We present a study of the Type IIn supernova (SN) 2005gl, in the relatively nearby (d - 66 Mpc) galaxy NGC 266. Photometry and spectroscopy of the SN indicate that it is a typical member of its ...class. Pre-explosion hubble Space Telescope (HST) imaging of the location of the SN, along with a precise localization of this event using the laser guide star assisted adaptive optics (LGS-AO) system at Keck Observatory, are combined to identify a luminous (M sub(V) = -10.3 mag) point source as the possible progenitor of SN 2005gl. If the source is indeed a single star, it was likely a member of the class of luminous blue variable stars (LBVs). This finding leads us to consider the possible general association of SNe IIn with LBV progenitors; it is indeed supported by observations of other SNe, and the known properties of LBV stars. For example, we argue that should the prototypical Galactic LBV Carina explode in a phase similar to its current state, it will likely produce a SN IIn. We discuss our findings in the context of current ideas about the evolution of massive stars and review the census of SNe with identified progenitors. The concept of the progenitor-SN map is introduced as a convenient means to discuss the present status and future prospects of direct searches for SN progenitors. We conclude that this field has matured considerably in recent years, and the transition from anecdotal information about rare single events to robust associations of progenitor classes with specific SN types has already begun.
Abstract
In this contribution, we achieve the primary goal of the active galactic nucleus (AGN)
STORM
campaign by recovering velocity–delay maps for the prominent broad emission lines (Ly
α
, C
iv
, ...He
ii
, and H
β
) in the spectrum of NGC 5548. These are the most detailed velocity–delay maps ever obtained for an AGN, providing unprecedented information on the geometry, ionization structure, and kinematics of the broad-line region. Virial envelopes enclosing the emission-line responses show that the reverberating gas is bound to the black hole. A stratified ionization structure is evident. The He
ii
response inside 5–10 lt-day has a broad single-peaked velocity profile. The Ly
α
, C
iv
, and H
β
responses extend from inside 2 to outside 20 lt-day, with double peaks at ±2500 km s
−1
in the 10–20 lt-day delay range. An incomplete ellipse in the velocity–delay plane is evident in H
β
. We interpret the maps in terms of a Keplerian disk with a well-defined outer rim at
R
= 20 lt-day. The far-side response is weaker than that from the near side. The line-center delay
τ
=
(
R
/
c
)
(
1
−
sin
i
)
≈
5
days gives the inclination
i
≈ 45°. The inferred black hole mass is
M
BH
≈ 7 × 10
7
M
⊙
. In addition to reverberations, the fit residuals confirm that emission-line fluxes are depressed during the “BLR Holiday” identified in previous work. Moreover, a helical “Barber-Pole” pattern, with stripes moving from red to blue across the C
iv
and Ly
α
line profiles, suggests azimuthal structure rotating with a 2 yr period that may represent precession or orbital motion of inner-disk structures casting shadows on the emission-line region farther out.
Type Ia supernovae are key tools for measuring distances on a cosmic scale. They are generally thought to be the thermonuclear explosion of an accreting white dwarf in a close binary system. The ...nature of the mass donor is still uncertain. In the single-degenerate model it is a main-sequence star or an evolved star, whereas in the double-degenerate model it is another white dwarf. We show that the velocity structure of absorbing material along the line of sight to 35 type Ia supernovae tends to be blueshifted. These structures are likely signatures of gas outflows from the supernova progenitor systems. Thus, many type Ia supernovae in nearby spiral galaxies may originate in single-degenerate systems.
We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved ...an almost daily cadence with observations from five ground-based telescopes. The Hβ and He ii λ4686 broad emission-line light curves lag that of the 5100 optical continuum by and , respectively. The Hβ lag relative to the 1158 ultraviolet continuum light curve measured by the Hubble Space Telescope is ∼50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is ∼50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for Hβ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the Hβ and He ii emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C iv, Ly , He ii(+O iii), and Si iv(+O iv) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured Hβ lag is a factor of five shorter than the expected value implied by the RBLR-LAGN relation based on the past behavior of NGC 5548.
