83 research outputs found
Identification of the donor in GRS 1915+105
We report on the results of medium-resolution spectroscopy of GRS 1915+105 in
the H and K band using the 8m VLT at ESO. We clearly identify absorption
bandheads from CO12 and CO13. Together with other features this results in a
classification of the donor as a K-M III star.Comment: 4 pages, Kluwer style, to appear in Astrophys. Space Sci. Rev, Proc.
of 3rd Microquasar workshop, Granada, Sep. 2000, Eds. A.J. Castro-Tirado, J.
Greiner, J.M. Paredes; all proceedings contr. available at
http://www.aip.de/~jcg/granada.htm
A Randomized Sublinear Time Parallel GCD Algorithm for the EREW PRAM
We present a randomized parallel algorithm that computes the greatest common
divisor of two integers of n bits in length with probability 1-o(1) that takes
O(n loglog n / log n) expected time using n^{6+\epsilon} processors on the EREW
PRAM parallel model of computation. We believe this to be the first randomized
sublinear time algorithm on the EREW PRAM for this problem
The Wide Integral Field Infrared Spectrograph: Commissioning Results and On-sky Performance
We have recently commissioned a novel infrared ( m) integral
field spectrograph (IFS) called the Wide Integral Field Infrared Spectrograph
(WIFIS). WIFIS is a unique instrument that offers a very large field-of-view
(50 x 20) on the 2.3-meter Bok telescope at
Kitt Peak, USA for seeing-limited observations at moderate spectral resolving
power. The measured spatial sampling scale is and
its spectral resolving power is and in the
( m) and ( m) modes, respectively.
WIFIS's corresponding etendue is larger than existing near-infrared (NIR)
IFSes, which are mostly designed to work with adaptive optics systems and
therefore have very narrow fields. For this reason, this instrument is
specifically suited for studying very extended objects in the near-infrared
such as supernovae remnants, galactic star forming regions, and nearby
galaxies, which are not easily accessible by other NIR IFSes. This enables
scientific programs that were not originally possible, such as detailed surveys
of a large number of nearby galaxies or a full accounting of nucleosynthetic
yields of Milky Way supernova remnants. WIFIS is also designed to be easily
adaptable to be used with larger telescopes. In this paper, we report on the
overall performance characteristics of the instrument, which were measured
during our commissioning runs in the second half of 2017. We present
measurements of spectral resolving power, image quality, instrumental
background, and overall efficiency and sensitivity of WIFIS and compare them
with our design expectations. Finally, we present a few example observations
that demonstrate WIFIS's full capability to carry out infrared imaging
spectroscopy of extended objects, which is enabled by our custom data reduction
pipeline.Comment: Published in the Proceedings of SPIE Astronomical Telescopes and
Instrumentation 2018. 17 pages, 13 figure
INTEGRAL and RXTE monitoring of GRS 1758-258 in 2003 and 2004. A transition from the dim soft state to the hard state
The Galactic Center black hole candidate (BHC) GRS 1758-258 has been observed
extensively within INTEGRAL's Galactic Center Deep Exposure (GCDE) program in
2003 and 2004, while also being monitored with RXTE. We present
quasi-simultaneous PCA, ISGRI, and SPI spectra from four GCDE observation
epochs, as well as the evolution of energy-resolved PCA and ISGRI light curves
on time scales of days to months. We find that during the first epoch GRS
1758-258 displayed another of its peculiar dim soft states like the one
observed in 2001, increasing the number of observed occurrences of this state
to three. During the other epochs the source was in the hard state. The hard
X-ray emission component in the epoch-summed spectra can be well described
either by phenomenological models, namely a cutoff power law in the hard state
and a pure power law in the dim soft state, or by thermal Comptonization
models. A soft thermal component is clearly present in the dim soft state and
might also contribute to the softer hard state spectra. We argue that in the
recently emerging picture of the hardness-intensity evolution of black hole
transient outbursts in which hard and soft states are observed to occur in a
large overlapping range of luminosities (hysteresis), the dim soft state is not
peculiar. As noted before for the 2001 dim soft state, these episodes seem to
be triggered by a sudden decrease (within days) of the hard emission, with the
soft spectral component decaying on a longer time scale (weeks). We discuss
this behavior in terms of the existence of two independent accretion flows, the
model previously suggested for the 2001 episode. (Abridged)Comment: Replaced to match accepted versio
An overview of jets and outflows in stellar mass black holes
In this book chapter, we will briefly review the current empirical
understanding of the relation between accretion state and and outflows in
accreting stellar mass black holes. The focus will be on the empirical
connections between X-ray states and relativistic (`radio') jets, although we
are now also able to draw accretion disc winds into the picture in a systematic
way. We will furthermore consider the latest attempts to measure/order jet
power, and to compare it to other (potentially) measurable quantities, most
importantly black hole spin.Comment: Accepted for publication in Space Science Reviews. Also to appear in
the Space Sciences Series of ISSI - The Physics of Accretion on to Black
Holes (Springer Publisher
Gravitational Waves From Known Pulsars: Results From The Initial Detector Era
We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper.United States National Science FoundationScience and Technology Facilities Council of the United KingdomMax-Planck-SocietyState of Niedersachsen/GermanyAustralian Research CouncilInternational Science Linkages program of the Commonwealth of AustraliaCouncil of Scientific and Industrial Research of IndiaIstituto Nazionale di Fisica Nucleare of ItalySpanish Ministerio de Economia y CompetitividadConselleria d'Economia Hisenda i Innovacio of the Govern de les Illes BalearsNetherlands Organisation for Scientific ResearchPolish Ministry of Science and Higher EducationFOCUS Programme of Foundation for Polish ScienceRoyal SocietyScottish Funding CouncilScottish Universities Physics AllianceNational Aeronautics and Space AdministrationOTKA of HungaryLyon Institute of Origins (LIO)National Research Foundation of KoreaIndustry CanadaProvince of Ontario through the Ministry of Economic Development and InnovationNational Science and Engineering Research Council CanadaCarnegie TrustLeverhulme TrustDavid and Lucile Packard FoundationResearch CorporationAlfred P. Sloan FoundationAstronom
Swift follow-up observations of candidate gravitational-wave transient events
We present the first multi-wavelength follow-up observations of two candidate
gravitational-wave (GW) transient events recorded by LIGO and Virgo in their
2009-2010 science run. The events were selected with low latency by the network
of GW detectors and their candidate sky locations were observed by the Swift
observatory. Image transient detection was used to analyze the collected
electromagnetic data, which were found to be consistent with background.
Off-line analysis of the GW data alone has also established that the selected
GW events show no evidence of an astrophysical origin; one of them is
consistent with background and the other one was a test, part of a "blind
injection challenge". With this work we demonstrate the feasibility of rapid
follow-ups of GW transients and establish the sensitivity improvement joint
electromagnetic and GW observations could bring. This is a first step toward an
electromagnetic follow-up program in the regime of routine detections with the
advanced GW instruments expected within this decade. In that regime
multi-wavelength observations will play a significant role in completing the
astrophysical identification of GW sources. We present the methods and results
from this first combined analysis and discuss its implications in terms of
sensitivity for the present and future instruments.Comment: Submitted for publication 2012 May 25, accepted 2012 October 25,
published 2012 November 21, in ApJS, 203, 28 (
http://stacks.iop.org/0067-0049/203/28 ); 14 pages, 3 figures, 6 tables;
LIGO-P1100038; Science summary at
http://www.ligo.org/science/Publication-S6LVSwift/index.php ; Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p110003
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