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  • 1
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    GBM Observations of Be X-Ray Binary Outbursts (2014)
    In:  CASI
    Details
    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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  • 2
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    All-Sky Monitoring of Variable Sources with Fermi GBM (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Using the Gamma ray Burst Monitor (GBM) on Fermi, we monitor the transient hard X-ray/soft gamma ray sky. The twelve GBM NaI detectors span 8 keV to 1 MeV, while the two BGO detectors span 150 keV to 40 MeV. We use the Earth occultation technique to monitor a number of sources, including X-ray binaries, AGN, and solar flaring activity. Our monitoring reveals predictable and unpredictable phenomena such as transient outbursts and state changes. With GBM we also track the pulsed flux and spin frequency of accretion powered pulsars using epoch-folding techniques. Searches for quasi-periodic oscillations and X-ray bursts are also possible with GBM all-sky monitoring. Highlights from the Earth Occultation and Pulsar projects will be presented including our recent surprising discovery of variations in the total flux from the Crab. Inclusion of an all-sky monitor is crucial for a successful future X-ray timing mission.
    Keywords: Astronomy
    Type: M11-0062 , Fast X-ray Timing and Spectroscopy at Extreme Count Rates/ISDC; Feb 07, 2011 - Feb 11, 2011; Champery; Switzerland
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  • 3
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    Crab Nebula Variations in Hard X-rays (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Crab Nebula was surprisingly variable from 2001-2010, with less variability before 2001 and since mid-2010. We presented evidence for spectral softening from RXTE, Swift/BAT, and Fermi GBM during the mid-2008-2010 flux decline. We see no clear connections between the hard X-ray variations and the GeV flares
    Keywords: Astronomy
    Type: M12-1897 , The Flaring Crab: Surprise and Impact Meeting; Jul 04, 2012 - Jul 06, 2012; Rome; Italy
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  • 4
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    Be/X-ray Binary Science for Future X-ray Timing Missions (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: For future missions, the Be/X-ray binary community needs to clearly define our science priorities for the future to advocate for their inclusion in future missions. In this talk, I will describe current designs for two potential future missions and Be X-ray binary science enabled by these designs. The Large Observatory For X-ray Timing (LOFT) is an X-ray timing mission selected in February 2011 for the assessment phase from the 2010 ESA M3 call for proposals. The Advanced X-ray Timing ARray (AXTAR) is a NASA explorer concept X-ray timing mission. This talk is intended to initiate discussions of our science priorities for the future.
    Keywords: Astronomy
    Type: M11-0562 , M11-0756 , BeXRB 2011; Jul 11, 2011 - Jul 14, 2011; Valencia; Spain
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  • 5
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    All-Sky Monitoring of Variable Sources with Fermi GBM (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This slide presentation reviews the monitoring of variable sources with the Fermi Gamma Ray Burst Monitor (GBM). It reviews the use of the Earth Occultation technique, the observations of the Crab Nebula with the GBM, and the comparison with other satellite's observations. The instruments on board the four satellites indicate a decline in the Crab from 2008-2010.
    Keywords: Astronomy
    Type: M11-0271 , M11-0872 , IXO HTRS 2011 Conference: Fast X-Ray Timing and Spectroscopy at Extreme Count Rates; Feb 07, 2011 - Feb 11, 2011; Champery; Switzerland
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  • 6
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    Earth Occultation Monitoring with the Fermi Gamma Ray Burst Monitor (2014)
    In:  CASI
    Details
    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 (EOT). 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 for daily monitoring. Light curves, updated daily, are available on our website http://heastro.phys.lsu.edu/gbm. Our software is also capable of performing the Earth occultation monitoring using up to 128 energy bands, or any combination of those bands, using our 128-channel, 4-s CSPEC data. The GBM BGO detectors, sensitive from about 200 keV to 40 keV, can also be used with this technique. In our standard application of the EOT, we use a catalog of sources to drive the measurements. To ensure that our catalog is complete, our team has developed an Earth occultation imaging method. In this talk, I will describe both techniques and the current data products available. I will highlight recent and important results from the GBM EOT, including the current status of our observations of hard X-ray variations in the Crab Nebula.
