305 research outputs found
Dense cores in the dark cloud complex LDN1188
We present a molecular line emission study of the LDN1188 dark cloud complex
located in Cepheus. In this work we focused on the densest parts of the cloud
and on the close neighbourhood of infrared point sources. We made ammonia
mapping with the Effelsberg 100-m radio telescope and identified 3 dense cores.
CS(1--0), CS(2--1) and HCO(1--0) measurements performed with the Onsala
20\,m telescope revealed the distribution of dense molecular material. The
molecular line measurements were supplemented by mapping the dust emission at
1.2\,mm in some selected directions using the IRAM 30\,m telescope. With these
data we could work out a likely evolutionary sequence in this dark clould
complex.Comment: YouResAstro2012 conference presentation; accepted to Astronomishen
Nachrichten (25-July-2013
The outburst of the eruptive young star OO Serpentis between 1995 and 2006
OO Serpentis is a deeply embedded pre-main sequence star that went into
outburst in 1995 and gradually faded afterwards. Its eruption resembled the
well-known FU Orionis-type or EX Lupi-type outbursts. Since very few such
events have ever been documented at infrared wavelengths, our aim is to study
the temporal evolution of OO Ser in the infrared. OO Ser was monitored with the
Infrared Space Observatory starting 4 months after peak brightness and covering
20 months. In 2004-2006 we again observed OO Ser from the ground and
complemented this dataset with archival Spitzer obsevations also from 2004. We
analysed these data with special attention to source confusion and constructed
light curves at 10 different wavelengths as well as spectral energy
distributions. The outburst caused brightening in the whole infrared regime.
According to the infrared light curves, OO Ser started a wavelength-independent
fading after peak brightness. Later the flux decay became slower but stayed
wavelength-independent. The fading is still ongoing, and current fading rates
indicate that OO Ser will not return to quiescent state before 2011. The
outburst timescale of OO Ser seems to be shorter than that of FUors, but longer
than that of EXors. The outburst timescale and the moderate luminosity suggest
that OO Ser is different from both FUors and EXors, and shows similarities to
the recently erupted young star V1647 Ori. Based on its spectral energy
distribution and bolometric temperature, OO Ser seems to be an early class I
object, with an age of < 10^5 yr. The object is probably surrounded by an
accretion disc and a dense envelope. Due to the shorter outburst timescales,
the viscosity in the circumstellar disc of OO Ser is probably an order of
magnitude higher than usual for FUors.Comment: 12 pages, 7 figures, accepted for publication in A&
V346 Nor: the post-outburst life of a peculiar young eruptive star
FU Orionis-type objects (FUors) are young low-mass stars undergoing powerful accretion outbursts. The increased accretion is often accompanied by collimated jets and energetic, large-scale molecular outflows. The extra heating during the outburst may also induce detectable geometrical, chemical, and mineralogical changes in the circumstellar material, affecting possible planet formation around these objects. V346 Nor is a southern FUor with peculiar spectral characteristics. Decades after the beginning of its outburst, it unexpectedly underwent a fading event around 2010 due to a decrease in the mass accretion rate onto the star by at least two orders of magnitude. Here we present optical and near-infrared photometry and spectroscopy obtained after the minimum. Our light curves show a gradual re-brightening of V346 Nor, with its K s-band brightness only 1.5 mag below the outburst brightness level. Our Very Large Telescope (VLT)/XSHOOTER spectroscopic observations display several strong forbidden emission lines toward the source from various metals and molecular hydrogen, suggesting the launch of a new jet. Our N-band spectrum obtained with VLT/VISIR outlines a deeper silicate absorption feature than before, indicating that the geometry of the circumstellar medium has changed in the post-outburst period compared to peak brightness.Peer reviewedFinal Published versio
A structural operational semantics of a concurrent class calculus
The concurrent -calculus has been investigated as a core calculus for imperative, object-oriented languages with multithreading and heap-allocated objects. From an abstract point of view, the combination of this form of concurrency with objects corresponds to features known from the popular language Java. One distinctive feature, however, of the concurrent object calculus is that it is \emph{object-based}, where as the mainstream of object-oriented languages is \emph{class-based.} This technical report extends the concurrent -calculus by introducing classes and explores some of the semantical consequences. The semantics will serve asthe basis for a proof of full abstraction wrt.\ to a may-testing based notion of observability
Identification of Young Stellar Object candidates in the DR2 x AllWISE catalogue with machine learning methods
The second Data Release (DR2) contains astrometric and photometric
data for more than 1.6 billion objects with mean magnitude 20.7,
including many Young Stellar Objects (YSOs) in different evolutionary stages.
In order to explore the YSO population of the Milky Way, we combined the
DR2 database with WISE and Planck measurements and made an all-sky
probabilistic catalogue of YSOs using machine learning techniques, such as
Support Vector Machines, Random Forests, or Neural Networks. Our input
catalogue contains 103 million objects from the DR2xAllWISE cross-match table.
