arXiv subjects

T. Montmerle

Publications and source records attributed to T. Montmerle.

39 records · Page 3Linked to original sources

arXiv2002

X-rays from star-forming regions: New objects, new physics, new visions

Star-forming regions have been the targets of X-ray observations since the dawn of satellite X-ray astronomy. The increase in sensitivity and/or spatial resolution offered by XMM-Newton and Chandra allows a dramatic improvement, both qualitative and quantitative, on our knowledge of high-energy phenomena in these regions and the underlying physical processes. We summarize here some recent developments: the Orion Nebula Cluster and its 1000+ stellar X-ray sources; Herbig-Haro objects and their high-speed shocks; protostars, brown dwarfs and their unusual magnetic activity; and the discovery of diffuse X-ray emission from HII regions, presumably related to strong winds from massive stars. The role that future X-ray missions may play in the field is already starting to be visible.

astro-ph↗

arXiv2001

ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster

We present the results of the first extensive mid-infrared (IR) imaging survey of the rho Ophiuchi embedded cluster, performed with the ISOCAM camera on board the ISO satellite. The main molecular cloud L1688, as well as L1689N and L1689S, have been completely surveyed for point sources at 6.7 and 14.3 micron. A total of 425 sources are detected including 16 Class I, 123 Class II, and 77 Class III young stellar objects (YSOs). Essentially all of the mid-IR sources coincide with near-IR sources, but a large proportion of them are recognized for the first time as YSOs. Our dual-wavelength survey allows us to identify essentially all the YSOs with IR excess in the embedded cluster down to Fnu ~ 10 - 15 mJy. It more than doubles the known population of Class II YSOs and represents the most complete census to date of newly formed stars in the rho Ophiuchi central region. The stellar luminosity function of the complete sample of Class II YSOs is derived with a good accuracy down to L= 0.03 Lsun. A modeling of this lumino- sity function, using available pre-main sequence tracks and plausible star for- mation histories, allows us to derive the mass distribution of the Class II YSOs which arguably reflects the IMF of the embedded cluster. We estimate that the IMF in rho Ophiuchi is well described by a two-component power law with a low- mass index of -0.35+/-0.25, a high-mass index of -1.7 (to be compared with the Salpeter value of -1.35), and a break occurring at M = 0.55+/-0.25 Msun. This IMF is flat with no evidence for a low-mass cutoff down to at least 0.06 Msun.

astro-ph↗

arXiv1999

Rotational modulation of X-ray flares on late-type stars: T Tauri Stars and Algol

We present evidence for rotational modulation of X-ray flares by an analysis of four outbursts on late-type stars. Three of these flares have been observed on T Tauri Stars and one on Algol. The structure of the X-ray lightcurves observed in this selection of flare events is untypical in that the maximum emission extends over several hours producing a round hump in the lightcurve instead of a sharp peak. We explain this deviation from the standard shape of a flare lightcurve as the result of a flare erupting on the back side of the star and gradually moving into the line of sight due to the star's rotation. An estimate for the decay timescale and the size of the X-ray emitting volume is derived. Spectral information supports our proposition that changes of the visible volume are responsible for the observed time development of these flares.

astro-ph↗