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WY Velorum
Location of WY Velorum (circled)
Observation data
Epoch J2000[1]      Equinox J2000[1]
Constellation Vela
Right ascension 09h 21m 59.13465s
Declination −52° 33′ 51.6424″
Apparent magnitude (V) 8.84–10.22[2]
Characteristics
Evolutionary stage Red supergiant (A)
Blue giant (B)
Spectral type M2 Ib pe[3] + B2III[4]
B−V color index +0.96[5][6]
J−H color index +1.096[7]
J−K color index +1.57[5][7]
Variable type Irregular variable
Astrometry
Proper motion (μ) RA: −6.313[1] mas/yr
Dec.: 4.538[1] mas/yr
Parallax (π)0.5187 ± 0.0891 mas[1]
Distance1900[8] pc
Details
WY Velorum A
Radius1,157[9] R☉
Other designations
WY Velorum, CD−52°3010, CPD−52°2262, Gaia DR3 5313125719158014208, HD 81137, TIC 294974397, TYC 8584-2732-1, GSC 08584-02732, IRAS 09203-5220, 2MASS J09215913-5233514, WISE J092158.85-523348.7[10]
Database references
SIMBADdata

WY Velorum, also known as HD 81137, is a binary system between a variable red supergiant (RSG) and a blue giant companion in the constellation of Vela. It is located approximately 1,900 parsecs (6,200 light-years) distant. Its apparent magnitude slowly varies over the course of years between 8.84 and 10.22. As such, it has been described as an irregular variable, though a rough 550-day period and a more uncertain 370-day period have been detected.[2] The primary star is among the largest stars discovered to date, with an estimated radius of 1,157 R☉[9] (5.38 AU). If it replaced the Sun, its surface would reach past Jupiter's orbit (5.20 AU[11]).

Physical properties

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Early publications in 1928 and 1939 classified the star as a possible R Coronae Borealis variable.[12] Later authors were split on whether it was a symbiotic star[13] or a VV Cephei-type star.[14] The two differ in that the former consists of a red giant and a white dwarf or neutron star,[15] while the latter is usually composed of a K- or M-type RSG and a massive early B-type star.[14] The latter was confirmed to be the case in a 1988 paper, and the companion was identified as a giant star with the spectral type B2. This study also presented the absolute magnitudes of the two stars, −4.8 for the primary and −1.7 for the secondary, albeit this has been calculated using a distance of 1400 pc, smaller than modern estimates.[4] With an updated value of 1900 pc, its KS band absolute magnitude is gauged at −11.3.[8] No radial velocity variations have been detected, so the binary likely has a small orbital inclination.[13]

Spectrum

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The star has a peculiar spectrum, as indicated by the "pe" suffix in the spectral type[3] (the "p" stands for peculiar, and the "e" stands for emission lines). It displays various strong[14] emission lines, namely of hydrogen, nitrogen, oxygen, silicon, sulfur, iron, nickel, copper, and possibly chromium, many of them forbidden lines.[12] Among them, the strong [Fe II] (forbidden line of singly ionized iron) emission is particularly unusual and recognizable.[16] However, in the ultraviolet region, as observed by the International Ultraviolet Explorer, it only shows the emission lines for Mg II (Mg+). In this regard, it is similar to the symbiotic star CH Cygni, except that CH Cygni also has neutral oxygen lines.[17]

Excess infrared emission signifies the existence of circumstellar dust at a temperature of 600 K (327 °C; 620 °F). The spectrum does not appear to be reddened.[4]

Historical observations

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Two light curves for WY Velorum. The upper plot, of ASAS-SN data,[18] shows the variability on the timescale of months. The lower plot, of AAVSO data,[19] shows the variability on the timescale of years. The purple dots show the yearly averages.

The star's variability was first discovered by Annie Jump Cannon. Between 1890 and 1901, the brightness gradually increased from magnitude 9.8 to 9.2, but it slowly dimmed since 1902 to reach magnitude 10.1 by May 1922.[20] Additional research on the light curves published in 1947 by Cecilia Payne-Gaposchkin indicate that the fading that began in 1902 halted around 1916, after which the star remained almost constant until 1933, when it began to brighten again.[12]

No discernible changes occurred in the spectrum of the star between 1944 and 1948, but in 1952, the H-α line shifted from a single line to a double line, and previously unseen faint H-β features appeared.[12] In 1956, it was reported that the calcium H and K lines swung from absorption to emission during two consecutive nights. By 1969, the RSG had likely become fainter than it was in the 1940s.[14]

