We conducted a search for luminous outbursts prior to the explosion of Type IIn supernovae (SNe IIn). We built a sample of 27 objects spectroscopically classified as SNe IIn and all located at z < ...0.015. Using deep archival SN fields images – taken up to nearly 20 yr prior to the SN explosions themselves – from transient surveys (PTF, ZTF, DES and CHASE) and major astronomical observatories (European Southern Observatory, ESO and National Optical Astronomy Observatory, NOAO), we found at least one outburst years to months before the explosion of seven SNe IIn, with the earliest precursor being 10 yr prior to the explosion of SN 2019bxq. The maximum absolute magnitudes of the outbursts range between −11.5 mag and −15 mag, and the eruptive phases last for a few weeks to a few years. The g − r colour measured for three objects during their outburst is relatively red, with g − r ranging between 0.5 and 1.0 mag. This is similar to the colour expected during the eruptions of luminous blue variables. We note that the light curves of SNe with pre-SN outbursts have faster decline rates than those of the SNe that do not show pre-SN outbursts. SN 2011fh is remarkable, as it is still visible 12 yr after the luminous SN-like event, indicating that the progenitor possibly survived, or that the interaction is still ongoing. We detect precursor activity in 29% of bona fide SNe IIn in our sample. However, a quantitative assessment of the observational biases affecting the sample suggests that this fraction is an underestimation of the intrinsic precursor occurrence rate.
Abstract
We present deep Chandra X-ray observations of two nearby Type Ia supernovae, SN 2017cbv and SN 2020nlb, which reveal no X-ray emission down to a luminosity
L
X
≲ 5.3 × 10
37
and ≲ 5.4 × 10
...37
erg s
−1
(0.3–10 keV), respectively, at ∼16–18 days after the explosion. With these limits, we constrain the pre-explosion mass-loss rate of the progenitor system to be
M
̇
< 7.2 × 10
−9
and < 9.7 × 10
−9
M
⊙
yr
−1
for each (at a wind velocity
v
w
= 100 km s
−1
and a radius of
R
≈ 10
16
cm), assuming any X-ray emission would originate from inverse Compton emission from optical photons upscattered by the supernova shock. If the supernova environment was a constant-density medium, we would find a number density limit of
n
CSM
< 36 and < 65 cm
−3
, respectively. These X-ray limits rule out all plausible symbiotic progenitor systems, as well as large swathes of parameter space associated with the single degenerate scenario, such as mass loss at the outer Lagrange point and accretion winds. We also present late-time optical spectroscopy of SN 2020nlb, and set strong limits on any swept up hydrogen (
L
H
α
< 2.7 × 10
37
erg s
−1
) and helium (
L
He,
λ
6678
< 2.7 × 10
37
erg s
−1
) from a nondegenerate companion, corresponding to
M
H
≲ 0.7–2 × 10
−3
M
⊙
and
M
He
≲ 4 × 10
−3
M
⊙
. Radio observations of SN 2020nlb at 14.6 days after explosion also yield a non-detection, ruling out most plausible symbiotic progenitor systems. While we have doubled the sample of normal Type Ia supernovae with deep X-ray limits, more observations are needed to sample the full range of luminosities and subtypes of these explosions, and set statistical constraints on their circumbinary environments.
We present the discovery and high-cadence follow-up observations of SN 2018ivc, an unusual SNe II that exploded in NGC 1068 (D = 10.1 Mpc). The light curve of SN 2018ivc declines piecewise-linearly, ...changing slope frequently, with four clear slope changes in the first 30 days of evolution. This rapidly changing light curve indicates that interaction between the circumstellar material and ejecta plays a significant role in the evolution. Circumstellar interaction is further supported by a strong X-ray detection. The spectra are rapidly evolving and dominated by hydrogen, helium, and calcium emission lines. We identify a rare high-velocity emission-line feature blueshifted at ∼7800 (in H , Hβ, Pβ, Pγ, He i, and Ca ii), which is visible from day 18 until at least day 78 and could be evidence of an asymmetric progenitor or explosion. From the overall similarity between SN 2018ivc and SN 1996al, the H equivalent width of its parent H ii region, and constraints from pre-explosion archival Hubble Space Telescope images, we find that the progenitor of SN 2018ivc could be as massive as 52 but is more likely <12 . SN 2018ivc demonstrates the importance of the early discovery and rapid follow-up observations of nearby supernovae to study the physics and progenitors of these cosmic explosions.
As we approach the aftermath of a global pandemic caused by Severe Acute Respiratory Syndrome-Corona Virus (SARS-CoV-2), the importance of quickly developing rapid screening tests has become very ...clear from the point of view of containment and also saving lives. Here, we present an explorative study to develop a telepathology-based screening tool using peripheral blood smears (PBS) to identify Coronavirus Disease (COVID-19)-positive cases from a group of 138 patients with flu-like symptoms, consisting of 82 positive and 56 negative samples. Stained blood smear slides were imaged using an automated slide scanner (AI 100) and the images uploaded to the cloud were analyzed by a pathologist to generate semi-quantitative leukocyte morphology-related data. These telepathology data were compared with the data generated from manual microscopy of the same set of smear slides and also the same pathologist. Besides good correlation between the data from telepathology and manual microscopy, we were able to achieve a sensitivity and specificity of 0.83 and 0.71, respectively, for identifying positive and negative COVID-19 cases using a six-parameter combination associated with leukocyte morphology. The morphological features included plasmacytoid cells, neutrophil dysplastic promyelocyte, neutrophil blast-like cells, apoptotic cells, smudged neutrophil, and neutrophil-to-immature granulocyte ratio. Although Polymerase Chain Reaction (PCR) and antibody tests have a superior performance, the PBS-based telepathology tool presented here has the potential to be an interim screening tool in resource-limited settings in underdeveloped and developing countries.
