2014A&A...567L...4P


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST06:58:47

2014A&A...567L...4P - Astronomy and Astrophysics, volume 567, L4-4 (2014/7-1)

Smooth X-ray variability from ρ Ophiuchi A+B. A strongly magnetized primary B2 star ?

PILLITTERI I., WOLK SCOTT J., GOODMAN A. and SCIORTINO S.

Abstract (from CDS):

X-rays from massive stars are ubiquitous yet not clearly understood. In an XMM-Newton observation devoted to observing the first site of star formation in the ρ Ophiuchi dark cloud, we detect smoothly variable X-ray emission from the B2IV+B2V system of ρ Ophiuchi. We tentatively assign the emission to the primary component. The light curve of the pn camera shows a first phase of low, almost steady rate, then a rise phase of duration of 10ks, followed by a high rate phase. The variability is seen primarily in the band 1.0-8.0keV while little variability is detected below 1keV. The spectral analysis of the three phases reveals the presence of a hot component at 3.0keV that adds up to two relatively cold components at 0.9keV and 2.2keV. We explain the smooth variability with the emergence of an extended active region on the surface of the primary star as being due to its fast rotation (vsini∼315km/s). We estimate that the region has a diameter in the range 0.5-0.6R*. The hard X-ray emission and its variability hint at a magnetic origin, as suggested for a few other late-O through early-B type stars. We also discuss an alternative explanation based on the emergence from occultation of a young (5-10Myr) low mass companion that is bright and hot in X-rays.

Abstract Copyright:

Journal keyword(s): stars: early-type - stars: activity - stars: magnetic field - stars: individual: ρ Ophiuchi - starspots

Simbad objects: 12

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Number of rows : 12

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 * tet01 Ori C ** 05 35 16.46375 -05 23 22.8486 4.20 5.15 5.13 4.91 4.73 O7Vp 1272 1
2 NGC 2264 OpC 06 40 58 +09 53.7     3.9     ~ 1588 1
3 * zet Pup BY* 08 03 35.04754 -40 00 11.3321 0.89 1.98 2.25 2.36 2.58 O4I(n)fp 1092 1
4 * bet Cru bC* 12 47 43.26877 -59 41 19.5792 0.03 1.02 1.25 1.38 1.64 B1IV 324 0
5 * rho Oph ** 16 25 35.11766 -23 26 49.8150 4.30 4.85 4.63 4.27 3.96 B2IV+B2V 608 2
6 GSS 35 TT* 16 26 34.1750440278 -24 23 28.331873112     16.53 14.75 12.51 B3 214 1
7 NAME rho Oph AB PoC 16 26 57.2 -24 23 24           ~ 8 0
8 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3027 0
9 * tau Sco * 16 35 52.9528530 -28 12 57.661515 1.55 2.56 2.81 2.93 3.18 B0.2V 854 0
10 * alf Pav SB* 20 25 38.85705 -56 44 06.3230 1.03 1.791 1.918     B2IV 273 0
11 Ass Cyg OB 2 As* 20 33.2 +41 19           ~ 790 0
12 NAME Carina Region reg ~ ~           ~ 152 0

    Equat.    Gal    SGal    Ecl

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2020.07.13-06:58:47

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