Pi2 Gruis

π² Gruis, Latinised as Pi² Gruis, is a binary star^[3] system in the southern constellation of Grus. It is faintly visible to the naked eye as a yellow-white hued star with an apparent visual magnitude of 5.622.^[2] Based upon an annual parallax shift of 25.1 mas as seen from the Earth,^[1] the system is located 130 light years from the Sun.

For other stars with this Bayer designation, see π Gruis.

Pi² Gruis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Grus
Right ascension	22h 23m 07.98704s[1]
Declination	−45° 55′ 42.5582″[1]
Apparent magnitude (V)	5.622[2] (5.71 + 11.3)[3]
Characteristics
Spectral type	F3 III-IV[4][3] or F0 V[5]
U−B color index	+0.016[2]
B−V color index	+0.365[2]
Astrometry
Radial velocity (Rv)	3.0[6] km/s
Proper motion (μ)	RA: +233.166[1] mas/yr Dec.: −58.205[1] mas/yr
Parallax (π)	25.1061 ± 0.1256 mas[1]
Distance	129.9 ± 0.6 ly (39.8 ± 0.2 pc)
Absolute magnitude (MV)	2.62[7]
Details
π2 Gru A
Mass	1.37[8] M☉
Radius	1.93±0.07[1] R☉
Luminosity	7.15±0.04[1] L☉
Surface gravity (log g)	4.20[8] cgs
Temperature	6788+138 −101[1] K
Metallicity [Fe/H]	−0.06[6] dex
Age	758[8] Myr
Other designations
π2 Gru, CD−46°14295, FK5 3786, HD 212132, HIP 110506, HR 8524, SAO 231111, WDS J22231-4556[9]
Database references
SIMBAD	data

The primary, component A, is an F-type star of uncertain luminosity class. Malaroda (1975) gave it a stellar classification of F3 III-IV,^[4] which would indicate an evolving subgiant/giant star hybrid spectrum, whereas Houk (1978) listed it as class F0 V,^[5] suggesting that it is an F-type main sequence star. It has been considered to be a chemically peculiar star,^[10] but this is now considered doubtful.^[11] It is 758^[8] million years old with 1.4^[8] times the mass of the Sun. The star is 1.9^[1] times the Sun's radius and is radiating 7^[1] times the luminosity of the Sun from its photosphere at an effective temperature of 6,788 K.^[1]

The companion is a magnitude 11.3 star at an angular separation of 4.6 arc seconds.^[3] Gaia Data Release 2 has measured a separate annual parallax for it of 25.3266±0.0871 mas, almost identical to the primary star, and indicates that it is a red dwarf.^[12]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. Cousins, A. W. J. (1983), "UBV photometry of E region standard stars of intermediate brightness", South African Astronomical Observatory Circular, 7 (7): 36–46, Bibcode:1983SAAOC...7...36C.
3. 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.
4. Malaroda, S. (August 1975), "Study of the F-type stars. I. MK spectral types", Astronomical Journal, 80: 637–641, Bibcode:1975AJ.....80..637M, doi:10.1086/111786.
5. Houk, N. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 2, Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
6. Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276, S2CID 56118016.
7. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
8. 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.
9. "pi.02 Gru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-25.{{cite web}}: CS1 maint: postscript (link)
10. De Vaucouleurs, A. (1957), "Spectral types and luminosities of B, A and F southern stars", Monthly Notices of the Royal Astronomical Society, 117 (4): 449–462, Bibcode:1957MNRAS.117..449D, doi:10.1093/mnras/117.4.449.
11. Renson, P.; Manfroid, J. (2009), "Catalogue of Ap, HGMN and Am stars", Astronomy and Astrophysics, 498 (3): 961, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
12. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.