495 research outputs found
Observations of SN 2017ein Reveal Shock Breakout Emission and A Massive Progenitor Star for a Type Ic Supernova
We present optical and ultraviolet observations of nearby type Ic supernova
SN 2017ein as well as detailed analysis of its progenitor properties from both
the early-time observations and the prediscovery Hubble Space Telescope (HST)
images. The optical light curves started from within one day to 275 days
after explosion, and optical spectra range from 2 days to 90 days
after explosion. Compared to other normal SNe Ic like SN 2007gr and SN 2013ge,
\mbox{SN 2017ein} seems to have more prominent C{\footnotesize II} absorption
and higher expansion velocities in early phases, suggestive of relatively lower
ejecta mass. The earliest photometry obtained for \mbox{SN 2017ein} show
indications of shock cooling. The best-fit obtained by including a shock
cooling component gives an estimate of the envelope mass as 0.02
M and stellar radius as 84 R. Examining the
pre-explosion images taken with the HST WFPC2, we find that the SN position
coincides with a luminous and blue point-like source, with an
extinction-corrected absolute magnitude of M8.2 mag and
M7.7 mag.Comparisons of the observations to the theoretical models
indicate that the counterpart source was either a single WR star or a binary
with whose members had high initial masses, or a young compact star cluster. To
further distinguish between different scenarios requires revisiting the site of
the progenitor with HST after the SN fades away.Comment: 28 pages, 19 figures; accepted for publication in The Astrophysical
Journa
Permselective ion electrosorption of subnanometer pores at high molar strength enables capacitive deionization of saline water
Capacitive deionization with porous carbon electrodes is an energy-efficient water treatment technique limited to the remediation of only brackish water due to the severe efficiency drop at high molar strength. Combining experiment and simulation, our work demonstrates the ability of subnanometer pores for permselective ion electrosorption, which enables capacitive deionization for saline media with high concentrations. Molecular dynamics simulations reveal the origin of permselective ion electrosorption in subnanometer pores at high molar strength. Within the subnanometer range, carbon pores with smaller size become more ionophobic and then express a higher ability of permselective ion electrosorption. This can be understood by the effects of the pore size on the microstructure of in-pore water and ions and the nanoconfinement effects on the ion hydration. These findings provide a new avenue for capacitive deionization of saline water (seawater-like ionic strength) to enable the application of highly concentrated saline media by direct use of porous carbons
Mesons in the massive Schwinger model on the light-cone
We investigate mesons in the bosonized massive Schwinger model in the
light-front Tamm-Dancoff approximation in the strong coupling region. We
confirm that the three-meson bound state has a few percent fermion six-body
component in the strong coupling region when expressed in terms of fermion
variables, consistent with our previous calculations. We also discuss some
qualitative features of the three-meson bound state based on the information
about the wave function.Comment: 19 pages, RevTex, included 6 figures which are compressed and
uuencode
Short-Lived Circumstellar Interaction in the Low-Luminosity Type IIP SN 2016bkv
While interaction with circumstellar material is known to play an important
role in Type IIn supernovae (SNe), analyses of the more common SNe IIP and IIL
have not traditionally included interaction as a significant power source.
However, recent campaigns to observe SNe within days of explosion have revealed
narrow emission lines of high-ionization species in the earliest spectra of
luminous SNe II of all subclasses. These "flash ionization" features indicate
the presence of a confined shell of material around the progenitor star. Here
we present the first low-luminosity (LL) SN to show flash ionization features,
SN 2016bkv. This SN peaked at mag and has H{\alpha} expansion
velocities under 1350 km/s around maximum light, placing it at the faint/slow
end of the distribution of SNe IIP (similar to SN 2005cs). The light-curve
shape of SN 2016bkv is also extreme among SNe IIP. A very strong initial peak
could indicate additional luminosity from circumstellar interaction. A very
small fall from the plateau to the nickel tail indicates unusually large
production of radioactive nickel compared to other LL SNe IIP. A comparison
between nebular spectra of SN 2016bkv and models raises the possibility that SN
2016bkv is an electron-capture supernova.Comment: Updated to match published version in ApJ. Photometry table and SYN++
input file available at righ
Evolution of A Peculiar Type Ibn Supernova SN 2019wep
We present a high-cadence short term photometric and spectroscopic monitoring
campaign of a type Ibn SN 2019wep, which is one of the rare SN Ibn after SNe
2010al and 2019uo to display signatures of flash ionization (\ion{He}{2},
\ion{C}{3}, \ion{N}{3}). We compare the decline rates and rise time of SN
2019wep with other SNe Ibn and fast transients. The post-peak decline in all
bands (0.1 mag d) are consistent with SNe Ibn but less than the fast
transients. On the other hand, the m values are slightly lower
than the average values for SNe Ibn but consistent with the fast transients.
