HD 133880

HD 133880, also known as HR 5624 and HR Lupi, is a Bp star about 340 light years from the Earth, in the constellation Lupus.[2] It is a 5th magnitude star, and will be faintly visible to the naked eye of an observer far from city lights. It is an SX Arietis variable star, varying from magnitude 5.76 to 5.81 over a period of 21.0594 hours.[3] HD 133880 is a member of the Upper Centaurus–Lupus association. It is a young star, estimated to have completed only 5±2 percent of its projected main sequence lifetime.[6] It is one of the few stars known to produce coherent pulsed radio radiation via electron cyclotron maser emission.[9]

HD 133880

A light curve for HR Lupi, plotted from TESS data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Lupus
Right ascension 15h 08m 12.12388s[2]
Declination −40° 35′ 02.1554″[2]
Apparent magnitude (V) 5.76 - 5.81[3]
Characteristics
Spectral type B8IVp Si λ4200[4]
Variable type SX Arietis[3]
Astrometry
Proper motion (μ) RA: −28.686±0.085[2] mas/yr
Dec.: −31.533±0.071[2] mas/yr
Parallax (π)9.4922 ± 0.0786 mas[2]
Distance344 ± 3 ly
(105.3 ± 0.9 pc)
Absolute magnitude (MV)0.53[5]
Details
Mass3.20±0.15[6] M☉
Radius2.01±0.32[7] R☉
Luminosity105[7] L☉
Surface gravity (log g)4.28[2] cgs
Temperature13,000±600[7] K
Rotational velocity (v sin i)103±10[7] km/s
Age16+4
−3[6] Myr
Other designations
HR Lupi, HIP 74066, HR 5624, SAO 225474,[8]
Database references
SIMBADdata

The spectrum of HD 133880 matches a B8 subgiant, but with unusually strong absorption lines of some metals, making it a member of the chemically peculiar Ap/Bp star class. For this particular star, silicon lines at 4,200 Å are notably strong.[6] Its rotation rate is unusually fast for a star of this type.[7]

In 1985, Christoffel Waelkens found that HD 133880 is a variable star with a period of 0.87746±0.00001 days, varying by 0.15, 0.10 and 0.06 magnitudes in the U, B and V bands respectively.[10] In 1986, the star was given the variable star designation HR Lupi.[11] Later measurements of the period varied significantly, and can only be reconciled if the period varies in time.[12]

In 1990, John Landstreet found that HD 133880 has a very strong (several kG) magnetic field, with the unusual property that its quadrupole term is stronger than the dipole term.[13] However a study in 2017 found the magnetic field was better described as a distorted asymmetric dipole, with a maximum strength of 12 kG, and an average strength of 4 kG.[14]

Much of the research interest in HD 133880 arises from its radio emissions. Jeremy Lim et al. observed the star with the Australia Telescope Compact Array in 1995, and found that because the star's magnetic and rotation axes are not aligned, the 6 cm wavelength radiation they measured showed variation in both strength and polarization as the star rotated.[15] In 2018 Barnali Das et al. detected electron cyclotron maser emission[16] from the star at 610 MHz, using the GMRT. HD 133880 was the second star found to radiate in this way (after CU Virginis). The radiation was found to vary by an order of magnitude as the star rotated, and had roughly 100 percent right circular polarization when the emission peaked.[12]

References
  1. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 22 January 2023.
  2. 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.
  3. "HR Lup". The International Variable Star Index. AAVSO. Retrieved 22 January 2023.
  4. Bychkov, V. D.; Bychkova, L. V.; Madej, J. (August 2021). "Catalog of averaged magnetic phase curves of stars. Second edition". Astronomy and Astrophysics. 652: A31. arXiv:2004.14099. Bibcode:2021A&A...652A..31B. doi:10.1051/0004-6361/202040215.
  5. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 119257644.
  6. Landstreet, J. D.; Bagnulo, S.; Andretta, V.; Fossati, L.; Mason, E.; Silaj, J.; Wade, G. A. (August 2007). "Searching for links between magnetic fields and stellar evolution: II. The evolution of magnetic fields as revealed by observations of Ap stars in open clusters and associations". Astronomy and Astrophysics. 470 (2): 685. arXiv:0706.0330. Bibcode:2007A&A...470..685L. doi:10.1051/0004-6361:20077343.
  7. Bailey, J. D.; Grunhut, J.; Shultz, M.; Wade, G.; Landstreet, J. D.; Bohlender, D.; Lim, J.; Wong, K.; Drake, S.; Linsky, J.; MiMeS Collaboration (June 2012). "An analysis of the rapidly rotating Bp star HD 133880". Monthly Notices of the Royal Astronomical Society. 423 (1): 328–343. arXiv:1203.5277. Bibcode:2012MNRAS.423..328B. doi:10.1111/j.1365-2966.2012.20881.x.
  8. "HR Lup -- alpha2 CVn Variable". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-01-22.
  9. Das, Barnali; Chandra, Poonam; Wade, Gregg A. (November 2020). "Unravelling the complex magnetosphere of the B star HD 133880 via wideband observation of coherent radio emission". Monthly Notices of the Royal Astronomical Society. 499 (1): 702–709. arXiv:2008.07170. Bibcode:2020MNRAS.499..702D. doi:10.1093/mnras/staa2499.
  10. Waelkens, C. (July 1985). "Photometric variations and period determination of eight southern CP stars". Astronomy and Astrophysics Supplement Series. 61: 127–139. Bibcode:1985A&AS...61..127W.
  11. Kholopov, P. N.; Samus, N. N.; Kazarovets, E. V. (August 1987). "The 68th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 3058 (1): 1. Bibcode:1987IBVS.3058....1K. Retrieved 23 January 2023.
  12. Das, Barnali; Chandra, Poonam; Wade, Gregg A. (February 2018). "Discovery of electron cyclotron MASER emission from the magnetic Bp star HD 133880 with the Giant Metrewave Radio Telescope". Monthly Notices of the Royal Astronomical Society: Letters. 474 (1): L61-L65. arXiv:1711.09836. Bibcode:2018MNRAS.474L..61D. doi:10.1093/mnrasl/slx193.
  13. Landstreet, J. D. (March 1990). "The Very Strong and Unusual Magnetic Field of the BP Silicon Star HD 133880". Astrophysical Journal Letters. 352: L5. Bibcode:1990ApJ...352L...5L. doi:10.1086/185680.
  14. Kochukhov, O.; Silvester, J.; Bailey, J. D.; Landstreet, J. D.; Wade, G. A. (September 2017). "Magnetic field topology and chemical abundance distributions of the young, rapidly rotating, chemically peculiar star HR 5624". Astronomy and Astrophysics. 605: A13. arXiv:1705.04966. Bibcode:2017A&A...605A..13K. doi:10.1051/0004-6361/201730919.
  15. Lim, Jeremy; Drake, Stephen A.; Linsky, Jeffrey L. (1996). "Rotation Modulation of Radio Emissionfrom the Magnetic Bp Star HR 5624". Radio Emission from the Stars and the Sun ASP Conference Series. 93: 324. Bibcode:1996ASPC...93..324L.
  16. Leto, P.; Trigilio, C.; Buemi, C. S.; Umana, G.; Ingallinera, A.; Cerrigone, L. (June 2016). "3D modelling of stellar auroral radio emission". Monthly Notices of the Royal Astronomical Society. 459 (2): 1159–1169. arXiv:1603.02423. Bibcode:2016MNRAS.459.1159L. doi:10.1093/mnras/stw639.
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