Detection and period measurements of GX1+4 at hard x ray energies with the SIGMA telescope

The galactic Low Mass X ray Binary GX1+4 was detected by the coded aperture hard X ray gamma ray SIGMA telescope during the Feb. to April 1991 observations of the galactic center regions. The source, whose emission varied during the survey of a factor greater than 40 pct., reached a maximum luminosity in the 40 to 140 energy range of 1.03 x 10(exp 37) erg/s (D = 8.5 kpc), thus approaching the emission level of the 1970 to 1980 high state. Two minute flux pulsations were detected on Mar. 22 and on Mar. 31 and Apr. 1. Comparison with the last period measurements shows that the current spin-down phase of GX1+4 is ending. Concerning the proposed association of this source with the galactic center 511 keV annihilation emission, upper limits were derived

Discrete Wavelet Transform and Optimal Spectral Transform Applied to Multicomponent Image Coding

ISBN 978-953-307-482-5 Chapitre 10International audienc

Swift monitoring of Cygnus X-2: investigating the NUV-X-ray connection

The neutron star X-ray binary (NSXRB) Cygnus X-2 was observed by the Swift satellite 51 times over a 4 month period in 2008 with the XRT, UVOT, and BAT instruments. During this campaign, we observed Cyg X-2 in all three branches of the Z track (horizontal, normal, and flaring branches). We find that the NUV emission is uncorrelated with the soft X-ray flux detected with the XRT, and is anticorrelated with the BAT X-ray flux and the hard X-ray color. The observed anticorrelation is inconsistent with simple models of reprocessing as the source of the NUV emission. The anticorrelation may be a consequence of the high inclination angle of Cyg X-2, where NUV emission is preferentially scattered by a corona that expands as the disk is radiatively heated. Alternatively, if the accretion disk thickens as Cyg X-2 goes down the normal branch toward the flaring branch, this may be able to explain the observed anticorrelation. In these models the NUV emission may not be a good proxy for $\dot m$ in the system. We also discuss the implications of using Swift/XRT to perform spectral modeling of the continuum emission of NSXRBs.Comment: 10 pages, 8 figures. ApJ Accepte

Resolving the Hard X-ray Emission of GX 5-1 with INTEGRAL

We present the study of one year of INTEGRAL data on the neutron star low mass X-ray binary GX 5-1. Thanks to the excellent angular resolution and sensitivity of INTEGRAL, we are able to obtain a high quality spectrum of GX 5-1 from ~5 keV to ~100 keV, for the first time without contamination from the nearby black hole candidate GRS 1758-258 above 20 keV. During our observations, GX 5-1 is mostly found in the horizontal and normal branch of its hardness intensity diagram. A clear hard X-ray emission is observed above ~30 keV which exceeds the exponential cut-off spectrum expected from lower energies. This spectral flattening may have the same origin of the hard components observed in other Z sources as it shares the property of being characteristic to the horizontal branch. The hard excess is explained by introducing Compton up-scattering of soft photons from the neutron star surface due to a thin hot plasma expected in the boundary layer. The spectral changes of GX 5-1 downward along the "Z" pattern in the hardness intensity diagram can be well described in terms of monotonical decrease of the neutron star surface temperature. This may be a consequence of the gradual expansion of the boundary layer as the mass accretion rate increases.Comment: 10 pages, 17 figures, accepted for publication in A&

Pore water exchange-driven inorganic carbon export from intertidal salt marshes

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tamborski, J. J., Eagle, M., Kurylyk, B. L., Kroeger, K. D., Wang, Z. A., Henderson, P., & Charette: 1774-1792, https://doi.org/10.1002/lno.11721.Respiration in intertidal salt marshes generates dissolved inorganic carbon (DIC) that is exported to the coastal ocean by tidal exchange with the marsh platform. Understanding the link between physical drivers of water exchange and chemical flux is a key to constraining coastal wetland contributions to regional carbon budgets. The spatial and temporal (seasonal, annual) variability of marsh pore water exchange and DIC export was assessed from a microtidal salt marsh (Sage Lot Pond, Massachusetts). Spatial variability was constrained from 224Ra : 228Th disequilibria across two hydrologic units within the marsh sediments. Disequilibrium between the more soluble 224Ra and its sediment-bound parent 228Th reveals significant pore water exchange in the upper 5 cm of the marsh surface (0–36 L m−2 d−1) that is most intense in low marsh elevation zones, driven by tidal overtopping. Surficial sediment DIC transport ranges from 0.0 to 0.7 g C m−2 d−1. The sub-surface sediment horizon intersected by mean low tide was disproportionately impacted by tidal pumping (20–80 L m−2 d−1) and supplied a seasonal DIC flux of 1.7–5.4 g C m−2 d−1. Export exceeded 10 g C m−2 d−1 for another marsh unit, demonstrating that fluxes can vary substantially across salt marshes under similar conditions within the same estuary. Seasonal and annual variability in marsh pore water exchange, constrained from tidal time-series of radium isotopes, was driven in part by variability in mean sea level. Rising sea levels will further inundate high marsh elevation zones, which may lead to greater DIC export.This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund, through the Ocean Frontier Institute. Additional funding was provided by the U.S. Geological Survey (USGS) Coastal & Marine Geology Program and the USGS Land Change Science Program's LandCarbon program