The rise time is typically shorter than SNe Ibn but longer than fast
transients. SN 2019wep lies at the fainter end of SNe Ibn but possesses an
average luminosity amongst the fast transients sample. The peculiar color
evolution places it between SNe Ib and the most extreme SNe Ibn. The bolometric
light curve modelling shows resemblance with SN 2019uo with ejecta masses
consistent with SNe Ib. SN 2019wep belongs to the "P cygni" sub-class of SNe
Ibn and shows faster evolution in line velocities as compared to the "emission"
sub-class. The post-maximum spectra show close resemblance with ASASSN-15ed
hinting it to be of SN Ib nature. The low \ion{He}{1} CSM velocities and
residual H further justifies it and gives evidence of an intermittent
progenitor between WR and LBV star.Comment: 19 pages, 14 figures, 2 Tables, Accepted for publication in ApJ main
journa
BLAST: Correlations in the Cosmic Far-Infrared Background at 250, 350, and 500 microns Reveal Clustering of Star-Forming Galaxies
We detect correlations in the cosmic far-infrared background due to the
clustering of star-forming galaxies in observations made with the Balloon-borne
Large Aperture Submillimeter Telescope, BLAST, at 250, 350, and 500 microns. We
perform jackknife and other tests to confirm the reality of the signal. The
measured correlations are well fit by a power law over scales of 5-25
arcminutes, with Delta I/I = 15.1 +/- 1.7%. We adopt a specific model for
submillimeter sources in which the contribution to clustering comes from
sources in the redshift ranges 1.3 <= z <= 2.2, 1.5 <= z <= 2.7, and 1.7 <= z
<= 3.2, at 250, 350, and 500 microns, respectively. With these distributions,
our measurement of the power spectrum, P(k_theta), corresponds to linear bias
parameters, b = 3.8 +/- 0.6, 3.9 +/- 0.6 and 4.4 +/- 0.7, respectively. We
further interpret the results in terms of the halo model, and find that at the
smaller scales, the simplest halo model fails to fit our results. One way to
improve the fit is to increase the radius at which dark matter halos are
artificially truncated in the model, which is equivalent to having some
star-forming galaxies at z >= 1 located in the outskirts of groups and
clusters. In the context of this model we find a minimum halo mass required to
host a galaxy is log (M_min / M_sun) = 11.5 (+0.4/-0.1), and we derive
effective biases $b_eff = 2.2 +/- 0.2, 2.4 +/- 0.2, and 2.6 +/- 0.2, and
effective masses log (M_eff / M_sun) = 12.9 +/- 0.3, 12.8 +/- 0.2, and 12.7 +/-
0.2, at 250, 350, and 500 microns, corresponding to spatial correlation lengths
of r_0 = 4.9, 5.0, and 5.2 +/- 0.7 h^-1 Mpc, respectively. Finally, we discuss
implications for clustering measurement strategies with Herschel and Planck.Comment: Accepted for publication in the Astrophysical Journal. Maps and other
results available at http://blastexperiment.info
Contrasting rift and subduction-related plagiogranites in the Jinshajiang ophiolitic mélange, southwest China, and implications for the Paleo-Tethys
The Jinshajiang ophiolitic mélange zone in southwest China represents a remnant of the eastern Paleo-Tethys Ocean. Field, geochronological and geochemical studies have identified two distinct suites of plagiogranites within the mélange, the Dongzhulin trondhjemite and Jiyidu tonalite, which represent rift and subduction settings, respectively, related to opening and closing of the ocean. SHRIMP U-Pb analysis on zircons extracted from the Dongzhulin trondhjemite yields a mean 206Pb/238U age of 347 ± 7 Ma. REE and isotopic characteristics suggest an origin from low pressure partial melting of an amphibolitic protolith. Highly variable Hf isotopic compositions for zircons from this body may indicate a heterogenous source involving both depleted mantle and enriched continental components. This, together with geologic relations, suggests formation near an embryonic spreading center in a continent-ocean transition setting. The Jiyidu tonalite has a U-Pb zircon age of 283 ± 3 Ma, and geochemical data indicates high Sr/Y, (La/Yb)N, Nb/Ta and low Y, and marked heavy REE depletion. These signatures suggest derivation from low degree partial melting of subducted slab at pressure high enough to stabilize garnet and rutile. A slab-melt origin is also supported by in situ Hf and O data for zircon that show isotopic compositions comparable with typical altered oceanic crust. Thus, the crystallization age of the Jiyidu high Sr/Y tonalite provides a constraint for the subduction of the Jinshajiang ocean floor. The rift-related Dongzhulin trondhjemite and subduction-related Jiyidu high-Sr/Y tonalite constrain the timing and setting of opening and closing of this segment of the Paleo-Tethys Ocean
A measurement of the millimetre emission and the Sunyaev-Zel'dovich effect associated with low-frequency radio sources
We present a statistical analysis of the millimetre-wavelength properties of 1.4GHz-selected sources and a detection of the Sunyaev–Zel’dovich (SZ) effect associated with the haloes that host them. We stack data at 148, 218 and 277GHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4GHz. The thermal SZ effect associated with the haloes that host the AGN is detected at the 5σ level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass haloes (average M 200 ≈ 10 13 M. h −1 70 ) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous haloes. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyse the contribution of radio sources to the angular power spectrum of the cosmic microwave background
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