Observational and Physical Classification of Supernovae

This chapter describes the current classification scheme of supernovae (SNe). This scheme has evolved over many decades and now includes numerous SN Types and sub-types. Many of these are universally recognized, while there are controversies regarding the definitions, membership and even the names of some sub-classes; we will try to review here the commonly-used nomenclature, noting the main variants when possible. SN Types are defined according to observational properties; mostly visible-light spectra near maximum light, as well as according to their photometric properties. However, a long-term goal of SN classification is to associate observationally-defined classes with specific physical explosive phenomena. We show here that this aspiration is now finally coming to fruition, and we establish the SN classification scheme upon direct observational evidence connecting SN groups with specific progenitor stars. Observationally, the broad class of Type II SNe contains objects showing strong spectroscopic signatures of hydrogen, while objects lacking such signatures are of Type I, which is further divided to numerous subclasses. Recently a class of super-luminous SNe (SLSNe, typically 10 times more luminous than standard events) has been identified, and it is discussed. We end this chapter by briefly describing a proposed alternative classification scheme that is inspired by the stellar classification system. This system presents our emerging physical understanding of SN explosions, while clearly separating robust observational properties from physical inferences that can be debated. This new system is quantitative, and naturally deals with events distributed along a continuum, rather than being strictly divided into discrete classes. Thus, it may be more suitable to the coming era where SN numbers will quickly expand from a few thousands to millions of events.Comment: Extended final draft of a chapter in the "SN Handbook". Comments most welcom

The Nearby Type Ibn Supernova 2015G: Signatures of Asymmetry and Progenitor Constraints

SN 2015G is the nearest known SN Ibn to date at 23.2 Mpc and it has proven itself a truly remarkable example of this rare subclass. We present the results of an extensive observational campaign including data from radio through ultraviolet wavelengths. SN 2015G was asymmetric, showing late-time nebular lines redshifted by 1000 km/s. It shared many features with the prototypical SN Ibn 2006jc, including extremely strong He I emission lines and a late-time blue pseudocontinuum. The young SN 2015G showed narrow P-Cygni profiles of He I, but never in its evolution did it show any signature of hydrogen - arguing for a dense, ionized, and hydrogen-free circumstellar medium moving outward with a velocity of 1000 km/s and created by relatively recent mass loss from the progenitor star. Ultraviolet through infrared observations show that the fading SN 2015G (which was probably discovered some 20 days post-peak) had a spectral energy distribution that was well described by a simple, single-component blackbody. Archival HST images provide upper limits on the luminosity of SN 2015G's progenitor, while nondetections of any luminous radio afterglow and optical nondetections of outbursts over the past two decades provide constraints upon its mass-loss history

Eta Carinae and the Luminous Blue Variables

We evaluate the place of Eta Carinae amongst the class of luminous blue variables (LBVs) and show that the LBV phenomenon is not restricted to extremely luminous objects like Eta Car, but extends luminosities as low as log(L/Lsun) = 5.4 - corresponding to initial masses ~25 Msun, and final masses as low as ~10-15 Msun. We present a census of S Doradus variability, and discuss basic LBV properties, their mass-loss behaviour, and whether at maximum light they form pseudo-photospheres. We argue that those objects that exhibit giant Eta Car-type eruptions are most likely related to the more common type of S Doradus variability. Alternative atmospheric models as well as sub-photospheric models for the instability are presented, but the true nature of the LBV phenomenon remains as yet elusive. We end with a discussion on the evolutionary status of LBVs - highlighting recent indications that some LBVs may be in a direct pre-supernova state, in contradiction to the standard paradigm for massive star evolution.Comment: 27 pages, 6 figures, Review Chapter in "Eta Carinae and the supernova imposters" (eds R. Humphreys and K. Davidson) new version submitted to Springe

The gamma-ray burst GRB060614 requires a novel explosive process

Over the past decade our physical understanding of gamma-ray bursts (GRBs) has progressed rapidly thanks to the discovery and observation of their long-lived afterglow emission. Long-duration (T < 2 s) GRBs are associated with the explosive deaths of massive stars (``collapsars''), which produce accompanying supernovae, while the short-duration (T > 2 s) GRBs arise from a different origin, which has been argued to be the merger of two compact objects, either neutron stars or black holes. Here we present observations of GRB060614, a 100-s long burst discovered by the Swift satellite, which require the invocation of a new explosive process: either a massive ``collapsar'' that powers a GRB without any associated supernova, or a new type of engine, as long-lived as the collapsar but without any such massive stellar host. We also discuss the properties of this burst's redshift z=0.125 host galaxy, which distinguish it from other long-duration GRBs and suggest that an entirely new type of GRB progenitor may be required

Measurement of the Lambda_b Lifetime in Lambda_b --> J/psi Lambda0 in p-pbar Collisions at sqrt(s)=1.96 TeV

We report a measurement of the Lambda_b lifetime in the exclusive decay Lambda_b --> J/psi Lambda0 in p-pbar collisions at sqrt(s) = 1.96 TeV using an integrated luminosity of 1.0 fb^{-1} of data collected by the CDF II detector at the Fermilab Tevatron. Using fully reconstructed decays, we measure tau(Lambda_b) = 1.593 ^{+0.083}_{-0.078} (stat.) +- 0.033 (syst.) ps. This is the single most precise measurement of tau(Lambda_b) and is 3.2 sigma higher than the current world average.Comment: 7 Pages, 2 Figures, 1 Table. Submitted to Phys. Rev. Let

