Optical and NIR observations of the Type Ia supernova SN 2014J in M82 are presented. The observed light curves are found to be similar to normal Type Ia supernovae (SNe Ia), with a decline rate ...parameter Δm
15(B) = 1.08 ± 0.03. The supernova reached B-band maximum on JD 2456690.14, at an apparent magnitude m
B
(max) = 11.94. The optical spectra show a red continuum with deep interstellar Na i absorption, but otherwise resemble those of normal SNe Ia. The Si ii λ6355 feature indicates a velocity of ∼12 000 km s−1 at B-band maximum, which places SN 2014J at the border of the normal velocity and high velocity group of SNe Ia. The velocity evolution of SN 2014J places it in the Low Velocity Gradient subclass, whereas the equivalent widths of Si ii features near B-band maximum place it at the border of the core normal and Broad Line subclasses of SNe Ia. An analytic model fit to the bolometric light curve indicates that a total of ∼1.3 M⊙ was ejected in the explosion, and the ejected 56Ni mass M
Ni ∼ 0.6 M⊙. The low Fe iii λ4701 to Fe ii λ5200 ratio in the nebular spectra of SN 2014J hints towards clumpiness in the ejecta. Optical broad-band, linear polarimetric observations of SN 2014J obtained on four epochs indicate an almost constant polarization (P
R ∼2.7 per cent; θ ∼ 37°), which suggests that the polarization signal is of interstellar origin.
We observed that ZnO bulk ceramics prepared by solid state reaction route at 1300 degree C exhibited unexpected room temperature ferromagnetic (RTFM) property. In the absence of any magnetic impurity ...the cause of room temperature ferromagnetic signal in the undoped system is certainly attributed to various kinds of native defects such as oxygen vacancies (V sub(O)) or zinc interstitials (I sub(Zn)) and their clusters created inside the bulk ceramics during heating by slow step sintering schedule (SSSS). The micro-Raman investigation and X-ray photoelectron spectroscopy studies on the ZnO sample sintered at high temperature confirm the presence of such lattice defects.
ABSTRACT
We present optical photometric and spectroscopic studies of three supernovae (SNe): SN 2013bz, PSN J0910 + 5003, and ASASSN-16ex (SN 2016ccj). UV–optical photometric data of ASASSN-16ex ...obtained with the Swift Ultraviolet/Optical Telescope (UVOT) are also analysed. These objects were initially classified as 09dc-like type Ia SNe. The decline-rate parameters (Δm15(B)true) are derived as 0.92 ± 0.04 (SN 2013bz), 0.70 ± 0.05 (PSN J0910 + 5003), and 0.73 ± 0.03 (ASASSN-16ex). The estimated B-band absolute magnitudes at maximum, −19.61 ± 0.20 mag for SN 2013bz, −19.44 ± 0.20 mag for PSN J0910 + 5003, and −19.78 ± 0.20 mag for ASASSN-16ex, indicate that all three objects are relatively bright. The peak bolometric luminosities for these objects are derived as $\log L_\text{bol}^\text{max} =$ 43.38 ± 0.07, 43.26 ± 0.07, and 43.40 ± 0.06 erg s−1, respectively. The spectral and velocity evolution of SN 2013bz is similar to that of a normal SN Ia, hence it appears to be a luminous, normal type Ia supernova. On the other hand, the light curves of PSN J0910 + 5003 and ASASSN-16ex are broad and exhibit properties similar to 09dc-like SNe Ia. Their spectroscopic evolution shows similarity with 09dc-like SNe: strong C ii lines are seen in the pre-maximum spectra of these two events. Their photospheric velocity evolution is similar to SN 2006gz. Further, in the UV bands, ASASSN-16ex is very blue, like other 09dc-like SNe Ia.
