We present the results of six Suzaku observations of the recurrent black hole transient 4U1630-472 during its decline from outburst from February 8 to March 23 in 2006. All observations show the ...typical high/soft state spectral shape in the 2-50keV band, roughly described by an optically thick disk spectrum in the soft energy band plus a weak power-law tail that becomes dominant only above \~20keV. The disk temperature decreases from 1.4keV to 1.2keV as the flux decreases by a factor 2, consistent with a constant radius as expected for disk-dominated spectra. All the observations reveal significant absorption lines from highly ionized (H-like and He-like) iron Ka at 7.0keV and 6.7keV. The brightest datasets also show significant but weaker absorption structures between 7.8keV and 8.2keV, which we identify as a blend of iron Kb and nickel Ka absorption lines. The energies of these absorption lines suggest a blue shift with an outflow velocity of ~1000km/s.. The H-like iron Ka equivalent width remains approximately constant at ~30 eV over all the observations, while that of the He-like Ka line increases from 7 eV to 20 eV. Thus the ionization state of the material decreases, as expected from the decline in flux. We fit the profiles with Voigt functions (curve of growth) to derive absorbing columns, then use these together with detailed photo-ionization calculations to derive physical parameters of the absorbing material. The data then constrain the velocity dispersion of the absorber to 200-2000 km/s, and the size of the plasma as ~1E10 cm assuming a source distance of 10 kpc.
We present the results of 4 simultaneous observations of Cygnus X-1 by Ginga
and OSSE. The X-ray/gamma-ray spectra can be described by an intrinsic
continuum and a component due to Compton reflection ...including an iron K-alpha
line. The intrinsic spectrum at X-ray energies is a power-law with a photon
spectral index of Gamma=1.6. The intrinsic gamma-ray spectrum can be
phenomenologically described by either a power-law without cutoff up to 150
keV, and an exponential cutoff above that energy, or by an exponentially cutoff
power law and a second hard component.
As a short introduction to the astronomy session, the response of the community to the Call for Themes issued by ESA and the specific themes selected by the Astronomy Working Group are briefly ...presented in connection with the four grand themes finally selected for the ESA Science Programme. They are placed in the context of the main discoveries of the past decade and the astronomy projects currently in their development or definition phase. Finally, possible strategies for their implementation are summarised.
Mon.Not.Roy.Astron.Soc. 288 (1997) 958-964 We present four X-ray/gamma-ray spectra of Cyg X-1 observed in the hard
('low') state simultaneously by Ginga and GRO/OSSE on 1991 July 6. The 3-30 keV
...Ginga spectra are well represented by power laws with an energy spectral index
of alpha~0.6 and a Compton reflection component including a fluorescent Fe
K-alpha corresponding to the solid angle of the reflector of ~0.3 times 2 Pi.
The overall Ginga/OSSE spectra can be modelled by repeated Compton scattering
in a mildly-relativistic, tau ~1, plasma. However, the high-energy cutoff is
steeper than that due to single-temperature thermal Comptonisation. It can be
described by a superposition of dominant optically-thin, thermal emission at
kT~140 keV and a Wien-like component from an optically-thick plasma at kT~50
keV. The X-ray spectra do not show the presence of an anisotropy break required
if thermal Compton scattering takes place in a corona above a cold disc. Also,
the flat spectral index shows that the plasma is soft-photon starved, i.e., the
luminosity in incident soft X-ray seed photons is very much less than that in
the hard X-rays. Furthermore, the observed solid angle of the reflector is
significantly less than 2 pi. These facts taken together strongly rule out a
disc-corona geometry. Rather, the observed spectra are consistent with a
geometry in which the cold accretion disc (which both supplies the seed soft
X-rays and reflects hard X-rays) only exists at large radii, while the
Comptonising hot plasma is located in an inner region with no cold disc. This
hot plasma consists of either pure electron-positron pairs if the source size
is ~5 Schwarzschild radii or it contains also protons if the size is larger.
We present the results of 4 simultaneous observations of Cygnus X-1 by Ginga and OSSE. The X-ray/gamma-ray spectra can be described by an intrinsic continuum and a component due to Compton reflection ...including an iron K-alpha line. The intrinsic spectrum at X-ray energies is a power-law with a photon spectral index of Gamma=1.6. The intrinsic gamma-ray spectrum can be phenomenologically described by either a power-law without cutoff up to 150 keV, and an exponential cutoff above that energy, or by an exponentially cutoff power law and a second hard component.
