V4024 Sagittarii

V4024 Sagittarii is a single[10] variable star in the southern constellation of Sagittarius. It has a blue-white hue and is dimly visible to the naked eye with an apparent visual magnitude that fluctuates around 5.49.[2] The star is located at a distance of approximately 1,700 light years based on stellar parallax,[1] but is drifting closer with a radial velocity of −20 km/s.[5] The position of this star near the ecliptic means it is subject to lunar occultations.[11]

V4024 Sagittarii
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension  19h 08m 16.70160s[1]
Declination −19° 17′ 25.0393″[1]
Apparent magnitude (V) 5.49[2]
Characteristics
Spectral type B2Ve[3]
B−V color index −0.06[2]
Variable type γ Cas[4]
Astrometry
Radial velocity (Rv)−20.3±2.9[5] km/s
Proper motion (μ) RA: +6.384[1] mas/yr
Dec.: −1.020[1] mas/yr
Parallax (π)1.9550 ± 0.2373[1] mas
Distanceapprox. 1,700 ly
(approx. 510 pc)
Absolute magnitude (MV)−2.39[5]
Details[6]
Mass8.8±0.6 M☉
Radius4.5[7] R☉
Luminosity (bolometric)7,551+1,119
−974 L☉
Surface gravity (log g)3.24±0.49 cgs
Temperature18,100±500 K
Rotational velocity (v sin i)105±10 km/s
Age25.1±1.3[8] Myr
Other designations
V4024 Sgr, BD−19°5312, HD 178175, HIP 93996, HR 7249, SAO 162229[9]
Database references
SIMBADdata

This object is a massive Be star with a stellar classification of B2Ve.[3] The 'e' suffix indicates the spectrum of the star displays emission lines, which are created by materials ejected from the equatorial region of this rapidly rotating star. It is classified as an eruptive Gamma Cassiopeiae variable and has been measured ranging in brightness from visual magnitude 5.34 down to 5.60.[4] The star is an estimated 5 million years old with 8.8 times the mass of the Sun[8] and about 4.5[7] times the Sun's radius. It is spinning with a projected rotational velocity of 105 m/s. V4024 Sagittarii is radiating 7,551 times the luminosity of the Sun from its photosphere at an effective temperature of 18,100 K.[6]

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. Chauville, J.; et al. (November 2001). "High and intermediate-resolution spectroscopy of Be stars 4481 lines". Astronomy and Astrophysics. 378: 861–882. Bibcode:2001A&A...378..861C. doi:10.1051/0004-6361:20011202.
  3. Jaschek, C.; Jaschek, M. (November 1992). "A southern Be star survey: Spectra and envelope radii". Astronomy and Astrophysics Supplement Series. 95 (3): 535–540. Bibcode:1992A&AS...95..535J.
  4. Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085.
  5. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015.
  6. Zorec, J.; et al. (November 2016), "Critical study of the distribution of rotational velocities of Be stars. I. Deconvolution methods, effects due to gravity darkening, macroturbulence, and binarity", Astronomy & Astrophysics, 595: 26, Bibcode:2016A&A...595A.132Z, doi:10.1051/0004-6361/201628760
  7. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  8. Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  9. "HD 178175". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-21.
  10. 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.
  11. Mason, Brian D. (November 1996). "ICCD Speckle Observations of Binary Stars. XV. An Investigation of Lunar Occultation Systems". Astronomical Journal. 112: 2260. Bibcode:1996AJ....112.2260M. doi:10.1086/118179.
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