707 research outputs found
Intact Leaves Exhibit a Climacteric-Like Rise in Ethylene Production before Abscission
Metabolism of 1-Aminocyclopropane-1-Carboxylic Acid in Etiolated Maize Seedlings Grown under Mechanical Impedance
Detection of Endogenous Gibberellins and Their Relationship to Hypocotyl Elongation in Soybean Seedlings
Swift-UVOT detection of GRB 050318
We present observations of GRB 050318 by the Ultra-Violet and Optical
Telescope (UVOT) on-board the Swift observatory. The data are the first
detections of a Gamma Ray Burst (GRB) afterglow decay by the UVOT instrument,
launched specifically to open a new window on these transient sources. We
showcase UVOTs ability to provide multi-color photometry and the advantages of
combining UVOT data with simultaneous and contemporaneous observations from the
high-energy detectors on the Swift spacecraft. Multiple filters covering
1,800-6,000 Angstroms reveal a red source with spectral slope steeper than the
simultaneous X-ray continuum. Spectral fits indicate that the UVOT colors are
consistent with dust extinction by systems at z = 1.2037 and z = 1.4436,
redshifts where absorption systems have been pre-identified. However, the data
can be most-easily reproduced with models containing a foreground system of
neutral gas redshifted by z = 2.8 +/- 0.3. For both of the above scenarios,
spectral and decay slopes are, for the most part, consistent with fireball
expansion into a uniform medium, provided a cooling break occurs between the
energy ranges of the UVOT and Swifts X-ray instrumentation.Comment: 15 pages, 4 figures, ApJ Letters, in pres
Ultraviolet, Optical, and X-Ray Observations of the Type Ia Supernova 2005am with Swift
We present ultraviolet and optical light curves in six broadband filters and
grism spectra obtained by Swift's Ultraviolet/Optical Telescope for the Type Ia
supernova SN2005am. The data were collected beginning about four days before
the B-band maximum, with excellent coverage of the rapid decline phase and
later observations extending out to 69 days after the peak. The optical and
near UV light curve match well those of SN1992A. The other UV observations
constitute the first set of light curves shorter than 2500 Angstroms and allow
us to compare the light curve evolution in three UV bands. The UV behavior of
this and other low redshift supernovae can be used to constrain theories of
progenitor evolution or to interpret optical light curves of high redshift
supernovae. Using Swift's X-Ray Telescope, we also report the upper limit to
SN2005am's X-ray luminosity to be 1.77 x 10^40 erg s^-1 in the 0.3--10 keV
range from 58,117 s of exposure time.Comment: 15 pages, including 3 figures and 2 tables, submitted to
Astrophysical Journa
Black Holes and Massive Remnants
This paper revisits the conundrum faced when one attempts to understand the
dynamics of black hole formation and evaporation without abandoning unitary
evolution. Previous efforts to resolve this puzzle assume that information
escapes in corrections to the Hawking process, that an arbitrarily large amount
of information is transmitted by a planckian energy or contained in a
Planck-sized remnant, or that the information is lost to another universe. Each
of these possibilities has serious difficulties. This paper considers another
alternative: remnants that carry large amounts of information and whose size
and mass depend on their information content. The existence of such objects is
suggested by attempts to incorporate a Planck scale cutoff into physics. They
would greatly alter the late stages of the evaporation process. The main
drawback of this scenario is apparent acausal behavior behind the horizon.Comment: 16 pages + 3 Fig
Qweak: A Precision Measurement of the Proton's Weak Charge
The Qweak experiment at Jefferson Lab aims to make a 4% measurement of the
parity-violating asymmetry in elastic scattering at very low of a
longitudinally polarized electron beam on a proton target. The experiment will
measure the weak charge of the proton, and thus the weak mixing angle at low
energy scale, providing a precision test of the Standard Model. Since the value
of the weak mixing angle is approximately 1/4, the weak charge of the proton
is suppressed in the Standard Model, making it
especially sensitive to the value of the mixing angle and also to possible new
physics. The experiment is approved to run at JLab, and the construction plan
calls for the hardware to be ready to install in Hall C in 2007. The
theoretical context of the experiment and the status of its design are
discussed.Comment: 5 pages, 2 figures, LaTeX2e, to be published in CIPANP 2003
proceeding
Paper II: Calibration of the Swift ultraviolet/optical telescope
The Ultraviolet/Optical Telescope (UVOT) is one of three instruments onboard
the Swift observatory. The photometric calibration has been published, and this
paper follows up with details on other aspects of the calibration including a
measurement of the point spread function with an assessment of the orbital
variation and the effect on photometry. A correction for large scale variations
in sensitivity over the field of view is described, as well as a model of the
coincidence loss which is used to assess the coincidence correction in extended
regions. We have provided a correction for the detector distortion and measured
the resulting internal astrometric accuracy of the UVOT, also giving the
absolute accuracy with respect to the International Celestial Reference System.
We have compiled statistics on the background count rates, and discuss the
sources of the background, including instrumental scattered light. In each case
we describe any impact on UVOT measurements, whether any correction is applied
in the standard pipeline data processing or whether further steps are
recommended.Comment: Accepted for publication in MNRAS. 15 pages, 21 figures, 4 table
- …