SV Vulpeculae

SV Vulpeculae is a Classical Cepheid (δ Cepheid) variable star in the constellation Vulpecula. It is a supergiant at a distance of 8,700 light years.

SV Vulpeculae
Observation data
Epoch J2000      Equinox J2000
Constellation Vulpecula
Right ascension  19h 51m 30.9060s[1]
Declination 27° 27′ 36.8356″[1]
Apparent magnitude (V) 6.72 - 7.79[2]
Characteristics
Spectral type F7Iab-K0Iab[2]
U−B color index +0.868 - +1.659[3]
B−V color index +1.149 - +1.786[3]
Variable type δ Cep[2]
Astrometry
Radial velocity (Rv)−2.00[4] km/s
Proper motion (μ) RA: −2.139±0.045[1] mas/yr
Dec.: −5.820±0.050[1] mas/yr
Parallax (π)0.3729 ± 0.0303[1] mas
Distance8,700 ± 700 ly
(2,700 ± 200 pc)
Absolute magnitude (MV)−6.21[5]
Details
Mass14.6 - 15.8[6] M☉
Radius187.9 - 238.4[7] R☉
Luminosity19,800[8] L☉
Surface gravity (log g)0.50 - 1.60[9] cgs
Temperature4,861 - 6,110[9] K
Metallicity+0.05[9]
Other designations
SV Vul, HD 187921, HIP 97717, BD+27°3536
Database references
SIMBADdata

SV Vulpeculae is a δ Cepheid variable whose visual apparent magnitude ranges from 6.72 to 7.79 over 45.0121 days. The light curve is highly asymmetric, with the rise from minimum to maximum taking more less than a third of the time for the fall from maximum to minimum.[10] The period has been decreasing on average by 214 seconds/year.[8]

SV Vulpeculae is a yellow bright supergiant around twenty thousand times as luminous as the sun, with a spectral type that varies from late F to early K. It pulsates and varies in temperature from below 5,000 K to above 6,000 K.[9] The radius is 216.5 R☉ at maximum, and varies from 188 R☉ to 238 R☉ as the star pulsates.[7]

The mass of SV Vulpeculae is now near 15 M☉, and is estimated to have been about 17 M☉ when it was on the main sequence. The rate of change of the period and the atmospheric abundances show that the star is crossing the instability strip for the second time. The first instability strip crossing occurs rapidly during the transition from the main sequence to becoming a red supergiant. The second crossing occurs during core helium burning when the star executes a blue loop, becoming hotter for a time before returning to the red supergiant stage.[8]

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. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. Berdnikov, L. N. (2008). "VizieR Online Data Catalog: Photoelectric observations of Cepheids in UBV(RI)c (Berdnikov, 2008)". VizieR On-line Data Catalog: II/285. Originally Published in: 2008yCat.2285....0B. 2285. Bibcode:2008yCat.2285....0B.
  4. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  5. Groenewegen, M. A. T. (2008). "Baade-Wesselink distances and the effect of metallicity in classical cepheids". Astronomy and Astrophysics. 488 (1): 25. arXiv:0807.1269. Bibcode:2008A&A...488...25G. doi:10.1051/0004-6361:200809859.
  6. Caputo, F.; Bono, G.; Fiorentino, G.; Marconi, M.; Musella, I. (2005). "Pulsation and Evolutionary Masses of Classical Cepheids. I. Milky Way Variables". The Astrophysical Journal. 629 (2): 1021–1033. arXiv:astro-ph/0505149. Bibcode:2005ApJ...629.1021C. doi:10.1086/431641.
  7. Imbert, M. (1999). "Détermination des rayons de Céphéides. V. Vitesses radiales et dimensions de 22 Céphéides galactiques. Determination of the radii of Cepheids V. Radial velocities and dimensions of 22 galactic Cepheids". Astronomy and Astrophysics Supplement. 140: 79–87. Bibcode:1999A&AS..140...79I. doi:10.1051/aas:1999515.
  8. Turner, D. G.; Berdnikov, L. N. (2004). "On the crossing mode of the long-period Cepheid SV Vulpeculae". Astronomy and Astrophysics. 423: 335–340. Bibcode:2004A&A...423..335T. doi:10.1051/0004-6361:20040163.
  9. Kovtyukh, V. V.; Andrievsky, S. M.; Belik, S. I.; Luck, R. E. (2005). "Phase-dependent Variation of the Fundamental Parameters of Cepheids. II. Periods Longer than 10 Days". The Astronomical Journal. 129 (1): 433–453. Bibcode:2005AJ....129..433K. doi:10.1086/426339.
  10. Schaltenbrand, R.; Tammann, G. A. (1971). "The light curve parameters of photoelectrically observed galactic Cepheids". Astronomy and Astrophysics Supplement. 4: 265. Bibcode:1971A&AS....4..265S.
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