scholarly journals The Origin of the Bimodal Distribution of Magnetic Fields in Early-type Stars

2020 ◽  
Vol 900 (2) ◽  
pp. 113 ◽  
Author(s):  
Adam S. Jermyn ◽  
Matteo Cantiello
Keyword(s):  
Magnetic Fields ◽  
Bimodal Distribution ◽  
Early Type ◽  
Early Type Stars

scholarly journals Magnetic Archaeology of Early-type Stellar Dynamos

2021 ◽  
Vol 923 (1) ◽  
pp. 104
Author(s):  
Adam S. Jermyn ◽  
Matteo Cantiello
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Mass Loss ◽  
Bimodal Distribution ◽  
Early Type ◽  
Surface Magnetism ◽  
Near Surface ◽  
Early Type Stars ◽  
Slow Evolution ◽  
Weak Fields

Abstract Early-type stars show a bimodal distribution of magnetic field strengths, with some showing very strong fields (≳1 kG) and others very weak fields (≲10 G). Recently, we proposed that this reflects the processing or lack thereof of fossil fields by subsurface convection zones. Stars with weak fossil fields process these at the surface into even weaker dynamo-generated fields, while in stars with stronger fossil fields magnetism inhibits convection, allowing the fossil field to remain as is. We now expand on this theory and explore the timescales involved in the evolution of near-surface magnetic fields. We find that mass loss strips near-surface regions faster than magnetic fields can diffuse through them. As a result, observations of surface magnetism directly probe the frozen-in remains of the convective dynamo. This explains the slow evolution of magnetism in stars with very weak fields: these dynamo-generated magnetic fields evolve on the timescale of the mass loss, not that of the dynamo.

Fossil magnetic fields and rotation of early-type stars

1994 ◽  
Vol 162 ◽  
pp. 184-185
Author(s):  
A.E. Dudorov
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Molecular Clouds ◽  
Main Sequence ◽  
Early Type ◽  
Main Sequence Stars ◽  
Early Type Stars ◽  
Quadrupole Magnetic Field ◽  
Interstellar Molecular Clouds

Observational data of the last 10 years allow two main conclusions:a) Main sequence stars can be separated in two classes: - magnetic (Bp) stars with surface strengths of a dipole or quadrupole magnetic field of Bs ≈ n · (102 − 103) G, n = 2,3,4…7, and - normal main sequence stars (F-O) with magnetic fields Bs ≈ 1 − 100 G (< 300 G);b) Typical star formation takes place in interstellar molecular clouds with magnetic field strengths B ≈ 10-5 G (See Dudorov 1990).

scholarly journals The B Fields in OB Stars (BOB) Survey

2014 ◽  
Vol 9 (S307) ◽  
pp. 342-347 ◽  
Author(s):  
T. Morel ◽  
N. Castro ◽  
L. Fossati ◽  
S. Hubrig ◽  
N. Langer ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Lower Bound ◽  
Magnetic Fields ◽  
Field Strength ◽  
Massive Stars ◽  
Occurrence Rate ◽  
Early Type ◽  
Ob Stars ◽  
Early Type Stars ◽  
Field Formation

AbstractThe B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. As of July 2014, a total of 98 objects were observed over 20 nights with FORS2 and HARPSpol. Our preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these objects. We discuss in this contribution some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects.

Microvariability of spectral line profiles and magnetic fields of early-type stars: ζ Ori A

2012 ◽  
Vol 67 (1) ◽  
pp. 67-72 ◽  
Author(s):  
V. V. Dushin ◽  
A. F. Kholtygin ◽  
G. A. Chountonov
Keyword(s):  
Magnetic Fields ◽  
Spectral Line ◽  
Line Profiles ◽  
Early Type ◽  
Early Type Stars

scholarly journals Magnetic observations of pulsating B and Be stars with ESPaDOnS and Narval

2008 ◽  
Vol 4 (S259) ◽  
pp. 391-392
Author(s):  
James Silvester ◽  
C. Neiner ◽  
H. F. Henrichs ◽  
G. A. Wade ◽  
E. Alecian ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Magnetic Fields ◽  
Critical Analysis ◽  
Be Stars ◽  
Early Type ◽  
Weak Magnetic Fields ◽  
Magnetic Stars ◽  
Early Type Stars ◽  
New Generation

AbstractDiscoveries of magnetic fields in pulsating B and Be stars have been claimed from low-resolution spectropolarimetric observations with FORS1 at VLT. We used the new generation of high-resolution spectropolarimeters, ESPaDOnS at CFHT and NARVAL at TBL, to check for the existence of these fields. We find that most of the claimed magnetic stars do not host a magnetic field. This work shows the importance of a critical analysis of FORS1 data when searching for weak magnetic fields in early-type stars and the advantage of using ESPaDOnS and NARVAL to study such type of stars.

scholarly journals Surface Magnetic Fields in Early-Type Stars

2000 ◽  
Vol 175 ◽  
pp. 334-336 ◽  
Author(s):  
V. S. Airapetian
Keyword(s):  
Magnetic Fields ◽  
Magnetic Activity ◽  
Stellar Atmospheres ◽  
Early Type ◽  
Inertial Oscillations ◽  
Early Type Stars ◽  
Stressed Surface

AbstractRecent observations imply magnetic activity in atmospheres of early-type stars. We explore the possibility that stressed surface magnetic fields can be driven by inertial oscillations, such as r-modes which are vorticity waves. We show that vorticIAL MOTIOns are able to supply helicity to drive magnetic activity in stellar atmospheres.

scholarly journals Global stellar magnetic fields: the crossover from fossils to dynamos

2006 ◽  
Vol 2 (14) ◽  
pp. 285-286 ◽  
Author(s):  
Gautier Mathys
Keyword(s):  
Magnetic Fields ◽  
Early Type ◽  
Origin And Evolution ◽  
Early Type Stars ◽  
Stellar Magnetic Fields ◽  
Ap Stars

AbstractAp stars comprise the majority of early-type stars in which magnetic fields have been definitely detected. Their observational properties are reviewed, with emphasis on those relevant to the understanding of the origin and evolution of their fields.

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