TY  - Preprint
T1  - Advances in mass-loss predictions
A1  - Vink, Jorick S. 
A1  - Benaglia, P. 
A1  - Davies, B. 
A1  - de Koter, A. 
A1  - Oudmaijer, R. D.
JO  - ArXiv e-prints
VL  - 0708
Y1  - 2007/8/1
SP  - 2066
KW  - Astrophysics
UR  - http://adsabs.harvard.edu/abs/2007arXiv0708.2066V
N2  - We present the results of Monte Carlo mass-loss predictions for massive 
stars covering a wide range of stellar parameters. We critically test 
our predictions against a range of observed mass-loss rates -- in light 
of the recent discussions on wind clumping. We also present a model to 
compute the clumping-induced polarimetric variability of hot stars and 
we compare this with observations of Luminous Blue Variables, for which 
polarimetric variability is larger than for O and Wolf-Rayet stars. 
Luminous Blue Variables comprise an ideal testbed for studies of wind 
clumping and wind geometry, as well as for wind strength calculations, 
and we propose they may be direct supernova progenitors.
ER  -


TY  - Preprint
T1  - The environs of the HII region Gum31
A1  - Cappa, C. 
A1  - Niemela, V. S. 
A1  - Amorin, R. 
A1  - Vasquez, J.
JO  - ArXiv e-prints
VL  - 0707
Y1  - 2007/7/1
SP  - 2004
KW  - Astrophysics
UR  - http://adsabs.harvard.edu/abs/2007arXiv0707.2004C
N2  - We analyze the distribution of the interstellar matter in the environs 
of the \hii region Gum 31, excited by the open cluster NGC 3324, located 
in the complex Carina region, with the aim of investigating the action 
of the massive stars on the surrounding neutral material. We use 
21cm-line data, radio continuum images at 0.843, 2.4 and 4.9 GHz, 
$^{12}${\bf CO(1-0)} observations, and IRAS and MSX infrared data. 
Adopting a distance of 3 kpc for the \hii\ region and the ionizing 
cluster, we have derived an electron density of 33$\pm$3 cm$^{-3}$ and 
an ionized mass of (3.3$\pm$1.1)$\times10^3$ M$_{\odot}$ based on the 
radio continuum data at 4.9 GHz. The \hi 21-cm line images revealed an 
\hi shell surrounding the H {\sc ii} region. The \hi structure is 
10.0$\pm$1.7 pc in radius, has a neutral mass of 1500$\pm$500 
M$_{\odot}$, and is expanding at 11 km s$^{-1}$. The associated 
molecular gas amounts to (1.5$\pm$0.5)$\times10^5$ M$_{\odot}$, being 
its volume density of about 500 cm^{-3}. This molecular material 
probably represents the remains of the cloud where the young open 
cluster NGC 3324 was born. The distributions of the ionized and 
molecular material, along with that of the emission in the MSX band A 
suggest that a photodissociation region has developed at the interface 
between the ionized and molecular gas. We conclude that either the 
massive stars in the open cluster have weak stellar winds or the stellar 
winds have blown during a very short period of time to create an 
interstellar bubble in an interstellar medium as dense as observed. 
IRAS, MSX, and 2MASS point sources projected onto the molecular envelope 
are compatible with protostellar candidates, showing the presence star 
forming regions. The expansion of the \hii region has triggered stellar 
formation in the molecular shell.
ER  -


TY  - Journal
T1  - Hard X-ray emission from the SNR G337.2+0.1
A1  - Combi, Jorge A. 
A1  - Albacete Colombo, Juan F. 
A1  - Romero, Gustavo E. 
A1  - Benaglia, Paula
JO  - Astrophysics and Space Science
VL  - 309
Y1  - 2007/6/1
SP  - 395
EP  - 399
KW  - X-rays: individual (AX J1635.9&minus/ 4719)/ (ISM:) supernova remnants/ ISM: individual (G337.2+0.1)/ X-rays: ISM/ Radiation mechanisms: non-thermal
UR  - http://adsabs.harvard.edu/abs/2007Ap%26SS.309..395C
N2  - We report hard X-ray emission of the non-thermal supernova remnant 
G337.2+0.1. The source presents centrally filled and diffuse X-ray 
emission. A spectral study confirms that the column density of the 
central part of the object is about N 
<SUB>H</SUB>Ëś5.9(±1.5)×10<SUP>22</SUP> 
cm<SUP>-2</SUP> and its X-ray spectrum is well represented by a 
single power-law with a photon index Gamma=0.96±0.56. Detailed 
spectral analysis indicates that the outer region is highly absorbed and 
quite softer than the inner region. Characteristics already observed in 
other well-known X-ray plerions. Based on the gathered information, we 
confirm the SNR nature of G337.2+0.1, and suggest that the central 
region of the source is a pulsar wind nebula (PWN), originated by an 
energetic though yet undetected pulsar.
ER  -


TY  - Journal
T1  - Secondary leptons synchrotron emission from microquasar jets
A1  - Bordas, P. 
A1  - Paredes, J. M. 
A1  - Bosch-Ramon, V. 
A1  - Orellana, M.
JO  - Astrophysics and Space Science
VL  - 309
Y1  - 2007/6/1
SP  - 339
EP  - 343
UR  - http://adsabs.harvard.edu/abs/2007Ap%26SS.309..339B
N2  - We present a model to estimate the synchrotron radio emission generated 
in microquasar (MQ) jets due to secondary pairs created via decay of 
charged pions produced in proton-proton collisions between stellar wind 
ions and jet relativistic protons. The synchrotron radiation produced by 
secondary electrons/positrons is computed using consistently derived 
particle energy distributions. Energy losses due to synchrotron and 
inverse Compton (IC) processes, and adiabatic expansion, are taken into 
account. The space parameter for the model is explored and the 
corresponding spectral energy distributions (SEDs) are presented. We 
conclude that secondary leptonic emission represents a significant 
though hardly dominant contribution to the total radio emission in MQs, 
with observational consequences that can be used to test some still 
unknown processes occurring in these objects as well as the nature of 
the matter outflowing in their jets.
ER  -


