KQ Velorum

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KQ Velorum
KQVelLightCurve.png
A light curve for KQ Velorum, adapted from Schöller et al. (2020) [1]
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Vela
Right ascension 10h 55m 01.002s [2]
Declination –21° 43′ 34.52″ [2]
Apparent magnitude  (V)6.112 [3]
Characteristics
Spectral type Ap(SiCr) [4]
A0p EuCrSi [3]
B−V color index −0.061±0.004 [5]
Variable type α2 CVn [6]
Astrometry
Radial velocity (Rv)+23.4±4.0 [7]  km/s
Proper motion (μ)RA: −36.021  mas/yr [2]
Dec.: 5.157  mas/yr [2]
Parallax (π)8.7507 ± 0.1578  mas [2]
Distance 373 ± 7  ly
(114 ± 2  pc)
Absolute magnitude  (MV)0.24 [5]
Orbit [3]
Period (P)848.96±0.13 d
Semi-major axis (a)≥ 187.3±1.2 Gm
Eccentricity (e)0.4476±0.0049
Periastron epoch (T)2,445,628.6±1.7  HJD
Argument of periastron (ω)
(secondary)		264.5±0.8°
Semi-amplitude (K1)
(primary)		17.94±0.11 km/s
Details [8]
KQ Vel A
Mass 3.0±0.2  M☉
Radius 2.53±0.37  R☉
Luminosity 105  L☉
Surface gravity (log g)4.18±0.20  cgs
Temperature 11,300±400  K
Rotation 2,800±200 d
Other designations
KQ Vel, CD−41 6220, GC  15014, HD  94660, HIP  53379, HR  4263, SAO  222422, PPM  315855, G 235 G. Vel. [9] [10]
Database references
SIMBAD data

KQ Velorum is a variable star system in the southern constellation of Vela. It has the identifier HD 94660 in the Henry Draper Catalogue ; KQ Vel is the variable star designation. This appears as a sixth magnitude star with an apparent visual magnitude of 6.112, [3] and thus is dimly visible to the naked eye under suitable viewing conditions. The system is located at a distance of approximately 373  light years from the Sun based on parallax measurements, [2] and is drifting further away with a radial velocity of around 23 km/s. [7]

This was first identified as a chemically peculiar star by Carlos and Mercedes Jaschek in 1959, who found spectral peculiarities in the silicon absorption bands. [11] The long-term photometric variability of this star was reported by H. Hensberge in 1993, who noted a possibly complicated light curve with an estimated period on the order of 2,700 days. [12] In 1975, E. F. Borra and J. D. Landstreet detected a strong magnetic field in excess of 1 kG on the star. [13] Radial velocity measurements by G. Mathys and associates (1997) demonstrated this is a spectroscopic binary system. [14]

This single-lined spectroscopic binary has a physical separation of at least 1.25 ± 0.01  AU, an orbital period of 2.32 years, and a high eccentricity (ovalness) of 0.45. [3] The visible component is an Ap star with a stellar classification of Ap(SiCr), [4] although the effective temperature of 11,300 K is a closer match to a spectral type of B8.5p. [1] P. Renson and associates (1991) gave a spectral type of A0p EuCrSi, [9] indicating the spectrum shows peculiarities in the europium, chromium, and silicon bands. It is classified as an Alpha2 Canum Venaticorum variable with a brightness that varies from 6.10 down to 6.12 in magnitude. [6]

KQ Vel is a frequently-studied object that is often used as a magnetic standard star. The magnetic field of this star has a dipole strength of 7.5 kG, while displaying additional quadropole and octopole moments. It is inclined to the rotation axis by 16°. The mean longitudinal field is almost constant, showing a strength of −2 kG. [8] The star is less than halfway through its main sequence lifespan, but is rotating very slowly with a period of around 2,800 days. It has three times the mass and 2.5 times the radius of the Sun, while radiating 105 times the Sun's luminosity. [8]

The mass function of the system indicates that the secondary must have more than two times the mass of the Sun, yet there is no sign of it in otherwise high-quality spectra. [1] A main sequence stellar companion of this mass would have a spectral type earlier than A5V. [1] This led to the suggestion that this companion must be a compact object, either a black hole, a neutron star, or a pair of white dwarfs. [8] In 2018 the companion was detected in the near infrared using the Pioneer instrument at the VLIT observatory, showing an H-band magnitude difference of 1.8±0.03 at an angular separation of 18.72±0.02  mas . This corresponds to a projected linear separation of a little over 2 AU. [1]

X-ray observations with the Chandra X-ray Observatory in 2016 strongly suggested that the companion is a neutron star, which would make KQ Velorum the first known pair of strongly magnetic Ap star and neutron star that have been discovered. [15] Radio emission has also been detected from the secondary object, raising the possibility that the secondary is actually itself a binary containing a magnetically active star. [16]

If KQ Velorum B is a neutron star, the system would be the product of a supernova explosion, possibly of the electron capture type that would not significantly disrupt the orbit. The strongly magnetic Ap star would likely be the result of a merger, perhaps from an W UMa close binary. The current neutron star may have been the tertiary member of the system, and it gained mass during a Roche lobe overflow of the binary components. [15]

Related Research Articles

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<span class="mw-page-title-main">Delta Velorum</span> Triple star system in the constellation Vela

Delta Velorum is a triple star system in the southern constellation of Vela, near the border with Carina, and is part of the False Cross. Based on parallax measurements, it is approximately 80.6 light-years from the Sun. It is one of the stars that at times lies near the south celestial pole due to precession.