Optical UBVRI photometry and low-resolution spectroscopy of the Type IIb supernova SN 2011dh in M51 are presented, covering the first year after the explosion. The light curve and spectral evolution ...are discussed. The early phase light-curve evolution of SN 2011dh is very similar to SN 1993J and SN 2008ax. In the late phase, however, SN 2011dh declines faster than SN 1993J. The late phase decline in the B band is steeper than in the R and I bands, indicating the possibility of dust formation. With a peak V-band absolute magnitude of M
V
= −17.123 ± 0.18 mag, SN 2011dh is a marginally faint type IIb event. The reddening corrected colour curves of SN 2011dh are found to be redder than other well-studied Type IIb supernovae. The bolometric light curve indicates ∼0.09 M of 56Ni is synthesized during the explosion. The He i
lines were detected in the spectra during the rise to maximum. The nebular spectra of SN 2011dh show a box-shaped emission in the red wing of the O i 6300−6363 Å feature, that is attributed to Hα emission from a shock-excited circumstellar material. The analysis of nebular spectra indicates that ∼0.2 M of oxygen was ejected during the explosion. Further, the Ca ii/O i line ratio in the nebular phase is ∼0.7, indicating a progenitor with a main-sequence mass of 10-15 M.
We present optical photometry and spectroscopy of the Type IIP supernova SN 2004et that occurred in the nearby galaxy NGC 6946. The observations span a time range of 8–541 d after explosion. The late ...time bolometric luminosity and the Hα luminosity in the nebular phase indicate that 0.06 ± 0.02 M⊙ of 56Ni was synthesized during the explosion. The plateau luminosity, its duration and the expansion velocity of the supernova at the middle of the plateau indicate an explosion energy of Eexp= 1.20+0.38−0.30× 1051 erg. The late time light curve and the evolution of the O i and Hα emission-line profiles indicate the possibility of an early dust formation in the supernova ejecta. The luminosity of O i 6300, 6364 Å doublet, before the dust formation phase, is found to be comparable to that of SN 1987A at similar epochs, implying an oxygen mass in the range 1.5–2 M⊙, and a main-sequence mass of 20 M⊙ for the progenitor.
Conventional solar cells exhibit limited efficiencies in part due to their inability to absorb the entire solar spectrum. Sub-band-gap photons are typically lost but could be captured if a material ...that performs up-conversion, which shifts photon energies higher, is coupled to the device. Recently, molecular chromophores that undergo triplet–triplet annihilation (TTA) have shown promise for efficient up-conversion at low irradiance, suitable for some types of solar cells. However, the molecular systems that have shown the highest up-conversion efficiency to date are ill suited to broadband light harvesting, reducing their applicability. Here we overcome this limitation by combining an organic TTA system with highly fluorescent CdSe semiconductor nanocrystals. Because of their broadband absorption and spectrally narrow, size-tunable fluorescence, the nanocrystals absorb the radiation lost by the TTA chromophores, returning this energy to the up-converter. The resulting nanocrystal-boosted system shows a doubled light-harvesting ability, which allows a green-to-blue conversion efficiency of ∼12.5% under 0.5 suns of incoherent excitation. This record efficiency at subsolar irradiance demonstrates that boosting the TTA by light-emitting nanocrystals can potentially provide a general route for up-conversion for different photovoltaic and photocatalytic applications.
This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following ...slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350°C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO3. Room temperature dielectric constant (εr) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40K for both 1350°C and 1700°C sintered GMO. Present findings showed the possibility of application of GdMnO3 at room temperature as multifunctional materials.
• Preparation of single-phasic polycrystalline GdMnO3 sample by the solid state sintering route.• Observation of square type P–E hysteresis loop with higher saturation and remnant polarization.• Observation of antiferromagnetic behavior at 40K in polycrystalline GdMnO3.• Possibility of room temperature application of GdMnO3 as multifunctional material.
