659 research outputs found
Chandra X-ray observation of the HII region Gum 31 in the Carina Nebula complex
(abridged) We used the Chandra observatory to perform a deep (70 ksec) X-ray
observation of the Gum 31 region and detected 679 X-ray point sources. This
extends and complements the X-ray survey of the central Carina nebula regions
performed in the Chandra Carina Complex Project. Using deep near-infrared
images from our recent VISTA survey of the Carina nebula complex, our Spitzer
point-source catalog, and optical archive data, we identify counterparts for
75% of these X-ray sources. Their spatial distribution shows two major
concentrations, the central cluster NGC 3324 and a partly embedded cluster in
the southern rim of the HII region, but majority of X-ray sources constitute a
rather homogeneously distributed population of young stars. Our color-magnitude
diagram analysis suggests ages of ~1-2 Myr for the two clusters, whereas the
distributed population shows a wider age range up to ~10 Myr. We also identify
previously unknown companions to two of the three O-type members of NGC 3324
and detect diffuse X-ray emission in the region. Our results suggests that the
observed region contains about 4000 young stars in total. The distributed
population is probably part of the widely distributed population of ~ 1-10 Myr
old stars, that was identified in the CCCP area. This implies that the global
stellar configuration of the Carina nebula complex is a very extended stellar
association, in which the (optically prominent) clusters contain only a
minority of the stellar population.Comment: Accepted for publication in Astronomy & Astrophysics. A high quality
preprint is available at
http://www.usm.uni-muenchen.de/people/preibisch/publications.htm
Key considerations for a regional SocMon strategy for the Bay of Bengal Large Marine Ecosystem countries in South Asia
Socio-economic Monitoring (SocMon) is an approach and set of tools for conducting socio-economic monitoring of changes in coastal communities. Key considerations included: importance of local partnerships; government and civil society partnerships; emphasis of adapting SocMon to local needs and priorities; capacity building; engaging with local stakeholders; inter and intra-regional collaboration; importance of language; and importance of language
Report of the SocMon capacity development workshop for the Bay of Bengal Large Marine Ecosystem countries in South Asia, St Martin's Island, Bangladesh, 2-11 January, 2015
Socio-economic Monitoring (SocMon) is an approach and set of tools for conducting socio-economic monitoring of changes in coastal communities. Planned outputs of the workshop included: training of local staff i SocMon methodologies; draft a SocMon report for St. Martin's Island; a workplan for implementing the SocMon; a communication strategy; and key inputs to a regional SocMon strateg
Molecular basis for modulation of the p53 target selectivity by KLF4
The tumour suppressor p53 controls transcription of various genes involved in apoptosis, cell-cycle arrest, DNA repair and metabolism. However, its DNA-recognition specificity is not nearly sufficient to explain binding to specific locations in vivo. Here, we present evidence that KLF4 increases the DNA-binding affinity of p53 through the formation of a loosely arranged ternary complex on DNA. This effect depends on the distance between the response elements of KLF4 and p53. Using nuclear magnetic resonance and fluorescence techniques, we found that the amino-terminal domain of p53 interacts with the KLF4 zinc fingers and mapped the interaction site. The strength of this interaction was increased by phosphorylation of the p53 N-terminus, particularly on residues associated with regulation of cell-cycle arrest genes. Taken together, the cooperative binding of KLF4 and p53 to DNA exemplifies a regulatory mechanism that contributes to p53 target selectivity
Report of the SocMon capacity development workshop for the Bay of Bengal Large Marine Ecosystem countries in South Asia, Vidathaltivu, Northern Province, Sri Lanka, 3-11 March, 2015
This Socioeconomic Monitoring (SocMon) training workshop was coordinated by the Small Fisher Federation of Lanka (SFFL). Planned outputs included: participants from Mannar trained in SocMon methodologies; draft SocMon reports fro Vidathaltivu; a workplan for Mannar; a communication strategy for Vidathaltivu/ Mannar; and key inputs to a regional SocMon strateg
On variations of the brightness of type Ia supernovae with the age of the host stellar population
Recent observational studies of type Ia supernovae (SNeIa) suggest
correlations between the peak brightness of an event and the age of the
progenitor stellar population. This trend likely follows from properties of the
progenitor white dwarf (WD), such as central density, that follow from
properties of the host stellar population. We present a statistically
well-controlled, systematic study utilizing a suite of multi-dimensional SNeIa
simulations investigating the influence of central density of the progenitor WD
on the production of Fe-group material, particularly radioactive Ni-56, which
powers the light curve. We find that on average, as the progenitor's central
density increases, production of Fe-group material does not change but
production of Ni-56 decreases. We attribute this result to a higher rate of
neutronization at higher density. The central density of the progenitor is
determined by the mass of the WD and the cooling time prior to the onset of
mass transfer from the companion, as well as the subsequent accretion heating
and neutrino losses. The dependence of this density on cooling time, combined
with the result of our central density study, offers an explanation for the
observed age-luminosity correlation: a longer cooling time raises the central
density at ignition thereby producing less Ni-56 and thus a dimmer event. While
our ensemble of results demonstrates a significant trend, we find considerable
variation between realizations, indicating the necessity for averaging over an
ensemble of simulations to demonstrate a statistically significant result.Comment: 5 pages, 4 figures, 1 table, accepted to ApJ
Theoretical Modeling of the Thermal State of Accreting White Dwarfs Undergoing Classical Novae
White dwarfs experience a thermal renaissance when they receive mass from a
stellar companion in a binary. For accretion rates < 10^-8 Msun/yr, the freshly
accumulated hydrogen/helium envelope ignites in a thermally unstable manner
that results in a classical novae (CN) outburst and ejection of material. We
have undertaken a theoretical study of the impact of the accumulating envelope
on the thermal state of the underlying white dwarf (WD). This has allowed us to
find the equilibrium WD core temperatures (T_c), the classical nova ignition
masses (M_ign) and the thermal luminosities for WDs accreting at rates of
10^-11 - 10^-8 Msun/yr. These accretion rates are most appropriate to WDs in
cataclysmic variables (CVs) of P_orb <~ 7 hr, many of which accrete
sporadically as dwarf novae. We have included ^3He in the accreted material at
levels appropriate for CVs and find that it significantly modifies the CN
ignition mass. We compare our results with several others from the CN
literature and find that the inclusion of ^3He leads to lower M_ign for
>~ 10^-10 Msun/yr, and that for below this the particular author's
assumption concerning T_c, which we calculate consistently, is a determining
factor. Initial comparisons of our CN ignition masses with measured ejected
masses find reasonable agreement and point to ejection of material comparable
to that accreted.Comment: 14 pages, 11 figures; uses emulateapj; accepted by the Astrophysical
Journal; revised for clarity, added short discussion of diffusio
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