Supernovae are thought to arise from two different physical processes. The cores of massive, short-lived stars undergo gravitational core collapse and typically eject a few solar masses during their ...explosion. These are thought to appear as type Ib/c and type II supernovae, and are associated with young stellar populations. In contrast, the thermonuclear detonation of a carbon-oxygen white dwarf, whose mass approaches the Chandrasekhar limit, is thought to produce type Ia supernovae. Such supernovae are observed in both young and old stellar environments. Here we report a faint type Ib supernova, SN 2005E, in the halo of the nearby isolated galaxy, NGC 1032. The ‘old’ environment near the supernova location, and the very low derived ejected mass (∼0.3 solar masses), argue strongly against a core-collapse origin. Spectroscopic observations and analysis reveal high ejecta velocities, dominated by helium-burning products, probably excluding this as a subluminous or a regular type Ia supernova. We conclude that it arises from a low-mass, old progenitor, likely to have been a helium-accreting white dwarf in a binary. The ejecta contain more calcium than observed in other types of supernovae and probably large amounts of radioactive 44Ti.
We present radio, optical/NIR, and X-ray observations of the afterglow of the short-duration Swift and Konus-Wind GRB 130603B, and uncover a break in the radio and optical bands at approximately 0.5 ...day after the burst, best explained as a jet break with an inferred jet opening angle of approximately 4degrees-8degrees. GRB 130603B is only the third short GRB with a radio afterglow detection to date, and represents the first time that a jet break has been evident in the radio band. We model the temporal evolution of the spectral energy distribution to determine the burst explosion properties and find an isotropic-equivalent kinetic energy of approximately (0.6-1.7)x 10 super(51) erg and a circumburst density of approximately 5 x 10 super(-3)-30cm super(-3). From the inferred opening angle of GRB 130603B, we calculate beaming-corrected energies of E sub( gamma ) approximately (0.5-2) x 10 super(49) erg and E sub(K) approximately (0.1-1.6) x 10 super(49) erg. Along with previous measurements and lower limits we find a median opening angle of approximately 10degrees. Using the all-sky observed rate of 10 Gpc super(-3) yr super(-1), this implies a true short GRB rate of approximately 20 yr super(-1) within 200 Mpc, the Advanced LIGO/VIRGO sensitivity range for neutron star binary mergers. Finally, we uncover evidence for significant excess emission in the X-ray afterglow of GRB 130603B at > ~ 1 day and conclude that the additional energy component could be due to fail-back accretion or spin-down energy from a magnetar formed following the merger.
Abstract
We present panchromatic observations and modeling of calcium-strong supernovae (SNe) 2021gno in the star-forming host-galaxy NGC 4165 and 2021inl in the outskirts of elliptical galaxy NGC ...4923, both monitored through the Young Supernova Experiment transient survey. The light curves of both, SNe show two peaks, the former peak being derived from shock cooling emission (SCE) and/or shock interaction with circumstellar material (CSM). The primary peak in SN 2021gno is coincident with luminous, rapidly decaying X-ray emission (
L
x
= 5 × 10
41
erg s
−1
) detected by Swift-XRT at
δ
t
= 1 day after explosion, this observation being the second-ever detection of X-rays from a calcium-strong transient. We interpret the X-ray emission in the context of shock interaction with CSM that extends to
r
< 3 × 10
14
cm. Based on X-ray modeling, we calculate a CSM mass
M
CSM
= (0.3−1.6) × 10
−3
M
⊙
and density
n
= (1−4) × 10
10
cm
−3
. Radio nondetections indicate a low-density environment at larger radii (
r
> 10
16
cm) and mass-loss rate of
M
̇
<
10
−
4
M
⊙
yr
−1
. SCE modeling of both primary light-curve peaks indicates an extended-progenitor envelope mass
M
e
= 0.02−0.05
M
⊙
and radius
R
e
= 30−230
R
⊙
. The explosion properties suggest progenitor systems containing either a low-mass massive star or a white dwarf (WD), the former being unlikely given the lack of local star formation. Furthermore, the environments of both SNe are consistent with low-mass hybrid He/C/O WD + C/O WD mergers.
Abstract We present photometric and spectroscopic data for SN 2022joj, a nearby peculiar Type Ia supernova (SN Ia) with a fast decline rate (Δ m 15,B = 1.4 mag). SN 2022joj shows exceedingly red ...colors, with a value of approximately B − V ≈ 1.1 mag during its initial stages, beginning from 11 days before maximum brightness. As it evolves, the flux shifts toward the blue end of the spectrum, approaching B − V ≈ 0 mag around maximum light. Furthermore, at maximum light and beyond, the photometry is consistent with that of typical SNe Ia. This unusual behavior extends to its spectral characteristics, which initially displayed a red spectrum and later evolved to exhibit greater consistency with typical SNe Ia. Spectroscopically, we find strong agreement between SN 2022joj and double detonation models with white dwarf masses of around 1 M ⊙ and a thin He shell between 0.01 and 0.05 M ⊙ . Moreover, the early red colors are explained by line-blanketing absorption from iron peak elements created by the double detonation scenario in similar mass ranges. The nebular spectra in SN 2022joj deviate from expectations for double detonation, as we observe strong Fe iii emission instead of Ca ii lines as anticipated, though this is not as robust a prediction as early red colors and spectra. The fact that as He shells get thinner these SNe start to look more like normal SNe Ia raises the possibility that this is the triggering mechanism for the majority of SNe Ia, though evidence would be missed if the SNe are not observed early enough.