<span class="mw-page-title-main">Mu Velorum</span> Binary star in the constellation Velorum

Mu Velorum is a binary star system in the southern constellation Vela. The two stars orbit each other with a semi-major axis of 1.437 arcseconds and a period of 116.24 years. The pair have a combined apparent visual magnitude of 2.69, making the system readily visible to the naked eye. From parallax measurements, the distance to this system is estimated to be 117 light-years. The system is about 360 million years old.

<span class="mw-page-title-main">Omicron Velorum</span> Variable star in the constellation Vela

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<span class="mw-page-title-main">Psi Velorum</span> Binary star in the constellation Vela

Psi Velorum, Latinized from ψ Velorum, is a binary star system in the southern constellation of Vela. Based upon an annual parallax shift of 53.15 mas as seen from Earth, it is located 61.4 light years from the Sun. It is visible to the naked eye with a combined apparent visual magnitude of +3.58. The motion of this system through space makes it a candidate member of the Castor stellar kinematic group.

<span class="mw-page-title-main">Chi Draconis</span>

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<span class="mw-page-title-main">Vela X-1</span> X-ray emission source in the constellation Vela

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<span class="mw-page-title-main">IC 2391</span> Open star cluster in the constellation Vela

IC 2391 is an open cluster in the constellation Vela consisting of hot, young, blueish stars, some of which binaries and one of which is a quadruple. Persian astronomer A. a.-R. Al Sufi first described it as "a nebulous star" in c. 964. It was re-found by Abbe Lacaille and cataloged as Lac II 5.

<span class="mw-page-title-main">DV Aquarii</span> Binary star in the constellation Aquarius

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<span class="mw-page-title-main">1 Serpentis</span> Red giant star in the constellation Virgo

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23 Comae Berenices is a binary star system in the northern constellation of Coma Berenices, situated a few degrees away from the North Galactic Pole. It is visible to the naked eye as a faint, white-hued point of light with an apparent visual magnitude of 4.80. The system is located around 310 light years away from the Sun, based on parallax. It is moving closer to the Earth with a heliocentric radial velocity of −16 km/s.

<span class="mw-page-title-main">HY Velorum</span> Star in the constellation Vela

HY Velorum is a binary star system in the southern constellation of Vela. It is a dim star but visible to the naked eye with an apparent visual magnitude of 4.83. The distance to this system, as estimated from its annual parallax shift of 7.1 mas, is 460 light years. HY Vel most likely forms a gravitationally bound pair with the magnitude 5.45 binary system KT Vel ; both are members of the IC 2391 open cluster. As of 1998, HY Vel and KT Vel had an angular separation of 76.1″ along a position angle of 311°.

4 Cygni is a binary star system in the northern constellation of Cygnus. It is a faintly visible to the naked eye with an apparent visual magnitude of 5.17. The distance to 4 Cygni, as determined from its annual parallax shift of 5.8 mas, is about 560 light years.

<span class="mw-page-title-main">HR 273</span> Binary star system in the constellation Cassiopeia

HR 273 is a chemically peculiar spectroscopic binary system in the northern circumpolar constellation of Cassiopeia. It has an apparent visual magnitude of 5.9 making it faintly visible to the naked eye from dark suburban skies. Parallax measurements with the Hipparcos spacecraft put this system at a distance of roughly 350 light years.

HD 142250 is a star in the constellation Scorpius. It has a visual apparent magnitude of 6.1, being visible to the naked eye only in excellent seeing conditions. From parallax measurements, it is located 486 light-years (149 parsecs) away from Earth. This distance, together with the star's proper motion, indicate that HIP 77900 is a member of the Upper Scorpius subgroup of the Scorpius–Centaurus association, the nearest OB association to the Sun. This subgroup is the youngest of the three of the association, with an estimated age of 11 million years.

<span class="mw-page-title-main">17 Comae Berenices</span> Multiple star system in the constellation Coma Berenices

17 Comae Berenices is a multiple star system in the northern constellation of Coma Berenices. The brighter component, 17 Com A, is a naked eye star with an apparent visual magnitude of 5.2. It has a faint companion of magnitude 6.6, 17 Com B, positioned at an angular separation of 146.4″ along a position angle of 251°, as of 2018. They are located at a distance of approximately 240 light years from the Sun based on parallax measurements.

