110 research outputs found
On the Progenitor and Supernova of the SN 2002cx-like Supernova 2008ge
We present observations of supernova (SN) 2008ge, which is spectroscopically
similar to the peculiar SN 2002cx, and its pre-explosion site that indicate
that its progenitor was probably a white dwarf. NGC 1527, the host galaxy of SN
2008ge, is an S0 galaxy with no evidence of star formation or massive stars.
Astrometrically matching late-time imaging of SN 2008ge to pre-explosion HST
imaging, we constrain the luminosity of the progenitor star. Since SN 2008ge
has no indication of hydrogen or helium in its spectrum, its progenitor must
have lost its outer layers before exploding, requiring that it be a white
dwarf, a Wolf-Rayet star, or a lower-mass star in a binary system. Observations
of the host galaxy show no signs of individual massive stars, star clusters, or
H II regions at the SN position or anywhere else, making a Wolf-Rayet
progenitor unlikely. Late-time spectroscopy of SN 2008ge show strong [Fe II]
lines with large velocity widths compared to other members of this class at
similar epochs. These previously unseen features indicate that a significant
amount of the SN ejecta is Fe (presumably the result of radioactive decay of
56Ni generated in the SN), further supporting a thermonuclear explosion.
Placing the observations of SN 2008ge in the context of observations of other
objects in the class of SN, we suggest that the progenitor was most likely a
white dwarf.Comment: 9 pages, 6 figures, accepted by A
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized
The Berkeley Sample of Stripped-Envelope Supernovae
We present the complete sample of stripped-envelope supernova (SN) spectra
observed by the Lick Observatory Supernova Search (LOSS) collaboration over the
last three decades: 888 spectra of 302 SNe, 652 published here for the first
time, with 384 spectra (of 92 SNe) having photometrically-determined phases.
After correcting for redshift and Milky Way dust reddening and reevaluating the
spectroscopic classifications for each SN, we construct mean spectra of the
three major spectral subtypes (Types IIb, Ib, and Ic) binned by phase. We
compare measures of line strengths and widths made from this sample to the
results of previous efforts, confirming that O I {\lambda}7774 absorption is
stronger and found at higher velocity in Type Ic SNe than in Types Ib or IIb
SNe in the first 30 days after peak brightness, though the widths of nebular
emission lines are consistent across subtypes. We also highlight newly
available observations for a few rare subpopulations of interest.Comment: 13 pages; 14 figures; 3 tables. Accepted for publication in MNRA
Berkeley Supernova Ia Program I: Observations, Data Reduction, and Spectroscopic Sample of 582 Low-Redshift Type Ia Supernovae
In this first paper in a series we present 1298 low-redshift (z\leq0.2)
optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 through
2008 as part of the Berkeley SN Ia Program (BSNIP). 584 spectra of 199 SNe Ia
have well-calibrated light curves with measured distance moduli, and many of
the spectra have been corrected for host-galaxy contamination. Most of the data
were obtained using the Kast double spectrograph mounted on the Shane 3 m
telescope at Lick Observatory and have a typical wavelength range of
3300-10,400 Ang., roughly twice as wide as spectra from most previously
published datasets. We present our observing and reduction procedures, and we
describe the resulting SN Database (SNDB), which will be an online, public,
searchable database containing all of our fully reduced spectra and companion
photometry. In addition, we discuss our spectral classification scheme (using
the SuperNova IDentification code, SNID; Blondin & Tonry 2007), utilising our
newly constructed set of SNID spectral templates. These templates allow us to
accurately classify our entire dataset, and by doing so we are able to
reclassify a handful of objects as bona fide SNe Ia and a few other objects as
members of some of the peculiar SN Ia subtypes. In fact, our dataset includes
spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present
spectroscopic host-galaxy redshifts of some SNe Ia where these values were
previously unknown. [Abridged]Comment: 34 pages, 11 figures, 11 tables, revised version, re-submitted to
MNRAS. Spectra will be released in January 2013. The SN Database homepage
(http://hercules.berkeley.edu/database/index_public.html) contains the full
tables, plots of all spectra, and our new SNID template
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Transcriptional profiling of long non-coding RNAs and novel transcribed regions across a diverse panel of archived human cancers
Background: Molecular characterization of tumors has been critical for identifying important genes in cancer biology and for improving tumor classification and diagnosis. Long non-coding RNAs, as a new, relatively unstudied class of transcripts, provide a rich opportunity to identify both functional drivers and cancer-type-specific biomarkers. However, despite the potential importance of long non-coding RNAs to the cancer field, no comprehensive survey of long non-coding RNA expression across various cancers has been reported. Results: We performed a sequencing-based transcriptional survey of both known long non-coding RNAs and novel intergenic transcripts across a panel of 64 archival tumor samples comprising 17 diagnostic subtypes of adenocarcinomas, squamous cell carcinomas and sarcomas. We identified hundreds of transcripts from among the known 1,065 long non-coding RNAs surveyed that showed variability in transcript levels between the tumor types and are therefore potential biomarker candidates. We discovered 1,071 novel intergenic transcribed regions and demonstrate that these show similar patterns of variability between tumor types. We found that many of these differentially expressed cancer transcripts are also expressed in normal tissues. One such novel transcript specifically expressed in breast tissue was further evaluated using RNA in situ hybridization on a panel of breast tumors. It was shown to correlate with low tumor grade and estrogen receptor expression, thereby representing a potentially important new breast cancer biomarker. Conclusions: This study provides the first large survey of long non-coding RNA expression within a panel of solid cancers and also identifies a number of novel transcribed regions differentially expressed across distinct cancer types that represent candidate biomarkers for future research
Revealing the progenitor of SN 2021zby through analysis of the shock-cooling light curve
We present early observations and analysis of the double-peaked Type IIb
supernova (SN IIb) 2021zby. captured the prominent early shock cooling
peak of SN 2021zby within the first 10 days after explosion with a
30-minute cadence. We present optical and near-infrared spectral series of SN
2021zby, including three spectra during the shock cooling phase. Using a
multi-band model fit, we find that the inferred properties of its progenitor
are consistent with a red supergiant or yellow supergiant, with an envelope
mass of 0.3-3.0 M and an envelope radius of 50-350. These inferred progenitor properties are similar to those of other
SNe IIb with double-peak feature, such as SNe 1993J, 2011dh, 2016gkg and
2017jgh. This study further validates the importance of the high cadence and
early coverage in resolving the shape of the shock cooling light curve, while
the multi-band observations, especially UV, is also necessary to fully
constrain the progenitor properties.Comment: 12 pages, 5 figures, 2 tables, submitted to ApJ
Berkeley sample of stripped-envelope supernovae
We present the complete sample of stripped-envelope supernova (SN) spectra observed by the Lick Observatory Supernova Search (LOSS) collaboration over the last three decades: 888 spectra of 302 SNe, 652 published here for the first time, with 384 spectra (of 92 SNe) having photometrically determined phases. After correcting for redshift and Milky Way dust reddening and reevaluating the spectroscopic classifications for each SN, we construct mean spectra of the three major spectral subtypes (Types IIb, Ib, and Ic) binned by phase. We compare measures of line strengths and widths made from this sample to the results of previous efforts, confirming that O I λ7774 absorption is stronger and found at higher velocity in Type Ic SNe than in Types Ib or IIb SNe in the first ∼30 days after peak brightness, though the widths of nebular emission lines are consistent across subtypes. We also highlight newly available observations for a few rare subpopulations of interest
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