We present the results of a search for rapidly evolving transients in the Dark Energy Survey Supernova Programme. These events are characterized by fast light-curve evolution (rise to peak in ≲10 d ...and exponential decline in ≲30 d after peak). We discovered 72 events, including 37 transients with a spectroscopic redshift from host galaxy spectral features. The 37 events increase the total number of rapid optical transients by more than a factor of two. They are found at a wide range of redshifts (0.05 < z < 1.56) and peak brightnesses (-15.75 > Mg > -22.25). The multiband photometry is well fit by a blackbody up to few weeks after peak. The events appear to be hot (T ≈ 10 000–30 000 K) and large (R ≈ 1014 - 2 × 1015 cm) at peak, and generally expand and cool in time, though some events show evidence for a receding photosphere with roughly constant temperature. Spectra taken around peak are dominated by a blue featureless continuum consistent with hot, optically thick ejecta. We compare our events with a previously suggested physical scenario involving shock breakout in an optically thick wind surrounding a core-collapse supernova, we conclude that current models for such a scenario might need an additional power source to describe the exponential decline. We find that these transients tend to favour star-forming host galaxies, which could be consistent with a core-collapse origin. However, more detailed modelling of the light curves is necessary to determine their physical origin.
MSTO1
encodes a cytosolic mitochondrial fusion protein, misato homolog 1 or MSTO1. While the full genotype–phenotype spectrum remains to be explored, pathogenic variants in
MSTO1
have recently been ...reported in a small number of patients presenting with a phenotype of cerebellar ataxia, congenital muscle involvement with histologic findings ranging from myopathic to dystrophic and pigmentary retinopathy. The proposed underlying pathogenic mechanism of
MSTO1
-related disease is suggestive of impaired mitochondrial fusion secondary to a loss of function of MSTO1. Disorders of mitochondrial fusion and fission have been shown to also lead to mitochondrial DNA (mtDNA) depletion, linking them to the mtDNA depletion syndromes, a clinically and genetically diverse class of mitochondrial diseases characterized by a reduction of cellular mtDNA content. However, the consequences of pathogenic variants in
MSTO1
on mtDNA maintenance remain poorly understood. We present extensive phenotypic and genetic data from 12 independent families, including 15 new patients harbouring a broad array of bi-allelic
MSTO1
pathogenic variants, and we provide functional characterization from seven
MSTO1
-related disease patient fibroblasts. Bi-allelic loss-of-function variants in
MSTO1
manifest clinically with a remarkably consistent phenotype of childhood-onset muscular dystrophy, corticospinal tract dysfunction and early-onset non-progressive cerebellar atrophy. MSTO1 protein was not detectable in the cultured fibroblasts of all seven patients evaluated, suggesting that pathogenic variants result in a loss of protein expression and/or affect protein stability. Consistent with impaired mitochondrial fusion, mitochondrial networks in fibroblasts were found to be fragmented. Furthermore, all fibroblasts were found to have depletion of mtDNA ranging from 30 to 70% along with alterations to mtDNA nucleoids. Our data corroborate the role of MSTO1 as a mitochondrial fusion protein and highlight a previously unrecognized link to mtDNA regulation. As impaired mitochondrial fusion is a recognized cause of mtDNA depletion syndromes, this novel link to mtDNA depletion in patient fibroblasts suggests that MSTO1-deficiency should also be considered a mtDNA depletion syndrome. Thus, we provide mechanistic insight into the disease pathogenesis associated with
MSTO1
mutations and further define the clinical spectrum and the natural history of
MSTO1
-related disease.
Genetic factors, externalizing personality traits such as impulsivity, and brain processing of salient stimuli all can affect individual risk for alcoholism. One of very few confirmed genetic ...association findings differentiating alcoholics from non-alcoholics is with variants in the inhibitory γ-amino butyric acid α2 receptor subunit (GABRA2) gene. Here we report the association of two of these GABRA2 variants with measures of alcohol symptoms, impulsivity and with insula cortex activation during anticipation of reward or loss using functional magnetic resonance imaging (fMRI). In a sample of 173 families (449 subjects), 129 of whom had at least one member diagnosed with alcohol dependence or abuse, carriers for the G allele in two single-nucleotide polymorphisms (SNPs) and haplotypes were more likely to have alcohol dependence symptoms (rs279858, P=0.01; rs279826, P=0.05; haplotype, P=0.02) and higher NEO Personality Inventory-Revised (NEO-PI-R) Impulsiveness scores (rs279858, P=0.016; rs279826, P=0.012; haplotype, P=0.032) with a stronger effect in women (rs279858, P=0.011; rs279826, P=0.002; haplotype, P=0.006), all P-values are corrected for family history and age. A subset of offspring from these families (n=44, 20 females), genotyped for GABRA2, participated in an fMRI study using a monetary incentive delay task. Increased insula activation during reward (r(2)=0.4; P=0.026) and loss (r(2)=0.38; P=0.039) anticipation was correlated with NEO-PI-R Impulsiveness and further associated with the GG genotype for both SNPs (P's<0.04). Our results suggest that GABRA2 genetic variation is associated with Impulsiveness through variation of insula activity responses, here evidenced during anticipatory responses.
