Delta2 Gruis

Delta2 Gruis, Latinized from δ2 Gruis, is a solitary,[7] red-hued star in the southern constellation of Grus. It is visible to the naked eye with an apparent visual magnitude of 4.11. [2] Based upon an annual parallax shift of 9.88 mas as seen from the Earth,[1] the star is located around 330 light years from the Sun. It is moving further away from the Sun with a radial velocity of +3 km/s.[4]

For other stars with this Bayer designation, see δ Gruis.
Delta2 Gruis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Grus
Right ascension 22h 29m 45.43402s[1]
Declination −43° 44′ 57.1968″[1]
Apparent magnitude (V) 4.11[2]
Characteristics
Spectral type M4.5 IIIa[3]
U−B color index +1.71[2]
B−V color index +1.57[2]
Astrometry
Radial velocity (Rv)+2.7±0.8[4] km/s
Proper motion (μ) RA: −14.08[1] mas/yr
Dec.: +2.57[1] mas/yr
Parallax (π)9.88 ± 0.23[1] mas
Distance330 ± 8 ly
(101 ± 2 pc)
Absolute magnitude (MV)−0.90±0.05[3]
Details
Rotational velocity (v sin i)+4.5±0.8[5] km/s
Other designations
δ2 Gru, CD−44° 14935, HD 213080, HIP 111043, HR 8560, SAO 231161, WDS J22298-4345A[6]
Database references
SIMBADdata

This is an evolved red giant star with a stellar classification of M4.5 IIIa.[3] It is a pulsating variable with multiple periods, including 20.6, 24.1, 24.5, and 32.3 days. The strongest period is 33.3 days with an amplitude of 0.043 magnitude.[8] It has a magnitude 9.71 visual companion at an angular separation of 60.4 arc seconds along a position angle of 210°, as of 2013.[9]

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. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73, S2CID 119187733.
  4. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  5. Zamanov, R. K.; et al. (October 2008), "Rotational velocities of the giants in symbiotic stars - III. Evidence of fast rotation in S-type symbiotics", Monthly Notices of the Royal Astronomical Society, 390 (1): 377–382, arXiv:0807.3817, Bibcode:2008MNRAS.390..377Z, doi:10.1111/j.1365-2966.2008.13751.x, S2CID 118697261.
  6. "del02 Gru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-18.
  7. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  8. Tabur, V.; Bedding, T. R. (2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–61, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380.
  9. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22
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