J/MNRAS/499/5379 Longitudinal magnetic field of 6 B stars (Shultz+, 2020)
The magnetic early B-type stars. IV. Breakout or leakage? Hα emission as
a diagnostic of plasma transport in centrifugal magnetospheres.
Shultz M.E., Owocki S., Rivinius T., Wade G.A., Neiner C., Alecian E.,
Kochukhov O., Bohlender D., Ud-doula A., Landstreet J.D., Sikora J.,
David-uraz A., Petit V., Cerrahoglu P., Fine R., Henson G.,
(the Mimes and Binamics Collaborations)
<Mon. Not. R. Astron. Soc., 499, 5379-5395 (2020)>
=2020MNRAS.499.5379S 2020MNRAS.499.5379S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, early-type ; Stars, B-type ; Magnetic fields
Keywords: stars: circumstellar matter - stars: early-type -
stars: magnetic field - stars: massive - stars: rotation
Abstract:
Rapidly rotating early-type stars with strong magnetic fields
frequently show Hα emission originating in centrifugal
magnetospheres (CMs), circumstellar structures in which centrifugal
support due to magnetically enforced corotation of the magnetically
confined plasma enables it to accumulate to high densities. It is not
currently known whether the CM plasma escapes via centrifugal breakout
(CB), or by an unidentified leakage mechanism. We have conducted the
first comprehensive examination of the Hα emission properties
of all stars currently known to display CM-pattern emission. We find
that the onset of emission is dependent primarily on the area of the
CM, which can be predicted simply by the value BK of the magnetic
field at the Kepler corotation radius RK. Emission strength is
strongly sensitive to both CM area and BK. Emission onset and
strength are not dependent on effective temperature, luminosity, or
mass-loss rate. These results all favour a CB scenario; however, the
lack of intrinsic variability in any CM diagnostics indicates that CB
must be an essentially continuous process, i.e. it effectively acts as
a leakage mechanism. We also show that the emission profile shapes are
approximately scale-invariant, i.e. they are broadly similar across a
wide range of emission strengths and stellar parameters. While the
radius of maximum emission correlates closely as expected to RK, it
is always larger, contradicting models that predict that emission
should peak at RK.
Description:
Longitudinal magnetic field measurements Bz of 6 stars obtained with
the ESPaDonS and Narval spectropolarimeters using the least-squares
deconvolution method.
Objects:
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RA (J2000) DE Designation(s)
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03 12 14.25 +27 15 25.1 HD 19832 = * 56 Ari
03 36 17.40 -17 28 01.5 HD 22470 = * 20 Eri
06 28 10.77 -04 53 56.5 HD 45583 = V* V682 Mon
15 54 39.53 -25 14 37.5 HD 142301 = * 3 Sco
16 06 06.39 -23 36 22.9 HD 144334 = HR 5988
16 11 58.53 -19 27 00.8 HD 145501 = * nu.02 Sco
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 34 6 List of stars with data in table A2
tablea2.dat 57 64 Longitudinal magnetic field measurements Bz of 6
stars obtained with the ESPaDonS and Narval
spectropolarimeters using the least-squares
deconvolution method
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Star Name of star
11- 12 I2 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 21 F5.2 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 34 F5.2 arcsec DEs Declination (J2000)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Star Name of star
11 A1 --- Inst [E/N] Instrument (E=ESOaDOnS, N=Narval)
13- 25 F13.5 d HJD Heliocentric Julian Date
27- 33 F7.1 G Bz Longitudinal magnetic field
36- 41 F6.1 G e_Bz Longitudinal magnetic field error
44- 49 F6.1 G Nz Null field
52- 57 F6.1 G e_Nz Null field error
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Acknowledgements:
Matthew Shultz, matt.shultz(at)gmail.com
(End) Patricia Vannier [CDS] 02-Feb-2022