| 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−Vcolor 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: −36.021mas/yr[2] Dec.: 5.157mas/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 |
| Periastronepoch (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 avariable star system in the southernconstellation ofVela. It has the identifierHD 94660 in theHenry Draper Catalogue;KQ Vel is thevariable star designation. This appears as a sixth magnitude star with anapparent 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 theSun based onparallax measurements,[2] and is drifting further away with aradial velocity of around 23 km/s.[7]
This was first identified as achemically peculiar star byCarlos and Mercedes Jaschek in 1959, who foundspectral peculiarities in thesiliconabsorption bands.[11] The long-termphotometric variability of this star was reported byH. Hensberge in 1993, who noted a possibly complicatedlight curve with an estimated period on the order of 2,700 days.[12] In 1975,E. F. Borra andJ. D. Landstreet detected astrong magnetic field in excess of1 kG on the star.[13]Radial velocity measurements byG. Mathys and associates (1997) demonstrated this is aspectroscopic binary system.[14]
This single-lined spectroscopic binary has a physical separation of at least 1.25 ± 0.01 AU, anorbital period of 2.32 years, and a higheccentricity (ovalness) of 0.45.[3] The visible component is anAp star with astellar classification of Ap(SiCr),[4] although theeffective 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 theeuropium,chromium, and silicon bands. It is classified as anAlpha2 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 adipole strength of7.5 kG, while displaying additionalquadropole andoctopolemoments. It is inclined to therotation axis by 16°. The mean longitudinal field is almost constant, showing a strength of−2 kG.[8] The star is less than halfway through itsmain 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]
Themass 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] Amain sequence stellar companion of this mass would have a spectral typeearlier thanA5V.[1] This led to the suggestion that this companion must be a compact object, either ablack hole, aneutron star, or a pair ofwhite dwarfs.[8] In 2018 the companion was detected in thenear infrared using thePioneer instrument at theVLIT observatory, showing anH-band magnitude difference of1.8±0.03 at anangular separation of18.72±0.02 mas. This corresponds to a projected linear separation of a little over2 AU.[1]
X-ray observations with theChandra X-ray Observatory in 2016 strongly suggested that the companion is aneutron 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 asupernova explosion, possibly of theelectron capture type that would not significantly disrupt the orbit. The strongly magnetic Ap star would likely be the result of a merger, perhaps from anW UMa close binary. The current neutron star may have been the tertiary member of the system, and it gained mass during aRoche lobe overflow of the binary components.[15]
{{cite web}}: CS1 maint: postscript (link)| Stars |
| ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| |||||||||||
| Star clusters |
| ||||||||||
| Nebulae |
| ||||||||||
| Galaxies |
| ||||||||||
| |||||||||||