References

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  1. ^ a b c d 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.
  2. ^ a b Payne-Gaposchkin, Cecilia (1952). "Variable Stars in Milton Field 49". Annals of Harvard College Observatory. 115 (6). Bibcode:1952AnHar.115...87P.
  3. ^ a b Malyuto, V.; Oestreicher, M. O.; Schmidt-Kaler, T. (1 April 1997). "Quantitative spectral classification of galactic disc K-M stars from sectrophotometric measurements" (PDF). Monthly Notices of the Royal Astronomical Society. 286 (2): 500–512. doi:10.1093/mnras/286.2.500. ISSN 0035-8711. Retrieved 3 January 2025.
  4. ^ a b c Buss, Richard H., Jr.; Snow, Theodore P., Jr. (1988). "Hot components and circumstellar grains in M supergiant syncretic binaries". The Astrophysical Journal. 335: 331. doi:10.1086/166931. ISSN 0004-637X.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. Bibcode:2002yCat.2237....0D.
  6. ^ Høg, E.; et al. (February 2000). "The Tycho-2 Catalogue of the 2.5 Million Brightest Stars". Astronomy and Astrophysics. 355 (1): L27 – L30. Bibcode:2000A&A...355L..27H.
  7. ^ a b Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  8. ^ a b Munari, U; Traven, G; Masetti, N; Valisa, P; Righetti, G-L; Hambsch, F-J; Frigo, A; Čotar, K; De Silva, G M; Freeman, K C; Lewis, G F; Martell, S L; Sharma, S; Simpson, J D; Ting, Y-S; Wittenmyer, R A; Zucker, D B (6 July 2021). "The GALAH survey and symbiotic stars – I. Discovery and follow-up of 33 candidate accreting-only systems". Monthly Notices of the Royal Astronomical Society. 505 (4): 6121–6154. arXiv:2104.02686. doi:10.1093/mnras/stab1620. ISSN 0035-8711.
  9. ^ a b Healy, Sarah; Horiuchi, Shunsaku; Molla, Marta Colomer; Milisavljevic, Dan; Tseng, Jeff; Bergin, Faith; Weil, Kathryn; Tanaka, Masaomi (23 March 2024). "Red Supergiant Candidates for Multimessenger Monitoring of the Next Galactic Supernova". Monthly Notices of the Royal Astronomical Society. 529 (4): 3630–3650. arXiv:2307.08785. Bibcode:2024MNRAS.529.3630H. doi:10.1093/mnras/stae738. ISSN 0035-8711.
  10. ^ "WY Vel". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 4 January 2025.
  11. ^ Williams, David R. (23 December 2021). "Jupiter Fact Sheet". NASA. Archived from the original on 29 December 2019. Retrieved 13 October 2017.
  12. ^ a b c d Sahade, Jorge (September 1954). "24. The Spectrum of WY Velorum". Transactions of the International Astronomical Union. 8: 842–848. doi:10.1017/S0251107X00033149.
  13. ^ a b Hernández, Carlos A.; Sahade, Jorge (1969). "Velocidades radiales de WY Velorum" [Radial Velocities of WY Velorum]. Boletín de la Asociación Argentina de Astronomía (in Spanish). 12: 10. ISSN 1669-9521.
  14. ^ a b c d Cowley, Anne P. (1969). "The VV Cephei Stars". Publications of the Astronomical Society of the Pacific. 81: 297. doi:10.1086/128784. ISSN 0004-6280. Retrieved 3 January 2025.
  15. ^ Mikołajewska, Joanna (2002). "Orbital and stellar parameters of symbiotic stars". ASP Conference Series. 303: 9. arXiv:astro-ph/0210489. Bibcode:2003ASPC..303....9M.
  16. ^ Bond, Howard E. (1 January 2017). "William Pendry Bidelman (1918–2011)". Publications of the Astronomical Society of the Pacific. 129 (971): 010201. doi:10.1088/1538-3873/129/971/010201. ISSN 0004-6280. Retrieved 3 January 2025.
  17. ^ Sahade, J.; Brandi, E. (1 January 1981). "IUE Observations of Symbiotic Stars" (PDF). The Universe of Ultraviolet Wavelengths: The First Two Years of International Ultraviolet Explorer. Goddard Space Flight Center: 451-454.
  18. ^ "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 5 January 2025.
  19. ^ "Download Data". aavso.org. AAVSO. Retrieved 4 January 2025.
  20. ^ Shapley, Harlow (March 1923). "New Variables with Remarkable Spectrum and Light Curve". Harvard College Observatory Bulletin. 783: 3. Bibcode:1923BHarO.783....3S.
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