ABSTRACT
We investigate the observational properties of a hydrogen-deficient superluminous supernova (SLSN) SN 2020ank (at z = 0.2485), with the help of early phase observations carried out between ...–21 and +52 d since g-band maximum. Photometrically, SN 2020ank is one of the brightest SLSN ($M_{\mathrm{ g,peak}}\, \sim$ –21.84 ± 0.10 mag), having fast pre-peak rising and post-peak decaying rates. The bolometric light curve of SN 2020ank exhibits a higher peak luminosity (Lmax) of ∼ (3.9 ± 0.7) × 1044 erg s−1 and appears to be symmetric around the peak with $L^{\mathrm{ rise}}_{\mathrm{ max}}$/e ${\approx}L^{\mathrm{ fall}}_{\mathrm{ max}}$/e ≈ 15 d. The semi-analytical light-curve modelling using the minim code suggests a spin-down millisecond magnetar with $P_i\, \sim$ 2.2 ± 0.5 ms and $B\, \sim$ (2.9 ± 0.1) $\times \, 10^{14}$ G as a possible powering source for SN 2020ank. The possible magnetar origin and excess ultraviolet flux at early epochs indicate a central-engine based powering source for SN 2020ank. Near-peak spectra of SN 2020ank are enriched with the W-shaped O ii features but with the weaker signatures of C ii and Fe iii. Using the estimated rise time of ∼ 27.9 d and the photospheric velocity of ∼ 12 050 km s−1, we constrain the ejecta mass to ∼ 7.2 M⊙ and the kinetic energy of ∼6.3 × 1051 erg. The near-peak spectrum of SN 2020ank exhibits a close spectral resemblance with that of fast-evolving SN 2010gx. The absorption features of SN 2020ank are blueshifted compared to Gaia16apd, suggesting a higher expansion velocity. The spectral similarity with SN 2010gx and comparatively faster spectral evolution than PTF12dam (a slow-evolving SLSN) indicate the fast-evolving behaviour of SN 2020ank.
Abstract
We present an extensive, panchromatic photometric (UV, optical, and near-IR) and low-resolution optical spectroscopic coverage of a Type IIP supernova SN 2018gj that occurred on the ...outskirts of the host galaxy NGC 6217. From the
V-
band light curve, we estimate the plateau length to be ∼ 70 ± 2 days, placing it among the very few well-sampled short plateau supernovae (SNe). With
V
-band peak absolute magnitude
M
V
≤ −17.0 ± 0.1 mag, it falls in the middle of the luminosity distribution of the Type II SNe. The color evolution is typical to other Type II SNe except for an early elbow-like feature in the evolution of
V
−
R
color owing to its early transition from the plateau to the nebular phase. Using the expanding photospheric method, we present an independent estimate of the distance to SN 2018gj. We report the spectral evolution to be typical of a Type II SNe. However, we see a persistent blueshift in emission lines until the late nebular phase, not ordinarily observed in Type II SNe. The amount of radioactive nickel (
56
Ni) yield in the explosion was estimated to be 0.026 ± 0.007
M
⊙
. We infer from semianalytical modeling, nebular spectrum, and 1D hydrodynamical modeling that the probable progenitor was a red supergiant with a zero-age-main-sequence mass ≤13
M
⊙
. In the simulated hydrodynamical model light curves, reproducing the early optical bolometric light curve required an additional radiation source, which could be the interaction with the proximal circumstellar matter.
Abstract
We report results of optical imaging and low-resolution spectroscopic monitoring of supernova (SN) 2017iro that occurred in the nearby (∼31 Mpc) galaxy NGC 5480. The He
i
λ
5876 feature ...present in the earliest spectrum (−7 days) classified it as a Type Ib SN. The follow-up observations span from −7 to +266 days with respect to the
B
-band maximum. With a peak absolute magnitude in
V
band
M
V
= −17.76 ± 0.15 mag and bolometric luminosity log
10
L
= 42.39 ± 0.09 erg s
−1
, SN 2017iro is a moderately luminous Type Ib SN. The overall light-curve evolution of SN 2017iro is similar to that of SN 2012au and SN 2009jf during the early (up to ∼100 days) and late phases (>150 days), respectively. The line velocities of both Fe
ii
λ
5169 and He
i
λ
5876 are ∼9000 km s
−1
near the peak. The analysis of the nebular phase spectrum (∼+209 days) indicates an oxygen mass of ∼0.35
M
⊙
. The smaller O
i
/Ca
ii
flux ratio of ∼1 favors a progenitor with a zero-age main-sequence mass in the range ∼13–15
M
⊙
, most likely in a binary system, similar to the case of iPTF13bvn. The explosion parameters are estimated by applying different analytical models to the quasi-bolometric light curve of SN 2017iro.
56
Ni mass synthesized in the explosion has a range of ∼0.05–0.10
M
⊙
, ejecta mass ∼1.4–4.3
M
⊙
, and kinetic energy ∼(0.8–1.9) × 10
51
erg.
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