Despite their small size and anucleate status, platelets have diverse roles in vascular biology. Not only are platelets the cellular mediator of thrombosis, but platelets are also immune cells that ...initiate and accelerate many vascular inflammatory conditions. Platelets are linked to the pathogenesis of inflammatory diseases such as atherosclerosis, malaria infection, transplant rejection, and rheumatoid arthritis. In some contexts, platelet immune functions are protective, whereas in others platelets contribute to adverse inflammatory outcomes. In this review, we will discuss platelet and platelet-derived mediator interactions with the innate and acquired arms of the immune system and platelet-vessel wall interactions that drive inflammatory disease. There have been many recent publications indicating both important protective and adverse roles for platelets in infectious disease. Because of this new accumulating data, and the fact that infectious disease continues to be a leading cause of death globally, we will also focus on new and emerging concepts related to platelet immune and inflammatory functions in the context of infectious disease.
We study the optical light curve (LC) relations of Type Ia supernovae (SNe Ia) for their use in cosmology using high-quality photometry published by the Carnegie Supernova Project (CSP-I). We revisit ...the classical luminosity decline rate (Δm15) relation and the Lira relation, as well as investigate the time evolution of the (B − V) color and B(B − V), which serves as the basis of the color-stretch relation and Color-MAgnitude Intercept Calibrations (CMAGIC). Our analysis is based on explosion and radiation transport simulations for spherically symmetric delayed-detonation models (DDT) producing normal-bright and subluminous SNe Ia. Empirical LC relations can be understood as having the same physical underpinnings, i.e., opacities, ionization balances in the photosphere, and radioactive energy deposition changing with time from below to above the photosphere. Some three to four weeks past maximum, the photosphere recedes to 56Ni-rich layers of similar density structure, leading to a similar color evolution. An important secondary parameter is the central density c of the WD because at higher densities, more electron-capture elements are produced at the expense of 56Ni production. This results in a Δm15 spread of 0.1 mag in normal-bright and 0.7 mag in subluminous SNe Ia and 0.2 mag in the Lira relation. We show why color-magnitude diagrams emphasize the transition between physical regimes and enable the construction of templates that depend mostly on Δm15 with little dispersion in both the CSP-I sample and our DDT models. This allows intrinsic SN Ia variations to be separated from the interstellar reddening characterized by E(B − V) and RB. Invoking different scenarios causes a wide spread in empirical relations, which may suggest one dominant scenario.
Genetic factors contribute to the risk of thrombotic diseases. Recent genome wide association studies have identified genetic loci including SLC44A2 which may regulate thrombosis. Here we show that ...Slc44a2 controls platelet activation and thrombosis by regulating mitochondrial energetics. We find that Slc44a2 null mice (Slc44a2(KO)) have increased bleeding times and delayed thrombosis compared to wild-type (Slc44a2(WT)) controls. Platelets from Slc44a2(KO) mice have impaired activation in response to thrombin. We discover that Slc44a2 mediates choline transport into mitochondria, where choline metabolism leads to an increase in mitochondrial oxygen consumption and ATP production. Platelets lacking Slc44a2 contain less ATP at rest, release less ATP when activated, and have an activation defect that can be rescued by exogenous ADP. Taken together, our data suggest that mitochondria require choline for maximum function, demonstrate the importance of mitochondrial metabolism to platelet activation, and reveal a mechanism by which Slc44a2 influences thrombosis.
We present the second installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ~ 2500 digital observations from both ...hemispheres selected from the Galactic O-Star Catalog (GOSC). In this paper we include bright stars and other objects drawn mostly from the first version of GOSC, all of them south of delta = -20degrees, for a total number of 258 O stars. We also revise the northern sample of Paper I to provide the full list of spectroscopically classified Galactic O stars complete to B = 8, bringing the total number of published GOSSS stars to 448. Extensive sequences of exceptional objects are given, including the early Of/WN, O Iafpe, Ofc, ON/OC, Onfp, Of?p, and Oe types, as well as double/triple-lined spectroscopic binaries. The new spectral subtype O9.2 is also discussed. The magnitude and spatial distributions of the observed sample are analyzed. We also present new results from OWN, a multi-epoch high-resolution spectroscopic survey coordinated with GOSSS that is assembling the largest sample of Galactic spectroscopic massive binaries ever attained. The OWN data combined with additional information on spectroscopic and visual binaries from the literature indicate that only a very small fraction (if any) of the stars with masses above 15-20 M sub(middot in circle) are born as single systems. In the future we will publish the rest of the GOSSS survey, which is expected to include over 1000 Galactic O stars.
