HD 40372

HD 40372, also known as 59 Orionis, V1004 Orionis and HR 2100, is a variable star in the constellation Orion. Its apparent magnitude varies between magnitude 5.88 and 5.92, making it faintly visible to the naked eye for an observer far from light polluted urban areas.[2] HD 40372 exhibits two types of variability; it is an eclipsing binary star and one of the two stars is a Delta Scuti variable star.[3]

Light curve for HD 40372, plotted from TESS data.[9] The data are folded with the eclipse period, and the 97 minute Delta Scuti variation period[3] is marked in red.
HD 40372
Location of HD 40372 (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Orion
Right ascension 05h 58m 24.44302s[1]
Declination +01° 50′ 13.5902″[1]
Apparent magnitude (V) 5.88 - 5.92[2]
Characteristics
Spectral type A5me[3] (kA7VmA7/F5III/Vp)[4]
Variable type Beta Lyrae[5] / Delta Scuti[2]
Astrometry
Proper motion (μ) RA: 7.208±0.033[1] mas/yr
Dec.: −7.999±0.032[1] mas/yr
Parallax (π)9.3752 ± 0.0360 mas[1]
Distance348 ± 1 ly
(106.7 ± 0.4 pc)
Orbit[6]
Period (P)2.7405 d
Eccentricity (e)0.02
Argument of periastron (ω)
(primary)		183.0°
Semi-amplitude (K1)
(primary)		55.6 km/s
Details
pulsating star
Mass2.15[3] M☉
Radius2.78[3] R☉
Luminosity25[3] L☉
Surface gravity (log g)3.71[3] cgs
Temperature7,706[3] K
companion
Mass0.73[7] M☉
Other designations
59 Orionis, BD+01 1171, V1004 Ori, HIP 28271, HR 2100, SAO 113315[8]
Database references
SIMBADdata

HD 40372 was discovered to be a spectroscopic binary by the examination of spectra taken at the DDO in 1943 and 1944. Further DDO spectra taken in 1946 and 1947 allowed the binary's orbit to be calculated, and the period derived from those data, 2.74050 days, is still used in 21st century publications.[10][3] In 1968, HD 40372 was found to have a "δ Del"-type spectrum.[11] Because such a spectrum can indicate variability, the star was monitored with a photoelectric photometer, and found to be a Delta Scuti variable in 1973.[12][13] It was given the variable star designation V1004 Orionis in 1974.[14] Remarkably, the fact that HD 40372 is an eclipsing binary appears to have gone unnoticed until the Hipparcos data were processed by an automated light curve classifier in 2011,[5] despite the fact that the brightness changes due to eclipses are far larger than the variations caused by the Delta Scuti pulsations.

The spectral type of the system is given as A5me, indicating an Am star. Such stars have unusual absorption line strengths for metals in comparison to hydrogen, and a detailed spectral classification of kA7VmA7/F5III/Vp indicates that the classification based on Calcium K-lines would be A7V, while the classification based on lines of other metals in the green part of the spectrum would be A7V and for metal lines in the violet F5III/IV.[4] Because of the unusual luminosity effects in the spectrum, it has been considered to be a Delta Delphini star.[15]

In 1985, HD 40372 was identified as a possible member of the Hyades Moving Group.[16] Two visible companions are listed, a 10th-magnitude star at 37″ and a 7th-magnitude A1 giant at 178″. The closer of the two is an unrelated background object, but the more distant shares a common proper motion and is at the same distance. Any orbit, assuming they were gravitationally bound, would require about a million years.[7]

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 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.
  3. Deb, Sukanta; Tiwari, S. K.; Singh, Harinder P.; Seshadri, T. R.; Chaubey, U. S. (September 2009). "Photometry of the delta Scuti star HD 40372" (PDF). Bull. Astr. Soc. India. 37: 109–123. Bibcode:2009BASI...37..109D. Retrieved 10 January 2023.
  4. Sreedhar Rao, S.; Abhyankar, K. D. (1991). "MK morphological study of AM stars at 66 A/Mm". Journal of Astrophysics and Astronomy. 12 (2): 133. Bibcode:1991JApA...12..133S. doi:10.1007/BF02709302. S2CID 59324843.
  5. Dubath, P.; Rimoldini, L.; Süveges, M.; Blomme, J.; López, M.; Sarro, L. M.; De Ridder, J.; Cuypers, J.; Guy, L.; Lecoeur, I.; Nienartowicz, K.; Jan, A.; Beck, M.; Mowlavi, N.; De Cat, P.; Lebzelter, T.; Eyer, L. (July 2011). "Random forest automated supervised classification of Hipparcos periodic variable stars". Monthly Notices of the Royal Astronomical Society. 414 (3): 2602–2617. arXiv:1101.2406. Bibcode:2011MNRAS.414.2602D. doi:10.1111/j.1365-2966.2011.18575.x. S2CID 118560311.
  6. Pourbaix, D.; et al. (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. S2CID 119387088.
  7. Tokovinin, Andrei (March 1, 2018), "The Updated Multiple Star Catalog", The Astrophysical Journal Supplement Series, 235 (1): 6, arXiv:1712.04750, Bibcode:2018ApJS..235....6T, doi:10.3847/1538-4365/aaa1a5, ISSN 0067-0049, S2CID 119047709.
  8. "59 Ori -- delta Sct Variable". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-01-09.
  9. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 January 2023.
  10. Nadeau, Paul H. (May 1951). "The orbit of the spectroscopic binary HD 40372". Publications of the David Dunlap Observatory. 1: 537–539. Bibcode:1951PDDO....1..537N.
  11. Cowley, A. P.; Cowley, C. R.; Hiltner, W. A.; Jaschek, M.; Jaschek, C. (December 1968). "Further Bright Peculiar A Stars". Publications of the Astronomical Society of the Pacific. 80 (477): 746. Bibcode:1968PASP...80..746C. doi:10.1086/128719. S2CID 122523455.
  12. Breger, M. (January 1973). "Short-period variability of B, A and F stars. VI. New Delta Scuti stars in selected regions". Astronomy and Astrophysics. 22: 247. Bibcode:1973A&A....22..247B.
  13. Breger, Michel (December 1969). "Short-Period Variability of b, a, and F Stars. III. a Survey of Delta Scuti Variable Stars". Astrophysical Journal Supplement. 19: 79. Bibcode:1969ApJS...19...79B. doi:10.1086/190199.
  14. Kukarkin, B. V.; Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (January 1975). "60th Name-List of Variable Stars". Information Bulletin on Variable Stars. 961 (1): 1. Bibcode:1975IBVS..961....1K.
  15. Renson, P.; Manfroid, J. (19 March 2009). "Catalogue of Ap, HgMn and Am stars". Astronomy & Astrophysics. 498 (3): 961–966. Bibcode:2009A&A...498..961R. doi:10.1051/0004-6361/200810788. eISSN 1432-0746. ISSN 0004-6361.
  16. Bubenicek, J.; Palous, J.; Piskunov, A. E. (December 1985). "Hyades moving group : new members, kinematics and age". Astronomicheskii Zhurnal. 62: 1073–1076. Bibcode:1985AZh....62.1073B.
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