ABSTRACT
We present the photometric and spectroscopic analysis of three Type II supernovae (SNe): 2014cx, 2014cy, and 2015cz. SN 2014cx is a conventional Type IIP with shallow slope (0.2 mag/50 d) ...and an atypical short plateau (∼86 d). SNe 2014cy and 2015cz show relatively large decline rates (0.88 and 1.64 mag/50 d, respectively) at early times before settling to the plateau phase, unlike the canonical Type IIP/L SN light curves. All of them are normal luminosity SN II with an absolute magnitude at mid-plateau of M$_{V,14\mathrm{ cx}}^{50}$=$-16.6\, \pm \, 0.4\, \rm {mag}$, M$_{V,14\mathrm{ cy}}^{50}$=$-16.5\, \pm \, 0.2\, \rm {mag}$, and M$_{V,15\mathrm{ cz}}^{50}$=$-17.4\, \pm \, 0.3\, \rm {mag}$. A relatively broad range of 56Ni masses is ejected in these explosions (0.027–0.070 M⊙). The spectra shows the classical evolution of SNe II, dominated by a blue continuum with broad H lines at early phases and narrower metal lines with P Cygni profiles during the plateau. High-velocity H i features are identified in the plateau spectra of SN 2014cx at 11 600 kms −1, possibly a sign of ejecta-circumstellar interaction. The spectra of SN 2014cy exhibit strong absorption profile of H i similar to normal luminosity events whereas strong metal lines akin to sub-luminous SNe. The analytical modelling of the bolometric light curve of the three events yields similar progenitor radii within errors (478, 507, and 660 R ⊙ for SNe 2014cx, 2014cy, and 2015cz, respectively), a range of ejecta masses (15.0, 22.2, and 20.6 M ⊙ for SNe 2014cx, 2014cy, and 2015cz), and a modest range of explosion energies (3.3–7.2 foe where 1 foe=10 51erg).
We present a method for automated synthesis of analog circuits using evolutionary search and a set of circuit design rules based on topological reuse. The system requires only moderate expert ...knowledge on part of the user. It allows circuit size, circuit topology, and device values to evolve. The circuit representation scheme employs a topological reuse-based approach-it uses commonly used subcircuits for analog design as inputs and utilizes these to create the final circuit. The connectivity between these blocks is governed by a well-defined set of rules and the scheme is capable of representing most standard analog circuit topologies. The system operation consists of two phases-in the first phase, the circuit size and topology are evolved. A limited amount of device sizing also occurs in this phase. The second phase consists entirely of device value optimization. The design of the evaluation function-which evaluates each generated circuit using SPICE simulations-has also been automated to a great extent. The evaluation function is generated automatically depending on a behavioral description of the circuit. We present several experimental results obtained using this scheme, including two types of comparators, two types of oscillators, and an XOR logic gate. The generated circuits closely resemble hand designed circuits. The computational needs of the system are modest.
Forbidden hugs in pandemic times Pastorello, A.; Valerin, G.; Fraser, M. ...
Astronomy and astrophysics (Berlin),
03/2023, Letnik:
671
Journal Article
Recenzirano
We present photometric and spectroscopic data on three extragalactic luminous red novae (LRNe):
AT 2018bwo
,
AT 2021afy
, and
AT 2021blu
.
AT 2018bwo
was discovered in
NGC 45
(at about 6.8 Mpc) a few ...weeks after the outburst onset. During the monitoring period, the transient reached a peak luminosity of 10
40
erg s
−1
.
AT 2021afy
, hosted by
UGC 10043
(∼49.2 Mpc), showed a double-peaked light curve, with the two peaks reaching a similar luminosity of 2.1(±0.6)×10
41
erg s
−1
. Finally, for
AT 2021blu
in
UGC 5829
(∼8.6 Mpc), the pre-outburst phase was well-monitored by several photometric surveys, and the object showed a slow luminosity rise before the outburst. The light curve of
AT 2021blu
was sampled with an unprecedented cadence until the object disappeared behind the Sun, and it was then recovered at late phases. The light curve of LRN
AT 2021blu
shows a double peak, with a prominent early maximum reaching a luminosity of 6.5 × 10
40
erg s
−1
, which is half of that of
AT 2021afy
. The spectra of
AT 2021afy
and
AT 2021blu
display the expected evolution for LRNe: a blue continuum dominated by prominent Balmer lines in emission during the first peak, and a redder continuum consistent with that of a K-type star with narrow absorption metal lines during the second, broad maximum. The spectra of
AT 2018bwo
are markedly different, with a very red continuum dominated by broad molecular features in absorption. As these spectra closely resemble those of LRNe after the second peak,
AT 2018bwo
was probably discovered at the very late evolutionary stages. This would explain its fast evolution and the spectral properties compatible with that of an M-type star. From the analysis of deep frames of the LRN sites years before the outburst, and considerations of the light curves, the quiescent progenitor systems of the three LRNe were likely massive, with primaries ranging from about 13
M
⊙
for
AT 2018bwo
, to 14
−1
+4
M
⊙
for
AT 2021blu
, and over 40
M
⊙
for
AT 2021afy
.
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