Ignimbrite flare-ups are periods of intense silicic volcanism characterized by multiple caldera-forming eruptions that together evacuate 103 to 104km3 of magma. Ignimbrite flare-ups of different ages ...and from different tectonic settings have been well documented; however, in the literature, the distinction between an ‘ignimbrite flare-up’ and a ‘magmatic flare-up’ is not always obvious. We argue that the distinction is an important one as magmatic flare-ups do not always necessitate an ignimbrite flare-up, and thus the drivers for both require more investigation. Here we focus our review on the North Island continental arc of New Zealand, which is rarely included in published comparative studies of arc magmatism. Yet, it is well known for its extraordinary production of high-silica rhyolite and intensity of caldera-forming eruptions relative to other active arc systems, and a highly resolved understanding of the subduction plate boundary characterized by a rapidly migrating arc. Much of the present-day geologic footprint of the active part of the arc, the Taupo Volcanic Zone (TVZ), was established in a remarkable ignimbrite flare-up event between ~350 and ~280ka. During this time, eight ignimbrite-forming eruptions occurred, evacuating ~3000km3 of magma, and formed calderas that pepper a 90×40km area. We divide the flare-up into 3 pulses of caldera activity, and track the magmatic input from the build-up to the first pulse, through to the final caldera forming eruption of the last pulse.
Based on a comparison between New Zealand and other documented examples worldwide, we propose three ignimbrite flare-up categories based on their longevity and intensity. Most ignimbrite flare-ups last 106 to 107years (categories 2 and 1, respectively), erupt magma volumes exceeding 104km3 and are interpreted to be driven from depth by high mantle flux (i.e. magmatic flare-ups). Here, we draw attention to a new, much shorter timescale flare-up (104 to 105years; category 3) as exemplified by the ~350 to ~280 TVZ example. Using the erupted volumes for several documented flare-ups at the three category timescales, we calculate a mantle input based on published silicic intrusive:extrusive ratios and isotopically derived ratios for basaltic input. Our results show that category 3 ignimbrite flare-up eruption rates typically exceed 10km3kyr−1, have multiple caldera-forming eruptions, and are defined by mantle input rates that can be sustained through the duration of the ignimbrite flare-up and are at least an order of magnitude above the longer timescale category 1 and 2 ignimbrite flare-ups. For the TVZ, such high ignimbrite productivity over just tens of thousands of years, is related to an efficient feedback loop between high mantle flux and accelerated rifting that together are responsible for a remarkably thin and extended continental crust. We argue, that despite its unique nature relative to other continental arcs, there may be important magmatic-tectonic feedbacks that can be gleaned from the highly resolved record of caldera and ignimbrite volcanism in the TVZ, and applied to studying short timescale ignimbrite flare-ups elsewhere.
We have developed NetPath as a resource of curated human signaling pathways. As an initial step, NetPath provides detailed maps of a number of immune signaling pathways, which include approximately ...1,600 reactions annotated from the literature and more than 2,800 instances of transcriptionally regulated genes - all linked to over 5,500 published articles. We anticipate NetPath to become a consolidated resource for human signaling pathways that should enable systems biology approaches.
Abstract
4-Dimensional Einstein-Gauss-Bonnet (4DEGB) gravity has garnered significant attention in the last few years as a phenomenological competitor
to general relativity. We consider the ...theoretical and observational implications of this theory in both the early and late universe, (re-)deriving background and perturbation equations and constraining its characteristic parameters with data from cosmological probes.
Our investigation surpasses the scope of previous studies by incorporating non-flat spatial sections. We explore consequences of 4DEGB on the sound and particle horizons in the very early universe, and demonstrate that 4DEGB can provide an independent solution to the horizon problem for some values of its characteristic parameter
α
. Finally, we constrain an unexplored regime of this theory in the limit of small coupling
α
(empirically supported in the post-Big Bang Nucleosynthesis era by prior constraints). This version of 4DEGB includes a geometric term that resembles dark radiation at the background level, but whose influence on the perturbed equations is qualitatively distinct from that of standard forms of dark radiation. In this limit, only one beyond-ΛCDM degree of freedom persists, which we denote as
α
̃
C
. Our analysis yields the estimate
α
̃
C
= (-9 ± 6) × 10
-6
thereby providing a new constraint of a previously untested sector of 4DEGB.
We model the ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 obtained with the Hubble Space Telescope during the 6 month reverberation mapping campaign in 2014. Our model of the emission from ...NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Ly and C iv, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Ly and C iv have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show a delayed response to continuum variations corresponding to recombination in gas with a density of ∼105 cm−3. The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in ∼2012 corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state.
During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the ...six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.
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