2010A&A...516A..38R


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.25CET10:40:22

2010A&A...516A..38R - Astronomy and Astrophysics, volume 516, A38-38 (2010/6-2)

X-ray emission from the remarkable A-type star HR 8799.

ROBRADE J. and SCHMITT J.H.M.M.

Abstract (from CDS):

We investigate a Chandra observation of the remarkable planet-bearing A5V star HR 8799, more precisely classified as a kA5hF0mA5 star. We search for intrinsic X-ray emission, a diagnostic for studying the possible activity of intermediate-mass stars. In the regime of mid/late A-type stars a strong decline in magnetic activity occurs towards hotter stars because of the vanishing of the outer convection zone. We clearly detect HR 8799 at soft X-ray energies with the ACIS-S detector in a 10 ks exposure; minor X-ray brightness variability is present during the observation. The coronal plasma is described well by a model with a temperature of around 3MK and an X-ray luminosity of about LX=1.3x1028erg/s in the 0.2-2.0keV band, corresponding to an activity level of log LX/Lbol≃-6.2. Altogether, these findings point to a rather weakly active and given a RASS detection, long-term stable X-ray emitting star. The X-ray emission from HR 8799 resembles those of late A/early F-type stars, in agreement with its classification on the basis of hydrogen lines and its effective temperature determination and thus resolving the apparent discrepancy with the standard picture of magnetic activity that predicts mid A-type stars to be virtually X-ray dark.

Abstract Copyright:

Journal keyword(s): stars: activity - stars: coronae - stars: individual: HR 8799 - X-rays: stars

Simbad objects: 4

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Number of rows : 4

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 * lam Boo dS* 14 16 23.0187965 +46 05 17.900526 4.31 4.26 4.18 4.16 4.13 A0Va_lB 327 0
2 * alf Aql dS* 19 50 46.99855 +08 52 05.9563 1.07 0.98 0.76 0.62 0.49 A7Vn 825 0
3 * alf Cep PM* 21 18 34.77233 +62 35 08.0681 2.770 2.680 2.460 2.22 2.11 A8Vn 341 0
4 HD 218396 El* 23 07 28.7156905667 +21 08 03.302133882   6.21 5.953     F0+VkA5mA5 916 0

    Equat.    Gal    SGal    Ecl

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2020.11.25-10:40:22

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