TY  - JOUR
A1  - Hubrig, Swetlana
A1  - Schoeller, Markus
A1  - Fossati, Luca
A1  - Morel, Thierry
A1  - Castro, Neves
A1  - Oskinova, Lida
A1  - Przybilla, Norbert
A1  - Eikenberry, Stephen S.
A1  - Nieva, Maria Fernanda
A1  - Langer, Norbert
T1  - B fields in OB stars (BOB): FORS2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. Massive B-type stars with strong magnetic fields and fast rotation are very rare and pose a mystery for theories of star formation and magnetic field evolution. Only two such stars, called sigma Ori E analogues, were known until recently. A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, announced the discovery of two additional rigidly rotating magnetosphere stars, HD 23478 and HD 345439. The magnetic fields in these newly discovered sOri E analogues have not been investigated so far.
 Methods. In the framework of our ESO Large Programme and one normal ESO programme, we carried out low-resolution FORS 2 spectropolarimetric observations of HD 23478 and HD 345439.
 Results. In the measurements of hydrogen lines, we discover a rather strong longitudinal magnetic field of up to 1.5 kG in HD 23478 and up to 1.3 kG using the entire spectrum. The analysis of HD 345439 using four subsequent spectropolarimetric subexposures does not reveal a magnetic field at a significance level of 3 sigma. On the other hand, individual subexposures indicate that HD 345439 may host a strong magnetic field that rapidly varies over 88 min. The fast rotation of HD 345439 is also indicated by the behaviour of several metallic and He I lines in the low-resolution FORS 2 spectra that show profile variations already on this short time-scale.
KW  - stars: early-type
KW  - stars: fundamental parameters
KW  - stars: variables: general
KW  - stars: magnetic field
KW  - stars: individual: HD 23478
KW  - stars: individual: HD 345439
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201526262
SN  - 0004-6361
SN  - 1432-0746
VL  - 578
PB  - EDP Sciences
CY  - Les Ulis
ER  -