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, with its brightness varying slightly from magnitude 5.48 to 5.53 over a period of 1.12 days.[1]

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 half the actual orbital period because his data did not allow him to distinguish between primary and secondary minima in the light curve.[2] It was given the variable star designation HX Velorum in 1980.[3] In 1983, Christoffel Waelkens and Frédy Rufener published the correct period of variability, 1.124 days.[4]

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).[5][6] The system's brightness variation is caused by the ellipsoidal Aa and Ab components orbiting each other.[6]

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 light years, while the distance to IC 2395 has been estimated to be 4,560 ± 200[7] 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.[6]

References

  1. ^ Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869
  2. ^ Shobbrook, R. R. (July 1981). "Short period variability of some early B stars". Monthly Notices of the Royal Astronomical Society. 196 (2): 129–134. Bibcode:1981MNRAS.196..129S. doi:10.1093/mnras/196.2.129
  3. ^ Kholopov, P. N.; Samus, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (February 1981). "65th Name-List of Variable Stars". Information Bulletin on Variable Stars. 1921: 1. Bibcode:1981IBVS.1921....1K. Retrieved 21 March 2023.
  4. ^ Waelkens, C. & Rufener, F. (May 1983). "An observational study of the influence of close companions on the pulsations of beta Cephei stars". Astronomy and Astrophysics. 121: 45–50. Bibcode:1983A&A...121...45W
  5. ^ "The Washington Double Star Catalog". The Washington Double Star Catalog. Georgia State University. Retrieved 21 March 2023.
  6. ^ Blackford, M. G.; Erdem, A.; Sürgit, D.; Özkardeş, B.; Budding, E.; Butland, R.; Demircan, O. (July 2019). "Absolute parameters of young stars: HX Velorum". Monthly Notices of the Royal Astronomical Society. 487 (1): 161–167. Bibcode:2019MNRAS.487..161B. doi:10.1093/mnras/stz1136
  7. ^ Jaehnig, Karl; Bird, Jonathan; Holley-Bockelmann, Kelly (December 2021). "Membership Lists for 431 Open Clusters in Gaia DR2 Using Extreme Deconvolution Gaussian Mixture Models". The Astrophysical Journal. 923 (1): 129. arXiv:2108.02783. Bibcode:2021ApJ...923..129J. doi:10.3847/1538-4357/ac1d51