We present four X-ray/gamma-ray spectra of Cyg X-1 observed in the hard ('low') state simultaneously by Ginga and GRO/OSSE on 1991 July 6. The 3-30 keV Ginga spectra are well represented by power ...laws with an energy spectral index of alpha~0.6 and a Compton reflection component including a fluorescent Fe K-alpha corresponding to the solid angle of the reflector of ~0.3 times 2 Pi. The overall Ginga/OSSE spectra can be modelled by repeated Compton scattering in a mildly-relativistic, tau ~1, plasma. However, the high-energy cutoff is steeper than that due to single-temperature thermal Comptonisation. It can be described by a superposition of dominant optically-thin, thermal emission at kT~140 keV and a Wien-like component from an optically-thick plasma at kT~50 keV. The X-ray spectra do not show the presence of an anisotropy break required if thermal Compton scattering takes place in a corona above a cold disc. Also, the flat spectral index shows that the plasma is soft-photon starved, i.e., the luminosity in incident soft X-ray seed photons is very much less than that in the hard X-rays. Furthermore, the observed solid angle of the reflector is significantly less than 2 pi. These facts taken together strongly rule out a disc-corona geometry. Rather, the observed spectra are consistent with a geometry in which the cold accretion disc (which both supplies the seed soft X-rays and reflects hard X-rays) only exists at large radii, while the Comptonising hot plasma is located in an inner region with no cold disc. This hot plasma consists of either pure electron-positron pairs if the source size is ~5 Schwarzschild radii or it contains also protons if the size is larger.
In September 2020, Western North America was impacted by a highly anomalous meteorological event. Over the Pacific Northwest, strong and dry easterly winds exceeded historically observed values for ...the time of year and contributed to the rapid spread of several large wildfires. Nine lives were lost and over 5000 homes and businesses were destroyed in Oregon. The smoke from the fires enveloped the region for nearly two weeks after the event. Concurrently, the same weather system brought record-breaking cold, dramatic 24-h temperature falls, and early-season snowfall to parts of the Rocky Mountains. Here we use synoptic analysis and air parcel backward trajectories to build a process-based understanding of this extreme event and to put it in a climatological context. The primary atmospheric driver was the rapid development of a highly amplified 500 hPa tropospheric wave pattern that persisted for several days. A record-breaking ridge of high pressure characterized the western side of the wave pattern with a record-breaking trough of low pressure to the east. A notable anticyclonic Rossby wave breaking event occurred as the wave train amplified. Air parcel backward trajectories show that dry air over the Pacific Northwest, which exacerbated the fire danger, originated in the mid-troposphere and descended through subsidence to the surface. At the same time, dramatic temperature falls were recorded along the east side of the Rocky Mountains, driven by strong transport of high-latitude air near the surface.
This paper uses empirical field research to examine whether short-term best practice interventions (BPIs) can lead to improvements that are sustained in the long term. In addition, this research ...investigates the implied conflict between striving for short-term results and achieving long-term development of capabilities. It also examines the tension between the lack of resources of the typical small and medium sized enterprise (SME) users of BPIs and the time required to develop a critical mass of capability. A longitudinal case-based study of eight SME contexts examined BPI outcomes and factors leading to short- and long-term success and sustaining best practices. The research identifies factors related to the intervention context, implementation and change-agent approach. The data indicate that in resource-limited SMEs BPIs are limited in their ability to develop adequate capability for long-term change.
Abstract
Real-time analyses and forecasts using an ensemble Kalman filter (EnKF) and the Advanced Hurricane Weather Research and Forecasting Model (AHW) are evaluated from the 2009 North Atlantic ...hurricane season. This data assimilation system involved cycling observations that included conventional in situ data, tropical cyclone (TC) position, and minimum SLP and synoptic dropsondes each 6 h using a 96-member ensemble on a 36-km domain for three months. Similar to past studies, observation assimilation systematically reduces the TC position and minimum SLP errors, except for strong TCs, which are characterized by large biases due to grid resolution. At 48 different initialization times, an AHW forecast on 12-, 4-, and 1.33-km grids is produced with initial conditions drawn from a single analysis member. Whereas TC track analyses and forecasts exhibit a pronounced northward bias, intensity forecast errors are similar to (lower than) the NWS Hurricane Weather Research Model (HWRF) and GFDL forecasts for forecast lead times ≤60 h (>60 h), with the largest track errors associated with the weakest systems, such as Tropical Storm (TS) Erika. Several shortcomings of the data assimilation system are addressed through postseason sensitivity tests, including using the maximum 800-hPa circulation to identify the TC position during assimilation and turning off the quality control for the TC minimum SLP observation when the initial intensity is far too weak. In addition, the improved forecast of TS Erika relative to HWRF is shown to be related to having initial conditions that are more representative of a sheared TC and not using a cumulus parameterization.
Reef Check Australia (RCA) has collected data on benthic composition and cover at >70 sites along >1000km of Australia's Queensland coast from 2002 to 2015. This paper quantifies the accuracy, ...precision and power of RCA benthic composition data, to guide its application and interpretation. A simulation study established that the inherent accuracy of the Reef Check point sampling protocol is high (<±7% error absolute), in the range of estimates of benthic cover from 1% to 50%. A field study at three reef sites indicated that, despite minor observer- and deployment-related biases, the protocol does reliably document moderate ecological changes in coral communities. The error analyses were then used to guide the interpretation of inter-annual variability and long term trends at three study sites in RCA's major 2002–2015 data series for the Queensland coast.
•Reef Check Australia conducts a major coral reef monitoring program in Queensland.•Inherent accuracy of the monitoring protocol used is high (<±7% error).•Ecologically important changes are detectable because measurement biases are low.