Abstract
We present an analysis of the host-galaxy environment of Swope Supernova Survey 2017a (SSS17a), the discovery of an electromagnetic counterpart to a gravitational-wave source, GW170817. ...SSS17a occurred 1.9 kpc (in projection; 10.″2) from the nucleus of NGC 4993, an S0 galaxy at a distance of 40 Mpc. We present a
Hubble Space Telescope
(
HST
) pre-trigger image of NGC 4993,
Magellan
optical spectroscopy of the nucleus of NGC 4993 and the location of SSS17a, and broadband UV-through-IR photometry of NGC 4993. The spectrum and broadband spectral-energy distribution indicate that NGC 4993 has a stellar mass of
log
(
M
/
M
⊙
)
=
10.49
−
0.20
+
0.08
and star formation rate of 0.003
M
⊙
yr
−1
, and the progenitor system of SSS17a likely had an age of >2.8 Gyr. There is no counterpart at the position of SSS17a in the
HST
pre-trigger image, indicating that the progenitor system had an absolute magnitude
M
V
>
−
5.8
mag. We detect dust lanes extending out to almost the position of SSS17a and >100 likely globular clusters associated with NGC 4993. The offset of SSS17a is similar to many short gamma-ray-burst offsets, and its progenitor system was likely bound to NGC 4993. The environment of SSS17a is consistent with an old progenitor system such as a binary neutron star system.
The Ninth Catalogue of Spectroscopic Binary Orbits (http:/ /sb9.astro.ulb.ac.be) continues the series of compilations of spectroscopic orbits carried out over the past 35 years by Batten and ...collaborators. As of 2004 May 1st, the new Catalogue holds orbits for 2386 systems. Some essential differences between this catalogue and its predecessors are outlined and three straightforward applications are presented: (1) completeness assessment: period distribution of SB1s and SB2s; (2) shortest periods across the H-R diagram; (3) period-eccentricity relation.
On 17 August 2017, gravitational waves (GWs) were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB 170817A. An optical transient source, Swope ...Supernova Survey 17a (SSS17a),was subsequently identified as the counterpart of this event. We present ultraviolet, optical, and infrared light curves of SSS17a extending from 10.9 hours to 18 days postmerger. We constrain the radioactively powered transient resulting from the ejection of neutron-rich material. The fast rise of the light curves, subsequent decay, and rapid color evolution are consistent with multiple ejecta components of differing lanthanide abundance. The late-time light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy elements, demonstrating that neutron star mergers play a role in rapid neutron capture (r-process) nucleosynthesis in the universe.
Abstract
Radiative transfer models of two transitional type Ia supernovae (SNe Ia) have been produced using the abundance stratification technique. These two objects – designated SN 2007on and SN ...2011iv – both exploded in the same galaxy, NGC 1404, which allows for a direct comparison. SN 2007on synthesized 0.25 $\rm M_{{\odot}}$ of 56Ni and was less luminous than SN 2011iv, which produced 0.31 $\rm M_{{\odot}}$ of 56Ni. SN 2007on had a lower central density (ρc) and higher explosion energy (Ekin ∼1.3 ± 0.3 × 1051erg) than SN 2011iv, and it produced less nuclear statistical equilibrium (NSE) elements (0.06 $\rm M_{{\odot}}$). Whereas, SN 2011iv had a larger ρc, which increased the electron capture rate in the lowest velocity regions, and produced 0.35 $\rm M_{{\odot}}$ of stable NSE elements. SN 2011iv had an explosion energy of ∼Ekin ∼0.9 ± 0.2 × 1051erg. Both objects had an ejecta mass consistent with the Chandrasekhar mass (Ch-mass), and their observational properties are well described by predictions from delayed-detonation explosion models. Within this framework, comparison to the sub-luminous SN 1986G indicates SN 2011iv and SN 1986G have different transition densities (ρtr) but similar ρc. Whereas SN 1986G and SN 2007on had a similar ρtr but different ρc. Finally, we examine the colour–stretch parameter sBV versus Lmax relation and determine that the bulk of SNe Ia (including the sub-luminous ones) are consistent with Ch-mass delayed-detonation explosions, where the main parameter driving the diversity is ρtr. We also find ρc to be driving the second-order scatter observed at the faint end of the luminosity–width relationship.
Eleven hours after the detection of gravitational wave source GW170817 by the Laser Interferometer Gravitational-Wave Observatory and Virgo Interferometers, an associated optical transient, SSS17a, ...was identified in the galaxy NGC 4993. Although the gravitational wave data indicate that GW170817 is consistent with the merger of two compact objects, the electromagnetic observations provide independent constraints on the nature of that system. We synthesize the optical to near-infrared photometry and spectroscopy of SSS17a collected by the One-Meter Two-Hemisphere collaboration, finding that SSS17a is unlike other known transients. The source is best described by theoretical models of a kilonova consisting of radioactive elements produced by rapid neutron capture (the r-process). We conclude that SSS17a was the result of a binary neutron star merger, reinforcing the gravitational wave result.
ASASSN-15lh: A highly super-luminous supernova Dong, Subo; Shappee, B. J.; Prieto, J. L. ...
Science (American Association for the Advancement of Science),
01/2016, Letnik:
351, Številka:
6270
Journal Article
Recenzirano
Odprti dostop
We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu,AB = −23.5 ± ...0.1 and bolometric luminosity Lbol = (2.2 ± 0.2) × 10⁴⁵ ergs s⁻¹, which is more than twice as luminous as any previously known supernova. It has several major features characteristic of the hydrogen-poor super-luminous supernovae (SLSNe-l), whose energy sources and progenitors are currently poorly understood. In contrast to most previously known SLSNe-l that reside in star-forming dwarf galaxies, ASASSN-15lh appears to be hosted by a luminous galaxy (MK ≈ −25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 ± 0.2) × 10⁵² ergs, challenging the magnetar model for its engine.
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