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The year of ecology
The keynote speaker comments on the advent of the “Year of Ecology,” with concerns that some of the current environmental rhetoric fails to understand the science behind pest control and the current practices of food production and food processing. In regard to pests, 4tThroughout history man has always made value judgements about other organisms that share our world, and always decides in favor of himself. It is a concern that we will almost certainly lose some of the more useful chemical tools used in pest control, as a result of the emotional concern about pollution, and it is already becoming increasingly difficult to get registration and residue tolerance for new pesticides. All pest control measures are going to continue to be under attack. The solution is to continue to depend up on the scientific method: do basic research, get the facts, and leave emotions out of our decisions, and lastly, speak out
FIRE Spectroscopy of Five Late-type T Dwarfs Discovered with the Wide-field Infrared Survey Explorer
We present the discovery of five late-type T dwarfs identified with the
Wide-field Infrared Survey Explorer (WISE). Low-resolution near-infrared
spectroscopy obtained with the Magellan Folded-port InfraRed Echellette (FIRE)
reveal strong water and methane absorption in all five sources, and spectral
indices and comparison to spectral templates indicate classifications ranging
from T5.5 to T8.5:. The spectrum of the latest-type source, WISE J1812+2721, is
an excellent match to that of the T8.5 companion brown dwarf Wolf 940B.
WISE-based spectrophotometric distance estimates place these T dwarfs at 12-13
pc from the Sun, assuming they are single. Preliminary fits of the spectral
data to the atmosphere models of Saumon & Marley indicate effective
temperatures ranging from 600 K to 930 K, both cloudy and cloud-free
atmospheres, and a broad range of ages and masses. In particular, two sources
show evidence of both low surface gravity and cloudy atmospheres, tentatively
supporting a trend noted in other young brown dwarfs and exoplanets. In
contrast, the high proper motion T dwarf WISE J2018-7423 exhibits a suppressed
K-band peak and blue spectrophotometric J-K colors indicative of an old,
massive brown dwarf; however, it lacks the broadened Y-band peak seen in
metal-poor counterparts. These results illustrate the broad diversity of
low-temperature brown dwarfs that will be uncovered with WISE.Comment: 19 pages, 13 figures; accepted for publication to Ap
Clouds in the Coldest Brown Dwarfs: FIRE Spectroscopy of Ross 458C
Condensate clouds are a salient feature of L dwarf atmospheres, but have been
assumed to play little role in shaping the spectra of the coldest T-type brown
dwarfs. Here we report evidence of condensate opacity in the near-infrared
spectrum of the brown dwarf candidate Ross 458C, obtained with the Folded-Port
Infrared Echellette (FIRE) spectrograph at the Magellan Telescopes. These data
verify the low-temperature nature of this source, indicating a T8 spectral
classification, log Lbol/Lsun = -5.62+/-0.03, Teff = 650+/-25 K, and a mass at
or below the deuterium burning limit. The data also reveal enhanced emission at
K-band associated with youth (low surface gravity) and supersolar metallicity,
reflecting the properties of the Ross 458 system (age = 150-800 Myr, [Fe/H] =
+0.2 to +0.3). We present fits of FIRE data for Ross 458C, the T9 dwarf ULAS
J133553.45+113005.2, and the blue T7.5 dwarf SDSS J141624.08+134826.7B, to
cloudless and cloudy spectral models from Saumon & Marley. For Ross 458C we
confirm a low surface gravity and supersolar metallicity, while the temperature
differs depending on the presence (635 [+25,-35] K) or absence (760 [+70,-45]
K) of cloud extinction. ULAS J1335+1130 and SDSS J1416+1348B have similar
temperatures (595 [+25,-45] K), but distinct surface gravities (log g = 4.0-4.5
cgs versus 5.0-5.5 cgs) and metallicities ([M/H] ~ +0.2 versus -0.2). In all
three cases, cloudy models provide better fits to the spectral data,
significantly so for Ross 458C. These results indicate that clouds are an
important opacity source in the spectra of young cold T dwarfs, and should be
considered when characterizing the spectra of planetary-mass objects in young
clusters and directly-imaged exoplanets. The characteristics of Ross 458C
suggest it could itself be regarded as a planet, albeit one whose cosmogony
does not conform with current planet formation theories.Comment: Accepted for publication to ApJ: 18 pages, 11 figures in emulateapj
forma
