Volume 610, February 2018
|Number of page(s)||4|
|Section||Letters to the Editor|
|Published online||13 February 2018|
Letter to the Editor
Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2★
INAF – Osservatorio Astronomico di Palermo G.S. Vaiana,
Piazza del Parlamento 1,
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA, USA
3 Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
4 Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA
5 Institut für Physik und Astronomie, Universität Potsdam Karl-Liebknecht-Strasse 24/25, 14476 Potsdam-Golm, Germany
6 Kazan Federal University, Kremlevskaya Str., 18, Kazan, Russia
Accepted: 2 December 2017
Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them (~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 ρ 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 ρ 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 ~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 ρ Oph A and further constrained its age. We conclude that ρ Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.
Key words: stars: activity / stars: early-type / stars: magnetic field / pulsars: individual: ρ Ophiuchi A
© ESO, 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.