TY  - JOUR
A1  - Pillitteri, Ignazio
A1  - Fossati, Luca
A1  - Rodriguez, N. Castro
A1  - Oskinova, Lida
A1  - Wolk, Scott J.
T1  - Detection of magnetic field in the B2 star rho Ophiuchi A with ESO FORS2
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them (similar to 10%) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star rho Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyze spectra of rho Oph A obtained with the FORS2 spectrograph at ESO Very Large Telescope (VLT) at two epochs, and detect a longitudinal component of the magnetic field of the order of similar to 500 G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of rho Oph A and further constrained its age. We conclude that rho Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.
KW  - stars: activity
KW  - stars: early-type
KW  - stars: magnetic field
KW  - pulsars: individual: rho Ophiuchi A
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201732078
SN  - 1432-0746
VL  - 610
PB  - EDP Sciences
CY  - Les Ulis
ER  -