The GLAST Balloon Flight Engineering Model (BFEM) represents one of 16 towers that constitute the Large Area Telescope (LAT), a high-energy (>20 MeV) gamma-ray pair-production telescope being built ...by an international partnership of astrophysicists and particle physicists for a satellite launch in 2006. The prototype tower consists of a Pb/Si pair-conversion tracker (TKR), a CsI hodoscopic calorimeter (CAL), an anti-coincidence detector (ACD) and an autonomous data acquisition system (DAQ). The self-triggering capabilities and performance of the detector elements have been previously characterized using positron, photon and hadron beams. External target scintillators were placed above the instrument to act as sources of hadronic showers. This paper provides a comprehensive description of the BFEM data-reduction process, from receipt of the flight data from telemetry through event reconstruction and background rejection cuts. The goals of the ground analysis presented here are to verify the functioning of the instrument and to validate the reconstruction software and the background-rejection scheme.
We present a discovery of the correlation between the X-ray spectral (photon) index and mass accretion rate observed in an active galactic nucleus, NGC 4051. We analyzed spectral transition episodes ...observed in NGC 4051 using XMM-Newton, Suzaku and RXTE. We applied a scaling technique for a black hole (BH) mass evaluation which uses a correlation between the photon index and normalization of the seed (disk) component, which is proportional to a mass accretion rate. We developed an analytical model that shows the spectral (photon) index of the BH emergent spectrum undergoes an evolution from lower to higher values depending on a mass accretion rate in the accretion disk. We considered Cygnus X-1 and GRO J1550–564 as reference sources for which distances, inclination angles and the BH masses are evaluated by dynamical measurements. Application of the scaling technique for the photon index−mass accretion rate correlation provides an estimate of the black hole mass in NGC 4051 to be more than 6 × 105 solar masses.
We present the discovery of correlations between the X-ray spectral (photon) index and mass accretion rate observed in active galactic nuclei (AGNs) 3C 454.3 and M 87. We analyzed spectral transition ...episodes observed in these AGNs using
Chandra
,
Swift
,
Suzaku
,
Beppo
SAX, ASCA and RXTE data. We applied a scaling technique for a black hole (BH) mass evaluation which uses a correlation between the photon index and normalization of the seed (disk) component which is proportional to a mass accretion rate. We developed an analytical model that shows that the photon index of the BH emergent spectrum undergoes an evolution from lower to higher values depending on disk mass accretion rate. To estimate a BH mass in 3C 454.3 we consider extra-galactic SMBHs NGC 4051 and NGC 7469 as well as Galactic BHs Cygnus X–1 and GRO J1550–564 as reference sources for which distances, inclination angles are known and the BH masses are already evaluated. For M 87 on the other hand, we provide the BH mass scaling using extra-galactic sources (IMBHs: ESO 243–49 HLX–1 and M 101 ULX–1) and Galactic sources (stellar mass BHs: XTE J1550–564, 4U 1630–472, GRS 1915+105 and H 1743–322) as reference sources. Application of the scaling technique for the photon index−mass accretion rate correlation provides estimates of the BH masses in 3C 454.3 and M 87 to be about 3.4 × 10
9
and 5.6 × 10
7
solar masses, respectively. We also compared our scaling BH mass estimates with a recent BH mass estimate of
M
87
= 6.5 × 10
9
M
⊙
made using the Event Horizon Telescope which gives an image at 1.3 mm and is based on the angular size of the “BH event horizon”. Our BH mass estimate in M 87 is at least two orders of magnitude lower than that made by the EHT team.
A new data mode and new analysis methods are used to detect Terrestrial Gamma‐ray Flashes (TGFs) with the Fermi Gamma‐ray Burst Monitor (GBM) 10 times more frequently than previously. In 1037 h of ...observations at times and over regions for which TGFs are expected, 384 new TGFs were found in addition to the 39 TGFs and two Terrestrial Electron Beam events already detected without the new data mode and methodology. Cosmic ray showers were found to be an important background; they show characteristic signatures in the data of both GBM and the Fermi Large Area Telescope Calorimeter that enable their removal, leaving a sample estimated to consist of ≈98% TGFs. The sample includes shorter TGFs than previously found with GBM. The true duration distribution likely contains additional short TGFs because their detection by GBM is limited by detector dead time. One‐third of this sample has matches with locations from the World Wide Lightning Location Network (WWLLN)—maps of these locations show the geographic and meteorological features more clearly than maps of spacecraft locations. The intrinsic TGF rate is evaluated using the lightning rate maps of the Lightning Imaging Sensor, accounting for the detection efficiency of GBM as a function of spacecraft‐source offset, from which we estimate a global TGF rate of ≈400,000 per year. With continuous production of data in the new mode we estimate that GBM will detect ≈850 TGFs per year.
Key Points
A new data mode and analysis techniques increase the TGF rate of GBM x10.
Shorter TGFs are detected.
The global TGF rate is estimated as about 400,000 per year.
