Magnetic Fields of CP Stars in the Orion OB1 Association. IV. Stars of Subgroup 1b

Romanyuk, I. I.; Semenko, E. A.; Moiseeva, A. V.; Yakunin, I. A.; Kudryavtsev, D. O.

doi:10.1134/s1990341321010090

“…The TESS period does not phase the Bz measurements. Romanyuk et al (2021a) noted the presence of other periods in the light curve, which they attributed to the rotation period of the cooler secondary; this periodicity appears to be only marginally significant. The light curve contains 11 harmonics of the rotational frequency; simultaneous fitting of the rotational frequency and all harmonics yields 0.58921(1) d, which still does not provide a coherent phasing of Bz .…”

Section: Starmentioning

confidence: 98%

“…C1). Romanyuk et al (2021a) used the TESS light curve to refine the period to 2.70418(1) d. However, this does not coherently phase the combined SAO and ES-PaDOnS dataset. Our own analysis of the TESS data gives 2.702(2) d, which also fails to phase the magnetic data.…”

Section: Starmentioning

confidence: 99%

“…The light curve contains 11 harmonics of the rotational frequency; simultaneous fitting of the rotational frequency and all harmonics yields 0.58921(1) d, which still does not provide a coherent phasing of Bz . The closest period that provides an acceptable phasing is 0.58884(2) d, which is used to phase the Romanyuk et al (2021a) and DAO Bz measurements in Fig. C6.…”

Section: Starmentioning

confidence: 99%

“…Romanyuk et al (2021a) obtained several Bz measurements from this SB2 star, and determined a rotation period of 0.58913 d from the TESS light curve.…”

mentioning

confidence: 99%

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MOBSTER -- VI. The crucial influence of rotation on the radio magnetospheres of hot stars

Shultz,

Owocki,

ud-Doula

et al. 2022

Preprint

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Numerous magnetic hot stars exhibit gyrosynchrotron radio emission. The source electrons were previously thought to be accelerated to relativistic velocities in the current sheet formed in the middle magnetosphere by the wind opening magnetic field lines. However, a lack of dependence of radio luminosity on the wind power, and a strong dependence on rotation, has recently challenged this paradigm. We have collected all radio measurements of magnetic early-type stars available in the literature. When constraints on the magnetic field and/or the rotational period are not available, we have determined these using previously unpublished spectropolarimetric and photometric data. The result is the largest sample of magnetic stars with radio observations that has yet been analyzed: 131 stars with rotational and magnetic constraints, of which 50 are radio-bright. We confirm an obvious dependence of gyrosynchrotron radiation on rotation, and furthermore find that accounting for rotation neatly separates stars with and without detected radio emission. There is a close correlation between Hα emission strength and radio luminosity. These factors suggest that radio emission may be explained by the same mechanism responsible for Hα emission from centrifugal magnetospheres, i.e. centrifugal breakout (CBO), however, whereas the Hα-emitting magnetosphere probes the cool plasma before breakout, radio emission is a consequence of electrons accelerated in centrifugally-driven magnetic reconnection.

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“…The first measurements of the stellar magnetic fields in Orion were made by Borra & Landstreet (1979) with the use of a Balmer-line In this paper, we present the results of a spectropolarimetric survey of all 56 known and potentially magnetic CP stars from Table 1. The individual measurements of the longitudinal magnetic field were reported previously in Romanyuk et al (2019Romanyuk et al ( , 2021a. These papers also describe the techniques used for measuring the magnetic field.…”

Section: Magnetic Field Of Cp Stars In Orion Ob1mentioning

confidence: 99%

Spectropolarimetry of Magnetic Chemically Peculiar Stars in the Orion OB1 Association

Semenko,

Romanyuk,

Yakunin

et al. 2022

Preprint

0

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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 = 6.23) is confidently almost three times stronger than in the older subgroups OB1a (log = 7.05) and OB1c (log = 6.66). In the Orion Nebula, a place with the youngest stellar population (log < 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.

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MOBSTER – VI. The crucial influence of rotation on the radio magnetospheres of hot stars

Shultz

¹

,

Owocki

²

,

ud‐Doula

³

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Numerous magnetic hot stars exhibit gyrosynchrotron radio emission. The source electrons were previously thought to be accelerated to relativistic velocities in the current sheet formed in the middle magnetosphere by the wind opening magnetic field lines. However, a lack of dependence of radio luminosity on the wind power, and a strong dependence on rotation, has recently challenged this paradigm. We have collected all radio measurements of magnetic early-type stars available in the literature. When constraints on the magnetic field and/or the rotational period are not available, we have determined these using previously unpublished spectropolarimetric and photometric data. The result is the largest sample of magnetic stars with radio observations that has yet been analyzed: 131 stars with rotational and magnetic constraints, of which 50 are radio-bright. We confirm an obvious dependence of gyrosynchrotron radiation on rotation, and furthermore find that accounting for rotation neatly separates stars with and without detected radio emission. There is a close correlation between Hα emission strength and radio luminosity. These factors suggest that radio emission may be explained by the same mechanism responsible for Hα emission from centrifugal magnetospheres, i.e. centrifugal breakout (CBO), however, whereas the Hα-emitting magnetosphere probes the cool plasma before breakout, radio emission is a consequence of electrons accelerated in centrifugally-driven magnetic reconnection.

show abstract

Magnetic Fields of CP Stars in the Orion OB1 Association. IV. Stars of Subgroup 1b

Cited by 19 publications

References 28 publications

MOBSTER -- VI. The crucial influence of rotation on the radio magnetospheres of hot stars

MOBSTER -- VI. The crucial influence of rotation on the radio magnetospheres of hot stars

Spectropolarimetry of Magnetic Chemically Peculiar Stars in the Orion OB1 Association

MOBSTER – VI. The crucial influence of rotation on the radio magnetospheres of hot stars

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