Issue |
A&A
Volume 610, February 2018
|
|
---|---|---|
Article Number | L3 | |
Number of page(s) | 4 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/201732078 | |
Published online | 13 February 2018 |
Letter to the Editor
Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2★
1
INAF – Osservatorio Astronomico di Palermo G.S. Vaiana,
Piazza del Parlamento 1,
90134
Palermo, Italy
e-mail: pilli@astropa.inaf.it
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
Received:
11
October
2017
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
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