1,155 research outputs found
The INTEGRAL legacy on High Mass X-ray Binaries
Observations with the INTEGRAL satellite have quadrupled the population of
supergiant High Mass X-ray Binaries (HMXBs), revealed a previously hidden
population of obscured supergiant HMXBs, and allowed the discovery of huge and
fast transient flares in supergiant HMXBs. Apart from these 3 observational
facts, has INTEGRAL allowed us to better understand these supergiant HMXBs? Do
we have now a better understanding of the 3 populations of HMXBs, and of their
accretion process, separated in the so-called Corbet diagram? Do we better
apprehend the accretion process in the supergiant HMXBs, and what makes the
fast transient flares so special, in the context of the clumpy wind model, and
of the formation of transient accretion disks? In summary, has the increased
population of supergiant HMXBs allowed a better knowledge of these sources,
compared to the ones that were already known before the launch of INTEGRAL? We
will review all these observational facts, comparing to the current models, to
objectively estimate what is the INTEGRAL legacy on High Mass X-ray Binaries.Comment: Contributed review during 8th INTEGRAL workshop, Dublin, Ireland,
27-30th Sept. 2010, 8 pages, 2 figure
Monitoring Supergiant Fast X-ray Transients with Swift. Rise to the outburst in IGR J16479-4514
IGR J16479-4514 is a Supergiant Fast X-ray Transient (SFXT), a new class of
High Mass X-ray Binaries, whose number is rapidly growing thanks to the
observations of the Galactic plane performed with the INTEGRAL satellite. IGR
J16479-4514 has been regularly monitored with Swift/XRT since November 2007, to
study the quiescent emission, the outburst properties and their recurrence. A
new bright outburst, reaching fluxes above 10 erg cm s,
was caught by the Swift/BAT.
Swift immediately re-pointed at the target with the narrow-field instruments
so that, for the first time, an outburst from a SFXT where a periodicity in the
outburst recurrence is unknown could be observed simultaneously in the 0.2--150
keV energy band. The X-ray emission is highly variable and spans almost four
orders of magnitude in count rate during the Swift/XRT observations covering a
few days before and after the bright peak. The X-ray spectrum in outburst is
hard and highly absorbed. The power-law fit resulted in a photon index of
0.98, and in an absorbing column density of
cm. These observations demonstrate that in this source (similarly to
what was observed during the 2007 outburst from the periodic SFXT IGR
J11215-5952), the accretion phase lasts much longer than a few hours.Comment: Accepted for publication on Astrophysical Journal Letters. 5 pages, 4
figure
Models for an Ecosystem Approach to Fisheries
This document is one outcome from a workshop held in Gizo in October 2010 attended by 82 representatives from government, NGO's private sector, and communities. The target audience for the document is primarily organizations planning to work with coastal communities of Solomon Islands to implement Community-Based Resource Management (CBRM). It is however also envisaged that the document will serve as a reference for communities to better understand what to expect from their partners and also for donors, to be informed about agreed approaches amongst Solomon Islands stakeholders. This document does not attempt to summarize all the outcomes of the workshop; rather it focuses on the Solomon Islands Coral Triangle Initiative (CTI) National Plan of Action (NPoA): Theme 1: Support and implementation of CBRM and specifically, the scaling up of CBRM in Solomon Islands. Most of the principles given in this document are derived from experiences in coastal communities and ecosystems as, until relatively recently, these have received most attention in Solomon Islands resource management. It is recognized however that the majority of these principles will be applicable to both coastal and terrestrial initiatives. This document synthesizes information provided by stakeholders at the October 2010 workshop and covers some basic principles of engagement and implementation that have been learned over more than twenty years of activities by the stakeholder partners in Solomon Islands. The document updates and expands on a summary of guiding principles for CBRM which was originally prepared by the Solomon Islands Locally Managed Marine Area Network (SILMMA) in 2007
Supergiant Fast X-ray Transients uncovered by the EXTraS project: flares reveal the development of magnetospheric instability in accreting neutron stars
The low luminosity, X-ray flaring activity, of the sub-class of high mass
X-ray binaries called Supergiant Fast X-ray Transients, has been investigated
using XMM-Newton public observations, taking advantage of the products made
publicly available by the EXTraS project. One of the goals of EXTraS was to
extract from the XMM-Newton public archive information on the aperiodic
variability of all sources observed in the soft X-ray range with EPIC (0.2-12
keV). Adopting a Bayesian block decomposition of the X-ray light curves of a
sample of SFXTs, we picked out 144 X-ray flares, covering a large range of soft
X-ray luminosities (1e32-1e36 erg/s). We measured temporal quantities, like the
rise time to and the decay time from the peak of the flares, their duration and
the time interval between adjacent flares. We also estimated the peak
luminosity, average accretion rate and energy release in the flares. The
observed soft X-ray properties of low-luminosity flaring activity from SFXTs is
in qualitative agreement with what is expected by the application of the
Rayleigh-Taylor instability model in accreting plasma near the neutron star
magnetosphere. In the case of rapidly rotating neutron stars, sporadic
accretion from temporary discs cannot be excluded.Comment: Accepted for publication in MNRAS (accepted 2019 May 1; received 2019
April 30; in original form 2019 February 25). 22 pages, 16 figures, 3 tables
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