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The effects of the interaction between Type Ia supernova ejecta and their circumstellar wind on the photometric properties of Type Ia supernovae are investigated. We assume that a hydrogen-rich, dense, and extended circumstellar matter (CSM) is formed by the steady mass-loss of their progenitor systems. The CSM density is assumed to be proportional to r −2. When the mass-loss rate is above 10−4 M⊙ yr−1 with a wind velocity of 100 km s−1, CSM interaction results in an early flux excess in optical light curves within 4 d of explosion. In these cases, the optical colour quickly evolves to the blue. The ultraviolet flux below 3000 Å is found to have a persistent flux excess compared to Type Ia supernovae as long as CSM interaction continues. Type Ia supernovae with progenitor mass-loss rates between 10−4 and 10−3 M⊙ yr−1 may not have a CSM that is dense enough to affect spectra to make them Type Ia CSM, but they may still result in Type Ia supernovae with an early optical flux excess. Because they have a persistent ultraviolet flux excess, ultraviolet light curves around the luminosity peak would be significantly different from those with a low-density CSM. [ABSTRACT FROM AUTHOR]

A new class of ultra-long-duration (more than 10,000 seconds) γ-ray bursts has recently been suggested (1-3). They may originate in the explosion of stars with much larger radii than those producing normal long-duration γ-ray bursts (3,4) or in the tidal disruption of a star (3). No clear supernova has yet been associated with an ultra-long-duration γ-ray burst. Here we report that a supernova (SN 2011kl) was associated with the ultra-long-duration γ-ray burst GRB 111209A, at a redshift z of 0.677. This supernova is more than three times more luminous than type Ic supernovae associated with long-duration γ-ray bursts (5-7), and its spectrum is distinctly different. The slope of the continuum resembles those of super-luminous supernovae (8,9), but extends further down into the rest-frame ultraviolet implying a low metal content. The light curve evolves much more rapidly than those of super-luminous supernovae. This combination of high luminosity and low metalline opacity cannot be reconciled with typical type Ic supernovae, but can be reproduced by a model where extra energy is injected by a strongly magnetized neutron star (a magnetar), which has also been proposed as the explanation for super-luminous supernovae (10)., GRB 111209A was detected by the Swift satellite at 07:12 UT on 9 December 2011. The X-ray and optical counterparts were discovered within minutes (11). The extraordinarily long duration of [...]

The binary neutron star merger observed and localized on 17 August 2017 by the LIGO and Virgo gravitational interferometers and by numerous telescopes on the ground and in orbit linked in an unambiguous way the coalescence of double neutron stars with the formation of a relativistic outflow (short gamma-ray burst GRB170817A) and of a thermal radioactive source (kilonova). The vicinity of the event (40 Mpc) made it possible to monitor the electromagnetic counterpart in detail at all wavelengths and to map its close environment in the outskirts of the lenticular galaxy NGC 4993. Radio VLBI images of GRB170817A allowed the first direct detection of superluminal motion in a GRB afterglow, pointing to a collimated ultra-relativistic jet rather than to a quasi-isotropically, mildly relativistically expanding source. The accurate spectroscopy of the kilonova at ultraviolet-to-infrared wavelengths with the X-Shooter spectrograph of the ESO Very Large Telescope showed the long-sought-after signature of rapid neutron capture process (in short: r-process) nucleosynthesis. Kilonova detection makes gravitational wave sources optimal tracers of heavy element formation sites. [ABSTRACT FROM AUTHOR]

The abundance distribution in the ejecta of the peculiar slowly declining Type Ia supernova (SN Ia) SN 1999aa is obtained by modelling a time series of optical spectra. Similar to SN 1991T, SN 1999aa was characterized by early-time spectra dominated by Fe  iii features and a weak Si  ii  6355 Å line, but it exhibited a high-velocity Ca  ii  H&K line and morphed into a spectroscopically normal SN Ia earlier. Three explosion models are investigated, yielding comparable fits. The innermost layers are dominated by ∼0.3 M⊙ of neutron-rich stable iron-group elements, mostly stable iron. Above that central region lies a 56Ni-dominated shell, extending to |$v \approx 11\, 000$| – |$12\, 000$| km s−1, with mass ∼0.65 M⊙. These inner layers are therefore similar to those of normal SNe Ia. However, the outer layers exhibit composition peculiarities similar to those of SN 1991T: The intermediate-mass elements shell is very thin, containing only ∼0.2 M⊙, and is sharply separated from an outer oxygen-dominated shell, which includes ∼0.22 M⊙. These results imply that burning suddenly stopped in SN 1999aa. This is a feature SN 1999aa shares with SN 1991T, and explains the peculiarities of both SNe, which are quite similar in nature apart from the different luminosities. The spectroscopic path from normal to SN 1991T-like SNe Ia cannot be explained solely by a temperature sequence. It also involves composition layering differences, suggesting variations in the progenitor density structure or in the explosion parameters. [ABSTRACT FROM AUTHOR]

