Astronomy:Pi Geminorum

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Short description: Star in the constellation Gemini
π Geminorum
Location of π Geminorum (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Gemini
Right ascension  07h 47m 30.32300s[1]
Declination +33° 24′ 56.5034″[1]
Apparent magnitude (V) 5.14[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M1 IIIa[4]
U−B color index +1.90[2]
B−V color index +1.59[2]
Variable type suspected[5]
Astrometry
Radial velocity (Rv)−13.36±0.34[6] km/s
Proper motion (μ) RA: -19.59[1] mas/yr
Dec.: -29.33[1] mas/yr
Parallax (π)4.93 ± 0.32[1] mas
Distance660 ± 40 ly
(200 ± 10 pc)
Absolute magnitude (MV)−1.04[7]
Details
Mass1.1[8] M☉
Radius57[9] R☉
Luminosity676[9] L☉
Surface gravity (log g)0.90[8] cgs
Temperature3,915[9] K
Metallicity [Fe/H]0.07[8] dex
Other designations
π Gem, 80 Geminorum, BD+33°1585, FK5 296, HD 62898, HIP 38016, HR 3013, SAO 60340.[10]
Database references
SIMBADdata

π Geminorum (Latinised as Pi Geminorum, abbreviated to π Gem or pi Gem) is a star located in the constellation Gemini, to the north of Castor. With an apparent visual magnitude of 5.14,[2] it is faintly visible to the naked eye on a dark night. Based upon an annual parallax shift of 4.93 mas,[1] Pi Geminorum is located roughly 660 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.033 due to interstellar dust.[7]

This is an evolved red giant star with a stellar classification of M1 IIIa.[4] The measured angular diameter of this star is 2.58±0.20 mas.[11] At the estimated distance of this star, this yields a physical size of about 56 times the radius of the Sun.[12] It is radiating roughly a thousand times the luminosity of the Sun from its outer atmosphere at an effective temperature of 3,900 K.

Unexpected for a red giant, Pi Geminorum was found to be a X-ray source during the ROSAT all-sky survey. The most likely source for this emission is a magnitude 11.4 star located at an angular separation of 21 arcseconds along a position angle of 214°.[13] This is a background star, not gravitationally bound to Pi Geminorum.[14]

In a 1930 study, Pi Geminorum was suspected to vary in brightness by a few hundredths of a magnitude, but this has not been confirmed by modern measurements.[5]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M. 
  3. ↑ Eggen, Olin J. (1992), "Asymptotic Giant Branch Stars Near the Sun", The Astronomical Journal 104: 275, doi:10.1086/116239, Bibcode: 1992AJ....104..275E. 
  4. ↑ 4.0 4.1 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  5. ↑ 5.0 5.1 Samus, N. N. et al. (2004). "VizieR Online Data Catalog: Combined General Catalogue of Variable Stars (Samus+ 2004)". Vizier Online Data Catalog. Bibcode: 2004yCat.2250....0S. 
  6. ↑ Famaey, B. et al. (2009), "Spectroscopic binaries among Hipparcos M giants. I. Data, orbits, and intrinsic variations", Astronomy and Astrophysics 498 (2): 627–640, doi:10.1051/0004-6361/200810698, Bibcode: 2009A&A...498..627F. 
  7. ↑ 7.0 7.1 Ryon, Jenna et al. (August 2009), "Comparing the Ca ii H and K Emission Lines in Red Giant Stars", Publications of the Astronomical Society of the Pacific 121 (882): 842–856, doi:10.1086/605456, Bibcode: 2009PASP..121..842R. 
  8. ↑ 8.0 8.1 8.2 Anders, F.; Khalatyan, A.; Chiappini, C.; Queiroz, A. B.; Santiago, B. X.; Jordi, C.; Girardi, L.; Brown, A. G. A. et al. (2019), "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18", Astronomy and Astrophysics 628: A94, doi:10.1051/0004-6361/201935765, Bibcode: 2019A&A...628A..94A. 
  9. ↑ 9.0 9.1 9.2 Fetherolf, Tara; Pepper, Joshua; Simpson, Emilie; Kane, Stephen R.; Močnik, Teo; English, John Edward; Antoci, Victoria; Huber, Daniel et al. (2023), "Variability Catalog of Stars Observed during the TESS Prime Mission", The Astrophysical Journal Supplement Series 268 (1): 4, doi:10.3847/1538-4365/acdee5, Bibcode: 2023ApJS..268....4F. 
  10. ↑ "pi. Gem". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=pi.+Gem. 
  11. ↑ Richichi, A. et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode: 2005A&A...431..773R. 
  12. ↑ Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1, https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41. . The radius (R*) is given by:
    2⋅R*=(203⋅2.58⋅10−3) AU0.0046491 AU/R⨀≈112.6⋅R⨀
  13. ↑ Hunsch, Matthias et al. (February 1998), "On the X-ray emission from M-type giants", Astronomy and Astrophysics 330: 225–231, Bibcode: 1998A&A...330..225H. 
  14. ↑ Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.



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