QZ Carinae

QZ Carinae (HD 93206) is a multiple star system in the constellation Carina. It is the brightest member of the loose open cluster Collinder 228 and one of the brightest stars in the Carina Nebula. The apparent magnitude is variable from +6.16 to +6.49 with a period of 6 days.

QZ Carinae
QZ Carinae
QZ Carinae (circled) in the Carina Nebula
Credit: ESO
Observation data
Epoch J2000      Equinox J2000
Constellation Carina
Right ascension 10h 44m 22.91114s[1]
Declination −59° 59′ 35.9550″[1]
Apparent magnitude (V) 6.24[2] (6.16 - 6.49[3])
Characteristics
Spectral type A1: O9.7I
A2: B2V
B1: O8III
B2: O9V[4]
U−B color index −0.84[2]
B−V color index +0.13[2]
Variable type β Lyr[3]
Astrometry
Radial velocity (Rv)−2.80[5] km/s
Proper motion (μ) RA: −6.63[1] mas/yr
Dec.: 2.48[1] mas/yr
Parallax (π)1.67 ± 0.40[1] mas
Distance2,300[4] pc
Orbit[4]
PrimaryA
CompanionB
Period (P)~25.4 yr
Semi-major axis (a)~35 AU
Eccentricity (e)0.0
Inclination (i)60°
Orbit[4]
PrimaryA1
CompanionA2
Period (P)20.72 days
Semi-major axis (a)116 R☉
Eccentricity (e)0.34
Inclination (i)60°
Argument of periastron (ω)
(secondary)		141°
Orbit[4]
PrimaryB1
CompanionB2
Period (P)5.999 days
Semi-major axis (a)49 R☉
Eccentricity (e)0.1
Inclination (i)86°
Argument of periastron (ω)
(secondary)		~20°
Details
A1
Mass27.1[6] M☉
Radius22.1[6] R☉
Luminosity400,000[6] L☉
Surface gravity (log g)3.2[6] cgs
Temperature30,463[6] K
A2
Mass6.5[6] M☉
Radius3.0[6] R☉
Luminosity1,260[6] L☉
Surface gravity (log g)4.3[6] cgs
Temperature20,000[6][4] K
B1
Mass25.4[6] M☉
Radius13.7[6] R☉
Luminosity200,000[6][4] L☉
Surface gravity (log g)3.6[6] cgs
Temperature33,961[6] K
B2
Mass17.1[6] M☉
Radius7.53[6] R☉
Luminosity50,100[6] L☉
Surface gravity (log g)3.92[6] cgs
Temperature32,882[6] K
Other designations
QZ Car, HD 93206, HIP 52526, CD−59 3287, GC 14784, SAO 238414, GSC 08626-02523
Database references
SIMBADdata

Description

QZ Carinae is approximately 2,300 parsecs (7,500 light-years) from Earth in the Carina Nebula star-forming region. It is composed of four massive luminous stars, designated A1 and A2, and B1 and B2. The A1/A2 and B1/B2 pairs take no more than 25 years to orbit each other, while the A pair completes an orbit around each other every 20.7 days and the B pair every 6.0 days. The system is bright at x-ray wavelengths primarily due to colliding stellar winds in the two close pairs. Pair A1/A2 contributes the bulk of the x-ray luminosity.[4]

Components

QZ Carinae A1 is a blue supergiant of spectral type O9.7I with around 40 times the Sun's mass that has expanded to 22.5 times the Sun's radius. With a surface temperature of 32,000 K, it is around 500,000 times as luminous as the Sun. Its partner A2 is a blue-white main sequence star of spectral type B2V with around 10 times the Sun's mass and 6 times its radius. With a surface temperature of 20,000 K, it is around 5,000 times as luminous as the Sun.

QZ Carinae B1 is a hot blue giant that is expanding and cooling away from the main sequence. It is of spectral type O8III with around 14.1 times the Sun's mass and 26.9 times its radius. With a surface temperature of 32,573 K, it is around 200,000 times as luminous as the Sun. Partner B2 is a hot main sequence star of spectral type O9V with around 28 times the Sun's mass and 8.9 times its radius. With a surface temperature of 32,463 K, it is around 80,000 times as luminous as the Sun. Star B1 is less massive than B2 and is assumed to have undergone significant mass loss or mass transfer to B2.[4] Together, all four stars have a combined mass 94 times that of the Sun.[7]

Variability

Star B is a Beta Lyrae variable eclipsing system. It causes the apparent magnitude of the system to vary regularly every 5.999 days from +6.16 at maximum to +6.49 at the primary minimum and +6.43 at the secondary minimum.[3] It was first noted to be variable in 1972 by observers in Auckland.[7]

References
  1. Van Leeuwen, F. (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. S2CID 18759600.
  2. 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. Samus, N. N.; Durlevich, O. V.; 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: 02025. Bibcode:2009yCat....102025S.
  4. Parkin, E. R.; Broos, P. S.; Townsley, L. K.; Pittard, J. M.; et al. (2011). "X-ray emission from the double-binary OB-star system QZ Car (HD 93206)". The Astrophysical Journal Supplement. 194 (1): article id. 8, 11 pp. arXiv:1103.0794. Bibcode:2011ApJS..194....8P. doi:10.1088/0067-0049/194/1/8. S2CID 119292907.
  5. Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; Levato, H.; Morrell, N. I.; Torres, G.; Udry, S. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. ISSN 0004-6361. S2CID 119387088.
  6. Rainot, A.; Reggiani, M.; Sana, H.; Bodensteiner, J.; Gomez-Gonzalez, C. A.; Absil, O.; Christiaens, V.; Delorme, P.; Almeida, L. A.; Caballero-Nieves, S.; De Ridder, J.; Kratter, K.; Lacour, S.; Le Bouquin, J. -B.; Pueyo, L.; Zinnecker, H. (2020). "Carina High-contrast Imaging Project for massive Stars (CHIPS). I. Methodology and proof of concept on QZ Car (≡ HD 93206)". Astronomy and Astrophysics. 640: A15. arXiv:2006.01914. Bibcode:2020A&A...640A..15R. doi:10.1051/0004-6361/201936448. S2CID 219260368.
  7. Walker, W. S. G; Marino, B. F. (May 1972). "HD 93206 (CSV 6797) an Eclipsing System Presenting Observational Problems". Information Bulletin on Variable Stars. 681 (1): 1. Bibcode:1972IBVS..681....1W.
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