Theta2 Sagittarii

Theta2 Sagittarii
Diagram showing star positions and boundaries of the Sagittarius constellation and its surroundings


Location of θ2 Sagittarii (circled)

Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagittarius
Right ascension 19h 59m 51.35684s[1]
Declination −34° 41′ 52.0797″[1]
Apparent magnitude (V) +5.30[2]
Characteristics
Spectral type A4/A5 IV[3]
U−B color index +0.06[2]
B−V color index +0.17[2]
Astrometry
Radial velocity (Rv)−17.60[4] km/s
Proper motion (μ) RA: +108.23[1] mas/yr
Dec.: −69.51[1] mas/yr
Parallax (π)20.62 ± 0.28[1] mas
Distance158 ± 2 ly
(48.5 ± 0.7 pc)
Details
Mass1.93[5] M☉
Luminosity14[6] L☉
Surface gravity (log g)4.07±0.14[5] cgs
Temperature8,113±276[5] K
Rotational velocity (v sin i)45.2±0.5[7] km/s
Age809[5] Myr
Other designations
θ2 Sgr, CPD−35° 8701, HD 189118, HIP 98421, HR 7624, SAO 211717, WDS J19599-3442[8]
Database references
SIMBADdata

Theta2 Sagittarii (θ2 Sagittarii) is a solitary[9] star in the zodiac constellation of Sagittarius. It is faintly visible to the naked eye with an apparent visual magnitude of +5.30.[2] The star is progressing in the general direction of the Sun with a radial velocity of −17.60 km/s.[4] Based upon an annual parallax shift of 20.62 mas as seen from Earth,[1] it is located around 158 light years from the Sun.

The spectrum of Theta2 Sagittarii matches a stellar classification of A4/A5 IV,[3] indicating that, at the estimated age of 809 million years,[5] this is an evolving A-type subgiant star. It is a suspected Am star and may display photometric variability, at least during a 1992 observation period.[10] The star has an estimated 1.93[5] times the mass of the Sun and is radiating 14[6] times the Sun's luminosity from its photoshere at an effective temperature of 8,113 K.[5] It is spinning with a projected rotational velocity of 45.2 km/s.[7]

Theta2 Sagittarii has a pair of visual companions. Component B is a magnitude 11.3 star at an angular separation of 32.8 arc seconds along a position angle of 165°, as of 2000. Component C lies at an angular separation of 1.5 arc seconds along a position angle of 104° from component B, as of 1965.[11] Neither is physically associated with Theta2 Sagittarii itself.[9]

References

  1. 1 2 3 4 5 6 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752 Freely accessible, doi:10.1051/0004-6361:20078357.
  2. 1 2 3 4 Mendoza, E. E.; et al. (June 1978), "UBVRI photometry of 225 AM stars", Astronomical Journal, 83: 606–614, Bibcode:1978AJ.....83..606M, doi:10.1086/112242.
  3. 1 2 Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 3, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1982MSS...C03....0H.
  4. 1 2 Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  5. 1 2 3 4 5 6 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, Bibcode:2015ApJ...804..146D, arXiv:1501.03154 Freely accessible, doi:10.1088/0004-637X/804/2/146.
  6. 1 2 McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, Bibcode:2012MNRAS.427..343M, arXiv:1208.2037 Freely accessible, doi:10.1111/j.1365-2966.2012.21873.x.
  7. 1 2 Díaz, C. G.; et al. (July 2011), "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum", Astronomy & Astrophysics, 531: A143, Bibcode:2011A&A...531A.143D, arXiv:1012.4858 Freely accessible, doi:10.1051/0004-6361/201016386.
  8. ↑ "tet02 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-07.
  9. 1 2 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, Bibcode:2008MNRAS.389..869E, arXiv:0806.2878 Freely accessible, doi:10.1111/j.1365-2966.2008.13596.x.
  10. ↑ Anders, G. J. (September 1992), "Theta2 Sgr: Serendipitous Discovery of Variability in an Am Star?", Information Bulletin on Variable Stars, 3768: 1, Bibcode:1992IBVS.3768....1A.
  11. ↑ Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.