SY Equulei

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SY Equulei
SYEquLightCurve.png
A light curve for SY Equulei, plotted from Hipparcos data [1]
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Equuleus
Right ascension 21h 23m 28.8086s [2]
Declination +09° 55′ 54.9204″ [2]
Apparent magnitude  (V)8.52 - 8.58 [3]
Characteristics
Spectral type B0.5 IIIn [4]
U−B color index −1.00 [5]
B−V color index −0.20 [5]
Variable type β Cephei [6]
Astrometry
Radial velocity (Rv)48±5.5 [7]  km/s
Proper motion (μ)RA: −0.185  mas/yr [2]
Dec.: −9.049  mas/yr [2]
Parallax (π)0.3869 ± 0.0558  mas [2]
Distance approx. 8,000  ly
(approx. 2,600  pc)
Absolute bolometric
magnitude  (Mbol)		−6.04 [8]
Details
Mass 14 [9]   M☉
Radius 10.44 [10]   R☉
Luminosity 2,490 [11]   L☉
Surface gravity (log g)3.8±0.2 [12]   cgs
Temperature 28,184+1,328
−1,268 [12]   K
Metallicity [Fe/H]0.00 [13]   dex
Rotational velocity (v sin i)180 [14]  km/s
Age ~7.5 [12]   Myr
Other designations
SY Equueli, AG+09°2978, BD+09°4793, HD  203664, HIP  105614, SAO  126757 [15]
Database references
SIMBAD data

SY Equulei, also known as HD 203664, is a single variable star located in the equatorial constellation Equuleus. It has an average apparent magnitude of about 8.5, varying by a few hundredths of a magnitude, making it readily visible in binoculars and small telescopes, but not to the naked eye. The star is relatively far away at a distance of 8,000 light years [2] and is receding with a heliocentric radial velocity of 48  km/s . [7] At that distance, SY Equulei is dimmed by 0.19 magnitudes due to interstellar dust. [16]

Throughout the late 20th century, HD 203664 was known to have a dust cloud surrounding it. Subsequent observations from Kenneth R. Sembach (1995) reveal it to contain high abundances of calcium as well as traces of magnesium, aluminum, and silicon. [17] The cloud probably came from outside the galactic plane and is moving towards the star at a rate of 70  km/s . [17] The star has a high galactic latitude, indicating its location in the galactic halo. HD 203664 was most likely ejected from its birthplace to its current distance. [9] However, its status as a Beta Cephei variable wasn't discovered until a survey of 2000 using Hipparcos data. [8] It was then given the designation SY Equulei. [18]

SY Equulei has a stellar classification of B0.5 IIIn, [4] indicating an evolved B-type star with nebulous (broad) absorption lines due to rapid rotation. Unlike most stars of its type, it spins rapidly with a projected rotational velocity of 180  km/s , [14] which is 40% of its break-up velocity. [12] It has 14 times the mass of the Sun [9] and a radius of 10.4  radius . [10] It radiates at 2,490 times the luminosity of the Sun [11] from its photosphere at an effective temperature of 28,184  K , [12] giving a whitish blue hue.

SY Equueli is a variable star with an amplitude of 0.07 magnitudes [6] and an average period of 3.98 hours. [19] In later observations, SY Equulei was found to have multiple periods. [12]