Degradation reactions on diclofenac-monoglycerides (3a,b), diclofenac-(p-hydroxybenzoate)-2-monoglyceride (3c), diclofenac (1), and diclofenac lactam (4) were performed at 37 °C in isotonic buffer ...solutions (apparent pH range 1-8) containing varying concentrations of acetonitrile (ACN). The concentration remaining of each analyte was measured versus time. Diclofenac-monoglycerides and diclofenac-(p-hydroxybenzoate)-2-monoglyceride (3c) were both found to undergo facile and complete hydrolysis in pH 7.4 isotonic phosphate buffer/10% ACN. Under mildly acidic, neutral or alkaline conditions, diclofenac-(p-hydroxybenzoate)-2-monoglyceride (3c) had the fastest hydrolysis rate (t1/2 = 3.23 h at pH 7.4), with simultaneous formation of diclofenac lactam (4) and diclofenac (1). Diclofenac-monoglycerides (3a,b) hydrolyzed more slowly under the same conditions, to again yield both diclofenac (1) and diclofenac lactam (4). There was also transesterification of diclofenac-2-monoglyceride (3b) to its regioisomer, diclofenac-1-monoglyceride (3a) across the pH range. Diclofenac was shown to be stable in neutral or alkaline conditions but cyclized to form the lactam (4) in acidic conditions. Conversely, the lactam (4) was stable under acidic conditions but was converted to an unknown species under alkaline or neutral conditions.
We show that the rate of association between terrestrial gamma ray flashes (TGFs) observed by the Fermi gamma ray burst monitor and VLF discharges detected by the World Wide Lightning Location ...Network (WWLLN) depends strongly on the duration of the TGF, with the shortest TGFs having associated WWLLN events over 50% of the time, and the longest TGFs showing a less than 10% match rate. This correlation is stronger if one excludes the WWLLN discharges that are not simultaneous (within 200 µs) with the TGF. We infer that the simultaneous VLF discharges are from the relativistic electron avalanches that are responsible for the flash of gamma rays and the nonsimultaneous VLF discharges are from related intracloud lightning strokes. The distributions of far‐field radiated VLF stroke energy measured by WWLLN for the simultaneous and nonsimultaneous discharges support the hypothesis of two discrete populations of VLF signals associated with TGFs, with the simultaneous discharges among the strongest measured by WWLLN.
Key PointsShort TGFs have high match rate with WWLLN. TGF electrons emit radio signalTGFs are also associated with lightning events, less often seen by WWLLNThe TGF radio signal is much more powerful than the lightning signal
The Fermi Gamma-ray Space Telescope has opened a new high-energy window in the study of gamma-ray bursts (GRBs). Here we present a thorough analysis of GRB 080825C, which triggered the Fermi ...Gamma-ray Burst Monitor (GBM), and was the first firm detection of a GRB by the Fermi Large Area Telescope (LAT). We discuss the LAT event selections, background estimation, significance calculations, and localization for Fermi GRBs in general and GRB 080825C in particular. We show the results of temporal and time-resolved spectral analysis of the GBM and LAT data. We also present some theoretical interpretation of GRB 080825C observations as well as some common features observed in other LAT GRBs.
A new data mode and new analysis methods are used to detect Terrestrial Gamma-ray Flashes (TGFs) with the Fermi Gamma-ray Burst Monitor (GBM) 10 times more frequently than previously. In 1037h of ...observations at times and over regions for which TGFs are expected, 384 new TGFs were found in addition to the 39 TGFs and two Terrestrial Electron Beam events already detected without the new data mode and methodology. Cosmic ray showers were found to be an important background; they show characteristic signatures in the data of both GBM and the Fermi Large Area Telescope Calorimeter that enable their removal, leaving a sample estimated to consist of asymptotically =98% TGFs. The sample includes shorter TGFs than previously found with GBM. The true duration distribution likely contains additional short TGFs because their detection by GBM is limited by detector dead time. One-third of this sample has matches with locations from the World Wide Lightning Location Network (WWLLN)--maps of these locations show the geographic and meteorological features more clearly than maps of spacecraft locations. The intrinsic TGF rate is evaluated using the lightning rate maps of the Lightning Imaging Sensor, accounting for the detection efficiency of GBM as a function of spacecraft-source offset, from which we estimate a global TGF rate of asymptotically =400,000 per year. With continuous production of data in the new mode we estimate that GBM will detect asymptotically =850 TGFs per year. Key Points A new data mode and analysis techniques increase the TGF rate of GBM x10. Shorter TGFs are detected. The global TGF rate is estimated as about 400,000 per year.
We present a discovery of the correlation between the X-ray spectral (photon) index and mass accretion rate observed in AGN NGC 4051. We analyzed spectral transition episodes observed in NGC 4051 ...using XMM/Newton, Suzaku and RXTE. We applied a scaling technique for a black hole (BH) mass evaluation which uses a correlation between the photon index and normalization of the seed (disk) component, which is proportional to a mass accretion rate. We developed an analytical model that shows the spectral (photon) index of the BH emergent spectrum undergoes an evolution from lower to higher values depending on a mass accretion rate in the accretion disk. We considered Cygnus X-1 and GRO~J1550-564 as reference sources for which distances, inclination angles and the BH masses are evaluated by dynamical measurements. Application of the scaling technique for the photon index-mass accretion rate correlation provides an estimate of the black hole mass in NGC 4051 to be more than 6x10^5 solar masses.
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