2017A&A...602A..92P


Query : 2017A&A...602A..92P

2017A&A...602A..92P - Astronomy and Astrophysics, volume 602A, 92-92 (2017/6-1)

The early B-type star Rho Ophiuchi A is an X-ray lighthouse.

PILLITTERI I., WOLK S.J., REALE F. and OSKINOVA L.

Abstract (from CDS):

We present the results of a 140ks XMM-Newton observation of the B2 star ρ Oph A. The star has exhibited strong X-ray variability: a cusp-shaped increase of rate, similar to that which we partially observed in 2013, and a bright flare. These events are separated in time by about 104ks, which likely correspond to the rotational period of the star (1.2-days). Time resolved spectroscopy of the X-ray spectra shows that the first event is caused by an increase of the plasma emission measure, while the second increase of rate is a major flare with temperatures in excess of 60MK (kT∼5keV). From the analysis of its rise, we infer a magnetic field of ≥300G and a size of the flaring region of ∼1.4-1.9x1011cm, which corresponds to ∼25%-30% of the stellar radius. We speculate that either an intrinsic magnetism that produces a hot spot on its surface or an unknown low mass companion are the source of such X-rays and variability. A hot spot of magnetic origin should be a stable structure over a time span of ≥2.5yr, and suggests an overall large scale dipolar magnetic field that produces an extended feature on the stellar surface. In the second scenario, a low mass unknown companion is the emitter of X-rays and it should orbit extremely close to the surface of the primary in a locked spin-orbit configuration, almost on the verge of collapsing onto the primary. As such, the X-ray activity of the secondary star would be enhanced by its young age, and the tight orbit as in RS Cvn systems. In both cases ρ Oph would constitute an extreme system that is worthy of further investigation.

Abstract Copyright: © ESO, 2017

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

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 * eps Eri BY* 03 32 55.8444911587 -09 27 29.739493865 5.19 4.61 3.73 3.00 2.54 K2V 1837 1
2 * sig Ori Y*O 05 38 44.7653828520 -02 36 00.283179888 2.54 3.58 3.79 3.87 4.11 O9.5V+B0.2V(n) 779 0
3 * sig Ori E Y*O 05 38 47.2050040320 -02 35 40.521424812 5.66 6.38 6.46 6.84 7.08 B2IV-Vp_He 441 0
4 * ksi01 CMa bC* 06 31 51.3663578 -23 25 06.318090 3.10 4.09 4.33 4.45 4.72 B0.7IV 313 0
5 CPD-62 2124 * 11 35 36.8614624296 -63 15 48.516783840 10.30 11.15 11.01 11.14   B2IIIHe 48 0
6 * rho Oph B * 16 25 35.0324153856 -23 26 46.923516744   5.26 6.66     B2V 125 0
7 * rho Oph ** 16 25 35.11766 -23 26 49.8150 4.30 4.85 4.63 4.27 3.96 B2IV+B2V 633 0
8 * rho Oph A * 16 25 35.1185711280 -23 26 49.831640736 4.3 5.22 5.05     B1V 400 0
9 HD 164492 Y*O 18 02 23.5527520992 -23 01 50.999556180 6.49 7.49 6.80 7.52   O7.5Vz 222 0

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2023.02.09-10:46:05

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