LA PALOMBARA, NICOLANICOLALA PALOMBARAMEREGHETTI, SandroSandroMEREGHETTIESPOSITO, PAOLOPAOLOESPOSITOTIENGO, ANDREAANDREATIENGO2021-01-212021-01-2120190004-6361http://hdl.handle.net/20.500.12386/29932We 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 = 3.4 × 10^(−14) erg cm^(−2) s^(−1) in the energy range 0.2–3 keV, 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 1.1 keV. 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.STAMPAenArticle10.1051/0004-6361/2019353392-s2.0-85090120747000470653200004https://www.aanda.org/articles/aa/abs/2019/06/aa35339-19/aa35339-19.html2019A&A...626A..29LFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_10 High energy and particle astronomy – X-rays, cosmic rays, gamma rays, neutrinos