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• 1
Publication Date: 2016-01-22
Description: We report the results of a spectral and timing analysis of the poorly studied transient X-ray pulsar 2S 1553–542 using data collected with the NuSTAR and Chandra observatories and the Fermi /GBM instrument during an outburst in 2015. The properties of the source at high energies (〉30 keV) are studied for the first time and the sky position has been essentially improved. The source broad-band spectrum has a quite complicated shape and can be reasonably described by a composite model with two continuum components – a blackbody emission with the temperature about 1 keV at low energies and a power law with an exponential cut-off at high energies. Additionally, an absorption feature at ~23.5 keV is discovered both in phase-averaged and phase-resolved spectra and interpreted as the cyclotron resonance scattering feature corresponding to the magnetic field strength of the neutron star B  ~ 3  x  10 12  G. Based on the Fermi /GBM data, the orbital parameters of the system were substantially improved, which allowed us to determine the spin period of the neutron star P  = 9.27880(3) s and a local spin-up $\dot{P} \simeq -7.5 \times 10^{-10}$  s s –1 due to the mass accretion during the NuSTAR observations. Assuming accretion from the disc and using standard torque models, we estimated the distance to the system as d  = 20 ± 4 kpc.
Print ISSN: 0035-8711
Electronic ISSN: 1365-2966
Topics: Physics
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• 2
Unknown
In:  CASI
Publication Date: 2019-07-20
Description: No abstract available
Keywords: Astronomy
Type: MSFC-E-DAA-TN66777 , MSFC-E-DAA-TN64113 , Meeting of the American Astronomical Society; Jan 06, 2019 - Jan 10, 2019; Seattle, WA; United States|Meeting of High Energy Astrophysics; Mar 17, 2019 - Mar 21, 2019; Monterey, CA; United States
Format: application/pdf
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• 3
Unknown
In:  CASI
Publication Date: 2019-07-19
Description: In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, approximately 7% (70 mcrab) decline was discovered in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/PCA was particularly variable, changing by up to approximately 3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003, Swift/BAT starting in 2005, and Fermi GBM starting in 2008. Before 2001 and since 2010, the Crab nebula flux has appeared more stable, varying by less than 2% per year. I will present updated light curves in multiple energy bands for the Crab nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL and MAXI, and a 16-year long light curve from RXTE/PCA.
Keywords: Astrophysics
Type: M13-2408 , High Energy Astrophysics Division 2013; Apr 07, 2013 - Apr 11, 2013; Monterey, CA; United States
Format: application/pdf
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• 4
Unknown
In:  CASI
Publication Date: 2019-07-19
Description: Using the Gamma Ray Burst Monitor (GBM) on-board Fermi, we are monitoring the hard X-ray/soft gamma ray sky using the Earth occultation technique. Each time a source in our catalog is occulted by (or exits occultation by) the Earth, we measure its flux using the change in count rates due to the occultation. Currently we are using CTIME data with 8 energy channels spanning 8 keV to 1 MeV for the GBM NaI detectors and spanning 150 keV to 40 MeV for the GBM BGO detectors. Our preliminary catalog consists of galactic X-ray binaries, the Crab Nebula, and active galactic nuclei. New sources are added to our catalog as they become active or upon request. In addition to Earth occultations, we have observed numerous occultations with Fermi's solar panels. We will present early results. Regularly updated results will be found on our website http://gammaray.nsstc.nasa.gov/gbm/science/occultation.
Keywords: Astronomy
Type: M10-0126 , M10-0094 , High Energy Astrophysics Division of American Astronomical Society (HEAD) 2010; Mar 01, 2010 - Mar 04, 2010; Big Island, HI; United States
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• 5
Unknown
In:  CASI
Publication Date: 2019-07-19
Description: RXTE played a crucial role in our surprising discovery that the Crab Nebula is variable in hard X-rays. In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008-2010, a approx.7% (70 mcrab) decline was discovered in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed in the ~15-50 keV band with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/PCA was particularly variable, changing by up to approx.3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003 and Swift/BAT starting in 2005. Before 2001 and since 2010, the Crab nebula 15-50 keV flux measured with RXTE/PCA appeared more stable, varying by less than 2% per year. In this talk I will present Crab light curves including RXTE data for the entire 16-year mission in multiple energy bands.
