Spectropolarimetry of Magnetic Chemically Peculiar Stars in the Orion OB1 Association

Abstract

We summarise the results of a spectropolarimetric survey of 56 chemically peculiar (CP) stars in the association of Orion OB1. We uniformly collected the observational material with the 6-m telescope BTA of the Special Astrophysical Observatory in 2013-2021. We identify 14 new magnetic CP stars with a longitudinal magnetic field exceeding approximately 500 G. The studied sample contains 31 magnetic stars or 55% of the whole CP population in Orion OB1. We show that the percentage of the magnetic CP stars and the field strength drops sharply with age. The mean longitudinal magnetic field in the young subgroup OB1b ($\log t=6.23$) is confidently almost three times stronger than in the older subgroups OB1a ($\log t=7.05$) and OB1c ($\log t=6.66$). In the Orion Nebula, a place with the youngest stellar population ($\log t<6.0$), we detect the magnetic field only in 20% of CP stars. Such occurrence drastically differs from 83% of magnetic CP stars in the nearby subgroup OB1c. We consider this effect an observational bias caused by a significant portion of a very young population with the signatures of Herbig Ae/Be stars. The technique we used for magnetic measurements, and the quality of available data do not allow us to detect weak fields in the case of stars with a limited number of lines and emissions in spectra.

Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal. Contains 14 pages, 11 figures

References in corpus (24)

• The Gaia mission
• The distance to the Orion Nebula
• Weak magnetic fields in Ap/Bp stars: Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomy
• How mergers magnetise massive stars
• Evolutionary state of magnetic chemically peculiar stars
• Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1
• Searching for links between magnetic fields and stellar evolution III. Measurement of magnetic fields in open cluster Ap stars with ESPaDOnS
• Rotational Velocities For B0-B3 Stars in 7 Young Clusters: Further Study of the Relationship between Rotation Speed and Density in Star-Forming Regions
• Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy
• The Magnetic Early B-type Stars I: Magnetometry and Rotation
• Variability Properties of 4 Million Sources in the $TESS$ Input Catalog Observed with the Kilodegree Extremely Little Telescope Survey
• OB associations and their origins
• Discovery of two magnetic massive stars in the Orion Nebula Cluster: a clue to the origin of neutron star magnetic fields?
• B fields in OB stars (BOB): Concluding the FORS2 observing campaign
• The distance to the Orion Nebula Cluster
• Magnetic OB[A] Stars with TESS: probing their Evolutionary and Rotational properties (MOBSTER) - I. First-light observations of known magnetic B and A stars
• Evidence of magnetic field decay in massive main-sequence stars
• Detailed 3D structure of OrionA in dust with Gaia DR2
• Orion A's complete 3D magnetic field morphology
• Mapping young stellar populations towards Orion with Gaia DR1
• Magnetic geometry and surface differential rotation of the bright Am star Alhena A
• Magnetic Fields of CP Stars in the OrionOB1 Association. IV. Stars of Subgroup 1b
• On the Discovery of Strong Magnetic Field in HD 34736 Binary System
• MOBSTER -- IV. Detection of a new magnetic B-type star from follow-up spectropolarimetric observations of photometrically selected candidates