134 research outputs found
Analytic Gradients for Complete Active Space Pair-Density Functional Theory
Analytic gradient routines are a desirable feature for quantum mechanical
methods, allowing for efficient determination of equilibrium and transition
state structures and several other molecular properties. In this work, we
present analytical gradients for multiconfiguration pair-density functional
theory (MC-PDFT) when used with a state-specific complete active space
self-consistent field reference wave function. Our approach constructs a
Lagrangian that is variational in all wave function parameters. We find that
MC-PDFT locates equilibrium geometries for several small- to medium-sized
organic molecules that are similar to those located by complete active space
second-order perturbation theory but that are obtained with decreased
computational cost
Analytic gradients for state-averaged multiconfiguration pair-density functional theory
Analytic gradients are important for efficient calculations of stationary points on potential energy surfaces, for interpreting spectroscopic observations, and for efficient direct dynamics simulations. For excited electronic states, as are involved in UV–Vis spectroscopy and photochemistry, analytic gradients are readily available and often affordable for calculations using a state-averaged complete active space self-consistent-field (SA-CASSCF) wave function. However, in most cases, a post-SA-CASSCF step is necessary for quantitative accuracy, and such calculations are often too expensive if carried out by perturbation theory or configuration interaction. In this work, we present the analytic gradients for multiconfiguration pair-density functional theory based on SA-CASSCF wave functions, which is a more affordable alternative. A test set of molecules has been studied with this method, and the stationary geometries and energetics are compared to values in the literature as obtained by other methods. Excited-state geometries computed with state-averaged pair-density functional theory have similar accuracy to those from complete active space perturbation theory at the second-order
SN 2013ab : A normal type IIP supernova in NGC 5669
We present densely-sampled ultraviolet/optical photometric and low-resolution
optical spectroscopic observations of the type IIP supernova 2013ab in the
nearby (24 Mpc) galaxy NGC 5669, from 2 to 190d after explosion.
Continuous photometric observations, with the cadence of typically a day to one
week, were acquired with the 1-2m class telescopes in the LCOGT network, ARIES
telescopes in India and various other telescopes around the globe. The light
curve and spectra suggest that the SN is a normal type IIP event with a plateau
duration of days with mid plateau absolute visual magnitude of
-16.7, although with a steeper decline during the plateau (0.92 mag 100 d in band) relative to other archetypal SNe of similar brightness.
The velocity profile of SN 2013ab shows striking resemblance with those of SNe
1999em and 2012aw. Following the Rabinak & Waxman (2011) prescription, the
initial temperature evolution of the SN emission allows us to estimate the
progenitor radius to be 800 R, indicating that the SN
originated from a red supergiant star. The distance to the SN host galaxy is
estimated to be 24.3 Mpc from expanding photosphere method (EPM). From our
observations, we estimate that 0.064 M of Ni was synthesized
in the explosion. General relativistic, radiation hydrodynamical modeling of
the SN infers an explosion energy of erg, a progenitor
mass (at the time of explosion) of M and an initial radius
of R.Comment: 22 pages, 18 figures, 5 tables. Accepted for publication in MNRA
SN~2012cg: Evidence for Interaction Between a Normal Type Ia Supernova and a Non-Degenerate Binary Companion
We report evidence for excess blue light from the Type Ia supernova SN 2012cg
at fifteen and sixteen days before maximum B-band brightness. The emission is
consistent with predictions for the impact of the supernova on a non-degenerate
binary companion. This is the first evidence for emission from a companion to a
SN Ia. Sixteen days before maximum light, the B-V color of SN 2012cg is 0.2 mag
bluer than for other normal SN~Ia. At later times, this supernova has a typical
SN Ia light curve, with extinction-corrected M_B = -19.62 +/- 0.02 mag and
Delta m_{15}(B) = 0.86 +/- 0.02. Our data set is extensive, with photometry in
7 filters from 5 independent sources. Early spectra also show the effects of
blue light, and high-velocity features are observed at early times. Near
maximum, the spectra are normal with a silicon velocity v_{Si} = -10,500$ km
s^{-1}. Comparing the early data with models by Kasen (2010) favors a
main-sequence companion of about 6 solar masses. It is possible that many other
SN Ia have main-sequence companions that have eluded detection because the
emission from the impact is fleeting and faint.Comment: accepted to Ap
Recommended from our members
Early Observations And Analysis Of The Type Ia SN 2014J In M82
We present optical and near infrared (NIR) observations of the nearby Type Ia SN 2014J. Seventeen optical and 23 NIR spectra were obtained from 10 days before (-10d) to 10 days after (+10d) the time of maximum B-band brightness. The relative strengths of absorption features and their patterns of development can be compared at one day intervals throughout most of this period. Carbon is not detected in the optical spectra, but we identify C I lambda 1.0693 in the NIR spectra. Mg II lines with high oscillator strengths have higher initial velocities than other Mg II lines. We show that the velocity differences can be explained by differences in optical depths due to oscillator strengths. The spectra of SN 2014J show that it is a normal SN Ia, but many parameters are near the boundaries between normal and high-velocity subclasses. The velocities for OI, Mg II, Si II, S Ca a, and Fell suggest that SN 