| 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 | |
| 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]
References
- ^ "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
- ^ a b c d e 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.
- ^ "SY Equ". International Variable Star Index. AAVSO. Retrieved 2022-07-31.
- ^ a b 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b c 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b c d e f 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.
- ^ 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.
- ^ a b 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.
- ^ "SY Equulei". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved July 29, 2022.
- ^ 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.
- ^ a b 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.
- ^ 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.
- ^ 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.
| 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 | |
| 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]
References
- ^ "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
- ^ a b c d e 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.
- ^ "SY Equ". International Variable Star Index. AAVSO. Retrieved 2022-07-31.
- ^ a b 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b c 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b c d e f 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.
- ^ 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.
- ^ a b 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.
- ^ "SY Equulei". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved July 29, 2022.
- ^ 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.
- ^ a b 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.
- ^ 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.
- ^ 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.