93 research outputs found
Motor Planning: Insects Do It on the Hop
SummaryPlanning a motor action in advance of its possible execution doesn't require cortical complexity: a recent paper demonstrates that even fruit flies prepare for movement some time before they decide whether or not to take action
Optical Spectra of 73 Stripped-Envelope Core-Collapse Supernovae
We present 645 optical spectra of 73 supernovae (SNe) of Types IIb, Ib, Ic,
and broad-lined Ic. All of these types are attributed to the core collapse of
massive stars, with varying degrees of intact H and He envelopes before
explosion. The SNe in our sample have a mean redshift = 4200 km/s. Most of
these spectra were gathered at the Harvard-Smithsonian Center for Astrophysics
(CfA) between 2004 and 2009. For 53 SNe, these are the first published spectra.
The data coverage range from mere identification (1-3 spectra) for a few SNe to
extensive series of observations (10-30 spectra) that trace the spectral
evolution for others, with an average of 9 spectra per SN. For 44 SNe of the 73
SNe presented here, we have well-determined dates of maximum light to determine
the phase of each spectrum. Our sample constitutes the most extensive spectral
library of stripped-envelope SNe to date. We provide very early coverage (as
early as 30 days before V-band max) for photospheric spectra, as well as
late-time nebular coverage when the innermost regions of the SNe are visible
(as late as 2 years after explosion, while for SN1993J, we have data as late as
11.6 years). This data set has homogeneous observations and reductions that
allow us to study the spectroscopic diversity of these classes of stripped SNe
and to compare these to SNe associated with gamma-ray bursts. We undertake
these matters in follow-up papers.Comment: Published by the Astronomical Journal in May 2015. All spectra are
publicly available at the CfA SN archive:
http://www.cfa.harvard.edu/supernova/SNarchive.html . A companion paper on
constructing SNID templates based on these spectra is by Liu & Modjaz (2014)
and the resulting SNID templates are available from the NYU website:
http://cosmo.nyu.edu/SNYU/spectra
SN 1994W: An Interacting Supernova or Two Interacting Shells?
We present a multi-epoch quantitative spectroscopic analysis of the Type IIn
SN 1994W, an event interpreted by Chugai et al. as stemming from the
interaction between the ejecta of a SN and a 0.4Msun circumstellar shell
ejected 1.5yr before core collapse. During the brightening phase, our models
suggest that the source of optical radiation is not unique, perhaps associated
with an inner optically-thick Cold Dense Shell (CDS) and outer optically-thin
shocked material. During the fading phase, our models support a single source
of radiation, an hydrogen-rich optically-thick layer with a near-constant
temperature of ~7000K that recedes from a radius of 4.3x10^15 at peak to
2.3x10^15cm 40 days later. We reproduce the hybrid narrow-core broad-wing line
profile shapes of SN 1994W at all times, invoking an optically-thick
photosphere exclusively (i.e., without any external optically-thick shell). In
SN 1994W, slow expansion makes scattering with thermal electrons a key escape
mechanism for photons trapped in optically-thick line cores, and allows the
resulting broad incoherent electron-scattering wings to be seen around narrow
line cores. In SNe with larger expansion velocities, the thermal broadening due
to incoherent scattering is masked by the broad profile and the dominant
frequency redshift occasioned by bulk motions. Given the absence of broad lines
at all times and the very low 56Ni yields, we speculate whether SN 1994W could
have resulted from an interaction between two ejected shells without core
collapse. The high conversion efficiency of kinetic to thermal energy may not
require a SN-like energy budget for SN1994W.Comment: 36 pages (includes online tables), 16 figures, paper accepted to
MNRAS, discussion section expanded, title re-worde
First draft genome assembly of the desert locust, Schistocerca gregaria
Background: At the time of publication, the most devastating desert locust crisis in decades is affecting East Africa, the Arabian Peninsula and South-West Asia. The situation is extremely alarming in East Africa, where Kenya, Ethiopia and Somalia face an unprecedented threat to food security and livelihoods. Most of the time, however, locusts do not occur in swarms, but live as relatively harmless solitary insects. The phenotypically distinct solitarious and gregarious locust phases differ markedly in many aspects of behaviour, physiology and morphology, making them an excellent model to study how environmental factors shape behaviour and development. A better understanding of the extreme phenotypic plasticity in desert locusts will offer new, more environmentally sustainable ways of fighting devastating swarms.
Methods: High molecular weight DNA derived from two adult males was used for Mate Pair and Paired End Illumina sequencing and PacBio sequencing. A reliable reference genome of Schistocerca gregaria was assembled using the ABySS pipeline, scaffolding was improved using LINKS.
Results: In total, 1,316 Gb Illumina reads and 112 Gb PacBio reads were produced and assembled. The resulting draft genome consists of 8,817,834,205 bp organised in 955,015 scaffolds with an N50 of 157,705 bp, making the desert locust genome the largest insect genome sequenced and assembled to date. In total, 18,815 protein-encoding genes are predicted in the desert locust genome, of which 13,646 (72.53%) obtained at least one functional assignment based on similarity to known proteins.
Conclusions: The desert locust genome data will contribute greatly to studies of phenotypic plasticity, physiology, neurobiology, molecular ecology, evolutionary genetics and comparative genomics, and will promote the desert locust’s use as a model system. The data will also facilitate the development of novel, more sustainable strategies for preventing or combating swarms of these infamous insects
Three Gravitationally Lensed Supernovae Behind CLASH Galaxy Clusters
We report observations of three gravitationally lensed supernovae (SNe) in
the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle
Treasury program. These objects, SN CLO12Car (z = 1.28), SN CLN12Did (z =
0.85), and SN CLA11Tib (z = 1.14), are located behind three different clusters,
MACSJ1720.2+3536 (z = 0.391), RXJ1532.9+3021 (z = 0.345), and Abell 383 (z =
0.187), respectively. Each SN was detected in Hubble Space Telescope (HST)
optical and infrared images. Based on photometric classification, we find that
SNe CLO12Car and CLN12Did are likely to be Type Ia supernovae (SNe Ia), while
the classification of SN CLA11Tib is inconclusive. Using multi-color
light-curve fits to determine a standardized SN Ia luminosity distance, we
infer that SN CLO12Car was approximately 1.0 +/- 0.2 mag brighter than field
SNe Ia at a similar redshift and ascribe this to gravitational lens
magnification. Similarly, SN CLN12Did is approximately 0.2 +/- 0.2 mag brighter
than field SNe Ia. We derive independent estimates of the predicted
magnification from CLASH strong+weak lensing maps of the clusters: 0.83 +/-
0.16 mag for SN CLO12Car, 0.28 +/- 0.08 mag for SN CLN12Did, and 0.43 +/- 0.11
mag for SN CLA11Tib. The two SNe Ia provide a new test of the cluster lens
model predictions: we find that the magnifications based on the SN Ia
brightness and those predicted by the lens maps are consistent. Our results
herald the promise of future observations of samples of cluster-lensed SNe Ia
(from the ground or space) to help illuminate the dark-matter distribution in
clusters of galaxies, through the direct determination of absolute
magnifications.Comment: ApJ in pres
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