2014J has a layered structure with little or no mixing. That result is consistent with the delayed detonation explosion models. We also report photometric observations, obtained from -10d to +29d, in the UBVRIJH and K-s bands. The template fitting package SNooPy is used to interpret the light curves and to derive photometric parameters. Using R-v = 1.46, which is consistent with previous studies, SNooPy finds that A(v) = 1.80 for E(B - V)(host) = 1.23 +/- 0.06 mag. The maximum B-band brightness of -19.19 +/- 0.10 mag was reached on February 1.74 UT +/- 0.13 days and the supernova has a decline parameter, Delta m(15), of 1.12 +/- 0.02 mag.Department of Space, Government of IndiaHungarian OTKA NN-107637NSF AST-1109801, AST-1151462, AST-1211196NSF Astronomy and Astrophysics Postdoctoral Fellowship AST-1302771NASA through a grant from the Space Telescope Science Institute GO-12540NASA NAS5-26555Swedish Research CouncilSwedish National Space BoardDanish Agency for Science and Technology and Innovation realized through a Sapere Aude Level 2 grantAstronom
The Very Young Type Ia Supernova 2013dy: Discovery, and Strong Carbon Absorption in Early-Time Spectra
The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ~ 13.7 Mpc) was
discovered by the Lick Observatory Supernova Search. Combined with a
prediscovery detection by the Italian Supernova Search Project, we are able to
constrain the first-light time of SN 2013dy to be only 0.10 +/- 0.05 d (2.4 +/-
1.2 hr) before the first detection. This makes SN 2013dy the earliest known
detection of an SN Ia. We infer an upper limit on the radius of the progenitor
star of R_0 < 0.25 R_sun, consistent with that of a white dwarf. The light
curve exhibits a broken power law with exponents of 0.88 and then 1.80. A
spectrum taken 1.63 d after first light reveals a C II absorption line
comparable in strength to Si II. This is the strongest C II feature ever
detected in a normal SN Ia, suggesting that the progenitor star had significant
unburned material. The C II line in SN 2013dy weakens rapidly and is undetected
in a spectrum 7 days later, indicating that C II is detectable for only a very
short time in some SNe Ia. SN 2013dy reached a B-band maximum of M_B = -18.72
+/- 0.03 mag ~17.7 d after first light.Comment: Accepted for Publication in ApJ Letter
The EMBRACE web service collection
The EMBRACE (European Model for Bioinformatics Research and Community Education) web service collection is the culmination of a 5-year project that set out to investigate issues involved in developing and deploying web services for use in the life sciences. The project concluded that in order for web services to achieve widespread adoption, standards must be defined for the choice of web service technology, for semantically annotating both service function and the data exchanged, and a mechanism for discovering services must be provided. Building on this, the project developed: EDAM, an ontology for describing life science web services; BioXSD, a schema for exchanging data between services; and a centralized registry (http://www.embraceregistry.net) that collects together around 1000 services developed by the consortium partners. This article presents the current status of the collection and its associated recommendations and standards definition
SN 2022jox: An extraordinarily ordinary Type II SN with Flash Spectroscopy
We present high cadence optical and ultraviolet observations of the Type II
supernova (SN), SN 2022jox which exhibits early spectroscopic high ionization
flash features of \ion{H}{1}, \ion{He}{2}, \ion{C}{4}, and \ion{N}{4} that
disappear within the first few days after explosion. SN 2022jox was discovered
by the Distance Less than 40 Mpc (DLT40) survey 0.75 days after explosion
with followup spectra and UV photometry obtained within minutes of discovery.
The SN reached a peak brightness of M 17.3 mag, and has an
estimated Ni mass of 0.04 M, typical values for normal Type II
SNe. The modeling of the early lightcurve and the strong flash signatures
present in the optical spectra indicate interaction with circumstellar material
(CSM) created from a progenitor with a mass loss rate of . There may also be some indication
of late-time CSM interaction in the form of an emission line blueward of
H seen in spectra around 200 days. The mass-loss rate is much higher
than the values typically associated with quiescent mass loss from red
supergiants, the known progenitors of Type II SNe, but is comparable to
inferred values from similar core collapse SNe with flash features, suggesting
an eruptive event or a superwind in the progenitor in the months or years
before explosion.Comment: Submitted to Ap
Multi-Messenger Astronomy with Extremely Large Telescopes
The field of time-domain astrophysics has entered the era of Multi-messenger
Astronomy (MMA). One key science goal for the next decade (and beyond) will be
to characterize gravitational wave (GW) and neutrino sources using the next
generation of Extremely Large Telescopes (ELTs). These studies will have a
broad impact across astrophysics, informing our knowledge of the production and
enrichment history of the heaviest chemical elements, constrain the dense
matter equation of state, provide independent constraints on cosmology,
increase our understanding of particle acceleration in shocks and jets, and
study the lives of black holes in the universe. Future GW detectors will
greatly improve their sensitivity during the coming decade, as will
near-infrared telescopes capable of independently finding kilonovae from
neutron star mergers. However, the electromagnetic counterparts to
high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus
demand ELT capabilities for characterization. ELTs will be important and
necessary contributors to an advanced and complete multi-messenger network.Comment: White paper submitted to the Astro2020 Decadal Surve
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