2019A&A...626A..29L


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST17:49:41

2019A&A...626A..29L - Astronomy and Astrophysics, volume 626A, 29-29 (2019/6-1)

Follow-up observations of X-ray emitting hot subdwarf stars: the compact He-poor sdO star Feige 34.

LA PALOMBARA N., MEREGHETTI S., ESPOSITO P. and TIENGO A.

Abstract (from CDS):

We report on results obtained with the XMM-Newton observation of Feige 34 carried out in April 2018. This is the first spectroscopic X-ray observation of a compact and helium-poor hot subdwarf star. The source was detected at a flux level fX=3.4x10–14erg/cm2/s in the energy range 0.2-3keV, which implies an X-ray-to-bolometric flux ratio fX/fbol~=10–6.5. The source spectrum can be described with the sum of two thermal-plasma components with subsolar abundances at temperatures of ~=0.3 and 1.1keV. These properties are similar to what is observed in early-type main-sequence stars, where the X-ray emission is attributed to turbulence and shocks in the stellar wind. Therefore, the same phenomenon could explain the X-ray properties of Feige 34. However, it is not possible to reproduce the observed spectrum with a thermal-plasma model if the elemental abundances are fixed at the values obtained from the optical and UV spectroscopy. Moreover, we show that the X-ray luminosity and spectrum are consistent with those expected from a young main-sequence star of late spectral type. Therefore, we discuss the possibility that the observed X-ray emission is due to the companion star of M0 spectral type, whose presence is suggested by the IR excess in the spectral energy distribution of Feige 34.

Abstract Copyright: © ESO 2019

Journal keyword(s): stars: early-type - subdwarfs - stars: individual: Feige 34 - X-rays: stars

Simbad objects: 6

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Number of rows : 6

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 BD+37 442 HS* 01 58 33.4340086125 +38 34 23.846108332   9.69 9.92     sdOHe 57 0
2 HD 49798 HXB 06 48 04.7000758397 -44 18 58.432035331 6.758 8.017 8.287 8.391 8.543 sdO6 283 0
3 BD+37 1977 HS* 09 24 26.3928822549 +36 42 53.293596680   9.86 10.15     sdO 39 0
4 Feige 34 HS* 10 39 36.7377085527 +43 06 09.209752646 9.613 10.91 11.14 11.319 11.464 sdOp 605 0
5 BD+18 2647 HS* 12 41 51.7901702595 +17 31 19.750592670 10.261 11.70 11.63 11.969 12.159 sdOpec 162 1
6 BD+28 4211 HS* 21 51 11.0220905905 +28 51 50.366090892 8.922 10.25 10.58 10.656 10.831 sdO2VIIIHe5 735 0

    Equat.    Gal    SGal    Ecl

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2020.07.14-17:49:41

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