<span class="mw-page-title-main">HD 125248</span> Binary star system in the constellation of Virgo

HD 125248 is a binary star system in the equatorial constellation of Virgo. It has the variable star designation CS Virginis, while HD 125248 is the designation from the Henry Draper Catalogue. This system is dimly visible to the naked eye as a point of light with an apparent visual magnitude that ranges from 5.84 down to 5.95. It is located at a distance of approximately 280 light years from the Sun based on parallax measurements, but is drifting closer with a heliocentric radial velocity of −8 km/s.

<span class="mw-page-title-main">AI Velorum</span> Variable star in the constellation of Lynx

AI Velorum is a variable star in the southern constellation of Vela, abbreviated AI Vel. It is a prototype for a class of high amplitude Delta Scuti variables. The apparent visual magnitude of this star fluctuates around 6.56, which is just bright enough to be dimly visible to the naked eye. The distance to AI Vel is approximately 327 light years based on parallax measurements, and it is drifting further away with a radial velocity of about 9 km/s.

References

  1. 1 2 3 4 5 Schöller, M.; et al. (October 2020), "The near-infrared companion to HD 94660 (=KQ Vel)", Astronomy & Astrophysics, 642: 6, arXiv: 2009.07060 , Bibcode:2020A&A...642A.188S, doi:10.1051/0004-6361/202038950, S2CID   221703222, A188.
  2. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  3. 1 2 3 4 5 Mathys, G. (May 2017), "Ap stars with resolved magnetically split lines: Magnetic field determinations from Stokes I and V spectra", Astronomy & Astrophysics, 601: 90, arXiv: 1612.03632 , Bibcode:2017A&A...601A..14M, doi:10.1051/0004-6361/201628429, S2CID   119474886, A14.
  4. 1 2 Houk, N. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 2, Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  5. 1 2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv: 1108.4971 , Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID   119257644.
  6. 1 2 Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID   125853869.
  7. 1 2 Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv: 1606.08053 . Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID   119231169.
  8. 1 2 3 4 Bailey, J. D.; et al. (March 2015), "A comprehensive analysis of the magnetic standard star HD 94660: Host of a massive compact companion?", Astronomy & Astrophysics, 575: 12, arXiv: 1501.07494 , Bibcode:2015A&A...575A.115B, doi:10.1051/0004-6361/201425316, S2CID   55189944, A115.
  9. 1 2 Renson, P.; et al. (September 1991), "General catalogue of AP and AM stars", Astronomy and Astrophysics Supplement Series, 89: 429, Bibcode:1991A&AS...89..429R.
  10. ↑ "KQ Vel". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2020-10-17.{{cite web}}: CS1 maint: postscript (link)
  11. ↑ Jaschek, Mercedes; Jaschek, Carlos (February 1959), "Southern Peculiar A Stars", Publications of the Astronomical Society of the Pacific, 71 (418): 48, Bibcode:1959PASP...71...48J, doi: 10.1086/127332 , S2CID   121714862.
  12. ↑ Hensberge, H. (January 1993), Dworetsky, M. M.; Castelli, F.; Faraggiana, R. (eds.), "Longterm Variability in Cp-Stars", Peculiar versus Normal Phenomena in A-type and Related Stars. International Astronomical Union, Colloquium No. 138, held in Trieste, Italy, July 1992, San Francisco, CA: Astronomical Society of the Pacific, vol. 44, no. 138, p. 547, Bibcode:1993ASPC...44..547H, ISBN   0937707635.
  13. ↑ Borra, E. F.; Landstreet, J. D. (December 1975), "Discovery of magnetic fields in four southern Ap stars", Publications of the Astronomical Society of the Pacific, 87: 961–963, Bibcode:1975PASP...87..961B, doi: 10.1086/129880 , S2CID   121297510.
  14. ↑ Mathys, G.; et al. (June 1997), "The mean magnetic field modulus of AP stars", Astronomy and Astrophysics Supplement Series, 123 (2): 353–402, Bibcode:1997A&AS..123..353M, doi: 10.1051/aas:1997103 .
  15. 1 2 Oskinova, Lidia M.; et al. (September 2020), "Chandra X-ray study confirms that the magnetic standard Ap star KQ Vel hosts a neutron star companion", Astronomy & Astrophysics, 641: 8, arXiv: 2007.11591 , Bibcode:2020A&A...641L...8O, doi:10.1051/0004-6361/202038214, S2CID   220713253, L8.
  16. ↑ Leto, P.; et al. (2022), "Discovery and origin of the radio emission from the multiple stellar system KQ Vel", Monthly Notices of the Royal Astronomical Society, 515 (4): 5523–5538, arXiv: 2207.14075 , Bibcode:2022MNRAS.515.5523L, doi:10.1093/mnras/stac2163.


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