Astronomy:V957 Scorpii

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V957 Scorpii
Scorpius constellation map.svg
Red circle.svg
Location of V957 Scorpii (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Scorpius
Right ascension  17h 52m 13.662s[1]
Declination −34° 47′ 57.11″[1]
Apparent magnitude (V) 5.87[2]
Characteristics
Spectral type B5 IIIp[3]
U−B color index −0.64[4]
B−V color index −0.10[4]
Variable type SX Ari[2]
Astrometry
Radial velocity (Rv)−9.70[5] km/s
Proper motion (μ) RA: 3.148[1] mas/yr
Dec.: −5.604[1] mas/yr
Parallax (π)3.6766 ± 0.1521[1] mas
Distance890 ± 40 ly
(270 ± 10 pc)
Absolute magnitude (MV)−1.441[6]
Details
Mass5.13[7] M☉
Radius4.00[7] R☉
Luminosity1,148[7] L☉
Surface gravity (log g)3.94[7] cgs
Temperature16,600[7] K
Metallicity [Fe/H]+0.01[8] dex
Rotational velocity (v sin i)30[9] km/s
Age50[7] Myr
Other designations
V957 Sco, HR 6647, HD 162374, CD−34°12165, SAO 209383, HIP 87460
Database references
SIMBADdata

V957 Scorpii is a variable star in the constellation of Scorpius. It is a blue straggler in the open cluster Messier 7, a star that is unexpectedly hot compared to other members of the cluster.

Spectrum

Messier 7 (M7), with V957 Scorpii the bright star to the right of the central square

V957 Scorpii shows a peculiar B5 or B6 spectrum. Its luminosity class has been given as main sequence (V), subgiant (IV), giant (III), and supergiant (Ib).[10] From its position in the H-R diagram, it is actually thought to be a main sequence star.[11] With a helium abundance 25 times lower than that of the sun,[12] it is classified as helium-weak. It also has a low carbon abundance and a strong magnetic field.[7]

Messier 7

A light curve for V957 Scorpii, plotted from TESS data.[13] The inset plot shows the same data averaged over several cycles.

Messier 7 is a naked-eye open cluster. Except for one obvious orange giant star, its brightest members are mostly early A and late B main sequence stars and giants. Several of them are also chemically peculiar stars. However, two stars are hotter than the others and lie to the left of the isochrone for the cluster. These are the blue stragglers HD 162586 and V957 Scorpii. V957 Scorpii is considered 92% likely to be a member of M7. M7 has an age around 220 million years, but the apparent age of V957 Scorpii is less than 100 million years.[12]

Variability

V957 Scorpii varies in brightness by about 0.05 magnitudes. This is thought to be due to its rotation and variations in its surface brightness. It is classified as an SX Arietis variable, also known as helium variables. Their spectral lines also vary as the stars rotate.[2]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 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. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 Samus, N. N. 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: B/gcvs. Bibcode: 2009yCat....102025S. 
  3. ↑ Abt, H. A. (1985). "The spectra and ages of blue stragglers". The Astrophysical Journal 294: L103. doi:10.1086/184518. Bibcode: 1985ApJ...294L.103A. 
  4. ↑ 4.0 4.1 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. Bibcode: 1995yCat.5050....0H. 
  5. ↑ Conti, P. S.; Hensberge, G.; Van Den Heuvel, E. P. J.; Stickland, D. J. (1974). "A study of the blue stragglers in Praesepe, M7 and the Hyades cluster". Astronomy and Astrophysics 34: 393. Bibcode: 1974A&A....34..393C. 
  6. ↑ Silaj, J.; Landstreet, J. D. (2014). "Accurate age determinations of several nearby open clusters containing magnetic Ap stars". Astronomy and Astrophysics 566: A132. doi:10.1051/0004-6361/201321468. Bibcode: 2014A&A...566A.132S. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 Glagolevskij, Yu. V. (2019). "On Properties of Main Sequence Magnetic Stars". Astrophysical Bulletin 74 (1): 66. doi:10.1134/S1990341319010073. Bibcode: 2019AstBu..74...66G. 
  8. ↑ Gontcharov, G. A. (2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters 38 (12): 771–782. doi:10.1134/S1063773712120031. Bibcode: 2012AstL...38..771G. 
  9. ↑ Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics 537: A120. doi:10.1051/0004-6361/201117691. Bibcode: 2012A&A...537A.120Z. 
  10. ↑ Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009- )". VizieR On-line Data Catalog. Bibcode: 2014yCat....1.2023S. 
  11. ↑ Mermilliod, J. -C (1982). "Stellar content of young open clusters. I. Blue stragglers". Astronomy and Astrophysics 109: 37. Bibcode: 1982A&A...109...37M. 
  12. ↑ 12.0 12.1 Andrievsky, S. M.; Schönberner, D.; Drilling, J. S. (2000). "Blue stragglers in open clusters. Part II". Astronomy and Astrophysics 356: 517. Bibcode: 2000A&A...356..517A. 
  13. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 



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