17.7656″[1]
Apparent magnitude (V) 5.52[2]
Characteristics
Spectral type F4 V[3] + M3/M4[4]
B−V color index +0.40[2]
Variable type δ Sct[5]
Astrometry
Proper motion (μ) RA: +34.52[1] mas/yr
Dec.: +130.66[1] mas/yr
Parallax (π)32.50 ± 0.37 mas[1]
Distance100 ± 1 ly
(30.8 ± 0.4 pc)
Absolute magnitude (MV)3.01[6]
Details
ο Gru A
Mass1.31[7] M☉
Surface gravity (log g)4.19[7] cgs
Temperature6,763±230[7] K
Metallicity [Fe/H]–0.10[3] dex
Rotational velocity (v sin i)20.4±0.3[6] km/s
Age1.026[7] Gyr
ο Gru B
Mass0.3[4] M☉
Age1.1[4] Gyr
Other designations
ο Gru, CD−53° 10461, HD 220729, HIP 115713, HR 8907, SAO 247874[8]
Database references
SIMBADdata

The pair form a close spectroscopic binary system with a physical separation of about 14.9 astronomical units.[4] The primary component is an F-type main sequence star with a stellar classification of F4 V,[3] a star that is currently fusing its core hydrogen. It is a probable delta scuti variable showing periodicities of 4.7 and 5.5 cycles per day with amplitudes of 0.014 and 0.011 magnitudes, respectively.[5] The secondary companion is a red dwarf with a mass of about 0.3 solar, suggesting a class of M3/M4.[4] Ehrenreich et al. (2010) noted the detection of a tertiary companion that is not causing the detected radial velocity shifts which would make this a triple star system.[4]

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. Lake, R. (1965), "Photometric Magnitudes and Colours for Bright Southern Stars (Sixth List)", Monthly Notes of the Astronomical Society of Southern Africa, 24: 41, Bibcode:1965MNSSA..24...41L.
  3. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  4. Ehrenreich, D.; et al. (November 2010), "Deep infrared imaging of close companions to austral A- and F-type stars", Astronomy and Astrophysics, 523: A73, arXiv:1007.0002, Bibcode:2010A&A...523A..73E, doi:10.1051/0004-6361/201014763, S2CID 54913363.
  5. Lampens, P.; et al. (April 2000), "delta Scuti stars in stellar systems: On the variability of HD 220392 and HD 220391", Astronomy and Astrophysics, 356: 895–902, arXiv:astro-ph/0002465, Bibcode:2000A&A...356..895L.
  6. Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
  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. "pi.02 Gru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-25.
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