Measurement of B(t->Wb)/B(t->Wq) at the Collider Detector at Fermilab

We present a measurement of the ratio of top-quark branching fractions R= B(t -> Wb)/B(t -> Wq), where q can be a b, s or a d quark, using lepton-plus-jets and dilepton data sets with integrated luminosity of ~162 pb^{-1} collected with the Collider Detector at Fermilab during Run II of the Tevatron. The measurement is derived from the relative numbers of t-tbar events with different multiplicity of identified secondary vertices. We set a lower limit of R > 0.61 at 95% confidence level.Comment: 7 pages, 2 figures, published in Physical Review Letters; changes made to be consistent with published versio

A Novel Protein LZTFL1 Regulates Ciliary Trafficking of the BBSome and Smoothened

Many signaling proteins including G protein-coupled receptors localize to primary cilia, regulating cellular processes including differentiation, proliferation, organogenesis, and tumorigenesis. Bardet-Biedl Syndrome (BBS) proteins are involved in maintaining ciliary function by mediating protein trafficking to the cilia. However, the mechanisms governing ciliary trafficking by BBS proteins are not well understood. Here, we show that a novel protein, Leucine-zipper transcription factor-like 1 (LZTFL1), interacts with a BBS protein complex known as the BBSome and regulates ciliary trafficking of this complex. We also show that all BBSome subunits and BBS3 (also known as ARL6) are required for BBSome ciliary entry and that reduction of LZTFL1 restores BBSome trafficking to cilia in BBS3 and BBS5 depleted cells. Finally, we found that BBS proteins and LZTFL1 regulate ciliary trafficking of hedgehog signal transducer, Smoothened. Our findings suggest that LZTFL1 is an important regulator of BBSome ciliary trafficking and hedgehog signaling

γ-Glutamyltransferase, but not markers of hepatic fibrosis, is associated with cardiovascular disease in older people with type 2 diabetes mellitus: the Edinburgh Type 2 Diabetes Study

AIMS/HYPOTHESIS: We examined the association of prevalent and incident cardiovascular disease (CVD) with chronic liver disease in a cohort of community-based people with type 2 diabetes, in order to clarify the relationship between these two important conditions. METHODS: 1,066 participants with type 2 diabetes aged 60–75 years underwent assessment of a range of liver injury markers (non-specific injury, steatosis, steatohepatitis, fibrosis, portal hypertension). Individuals were followed up for incident cardiovascular events. RESULTS: At baseline there were 370/1,033 patients with prevalent CVD, including 317/1,033 with coronary artery disease (CAD). After a mean follow-up of 4.4 years there were 44/663 incident CVD events, including 27/663 CAD events. There were 30/82 CVD-related deaths. Risk of dying from or developing CVD was no higher in participants with steatosis than in those without (HR 0.90; 95% CI 0.40, 2.00; p > 0.05). The only notable relationship was with γ-glutamyltransferase (GGT) (incident CVD: adjusted HR for doubling GGT 1.24 [95% CI 0.97, 1.59] p = 0.086; incident CAD: adjusted HR 1.33 [95% CI 1.00, 1.78] p = 0.053), suggesting that in our study population, chronic liver disease may have little effect on the development of, or mortality from, CVD. CONCLUSIONS/INTERPRETATION: An independent association between GGT and CVD warrants further exploration as a potentially useful addition to current cardiovascular risk prediction models in diabetes. However, overall findings failed to suggest that there is a clinical or pathophysiological association between chronic liver disease and CVD in elderly people with type 2 diabetes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00125-015-3575-y) contains peer-reviewed but unedited supplementary material, which is available to authorised users

IQGAP1 Interacts with Components of the Slit Diaphragm Complex in Podocytes and Is Involved in Podocyte Migration and Permeability In Vitro

IQGAP1 is a scaffold protein that interacts with proteins of the cytoskeleton and the intercellular adhesion complex. In podocytes, IQGAP1 is associated with nephrin in the glomerular slit diaphragm (SD) complex, but its role remains ill-defined. In this work, we investigated the interaction of IQGAP1 with the cytoskeleton and SD proteins in podocytes in culture, and its role in podocyte migration and permeability. Expression, localization, and interactions between IQGAP1 and SD or cytoskeletal proteins were determined in cultured human podocytes by Western blot (WB), immunocytolocalization (IC), immunoprecipitation (IP), and In situ Proximity Ligation assay (IsPL). Involvement of IQGAP1 in migration and permeability was also assessed. IQGAP1 expression in normal kidney biopsies was studied by immunohistochemistry. IQGAP1 expression by podocytes increased during their in vitro differentiation. IC, IP, and IsPL experiments showed colocalizations and/or interactions between IQGAP1 and SD proteins (nephrin, MAGI-1, CD2AP, NCK 1/2, podocin), podocalyxin, and cytoskeletal proteins (α-actinin-4). IQGAP1 silencing decreased podocyte migration and increased the permeability of a podocyte layer. Immunohistochemistry on normal human kidney confirmed IQGAP1 expression in podocytes and distal tubular epithelial cells and also showed an expression in glomerular parietal epithelial cells. In summary, our results suggest that IQGAP1, through its interaction with components of SD and cytoskeletal proteins, is involved in podocyte barrier properties