The origin of iPTF14hls, which had Type IIP supernova-like spectra but kept bright for almost two years with little spectral evolution, is still unclear. We here propose that iPTF14hls was not a sudden outburst like supernovae but rather a long-term outflow similar to stellar winds. The properties of iPTF14hls, which are at odds with a supernova scenario, become natural when interpreted as a stellar wind with variable mass-loss rate. Based on the wind hypothesis, we estimate the mass-loss rates of iPTF14hls in the bright phase. We find that the instantaneous mass-loss rate of iPTF14hls during the 2-yr bright phase was more than a few M⊙ yr−1 ('hyper-wind') and it reached as much as 10 M⊙ yr−1. The total mass lost over two years was about 10 M⊙. Interestingly, we find that the light curve of iPTF14hls has a very similar shape to that of η Carinae during the Great Eruption, which also experienced a similar but less extreme brightening accompanied by extraordinary mass-loss, shedding more than 10 M⊙ in 10 yr. The progenitor of iPTF14hls is less than 150 M⊙ if it still exists, which is similar to η Carinae. The two phenomena may be related to a continuum-driven extreme wind from very massive stars. [ABSTRACT FROM AUTHOR]

We show that the jet power Pj and geometrically corrected γ-ray luminosity Lγ for the X-ray binaries (XRBs) Cygnus X-1, Cygnus X-3, and V404 Cygni, and γ-ray upper limits for GRS 1915+105 and GX339-4, follow the universal scaling for the energetics of relativistic jets from black hole (BH) systems found by Nemmen et al. for blazars and GRBs. The observed peak γ-ray luminosity for XRBs is geometrically corrected, and theminimum jet power is estimated from the peak flux density of radio flares and the flare rise time. The Lγ-Pj correlation holds across ~17 orders of magnitude. The correlation suggests a jet origin for the high-energy emission from XRBs, and indicates a common mechanism or efficiency for the high-energy emission 0.1-100 GeV from all relativistic BH systems. [ABSTRACT FROM AUTHOR]

We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSSJ110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to ~5μm in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of αν ~ -1.4, where fν - ναν , synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seemsmost plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low νpeak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations. [ABSTRACT FROM AUTHOR]

BL Lac objects are active nuclei, hosted in massive elliptical galaxies, the emission of which is dominated by a relativistic jet closely aligned with the line of sight. This implies the existence of a parent population of sources with a misaligned jet that have been identified with low-power radiogalaxies. The spectrum of BL Lacs, dominated by non-thermal emission over the whole electromagnetic range, together with bright compact radio cores, high luminosities, rapid and large amplitude flux variability at all frequencies and strong polarization makes these sources an optimal laboratory for high energy astrophysics. A most distinctive characteristic of the class is the weakness or absence of spectral lines, that historically hindered the identification of their nature and ever thereafter proved to be a hurdle in the determination of their distance. In this paper, we review the main observational facts that contribute to the present basic interpretation of this class of active galaxies. We overview the history of the BL Lac objects research field and their population as it emerged from multi-wavelength surveys. The properties of the flux variability and polarization, compared with those at radio, X-ray and gamma-ray frequencies, are summarized together with the present knowledge of the host galaxies, their environments, and central black hole masses. We focus this review on the optical observations, which played a crucial role in the early phase of BL Lacs studies, and in spite of extensive radio, X-ray, and recently gamma-ray observations, could represent the future major contribution to the unveiling of the origin of these sources. In particular, they could provide a firm conclusion on the long debated issue of the cosmic evolution of this class of active galactic nuclei and on the connection between formation of supermassive black holes and relativistic jets. [ABSTRACT FROM AUTHOR]

At the end of IAU Symposium 279, Shri Kulkarni delivered the concluding remarks. This paper presents a summary of his comments as interpreted by the Chairs of the Science Organizing Committee. [ABSTRACT FROM PUBLISHER]

Studying a multi-dimensional structure of supernovae (SNe) gives important constraints on the mechanism of the SN explosion. Polarization measurement is one of the most powerful methods to study the explosion geometry of extragalactic SNe. Especially, Type Ib/c SNe are the ideal targets because the core of the explosion is bare. We have performed spectropolarimetric observations of Type Ib/c SNe with the Subaru telescope. We detect a rotation of the polarization angle across the line, which is seen as a loop in the Q - U plane. This indicates that axisymmetry is broken in the SN ejecta. Adding our new data to the sample of stripped-envelope SNe with high-quality spectropolarimetric data, five SNe out of six show a loop in the Q - U plane. This implies that the SN explosion commonly has a non-axisymmetric, three-dimensional geometry. [ABSTRACT FROM PUBLISHER]

In 2007 July, the blazar 3C 454.3 underwent a flare in the optical, reaching R∼ 13 on July 19. Then the optical flux decreased by one magnitude, being R∼ 14 when the source was detected by the gamma-ray satellite AGILE, which observed the source on July 24–30. At the same time, the Swift satellite performed a series of snapshots. We can construct the simultaneous spectral energy distribution using optical, ultraviolet, X-ray and gamma-ray data. These show that an increased gamma-ray flux is accompanied by a weaker optical/X-ray flux with respect to the flare observed in the spring of 2005 by INTEGRAL and Swift. This confirms earlier suggestions about the behaviour of the jet of 3C 454.3. [ABSTRACT FROM AUTHOR]