35,716 research outputs found
Spectral reflectivity of solid surfaces at low temperatures
Spectral reflectivity of solid surfaces at low temperature
SGR 1806-20 Is a Set of Independent Relaxation Systems
The Soft Gamma Repeater 1806-20 produced patterns of bursts during its 1983
outburst that indicate multiple independent energy accumulation sites, each
driven by a continuous power source, with sudden, incomplete releases of the
accumulated energy. The strengths of the power sources and their durations of
activity vary over several orders of magnitude.Comment: Accepted ApJLett, 15 pages, 3 figure
A General Expression for Symmetry Factors of Feynman Diagrams
The calculation of the symmetry factor corresponding to a given Feynman
diagram is well known to be a tedious problem. We have derived a simple formula
for these symmetry factors. Our formula works for any diagram in scalar theory
( and interactions), spinor QED, scalar QED, or QCD.Comment: RevTex 11 pages with 10 figure
Algae of Steuben County, Indiana
No published record has yet been made, apparently, of the algal flora of Steuben county, Indiana. The many lakes and bogs, together with several streams which are in the county, make the area an excellent one for collecting algae. The writer visited the county in May, 1929, July and September, 1933, and obtained specimens particularly from the following lakes: Bass, Crooked, Failing, Fox, Hogback, James, Nevada Mills and Snow. Approximately fifty algae have so far been identified from the collections. Those that have not previously been reported for Indiana are printed in boldface type. It is hoped that additional lists of the algae of Steuben county may be published from time to time. No desmids or diatoms are included in this first paper
Algae of Marion County, Indiana
Reverend George L. Curtiss, in 1882, published in the Twelfth Report of the State Geologist (Indiana) an article entitled, Diatoms of the Waters of Indiana. It includes, from Marion county, a list and illustrations of seventy-eight forms. One of these, Staurastrum asperum, is considered now as a desmid rather than a diatom. This paper by Curtiss is, apparently, the only one which has been published on the algae of Marion county in which genera or species are given
Strong spectral evolution during the prompt emission of GRB 070616
Swift has revealed features in GRB early light curves, such as steep decays
and X-ray flares, whose properties are consistent with an internal origin
though they are far from understood. The steep X-ray decay is often explained
using the curvature effect; however a significant number of GRBs display strong
spectral evolution during this phase, and a new mechanism must be invoked to
explain this. Of particular interest are the longest duration GRBs in which the
early emission can be studied in most detail. Here we present data for GRB
070616, in which the prompt emission shows a complex multipeaked structure,
leading to one of the longest prompt emission durations ever recorded. We take
advantage of extensive coverage of such a long burst by all Swift instruments.
Combining data from Swift and Suzaku we study the evolution of the prompt
emission spectrum, following the temporal variability of the peak energy and
spectral slope.Comment: 4 pages, 2 figures (Fig 1 in colour), contributed talk, submitted to
the proceedings of Gamma Ray Bursts 2007, Santa Fe, New Mexico, November 5-9
200
A Burst and Simultaneous Short-Term Pulsed Flux Enhancement from the Magnetar Candidate 1E 1048.1-5937
We report on the 2004 June 29 burst detected from the direction of the
Anomalous X-ray Pulsar (AXP) 1E 1048.1-5937 using the Rossi X-ray Timing
Explorer (RXTE). We find a simultaneous increase of ~3.5 times the quiescent
value in the 2-10 keV pulsed flux of 1E 1048.1-5937 during the tail of the
burst which identifies the AXP as the burst's origin. The burst was overall
very similar to the two others reported from the direction of this source in
2001. The unambiguous identification of 1E 1048.1-5937 as the burster here
confirms it was the origin of the 2001 bursts as well. The epoch of the burst
peak was very close to the arrival time of 1E 1048.1-5937's pulse peak. The
burst exhibited significant spectral evolution with the trend going from hard
to soft. During the 11 days following the burst, the AXP was observed further
with RXTE, XMM-Newton and Chandra. Pre- and post-burst observations revealed no
change in the total flux or spectrum of the quiescent emission. Comparing all
three bursts detected thus far from this source we find that this event was the
most fluent (>3.3x10^-8 erg/cm^2 in the 2-20 keV band), had the highest peak
flux (59+/-9x10^-10 erg/s/cm^2 in the 2-20 keV band), and the longest duration
(>699 s). The long duration of the burst differentiates it from Soft Gamma
Repeater (SGR) bursts which have typical durations of ~0.1 s. Bursts that occur
preferentially at pulse maximum, have fast-rises and long X-tails containing
the majority of the total burst energy have been seen uniquely from AXPs. The
marked differences between AXP and SGRs bursts may provide new clues to help
understand the physical differences between these objects.Comment: 24 pages, 4 figures, submitted to the Astrophysical Journa
Plankton Algae of White River in Marion County and Morgan County, Indiana
During a period of thirteen months in 1930 and 1931, the algae from 176 samples of White river water were identified
- …