Search results for " X-rays: ISM"

X-RAY EMISSION FROM PROTOSTELLAR JET HH 154: THE FIRST EVIDENCE OF A DIAMOND SHOCK?

2011

X-ray emission from about ten protostellar jets has been discovered and it appears as a feature common to the most energetic jets. Although X-ray emission seems to originate from shocks internal to jets, the mechanism forming these shocks remains controversial. One of the best studied X-ray jet is HH 154 that has been observed by Chandra over a time base of about 10 years. We analyze the Chandra observations of HH 154 by investigating the evolution of its X-ray source. We show that the X-ray emission consists of a bright stationary component and a faint elongated component. We interpret the observations by developing a hydrodynamic model describing a protostellar jet originating from a nozz…

The Complex Morphology of the X-ray and Optical Emission from HH 154: The Pulsed Jet Scenario

2009

We study the optical and X-ray emission from protostellar jets, focusing, in particular, on the case of HH 154. This project consists of two different and complementary approaches: the development of hydrodynamical models of the jet/ambient interaction, and the analysis of multi-wavelength observations. Comparing the results derived from the simulations with the observations we can infer the physical mechanisms leading to the complex morphology of the X-rays source observed at the base of HH 154.

Generation of radiative knots in a randomly pulsed protostellar jet

2009

HH objects are characterized by a complex knotty morphology detected mainly along the axis of protostellar jets in a wide range of bands. Evidence of interactions between knots formed in different epochs have been found, suggesting that jets may result from the ejection of plasma blobs from the source. We aim at investigating the physical mechanism leading to the irregular knotty structure observed in jets in different bands and the complex interactions occurring among blobs of plasma ejected from the stellar source. We perform 2D axisymmetric HD simulations of a randomly ejected pulsed jet. The jet consists of a train of blobs which ram with supersonic speed into the ambient medium. The in…

The X-ray emission mechanism in the protostellar jet HH 154

2004

We study the mechanism causing the X-ray emission recently detected in protostellar jets, by performing a detailed modeling of the interaction between a supersonic jet originating from a young stellar object and the ambient medium, for various values of density contrast, ν, between the ambient density and the jet, and of Mach number, M; radiative losses and thermal conduction have been taken into account. Here we report a representative case which reproduces, without any ad hoc assumption, the characteristics of the X-ray emission recently observed in the protostellar jet HH 154. We find that the X-ray emission originates from a localized blob, consistent with observations, which moves with…

X-rays from protostellar jets: emission from continuous flows

2006

Recently X-ray emission from protostellar jets has been detected with both XMM-Newton and Chandra satellites, but the physical mechanism which can give rise to this emission is still unclear. We performed an extensive exploration of a wide space of the main parameters influencing the jet/ambient interaction. Aims include: 1) to constrain the jet/ambient interaction regimes leading to the X-ray emission observed in Herbig-Haro objects in terms of the emission by a shock forming at the interaction front between a continuous supersonic jet and the surrounding medium; 2) to derive detailed predictions to be compared with optical and X-ray observations of protostellar jets; 3) to get insight int…

Soft X-Ray Irradiation of Methanol Ice: Implication for H2CO Formation in Interstellar Regions

2010

We performed 0.3 keV soft X-ray irradiation of a methanol ice at 8 K under ultra-high vacuum conditions. To the best of our knowledge, this is the first time that soft X-rays are used to study photolysis of ice analogs. Despite the low irradiation dose of 10{sup -6} photons molecule{sup -1}, the formation of formaldehyde has been observed. The results of our experiments suggest that X-rays may be a promising candidate to the formation of complex molecules in regions where UV radiation is severely inhibited.

X-raying the interstellar medium: the study of SNR shells at the OAPa

2006

X-ray emission mechanisms in protostellar jets

2005

Prompted by the recent detection of X-ray emission from Herbig-Haro objects, we studied the interaction between a supersonic jet originating from a young stellar object and the ambient medium; our aim is to investigate the mechanisms causing the X-ray emission. Our model takes into account the radiative losses from optically in plasmas and Spitzer's thermal conduction including saturation effects. We explored the parameter space defined by the density contrast between the ambient medium and the jet and by the Mach number, to infer the configurations which can give rise to X-ray emission. From the models, we derived the X-ray emission as it would be observed with Chandra/ACIS-I and XMM-Newto…

XMM-Newton large programme on SN1006 - II. Thermal emission

2016

Based on the XMM-Newton large program on SN1006 and our newly developed spatially resolved spectroscopy tools (Paper~I), we study the thermal emission from ISM and ejecta of SN1006 by analyzing the spectra extracted from 583 tessellated regions dominated by thermal emission. With some key improvements in spectral analysis as compared to Paper~I, we obtain much better spectral fitting results with less residuals. The spatial distributions of the thermal and ionization states of the ISM and ejecta show different features, which are consistent with a scenario that the ISM (ejecta) is heated and ionized by the forward (reverse) shock propagating outward (inward). Different elements have differe…

Modeling nonthermal emission from stellar bow shocks

2016

Context. Runaway O- and early B-type stars passing through the interstellar medium at supersonic velocities and characterized by strong stellar winds may produce bow shocks that can serve as particle acceleration sites. Previous theoretical models predict the production of high-energy photons by nonthermal radiative processes, but their efficiency is still debated. Aims: We aim to test and explain the possibility of emission from the bow shocks formed by runaway stars traveling through the interstellar medium by using previous theoretical models. Methods: We applied our model to AE Aurigae, the first reported star with an X-ray detected bow shock, to BD+43 3654, in which the observations fa…