Gamma Velorum

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Gamma2 Velorum
Location of Gamma Velorum
Cercle rouge 100%.svg

Gamma Velorum (circled) in the constellation Vela.
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 09m 31.95013s[1]
Declination –47° 20′ 11.7108″[1]
Apparent magnitude (V) 1.83[2]
Characteristics
Spectral type WC8 + O7.5[3]
U−B color index −0.94[2]
B−V color index −0.25[2]
Variable type Wolf-Rayet
Astrometry
Radial velocity (Rv) +12 ± 1[4] km/s
Proper motion (μ) RA: –6.07[1] mas/yr
Dec.: +10.43[1] mas/yr
Parallax (π) 2.92 ± 0.30[1] mas
Distance 336+8
−7
[5] pc
Absolute magnitude (MV) −4.23 + −5.63[5]
Details
WR
Mass 9.0 ± 0.6[5] M
Radius 6 ± 3[5] R
Luminosity (bolometric) 170,000[5] L
Temperature 57,000[3] K
Age 3.5[6] -5.5[7] Myr
O
Mass 28.5 ±1.1[5] M
Radius 17 ± 2[5] R
Luminosity (bolometric) 280,000[5] L
Temperature 35,000[3] K
Age 3.5[6]-5.5[7] Myr
Orbit[8]
Primary O
Companion WR
Period (P) 78.53 ± 0.01 days
Semi-major axis (a) 1.2[5] AU
Eccentricity (e) 0.326 ± 0.01
Inclination (i) 65 ± 8°
Longitude of the node (Ω) 248 ± 4°
Periastron epoch (T) 2,450,120.5 ± 2
Semi-amplitude (K1)
(primary)
38.4 ± 2 km/s
Semi-amplitude (K2)
(secondary)
122 ± 2 km/s
Other designations
Regor, Suhail[citation needed], Suhail Al-Muhlif[citation needed], CD −46° 3847, FK5 309, HD 68273, HIP 39953, HR 3207, SAO 219504, WR 11
Database references
SIMBAD data
Gamma1 Velorum
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 09m 29.3260s[9]
Declination –47° 20′ 43.027″[9]
Apparent magnitude (V) 4.27[10]
Characteristics
Spectral type B2III[6]
U−B color index −0.92[10]
B−V color index −0.22[10]
Astrometry
Radial velocity (Rv) +9.7 ± 1[10] km/s
Proper motion (μ) RA: –0.6[11] mas/yr
Dec.: +9.7[11] mas/yr
Absolute magnitude (MV) −3.62[6]
Details
Mass 14[6] M
Age 8[6] Myr
Other designations
CD −46° 3846, HD 68243, HR 3206, SAO 219501
Database references
SIMBAD data

Gamma Velorum (γ Vel, γ Velorum) is a multiple star system in the constellation Vela. At magnitude +1.7, it is one of the brightest stars in the night sky, and by far the closest and brightest Wolf-Rayet star. It has the traditional names Suhail and Suhail al Muhlif, which confusingly also apply to Lambda Velorum. It also has a more modern popular name Regor.

Distance[edit]

Gamma Velorum is close enough to have accurate parallax measurements as well as distance estimates by more indirect means. The Hipparcos parallax for γ2 implies a distance of 342 pc. A dynamical parallax derived from calculations of the orbital parameters gives a value of 336 pc, similar to spectrophotometric derivations. A VLTI interferometry measurement of the distance gives a slightly larger value of 368+38
−13
pc. All these distances are somewhat less than the commonly assumed distance of 450 pc for the Vela OB2 association which is the closest grouping of young massive stars.[12]

Components[edit]

The Gamma Velorum system is composed of at least four stars. The brightest member, γ² Velorum or γ Velorum A, is a spectroscopic binary composed of a blue supergiant of spectral class O7.5 (~30 M), and a massive Wolf-Rayet star (~9 M, originally ~35 M).[7] The binary has an orbital period of 78.5 days and separation varying from 0.8 to 1.6 astronomical units. The Wolf-Rayet star is likely to end its life in a Type Ib supernova explosion; it is one of the nearest supernova candidates to the Sun.[13] The Wolf Rayet star has traditionally been regarded as the primary since its emission lines dominate the spectrum, but the O star is visually brighter and also more luminous. For clarity, the components are now often referred to as WR and O.[5]

The bright (apparent magnitude +4.2) γ¹ Velorum or γ Velorum B, is a spectroscopic binary with a period of 1.48 days. Only the primary is detected and it is a blue-white giant. It is separated from the Wolf-Rayet binary by 41.2", easily resolved with binoculars.[6]

Gamma Velorum has several fainter companions that share a common motion and are likely to be members of the Vela OB2 association.[6] The magnitude +7.3 CD-46 3848 is a white F0 star at is 62.3 arcseconds from the A component. At 93.5 arcseconds is another binary star, an F0 star of magnitude +9.2.

