340 research outputs found
Alien Registration- Cowperthwaite, Georgia M. (Monticello, Aroostook County)
https://digitalmaine.com/alien_docs/33941/thumbnail.jp
Thermodynamics of the Adiabatic Expansion of a Mixture of Two Phases
The thermodynamics of the adiabatic expansion of a mixture of two phases capable of interchanging heat and matter across the phase boundary is presented. The law of conservation of energy is applied to each phase considered as an open system and to the mixture of phases considered as a closed system. Expressions for the entropy production resulting from internal irreversible processes demonstrate the difference between adiabatic and isentropic changes and specify conditions under which the expansion of a closed two-phase system is isentropic. Three such possible isentropic processes are defined, and expressions are derived for the temperature-pressure-volume states achieved in them. The thermodynamic treatment is useful in studies of the adiabatic release of a shock-induced mixture of phases
Simulation of the dynamics of vibrationally mediated photodissociation for deuterated pyrrole
The dynamics of photodissociation for vibrationally pre-excited deuterated pyrrole molecules is simulated using ab initio multiple cloning (AIMC) approach. Total kinetic energy release (TKER) spectra and dissociation times are calculated. The results for pyrrole and deuterated pyrrole molecules with and without vibrational pre-excitation are compared. Calculations show that, as expected, the kinetic energy of additional dissociation fragments is lower in deuterated pyrrole and mostly located in the upper-middle part of the TKER spectrum. However, despite lower energy of dissociative bond vibrations, pre-excitation of deuterated pyrrole leads to higher dissociation yield increase than in pyrrole and significantly shortens dissociation time
Spitzer Space Telescope Infrared Observations of the Binary Neutron Star Merger GW170817
We present Spitzer Space Telescope 3.6 and 4.5 micron observations of the
binary neutron star merger GW170817 at 43, 74, and 264 days post-merger. Using
the final observation as a template, we uncover a source at the position of
GW170817 at 4.5 micron with a brightness of 22.9+/-0.3 AB mag at 43 days and
23.8+/-0.3 AB mag at 74 days (the uncertainty is dominated by systematics from
the image subtraction); no obvious source is detected at 3.6 micron to a
3-sigma limit of >23.3 AB mag in both epochs. The measured brightness is dimmer
by a factor of about 2-3 times compared to our previously published kilonova
model, which is based on UV, optical, and near-IR data at <30 days. However,
the observed fading rate and color (m_{3.6}-m_{4.5}> 0 AB mag) are consistent
with our model. We suggest that the discrepancy is likely due to a transition
to the nebular phase, or a reduced thermalization efficiency at such late time.
Using the Spitzer data as a guide, we briefly discuss the prospects of
observing future binary neutron star mergers with Spitzer (in LIGO/Virgo
Observing Run 3) and the James Webb Space Telescope (in LIGO/Virgo Observing
Run 4 and beyond).Comment: 6 pages, 2 figures, submitted to ApJ
The low-frequency radio catalog of flat spectrum sources
A well known property of the gamma-ray sources detected by COS-B in the
1970s, by the Compton Gamma-ray Observatory in the 1990s and recently by the
Fermi observations is the presence of radio counterparts, in particular for
those associated to extragalactic objects. This observational evidence is the
basis of the radio-gamma-ray connection established for the class of active
galactic nuclei known as blazars. In particular, the main spectral property of
the radio counterparts associated with gamma-ray blazars is that they show a
flat spectrum in the GHz frequency range. Our recent analysis dedicated to
search blazar-like candidates as potential counterparts for the unidentified
gamma-ray sources (UGSs) allowed us to extend the radio-gamma-ray connection in
the MHz regime. We also showed that below 1 GHz blazars maintain flat radio
spectra. Thus on the basis of these new results, we assembled a low-frequency
radio catalog of flat spectrum sources built by combining the radio
observations of the Westerbork Northern Sky Survey (WENSS) and of the
Westerbork in the southern hemisphere (WISH) catalog with those of the NRAO
Very Large Array Sky survey (NVSS). This could be used in the future to search
for new, unknown blazar-like counterparts of the gamma-ray sources. First we
found NVSS counterparts of WSRT radio sources and then we selected flat
spectrum radio sources according to a new spectral criterion specifically
defined for radio observations performed below 1 GHz. We also described the
main properties of the catalog listing 28358 radio sources and their logN-logS
distributions. Finally a comparison with with the Green Bank 6-cm radio source
catalog has been performed to investigate the spectral shape of the
low-frequency flat spectrum radio sources at higher frequencies.Comment: 10 pages, 10 figures, 1 table, ApJS published in 2014 (pre-proof
version uploaded
Improved constraints on H0 from a combined analysis of gravitational-wave and electromagnetic emission from GW170817
The luminosity distance measurement of GW170817 derived from GW analysis in
Abbott et al. 2017 (here, A17:H0) is highly correlated with the measured
inclination of the NS-NS system. To improve the precision of the distance
measurement, we attempt to constrain the inclination by modeling the broad-band
X-ray-to-radio emission from GW170817, which is dominated by the interaction of
the jet with the environment. We update our previous analysis and we consider
the radio and X-ray data obtained at days since merger. We find that the
afterglow emission from GW170817 is consistent with an off-axis relativistic
jet with energy
propagating into an environment with density , with preference for wider jets (opening angle
deg). For these jets, our modeling indicates an off-axis angle deg. We combine our constraints on with the
joint distance-inclination constraint from LIGO. Using the same
km/sec peculiar velocity uncertainty assumed in A17:H0 but with an inclination
constraint from the afterglow data, we get a value of \mbox{km/s/Mpc}, which is higher than the value of
\mbox{km/s/Mpc} found in A17:H0. Further,
using a more realistic peculiar velocity uncertainty of 250 km/sec derived from
previous work, we find km/s/Mpc for H0 from
this system. We note that this is in modestly better agreement with the local
distance ladder than the Planck CMB, though a significant such discrimination
will require such events. Future measurements at days of the
X-ray and radio emission will lead to tighter constraints.Comment: Submitted to ApJL. Comments Welcome. Revised uncertainties in v
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