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References

  1. ↑ "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
  2. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. ↑ "SY Equ". International Variable Star Index. AAVSO . Retrieved 2022-07-31.
  4. 1 2 Walborn, Nolan R. (August 1971). "Some Spectroscopic Characteristics of the OB Stars: an Investigation of the Space Distribution of Certain OB Stars and the Reference Frame of the Classification". The Astrophysical Journal Supplement Series. 23: 257. Bibcode:1971ApJS...23..257W. doi: 10.1086/190239 . eISSN   1538-4365. ISSN   0067-0049.
  5. 1 2 Guetter, H. H. (October 1974). "UBV photometry of 180 early-type stars". Publications of the Astronomical Society of the Pacific. 86: 795. Bibcode:1974PASP...86..795G. doi: 10.1086/129675 . eISSN   1538-3873. ISSN   0004-6280.
  6. 1 2 Samus’, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. eISSN   1562-6881. ISSN   1063-7729. S2CID   125853869.
  7. 1 2 Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (November 2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889–896. arXiv: 0705.0878 . Bibcode:2007AN....328..889K. doi: 10.1002/asna.200710776 . ISSN   0004-6337.
  8. 1 2 Aerts, C. (September 2000). "Follow-up photometry of six new beta Cephei stars discovered from the HIPPARCOS mission". Astronomy and Astrophysics. 361: 245–257. Bibcode:2000A&A...361..245A. ISSN   0004-6361.
  9. 1 2 3 Keenan, F. P.; Dufton, P. L.; McKeith, C. D. (1 October 1982). "Atmospheric parameters and chemical compositions of eighteen halo OB stars". Monthly Notices of the Royal Astronomical Society. 200 (3): 673–685. Bibcode:1982MNRAS.200..673K. doi: 10.1093/mnras/200.3.673 . eISSN   1365-2966. ISSN   0035-8711.
  10. 1 2 Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (2022). "Stellar and substellar companions from Gaia EDR3". Astronomy & Astrophysics. 657: A7. arXiv: 2109.10912 . Bibcode:2022A&A...657A...7K. doi: 10.1051/0004-6361/202142146 . eISSN   1432-0746. ISSN   0004-6361.
  11. 1 2 McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv: 1208.2037 . Bibcode:2012MNRAS.427..343M. doi: 10.1111/j.1365-2966.2012.21873.x . ISSN   0035-8711.
  12. 1 2 3 4 5 6 Aerts, C.; De Cat, P.; De Ridder, J.; Van Winckel, H.; Raskin, G.; Davignon, G.; Uytterhoeven, K. (16 March 2006). "Multiperiodicity in the large-amplitude rapidly-rotating β Cephei star HD 203664". Astronomy & Astrophysics. 449 (1): 305–311. arXiv: astro-ph/0511306 . Bibcode:2006A&A...449..305A. doi: 10.1051/0004-6361:20054142 . eISSN   1432-0746. ISSN   0004-6361.
  13. ↑ Anders, F.; et al. (February 2022). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G = 18.5". Astronomy & Astrophysics. 658: A91. arXiv: 2111.01860 . Bibcode:2022A&A...658A..91A. doi: 10.1051/0004-6361/202142369 . eISSN   1432-0746. ISSN   0004-6361.
  14. 1 2 Walker, G. A. H.; Hodge, S. M. (1965). "Equivalent widths and halfwidths of the λ4388 and λ4471 He I lines, rotational velocities and λ4430 central depths for 450O to B5 stars". Publications of the Dominion Astrophysical Observatory Victoria. 12: 401. Bibcode:1965PDAO...12..401W. ISSN   0078-6950.
  15. ↑ "SY Equulei". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved July 29, 2022.
  16. ↑ Neckel, T.; Klare, G.; Sarcander, M. (July 1980). "Catalogue of Extinction Data of 12547 O-Stars to F-Stars Galactic Clusters and Delta-Cephei Stars". Bulletin d'Information du Centre de Donnees Stellaires. 19: 61. Bibcode:1980BICDS..19...61N. ISSN   1169-8837.
  17. 1 2 Sembach, Kenneth R. (May 1995). "Properties of the +70 kilometers per second cloud toward HD 203664". The Astrophysical Journal. 445: 314. Bibcode:1995ApJ...445..314S. doi: 10.1086/175695 . eISSN   1538-4357. ISSN   0004-637X.
  18. ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Frolov, M. S.; Antipin, S. V.; Kireeva, N. N.; Pastukhova, E. N. (January 1999). "The 74th Special Name-list of Variable Stars". Information Bulletin on Variable Stars. 4659: 1. Bibcode:1999IBVS.4659....1K. ISSN   0374-0676.
  19. ↑ Watson, C. L.; Henden, A. A.; Price, A. (May 2006). "The International Variable Star Index (VSX)". Society for Astronomical Sciences Annual Symposium. 25: 47. Bibcode:2006SASS...25...47W.
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