γ Velorum is associated with several hundred pre main sequence stars within less than a degree. The ages of these stars would be at least 5 million years.[6]

Etymology[edit]

The medieval name Suhail (Al Suhail, Alsuhail, Suhail al Muhlif, Muliphein) is short for the Arabic سهيل المحلف suhayl al-muħlif "The glorious (star) of the oath".[citation needed]

The Chinese name for the star is 天社一 (Mandarin: tiān shè yī), which means "The First Star of the Celestial Altar."[citation needed]

The name Regor was invented as a practical joke by the Apollo 1 astronaut Gus Grissom for his fellow astronaut Roger Chaffee.[14]

Due to the exotic nature of its spectrum (bright emission lines in lieu of dark absorption lines) it is also dubbed the Spectral Gem of Southern Skies.[15]

See also[edit]

References[edit]

  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues 2237: 0. Bibcode:2002yCat.2237....0D. 
  3. ^ a b c De Marco, O.; Schmutz, W.; Crowther, P. A.; Hillier, D. J.; Dessart, L.; De Koter, A.; Schweickhardt, J. (2000). "The gamma Velorum binary system. II. WR stellar parameters and the photon loss mechanism". Astronomy and Astrophysics 358: 187. arXiv:astro-ph/0004081. Bibcode:2000A&A...358..187D. 
  4. ^ Niemela, V. S.; Sahade, J. (1980). "The orbital elements of Gamma 2 Velorum". The Astrophysical Journal 238: 244. doi:10.1086/157981. ISSN 0004-637X. 
  5. ^ a b c d e f g h i j North, J. R.; Tuthill, P. G.; Tango, W. J.; Davis, J. (2007). "Γ2 Velorum: Orbital solution and fundamental parameter determination with SUSI". Monthly Notices of the Royal Astronomical Society 377: 415. arXiv:astro-ph/0702375. Bibcode:2007MNRAS.377..415N. doi:10.1111/j.1365-2966.2007.11608.x. 
  6. ^ a b c d e f g h i Jeffries, R. D.; Naylor, T.; Walter, F. M.; Pozzo, M. P.; Devey, C. R. (2009). "The stellar association around Gamma Velorum and its relationship with Vela OB2". Monthly Notices of the Royal Astronomical Society 393 (2): 538. doi:10.1111/j.1365-2966.2008.14162.x. 
  7. ^ a b c Eldridge, J. J. (2009). "A new-age determination for γ2 Velorum from binary stellar evolution models". Monthly Notices of the Royal Astronomical Society: Letters 400: L20–L23. arXiv:0909.0504. Bibcode:2009MNRAS.400L..20E. doi:10.1111/j.1745-3933.2009.00753.x. 
  8. ^ . Bibcode:997A&A...328..219S.  Missing or empty |title= (help)
  9. ^ a b Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics 335: L65. Bibcode:1998A&A...335L..65H. 
  10. ^ a b c d Hernandez, C. A.; Sahade, J. (1980). "The Spectroscopic Binary GAMMA-1-VELORUM". Publications of the Astronomical Society of the Pacific 92: 819. doi:10.1086/130756. ISSN 0004-6280. 
  11. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27. Bibcode:2000A&A...355L..27H. 
  12. ^ Millour, F.; Petrov, R. G.; Chesneau, O.; Bonneau, D.; Dessart, L.; Bechet, C.; Tallon-Bosc, I.; Tallon, M.; Thiébaut, E.; Vakili, F.; Malbet, F.; Mourard, D.; Antonelli, P.; Beckmann, U.; Bresson, Y.; Chelli, A.; Dugué, M.; Duvert, G.; Gennari, S.; Glück, L.; Kern, P.; Lagarde, S.; Le Coarer, E.; Lisi, F.; Perraut, K.; Puget, P.; Rantakyrö, F.; Robbe-Dubois, S.; Roussel, A.; Tatulli, E.; Weigelt, G.; Zins, G.; Accardo, M.; Acke, B.; Agabi, K.; Altariba, E.; Arezki, B.; Aristidi, E.; Baffa, C.; Behrend, J.; Blöcker, T.; Bonhomme, S.; Busoni, S.; Cassaing, F.; Clausse, J.-M.; Colin, J.; Connot, C.; Delboulbé, A.; Domiciano de Souza, A.; Driebe, T.; Feautrier, P.; Ferruzzi, D.; Forveille, T.; Fossat, E.; Foy, R.; Fraix-Burnet, D.; Gallardo, A.; Giani, E.; Gil, C.; Glentzlin, A.; Heiden, M.; Heininger, M.; Hernandez Utrera, O.; Hofmann, K.-H.; Kamm, D.; Kiekebusch, M.; Kraus, S.; Le Contel, D.; Le Contel, J.-M.; Lesourd, T.; Lopez, B.; Lopez, M.; Magnard, Y.; Marconi, A.; Mars, G.; Martinot-Lagarde, G.; Mathias, P.; Mège, P.; Monin, J.-L.; Mouillet, D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.; Perrier, C.; Rabbia, Y.; Rebattu, S.; Reynaud, F.; Richichi, A.; Robini, A.; Sacchettini, M.; Schertl, D.; Schöller, M.; Solscheid, W.; Spang, A.; Stee, P.; Stefanini, P.; Tasso, D.; Testi, L.; von der Lühe, O.; Valtier, J.-C.; Vannier, M.; Ventura, N. (2007). "Direct constraint on the distance of γ2 Velorum from AMBER/VLTI observations". Astronomy and Astrophysics 464 (1): 107–118. doi:10.1051/0004-6361:20065408. ISSN 0004-6361. 
  13. ^ Beech, Martin (2011). "The past, present and future supernova threat to Earth's biosphere". Astrophysics and Space Science 336 (2): 287. Bibcode:2011Ap&SS.336..287B. doi:10.1007/s10509-011-0873-9. 
  14. ^ Apollo 15 Lunar Surface Journal, Post-landing Activities, commentary at 105:11:33
  15. ^ Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven, Conn.: Yale University Observatory, 5th rev.ed. Bibcode:1991bsc..book.....H.