Astronomy:4 Sagittarii

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Short description: Astrometric binary star in the constellation Sagittarius
4 Sagittarii
Sagittarius constellation map.svg
Red circle.svg
Location of 4 Sagittarii (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Sagittarius
Right ascension  17h 59m 47.55132s[1]
Declination −23° 48′ 58.0269″[1]
Apparent magnitude (V) 4.74[2]
Characteristics
Spectral type B9V[3]
U−B color index −0.03[4]
B−V color index -0.05[4]
Astrometry
Radial velocity (Rv)−18.00[5] km/s
Proper motion (μ) RA: +3.673[1] mas/yr
Dec.: −50.327[1] mas/yr
Parallax (π)8.3677 ± 0.4521[1] mas
Distance390 ± 20 ly
(120 ± 6 pc)
Absolute magnitude (MV)−0.77[2]
Details
Mass3.23[6] M
Luminosity240[6] L
Temperature9,661[6] K
Rotational velocity (v sin i)149[6] km/s
Other designations
4 Sgr, CD−23°13731, FK5 3430, GC 24483, HD 163955, HIP 88116, HR 6700, SAO 186061, GSC 06841-01403[7]
Database references
SIMBADdata

4 Sagittarii is a suspected astrometric binary[8] star system in the zodiac constellation of Sagittarius, located approximately 390 light years away based on parallax.[1] It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of 4.74,[2] The system is moving closer to the Earth with a heliocentric radial velocity of −18 km/s.[5]

The visible component is a B-type main-sequence star with a stellar classification of B9 V.[3] It has a high rate of spin, displaying a projected rotational velocity of 149 km/s.[6] This is giving it an oblate shape with an equatorial bulge that is an estimated 14% larger than the polar radius.[9] 4 Sagittarii has 3.23 times the mass of the Sun and is radiating 240 times the Sun's luminosity from its photosphere at an effective temperature of 9,661 K.[6]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. 2.0 2.1 2.2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode2012AstL...38..331A.  Vizier catalog entry
  3. 3.0 3.1 Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H 5050. Bibcode1995yCat.5050....0H. 
  4. 4.0 4.1 Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers 42 (2): 443. Bibcode2014JAVSO..42..443M. Vizier catalog entry
  5. 5.0 5.1 Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. Bibcode2006AstL...32..759G. 
  6. 6.0 6.1 6.2 6.3 6.4 6.5 Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars". Astronomy & Astrophysics 537: A120. doi:10.1051/0004-6361/201117691. Bibcode2012A&A...537A.120Z.  Vizier catalog entry
  7. "4 Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=4+Sgr. 
  8. Eggleton, P. P.; Tokovinin, A. A. (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. Bibcode2008MNRAS.389..869E. 
  9. van Belle, Gerard T. (March 2012). "Interferometric observations of rapidly rotating stars". The Astronomy and Astrophysics Review 20 (1): 51. doi:10.1007/s00159-012-0051-2. Bibcode2012A&ARv..20...51V.