HX Velorum

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HX Velorum
HXVelLightCurve.png
A light curve for HX Velorum, plotted from TESS data. [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Vela
Right ascension 08h 42m 16.19252s [2]
Declination −48° 05 56.7481 [2]
Apparent magnitude  (V)5.48 - 5.53 [3]
Characteristics
Spectral type B1.5V [4]
U−B color index −0.9 [4]
B−V color index −0.17 [4]
Variable type ELL [3]
Astrometry
Radial velocity (Rv)42.0±4.5 [5]  km/s
Proper motion (μ)RA: −3.714±0.128 [2]   mas/yr
Dec.: 4.758±0.138 [2]   mas/yr
Parallax (π)0.9479 ± 0.1121  mas [2]
Distance approx. 3,400  ly
(approx. 1,100  pc)
Absolute magnitude  (MV)−2.32 [6]
Details [4]
Aa
Mass 8.5±1.7  M
Radius 5.0±0.3  R
Luminosity 8,700±1,500  L
Temperature 25,000±1,300  K
Ab
Mass 5.4±1.2  M
Radius 3.1±0.3  R
Luminosity1,400±800  L
Temperature 20,000±2,500  K
Other designations
HD  74455, HR  3462, HIP  42712, SAO  220313 [7]
Database references
SIMBAD data

HX Velorum, also known as HR 3462 and HD 74455, is a star in the constellation Vela. It is a 5th magnitude star, so it will be faintly visible to the naked eye of an observer far from city lights. It is a variable star, whose brightness varies slightly from magnitude 5.48 to 5.53 over a period of 1.12 days. [3]

In 1981, Robert Shobbrook announced that HR 3462 is a variable star based on observations made in 1976. He correctly classified it as an ellipsoidal variable, but the period he derived, 0.56205±0.00005 days, was a factor of two too short because his data did not allow him to distinguish between primary and secondary minima in the light curve. [8] It was given the variable star designation HX Velorum in 1980. [9] In 1983, Christoffel Waelkens and Frédy Rufener published the correct period of variability, 1.124 days. [10]

HX Velorum is a triple star, consisting of a pair (components A, magnitude 5.5, and B, magnitude 8.28) separated by 0.5 arc seconds. Component A is itself a close binary pair (components Aa and Ab). [11] [4] The system's brightness variation is caused by the ellipsoidal Aa and Ab components orbiting each other. [4]

HX Velorum is only about 2 arc minutes from the center of IC 2395, so it appears to be within that cluster. However the Gaia DR3 dataset lists the parallax of HX Velorum as 0.9479±0.1121  mas , yielding a distance of 3,400+500
−300
light years, while the distance to IC 2395 has been estimated to be 4,560±200 [12] light years, so HX Velorum might be a foreground object rather than a true cluster member. Mark Blackford et al. concluded HX Velorum is a member of the cluster, but that conclusion was based in part on earlier, significantly different distance estimates for both the star and the cluster. [4]

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References

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