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  • Astronomy  (2)
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  • 1
    Publikationsdatum: 2019-08-16
    Beschreibung: We report the results of an XMM-Newton observation of the Lagoon Nebula (M 8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experiences a flare-like increase of its X-ray flux making it the second brightest source in M 8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT approximately a few keV. Only a few of the X-ray selected PMS candidates are known to display H(alpha) emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC 6530 are weak line T Tauri stars. In addition to 9 Sgr, our EPIC field of view contains also a few early-type stars. The X-ray emission from HD 164816 is found to be typical for an O9.5III-IV star. At least one of the known Herbig Be stars in NGC 6530 (LkH(alpha) 115) exhibits a relatively strong X-ray emission, while most of the main sequence stars of spectral type B1 and later are not detected. We also detect (probably) diffuse X-ray emission from the Hourglass Region that might reveal a hot bubble blown by the stellar wind of Herschel 36, the ionizing star of the Hourglass Region.
    Schlagwort(e): Astronomy
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-07-13
    Beschreibung: We report preliminary results of an XMM-Newton observation of the 04 V star 9 Sgr (= HD 164794). 9 Sgr is one of a few single OB stars that display a non-thermal radio emission attributed to synchrotron emission by relativistic electrons. Inverse Compton scattering of photospheric UV photons by these relativistic electrons is a priori expected to generate a non-thermal power-law tail in the X-ray spectrum. Our EPIC and RGS spectra of 9 Sgr suggest a more complex situation than expected from this 'simple' theoretical picture. Furthermore, soft-band EPIC images of the region around 9 Sgr reveal a number of point sources inside the Lagoon Nebula (M8). Most of these sources have optical counterparts inside the very young open cluster NGC 6530 and several X-ray sources are associated with low and intermediate mass pre-main sequence stars. Finally, we also detect (probably) diffuse X-ray emission from the Hourglass Region that might reveal a hot bubble blown by the stellar wind of Herschel 36, the ionizing star of the HG region.
    Schlagwort(e): Astronomy
    Materialart: New Visions of the X-Ray Universe in the XMM-Newton and Chandra Era; Nov 26, 2001 - Nov 30, 2001; Netherlands
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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