The ECLAIRs micro-satellite mission for gamma-ray burst multi-wavelength observations

Gamma-ray bursts (GRB), at least those with a duration longer than a few seconds are the most energetic events in the Universe and occur at cosmological distances. The ECLAIRs micro-satellite, to be launched in 2009, will provide multi-wavelength observations of GRB, to study their astrophysics and to use them as cosmological probes. Furthermore in 2009 ECLAIRs is expected to be the only space borne instrument capable of providing a GRB trigger in near real-time with sufficient localization accuracy for GRB follow-up observations with the powerful ground based spectroscopic telescopes available by then. A "Phase A study" of the ECLAIRs project has recently been launched by the French Space Agency CNES, aiming at a detailed mission design and selection for flight in 2006. The ECLAIRs mission is based on a CNES micro-satellite of the "Myriade" family and dedicated ground-based optical telescopes. The satellite payload combines a 2 sr field-of-view coded aperture mask gamma-camera using 6400 CdTe pixels for GRB detection and localization with 10 arcmin precision in the 4 to 50 keV energy band, together with a soft X-ray camera for onboard position refinement to 1 arcmin. The ground-based optical robotic telescopes will detect the GRB prompt/early afterglow emission and localize the event to arcsec accuracy, for spectroscopic follow-up observations.Comment: 7 pages, 1 figure, proceedings of the conference "New Developments in Photodetection", Beaune (France), June 25005. Submitted to NIM-A (Elsevier Science

New Evidence for Black Hole Event Horizons from Chandra

Previously we claimed that Black Hole X-ray Novae (BHXN) in quiescence are much less luminous than equivalent Neutron Star X-ray Novae (NSXN). This claim was based on the quiescent detection of a single short period BHXN (A0620-00, P(orb)=7.8 hrs) and two longer period BHXN (GRO J1655-40, P(orb)=62.9 hrs; V404 Cyg, P(orb)=155.3 hrs), along with sensitive upper limits. We announce the detection of two more short period BHXN (GRO J0422+32, P(orb)=5.1 hrs; GS 2000+25, P(orb)=8.3 hrs), an upper limit for a third which is improved by two orders of magnitude (4U 1543-47, P(orb)=27.0 hrs) and a new, much lower quiescent measurement of GRO J1655-40. Taken together, these new Chandra measurements confirm that the quiescent X-ray luminosities of BHXN are significantly lower than those of NSXN. We argue that this provides strong evidence for the existence of event horizons in BHXN.Comment: Submitted to ApJ Letters, 4 pages, 2 figure

Moyo Vol. VIII N 2

Durica, Paul. Editor\u27s Letter . 4. Fisher, Dan. Heaven for Thunder (Thoughts on the Last Execution) . 5. Anshuman, Karan. Return to Sender (Mail-Order Brides Log-On Love) . 6. Grindstaff, Michelle. Madonna or Whore (Language Traps Female Sexuality) . 7. Thackeray, Alex. Strike Against the Right (Canada Collegians Take Action) . 8. Dotson, Dorothy. Tori Listening to Mullet Boy . 10. Stine, Alison. Tori Story (Secrets of a Toriphile: Good Girl Gets Plugged) . 11. Barret, Laura. Late Night Crush (Girl Crazy for Conan) . 15. Hankinson, Tom. Environmentally friendly, or Else (DURP tough on DU Junk) . 16. Bussan, David. Fantasy\u27s Island (Alums Find Paradise in Northern Cyprus) . 18. Burt, Kara. Innocents on Break (Students Exercise Alternatives in New York) . 21. Werne, Kirsten. Two Turntables and a Ten-Gallon Hat . 23. Million, Chris. Friendship a Modem Away, Sigh (AOL Alters Denison Social Scene) . 34