The Discovery of Y Dwarfs Using Data from the Wide-field Infrared Survey Explorer (WISE)
We present the discovery of seven ultracool brown dwarfs identified with the
Wide-field Infrared Survey Explorer (WISE). Near-infrared spectroscopy reveals
deep absorption bands of H_2O and CH_4 that indicate all seven of the brown
dwarfs have spectral types later than UGPS J072227.51-054031.2, the latest type
T dwarf currently known. The spectrum of WISEP J182831.08+265037.8 is distinct
in that the heights of the J- and H-band peaks are approximately equal in units
of f_lambda, so we identify it as the archetypal member of the Y spectral
class. The spectra of at least two of the other brown dwarfs exhibit absorption
on the blue wing of the H-band peak that we tentatively ascribe to NH_3. These
spectral morphological changes provide a clear transition between the T dwarfs
and the Y dwarfs. In order to produce a smooth near-infrared spectral sequence
across the T/Y dwarf transition, we have reclassified UGPS J0722-0540 as the T9
spectral standard and tentatively assign WISEP J173835.52+273258.9 as the Y0
spectral standard. In total, six of the seven new brown dwarfs are classified
as Y dwarfs: four are classified as Y0, one is classified as Y0 (pec?), and
WISEP J1828+2650 is classified as >Y0. We have also compared the spectra to the
model atmospheres of Marley and Saumon and infer that the brown dwarfs have
effective temperatures ranging from 300 K to 500 K, making them the coldest
spectroscopically confirmed brown dwarfs known to date.Comment: Submitted June 11 and accepted August 2 for publication in the
Astrophysical Journa
The Science Case for an Extended Spitzer Mission
Although the final observations of the Spitzer Warm Mission are currently
scheduled for March 2019, it can continue operations through the end of the
decade with no loss of photometric precision. As we will show, there is a
strong science case for extending the current Warm Mission to December 2020.
Spitzer has already made major impacts in the fields of exoplanets (including
microlensing events), characterizing near Earth objects, enhancing our
knowledge of nearby stars and brown dwarfs, understanding the properties and
structure of our Milky Way galaxy, and deep wide-field extragalactic surveys to
study galaxy birth and evolution. By extending Spitzer through 2020, it can
continue to make ground-breaking discoveries in those fields, and provide
crucial support to the NASA flagship missions JWST and WFIRST, as well as the
upcoming TESS mission, and it will complement ground-based observations by LSST
and the new large telescopes of the next decade. This scientific program
addresses NASA's Science Mission Directive's objectives in astrophysics, which
include discovering how the universe works, exploring how it began and evolved,
and searching for life on planets around other stars.Comment: 75 pages. See page 3 for Table of Contents and page 4 for Executive
Summar
Virology, Pathology, and Clinical Manifestations of West Nile Virus Disease
Virologic characteristics of WNV likely interact with host factors in the pathogenesis of fever, meningitis, encephalitis, and flaccid paralysis
Voltinism and resilience to climate-induced phenological mismatch
SJT was supported by NERC grant NE/J02080X/
The SPIRITS Sample of Luminous Infrared Transients: Uncovering Hidden Supernovae and Dusty Stellar Outbursts in Nearby Galaxies
We present a systematic study of the most luminous (M IR [Vega magnitudes] brighter than −14) infrared (IR) transients discovered by the SPitzer InfraRed Intensive Transients Survey (SPIRITS) between 2014 and 2018 in nearby galaxies (D 12) show multiple, luminous IR outbursts over several years and have directly detected, massive progenitors in archival imaging. With analyses of extensive, multiwavelength follow-up, we suggest the following possible classifications: five obscured core-collapse supernovae (CCSNe), two erupting massive stars, one luminous red nova, and one intermediate-luminosity red transient. We define a control sample of all optically discovered transients recovered in SPIRITS galaxies and satisfying the same selection criteria. The control sample consists of eight CCSNe and one Type Iax SN. We find that 7 of the 13 CCSNe in the SPIRITS sample have lower bounds on their extinction of 2 < A V < 8. We estimate a nominal fraction of CCSNe in nearby galaxies that are missed by optical surveys as high as (90% confidence). This study suggests that a significant fraction of CCSNe may be heavily obscured by dust and therefore undercounted in the census of nearby CCSNe from optical searches
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