We present an analysis of the luminosity distances of Type Ia Supernovae (SNe) from the Sloan Digital Sky Survey-II (SDSS-II) SN Survey in conjunction with other intermediate-redshift (z < 0.4) ...cosmological measurements including redshift-space distortions from the Two-Degree Field Galaxy Redshift Survey (2dFGRS), the integrated Sachs–Wolfe (ISW) effect seen by the SDSS and the latest baryon acoustic oscillation (BAO) distance scale from both the SDSS and 2dFGRS. We have analysed the SDSS-II SN data alone using a variety of ‘model-independent’ methods and find evidence for an accelerating Universe at a >97 per cent level from this single data set. We find good agreement between the SN and BAO distance measurements, both consistent with a Λ-dominated cold dark matter cosmology, as demonstrated through an analysis of the distance duality relationship between the luminosity (dL) and angular diameter (dA) distance measures. We then use these data to estimate w within this restricted redshift range (z < 0.4). Our most stringent result comes from the combination of all our intermediate-redshift data (SDSS-II SNe, BAO, ISW and redshift-space distortions), giving w=−0.81+0.16−0.18 (stat) ± 0.15 (sys) and ΩM= 0.22+0.09−0.08 assuming a flat universe. This value of w and associated errors only change slightly if curvature is allowed to vary, consistent with constraints from the cosmic microwave background. We also consider more limited combinations of the geometrical (SN, BAO) and dynamical (ISW, redshift-space distortions) probes.
Abstract
We present results for the first three years of OzDES, a six year programme to obtain redshifts for objects in the Dark Energy Survey (DES) supernova fields using the 2dF fibre positioner ...and AAOmega spectrograph on the Anglo-Australian Telescope. OzDES is a multi-object spectroscopic survey targeting multiple types of targets at multiple epochs over a multiyear baseline and is one of the first multi-object spectroscopic surveys to dynamically include transients into the target list soon after their discovery. At the end of three years, OzDES has spectroscopically confirmed almost 100 supernovae, and has measured redshifts for 17 000 objects, including the redshifts of 2566 supernova hosts. We examine how our ability to measure redshifts for targets of various types depends on signal-to-noise ratio (S/N), magnitude and exposure time, finding that our redshift success rate increases significantly at a S/N of 2–3 per 1-Å bin. We also find that the change in S/N with exposure time closely matches the Poisson limit for stacked exposures as long as 10 h. We use these results to predict the redshift yield of the full OzDES survey, as well as the potential yields of future surveys on other facilities such as (i.e. the 4-m Multi-Object Spectroscopic Telescope, the Subaru Prime Focus Spectrograph and the Maunakea Spectroscopic Explorer). This work marks the first OzDES data release, comprising 14 693 redshifts. OzDES is on target to obtain over 30 000 redshifts over the 6-yr duration of the survey, including a yield of approximately 5700 supernova host-galaxy redshifts.
Objective
Mutations in TPM3, encoding Tpm3.12, cause a clinically and histopathologically diverse group of myopathies characterized by muscle weakness. We report two patients with novel de novo ...Tpm3.12 single glutamic acid deletions at positions ΔE218 and ΔE224, resulting in a significant hypercontractile phenotype with congenital muscle stiffness, rather than weakness, and respiratory failure in one patient.
Methods
The effect of the Tpm3.12 deletions on the contractile properties in dissected patient myofibers was measured. We used quantitative in vitro motility assay to measure Ca2+ sensitivity of thin filaments reconstituted with recombinant Tpm3.12 ΔE218 and ΔE224.
Results
Contractility studies on permeabilized myofibers demonstrated reduced maximal active tension from both patients with increased Ca2+ sensitivity and altered cross‐bridge cycling kinetics in ΔE224 fibers. In vitro motility studies showed a two‐fold increase in Ca2+ sensitivity of the fraction of filaments motile and the filament sliding velocity concentrations for both mutations.
Interpretation
These data indicate that Tpm3.12 deletions ΔE218 and ΔE224 result in increased Ca2+ sensitivity of the troponin–tropomyosin complex, resulting in abnormally active interaction of the actin and myosin complex. Both mutations are located in the charged motifs of the actin‐binding residues of tropomyosin 3, thus disrupting the electrostatic interactions that facilitate accurate tropomyosin binding with actin necessary to prevent the on‐state. The mutations destabilize the off‐state and result in excessively sensitized excitation–contraction coupling of the contractile apparatus. This work expands the phenotypic spectrum of TPM3‐related disease and provides insights into the pathophysiological mechanisms of the actin–tropomyosin complex. Ann Neurol 2015;78:982–994
PDF
