1,301 research outputs found
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High resolution CO observations of S88-B
CO J = 2-1 and 13CO J = 2-1 and 1-0 observations have been made of the H II region S88-B, using the 15-m James Clerk Maxwell telescope in Hawaii and the 20-m telescope at Onsala. The core of the cloud is resolved into a horseshoelike structure which surrounds a diffuse reflection nebula. The central core has a mass of ≥ 1000 M⊙, with 400 M⊙ in the horseshoe structure. The gas in the horse in the horseshoe appears highly fragmented, and has a kinetic temperature of ≈ 60 K, suggesting it is closely coupled to the dust temperature. A recently formed high mass star appears to be in the process of evacuating a cavity, possibly through a large molecular outflow that is found to show an accelerated component in its blue-shifted lobe. A velocity gradient across the horseshoe structure suggest ordered motion, and could represent rotation in the parental cloud
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High signal/noise <sup>13</sup>CO observations of the bipolar outflow in L1551
New high-signal/noise 13CO observations of the bipolar outflow in the molecular cloud L1551 are reported. Contrary to earlier observations of CO J = 1-0 and 2-1, no strong spatial dependence is found for the velocity profile of these spectra. The implications of these observations are such that the model of an empty shell for this source is less likely, and a model consisting of a shell which contains significant amounts of outflowing molecular gas inside the swept-up cavity walls is suggested
I.2 Seeds take root in Europe
This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered
Discovery of X-ray emission from the proto-stellar jet L1551 IRS5 (HH 154)
We have for the first time detected X-ray emission associated with a
proto-stellar jet, on the jet emanating from L1551 IRS5. The IRS5 proto-star is
hidden beyond a very large absorbing column density, making the direct
observation of the jet's emission possible. The observed X-ray emission is
likely associated with the shock ``working surface'', i.e. the interface
between the jet and the circumstellar medium. The X-ray luminosity emanating
from the jet is moderate, at LX ~ 3 times 10^29 erg/s, a significant fraction
of the luminosity normally associated with the coronal emission from young
stars. The spectrum of the X-ray emission is compatible with thermal emission
from a hot plasma, with T ~ 0.5 MK, fully compatible with the temperature
expected (on the basis of the jet's velocity) for the shock front produced by
the jet hitting the circumstellar medium.Comment: To appear in "Stellar Coronae in the Chandra and XMM Era", ASP
Conference Series in press, F. Favata & J. Drake ed
The discovery of an expanding X-ray source in the HH 154 protostellar jet
We have performed, in October 2005, a deep Chandra X-ray observation of HH
154. Comparison with the previous (2001) Chandra observation allows to detect
proper motion down to the level predicted by models of X-ray emitting shocks in
the jet. The 2005 Chandra observation of HH 154 shows unexpected morphological
changes of the X-ray emission in comparison with the 2001 data. Two components
are present: a stronger, point-like component with no detectable motion and a
weaker component which has expanded in size by approximately 300 AU over the 4
years time base of the two observations. This expansion corresponds to
approximately 500 km/s, very close to the velocity of the X-ray emitting shock
in the simple theoretical models. The 2005 data show a more complex system than
initially thought (and modeled), with multiple components with different
properties. The observed morphology is possibly indicating a pulsed jet
propagating through a non-homogeneous medium, likely with medium density
decreasing with distance from the driving source. Detailed theoretical modeling
and deeper X-ray observations will be needed to understand the physics of this
fascinating class of sources.Comment: Accepted for publication in A&A Letter
High Angular Resolution, Sensitive CS J=2-1 and J=3-2 Imaging of the Protostar L1551 NE: Evidence for Outflow-Triggered Star Formation ?
High angular resolution and sensitive aperture synthesis observations of CS
() and CS () emissions toward L1551 NE, the second brightest
protostar in the Taurus Molecular Cloud, made with the Nobeyama Millimeter
Array are presented. L1551 NE is categorized as a class 0 object deeply
embedded in the red-shifted outflow lobe of L1551 IRS 5. Previous studies of
the L1551 NE region in CS emission revealed the presence of shell-like
components open toward L1551 IRS 5, which seem to trace low-velocity shocks in
the swept-up shell driven by the outflow from L1551 IRS 5. In this study,
significant CS emission around L1551 NE was detected at the eastern tip of the
swept-up shell from = 5.3 km s to 10.1 km s, and
the total mass of the dense gas is estimated to be 0.18 0.02 .
Additionally, the following new structures were successfully revealed: a
compact disklike component with a size of 1000 AU just at L1551 NE,
an arc-shaped structure around L1551 NE, open toward L1551 NE, with a size of
AU, i.e., a bow shock, and a distinct velocity gradient of the
dense gas, i.e., deceleration along the outflow axis of L1551 IRS 5. These
features suggest that the CS emission traces the post-shocked region where the
dense gas associated with L1551 NE and the swept-up shell of the outflow from
L1551 IRS 5 interact. Since the age of L1551 NE is comparable to the timescale
of the interaction, it is plausible that the formation of L1551 NE was induced
by the outflow impact. The compact structure of L1551 NE with a tiny envelope
was also revealed, suggesting that the outer envelope of L1551 NE has been
blown off by the outflow from L1551 IRS 5.Comment: 29 pages, 12 figures, Accepted for Publication in the Astrophysical
Journa
Exoplanets and space research
Inaugural lecture by Prof.dr. M. Fridlund on the acceptance of his position of professor of Space Observations of Exoplanets at the Universiteit Leiden on Friday April 26 2013Inaugural lecture by Prof.dr. M. Fridlund on the acceptance of his position of professor of Space Observations of Exoplanets at the Universiteit Leiden on Friday April 26 2013
Transmission measurement at 10.6 microns of Te2As3Se5 rib-waveguides on As2S3 substrate
The feasibility of chalcogenide rib waveguides working at lambda = 10.6
microns has been demonstrated. The waveguides comprised a several microns thick
Te2As3Se5 film deposited by thermal evaporation on a polished As2S3 glass
substrate and further etched by physical etching in Ar or CF4/O2 atmosphere.
Output images at 10.6 microns and some propagation losses roughly estimated at
10dB/cm proved that the obtained structures behaved as channel waveguides with
a good lateral confinement of the light. The work opens the doors to the
realisation of components able to work in the mid and thermal infrared up to 20
microns and even more.Comment: The following article appeared in Vigreux-Bercovici et al., Appl.
Phys. Lett. 90, 011110 (2007) and may be found at
http://link.aip.org/link/?apl/90/01111
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