Keywords: Astrophysics
Type: M12-1577 , 16 Years of Discovery with RXTE: A Celebration of the Mission; Mar 29, 2012 - Mar 30, 2012; Greenbelt, MD; United States
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• 6
Unknown
In:  CASI
Publication Date: 2019-07-19
Description: In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM) since August 2008, a ~7% (70 mcrab) decline was observed in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline is independently confirmed in the ~15-50 keV band with four other instruments: Swift/BAT, the RXTE/PCA, INTEGRAL/IBIS, and INTEGRAL/SPI. A similar decline is also observed in the ~3-15 keV data from the RXTE/PCA and in the 50-100 keV band with GBM, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA since 1999 is consistent with the pulsar spin-down, indicating that the observed changes are nebular. Correlated variations in the Crab Nebula flux on a ~3 year timescale are also seen independently with the PCA, BAT, IBIS, and SPI from 2005 to 2008, with a flux minimum in April 2007. As of April 2011, the Crab nebula flux has stopped declining and may be beginning to increase. We will present updated results on our multi-instrument study of long-term Crab nebula variations.
Keywords: Astronomy
Type: M11-0563 , 2011 meeting of the High Energy Astrophysics Division of the American Astronomical Society; Sep 07, 2011 - Sep 10, 2011; Providence, RI; United States
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• 7
Unknown
In:  CASI
Publication Date: 2019-07-20
Description: We describe a probe-class mission concept that provides an unprecedented view of the X-ray sky, performing timing and 0.2-30 keV spectroscopy over timescales from microseconds to years. The Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) has three key science drivers: (1) measuring the spin distribution of accreting black holes, (2) understanding the equation of state of dense matter, and (3) exploring the properties of the precursors and electromagnetic counterparts of gravitational wave sources. To perform these science investigations, STROBE-X comprises three primary instruments. The first uses an array of lightweight optics (3-m focal length) that concentrate incident photons onto solid state detectors with CCD-level (85-130 eV) energy resolution, 100 ns time resolution, and low background rates to cover the 0.2-12 keV band. This technology is scaled up from NICER, with enhanced optics to take advantage of the longer focal length of STROBE-X. The second uses large-area collimated silicon drift detectors, developed for ESA's LOFT, to cover the 2-30 keV band. These two instruments each provide an order of magnitude improvement in effective area compared with its predecessor (NICER and RXTE, respectively). Finally, a sensitive sky monitor triggers pointed observations, provides high duty cycle, high time resolution, high spectral resolution monitoring of the X-ray sky with ~20 times the sensitivity of the RXTE ASM, and enables multi-wavelength and multi-messenger studies on a continuous, rather than scanning basis. The STROBE-X mission concept is a rapidly repointable observatory in low-Earth orbit, similar to RXTE or Swift, and will be presented to the 2020 Astrophysics Decadal Survey for consideration as a probe-class mission.
Keywords: Astrophysics
Type: MSFC-E-DAA-TN64215 , Meeting of the American Astronomical Society (AAS); Jan 06, 2019 - Jan 10, 2019; Seattle,WA; United States
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• 8
Unknown
In:  CASI
Publication Date: 2019-07-19
Description: In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, an approximately 7% (70 mcrab) decline was discovered in the overall Crab nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/PCA was particularly variable, changing by up to approximately 3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003, Swift/BAT starting in 2005, and Fermi GBM starting in 2008. Before 2001 and since 2010, the Crab nebula flux has appeared more stable, varying by less than 2% per year. At higher energies, above 50 keV, the Crab flux appears to be slowly recovering to its 2008 levels. I will present updated light curves in multiple energy bands for the Crab nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL, MAXI, and NuSTAR and a 16-year long light curve from RXTE/PCA.
Type: M14-3745 , INTEGRAL Workshop; Sep 15, 2014 - Sep 19, 2014; Annapolis, MD; United States
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• 9
Unknown
In:  CASI
Publication Date: 2019-07-19
Description: Since 2008 we have been monitoring accreting pulsars using the Gamma ray Burst Monitor (GBM) on Fermi. This monitoring program includes daily blind full sky searches for previously unknown or previously quiescent pulsars and source specific analysis to track the frequency evolution of all detected pulsars. To date we have detected outbursts from 23 transient accreting pulsars, including 21 confirmed or likely Be/Xray binaries. I will describe our techniques and highlight results for selected pulsars.
Keywords: Astronomy
Type: M14-3642 , Be X-Ray Binary Systems (BeXRB) 2014 Worksbop; Jul 07, 2014 - Jul 11, 2014; Valencia; Spain
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• 10
Unknown
In:  CASI
Publication Date: 2019-07-13
Description: No abstract available
Keywords: Astronomy
Type: M14-3742 , BeXRB 2014; Jul 07, 2014 - Jul 10, 2014; Valencia; Spain
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