TY  - Journal
T1  - High-energy gamma-ray emission from the inner jet of LS I +61 303: the hadronic contribution revisited
A1  - Orellana, M. 
A1  - Romero, G. E.
JO  - Astrophysics and Space Science
VL  - 309
Y1  - 2007/6/1
SP  - 333
EP  - 338
UR  - http://adsabs.harvard.edu/abs/2007Ap%26SS.309..333O
N2  - LS I +61 303 has been detected by the Cherenkov telescope MAGIC at very 
high energies, presenting a variable flux along the orbital motion with 
a maximum clearly separated from the periastron passage. In the light of 
the new observational constraints, we revisit the discussion of the 
production of high-energy gamma rays from particle interactions in the 
inner jet of this system. The hadronic contribution could represent a 
major fraction of the TeV emission detected from this source. The 
spectral energy distribution resulting from pp interactions is 
recalculated. Opacity effects introduced by the photon fields of the 
primary star and the stellar decretion disk are shown to be essential in 
shaping the high-energy gamma-ray light curve at energies close to 200 
GeV. We also present results of Monte Carlo simulations of the 
electromagnetic cascades developed very close to the periastron passage. 
We conclude that a hadronic microquasar model for the gamma-ray emission 
in LS I +61 303 can reproduce the main features of its observed 
high-energy gamma-ray flux.
ER  -


TY  - Journal
T1  - INTEGRAL/XMM views on the MeV source GRO J1411-64
A1  - Torres, Diego F. 
A1  - Zhang, Shu 
A1  - Reimer, Olaf 
A1  - Barcons, Xavier 
A1  - Corral, Amalia 
A1  - Bosch-Ramon, Valentí 
A1  - Paredes, Josep M. 
A1  - Romero, Gustavo E. 
A1  - Qu, Jin 
A1  - Collmar, Werner 
A1  - Schönfelder, Volker 
A1  - Butt, Yousaf
JO  - Astrophysics and Space Science
VL  - 309
Y1  - 2007/6/1
SP  - 17
EP  - 21
UR  - http://adsabs.harvard.edu/abs/2007Ap%26SS.309...17T
N2  - The COMPTEL unidentified source GRO J 1411-64 was observed by INTEGRAL 
and XMM-Newton in 2005. The Circinus Galaxy is the only source detected 
within the 4sigma location error of GRO J1411-64, but in here excluded 
as the possible counterpart. At soft X-rays, 22 reliable and 
statistically significant sources (likelihood >10) were extracted and 
analyzed from XMM-Newton data. Only one of these sources, XMMU 
J141255.6-635932, is spectrally compatible with GRO J1411-64 although 
the fact the soft X-ray observations do not cover the full extent of the 
COMPTEL source position uncertainty make an association hard to quantify 
and thus risky. At the best location of the source, detections at hard 
X-rays show only upper limits, which, together with MeV results obtained 
by COMPTEL suggest the existence of a peak in power output located 
somewhere between 300 700 keV for the so-called low state. Such a 
spectrum resembles those in blazars or microquasars, and might suggest 
at work by the models accordingly. However, an analysis using a 
microquasar model consisting on a magnetized conical jet filled with 
relativistic electrons, shows that it is hard to comply with all 
observational constrains. This fact and the non-detection at hard X-rays 
introduce an a-posteriori question mark upon the physical reality of 
this source, what is discussed here.
ER  -


TY  - Conference
T1  - A multifrequency study of the active star forming region NGC 6357
A1  - Cappa, C. E. 
A1  - Barbá, R. H. 
A1  - Arnal, M. 
A1  - Duronea, N. 
A1  - Fernández Lajús, E. 
A1  - Goss, W. M. 
A1  - Vasquez, J.
JO  - IAU Symposium
VL  - 237
Y1  - 2007/0/1
SP  - 400
EP  - 400
UR  - http://adsabs.harvard.edu/abs/2007IAUS..237..400C
N2  - We investigate the distribution of the ionized, atomic neutral and  
molecular gas, and of the interstellar dust in the complex star forming  
region NGC 6357, with the aim of studying the interplay between the  
massive stars and the surrounding interstellar matter. We based the  
study of the ionized gas on narrow-band optical images (Halpha, [SII], 
[OIII]) obtained with the Curtis-Schmidt Camera at CTIO, Chile, and on  
radio continuum observations at 1465 MHz taken with the VLA, USA, with a 
synthesized beam of 40 seconds of arc. The distribution of the neutral  
atomic gas is analyzed using HI 21cm line data from the Southern  
Galactic Plane Survey obtained with the ATCA and Parkes radiotelescopes  
(synthesized beam = 2.3 minutes of arc). The distribution of the  
molecular gas was investigated using CO(1-0) data obtained with the  
Nanten radiotelescope (angular resolution = 2.7 minutes of arc), in  
Chile. The interstellar dust distribution was studied using infrared  
data from the IRAS satellite (HIRES) and MSX. The images show neutral  
atomic and molecular gas with velocities in the range -12 to +1 km/s  
associated with the outer ionized nebula. A detailed analysis of the  
region reveals the presence of interstellar bubbles and  
photodissociation regions created by the massive stars in the open  
cluster Pis 24 and by undiscovered ionizing sources.
ER  -