We classified each object into four main classes: YSOs, extragalactic objects,
main-sequence stars and evolved stars. At a 90% probability threshold we
identified 1,129,295 YSO candidates. To demonstrate the quality and potential
of our YSO catalogue, here we present two applications of it. (1) We explore
the 3D structure of the Orion A star forming complex and show that the spatial
distribution of the YSOs classified by our procedure is in agreement with
recent results from the literature. (2) We use our catalogue to classify
published Science Alerts. As measures the sources at multiple
epochs, it can efficiently discover transient events, including sudden
brightness changes of YSOs caused by dynamic processes of their circumstellar
disk. However, in many cases the physical nature of the published alert sources
are not known. A cross-check with our new catalogue shows that about 30% more
of the published alerts can most likely be attributed to YSO activity.
The catalogue can be also useful to identify YSOs among future alerts.Comment: 19 pages, 12 figures, 3 table
A Deductive Proof System for Multithreaded Java with Exceptions
Besides the features of a class-based object-oriented language, Java integrates concurrency via its thread-classes, allowing for a multithreaded flow of control.Besides that, the language offers a flexible exception mechanism for handling errors or exceptional program conditions. To reason about safety-properties Java-programs and extending previous work on the proof theory for monitor synchronization, we introduce in this report an assertional proof method for JavaMT (Multi-Threaded Java), a small concurrent sublanguage of Java, covering concurrency and especially (exception handling). We show soundness and relative completeness of the proof method
The Potential and Challenges of CAD with Equational Constraints for SC-Square
Cylindrical algebraic decomposition (CAD) is a core algorithm within Symbolic
Computation, particularly for quantifier elimination over the reals and
polynomial systems solving more generally. It is now finding increased
application as a decision procedure for Satisfiability Modulo Theories (SMT)
solvers when working with non-linear real arithmetic. We discuss the potentials
from increased focus on the logical structure of the input brought by the SMT
applications and SC-Square project, particularly the presence of equational
constraints. We also highlight the challenges for exploiting these: primitivity
restrictions, well-orientedness questions, and the prospect of incrementality.Comment: Accepted into proceedings of MACIS 201
Estrogen induces estrogen receptor alpha-dependent cAMP response element-binding protein phosphorylation via mitogen activated protein kinase pathway in basal forebrain cholinergic neurons in vivo
In addition to classical genomic mechanisms, estrogen also exerts
nonclassical effects via a signal transduction system on neurons. To
study whether estrogen has a nonclassical effect on basal forebrain
cholinergic system, we measured the intensity of cAMP response
element-binding protein (CREB) phosphorylation (pCREB) in cholinergic
neurons after administration of 17 beta-estradiol to ovariectomized
(OVX) mice. A significant time-dependent increase in the number of
pCREB-positive cholinergic cells was detected after estrogen
administration in the medial septum-diagonal band (MS-DB) and the
substantia innominata ( SI). The increase was first observed 15 min
after estrogen administration. The role of classical estrogen receptors
(ERs) was evaluated using ER knock-out mice in vivo. The
estrogen-induced CREB phosphorylation in cholinergic neurons was
present in ER beta knock-out mice but completely absent in ER beta
knock-out mice in MS-DB and SI. A series of in vitro studies
demonstrated that estrogen acted directly on cholinergic neurons.
Selective blockade of the mitogen activated protein kinase (MAPK)
pathway in vivo completely prevented estrogen-induced CREB
phosphorylation in cholinergic neurons in MS-DB and SI. In contrast,
blockade of protein kinase A (PKA) was effective only in SI. Finally,
studies in intact female mice revealed levels of CREB phosphorylation
within cholinergic neurons that were similar to those of
estrogen-treated OVX mice. These observations demonstrate an ER
alpha-mediated nonclassical effect of estrogen on the cholinergic
neurons and that these actions are present under physiological
conditions. They also reveal the role of MAPK and PKA-MAPK pathway
activation in nonclassical estrogen signaling in the basal forebrain
cholinergic neurons in vivo
Inductive Proof Outlines for Monitors in Java
Abstract. The research concerning Java’s semantics and proof theory has mainly focussed on various aspects of sequential sub-languages. Java, however, integrates features of a class-based object-oriented language with the notion of multi-threading, where multiple threads can concurrently execute and exchange information via shared instance variables. Furthermore, each object can act as a monitor to assure mutual exclusion or to coordinate between threads. In this paper we present a sound and relatively complete assertional proof system for Java’s monitor concept, which generates verification conditions for a concurrent sublanguage JavaMT of Java. This work extends previous results by incorporating Java’s monitor methods
The X-ray emission from Z CMa during an FUor-like outburst and the detection of its X-ray jet
Accretion shocks have been recognized as important X-ray emission mechanism
for pre-main sequence stars. Yet the X-ray properties of FUor outbursts, events
that are caused by violent accretion, have been given little attention. We have
observed the FUor object Z CMa during optical outburst and quiescence with
Chandra. No significant changes in X-ray brightness and spectral shape are
found, suggesting that the X-ray emission is of coronal nature. Due to the
binary nature of Z CMa the origin of the X-ray source is ambiguous. However,
the moderate hydrogen column density derived from our data makes it unlikely
that the embedded primary star is the X-ray source. The secondary star, which
is the FUor object, is thus responsible for both the X-ray emission and the
presently ongoing accretion outburst, which seem however to be unrelated
phenomena. The secondary is also known to drive a large outflow and jet, that
we detect here for the first time in X-rays. The distance of the X-ray emitting
outflow source to the central star is higher than in jets of low-mass stars.Comment: 5 pages, accepted for publication in Astronomy & Astrophysic
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