    Keywords: Astronomy
    Type: M14-3744 , Fermi Asian Network Workshop; Jul 28, 2014 - Aug 01, 2014; Yilan; Taiwan, Province of China
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  • 7
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    Monitoring the Crab Nebula with LOFT (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: From 2008-2010, the Crab Nebula was found to decline by 7% in the 15-50 keV band, consistently in Fermi GBM, INTEGRAL IBIS, SPI, and JEMX, RXTE PCA, and Swift BAT. From 2001-2010, the 15-50 keV flux from the Crab Nebula typically varied by about 3.5% per year. Analysis of RXTE PCA data suggests possible spectral variations correlated with the flux variations. I will present estimates of the LOFT sensitivity to these variations. Prior to 2001 and since 2010, the observed flux variations have been much smaller. Monitoring the Crab with the LOFT WFM and LAD will provide precise measurements of flux variations in the Crab Nebula if it undergoes a similarly active episode.
    Keywords: Astronomy
    Type: M12-2008 , 2nd LOFT Science Meeting; Sep 24, 2012 - Sep 27, 2012; Toulouse; France
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  • 8
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    Be/X-Ray Pulsar Binary Science with LOFT (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Accretion disks are ubiquitous in astronomical sources. Accretion powered pulsars are a good test bed for accretion disk physics, because unlike for other objects, the spin of the neutron star is directly observable allowing us to see the effects of angular momentum transfer onto the pulsar. The combination of a sensitive wide-field monitor and the large area detector on LOFT will enable new detailed studies of accretion powered pulsars which I will review. RXTE observations have shown an unusually high number of Be/X-ray pulsar binaries in the SMC. Unlike binaries in the Milky Way, these systems are all at the same distance, allowing detailed population studies using the sensitive LOFT WFM, potentially providing connections to star formation episodes. For Galactic accreting pulsar systems, LOFT will allow measurement of spectral variations within individual pulses, mapping the accretion column in detail for the first time. LOFT will also provide better constraints on magnetic fields in accreting pulsars, allowing measurements of cyclotron features, observations of transitions into the centrifugal inhibition regime, and monitoring of spin-up rate vs flux correlations. Coordinated multi-wavelength observations are crucial to extracting the best science from LOFT from these and numerous other objects.
    Keywords: Astronomy
    Type: M11-1105 , 1st Large Observatory for X-ray Timing (LOFT) Science Meeting; Oct 26, 2011 - Oct 28, 2011; Amsterdam; Netherlands
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  • 9
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    Fermi GBM Observations of Terrestrial Gamma Flashes (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: In its first two years of operation, the Fermi Gamma Ray Burst Monitor (GBM) has observed more than 77 Terrestrial Gamma Flashes (TGFs). The thick Bismuth Germanate (BGO) detectors are excellent for TGF spectroscopy, having a high probability of recording the full energy of an incident photon, spanning a broad energy range from 150 keV to 40 MeV, and recording a large number of photons per TGF. Correlations between GBM TGF triggers and lightning sferics detected with the World-Wide Lightning Location Network indicate that TGFs and lightning are simultaneous to within tens of microseconds. The energy spectra of some TGFs have strong 511 keV positron annihilation lines, indicating that these TGFs contain a large fraction of positrons
    Keywords: Astronomy
    Type: M10-0872 , Scineghe2010 - 8th Workshop on Science with the New Generation of High Energy Gamma-Ray Experiments: Gamma-Ray Astrophysics in the Multimessenger Context; Sep 08, 2010 - Sep 10, 2010; Trieste, Italy; Italy
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  • 10
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    When a Standard Candle Flickers: Crab Nebula Variations in Hard X-rays (2011)
    In:  CASI
    Details
    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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