Simplified analytic methods are frequently used to model the light curves of supernovae and other energetic transients and to extract physical quantities, such as the ejecta mass and amount of ...radioactive heating. The applicability and quantitative accuracy of these models, however, have not been clearly delineated. Here we carry out a systematic study comparing certain analytic models to numerical radiation transport calculations. We show that the neglect of time-dependent diffusion limits the accuracy of common Arnett-like analytic models, and that the widely applied Arnett's rule for inferring radioactive mass does not hold in general, with an error that increases for models with longer diffusion times or more centralized heating. We present new analytic relations that accurately relate the peak time and luminosity of an observed light curve to the physical ejecta and heating parameters. We further show that recombination and spatial distribution of heating modify the peak of the light curve and that these effects can be accounted for by varying a single dimensionless parameter in the new relations. The results presented should be useful for estimating the physical properties of a wide variety of transient phenomena.
Abstract
We perform a systematic study of the
56
Ni mass (
M
Ni
) of 27 stripped-envelope supernovae (SESNe) by modeling their light-curve tails, highlighting that use of “Arnett’s rule” ...overestimates
M
Ni
for SESNe by a factor of ∼2. Recently, Khatami & Kasen presented a new model relating the peak time (
t
p
) and luminosity (
L
p
) of a radioactively powered supernova to its
M
Ni
that addresses several limitations of Arnett-like models, but depends on a dimensionless parameter,
β
. Using observed
t
p
,
L
p
, and tail-measured
M
Ni
values for 27 SESNe, we observationally calibrate
β
for the first time. Despite scatter, we demonstrate that the model of Khatami & Kasen with empirically calibrated
β
values provides significantly improved measurements of
M
Ni
when only photospheric data are available. However, these observationally constrained
β
values are systematically lower than those inferred from numerical simulations, primarily because the observed sample has significantly higher (0.2–0.4 dex)
L
p
for a given
M
Ni
. While effects due to composition, mixing, and asymmetry can increase
L
p
none can explain the systematically low
β
values. However, the discrepancy can be alleviated if ∼7%–50% of
L
p
for the observed sample comes from sources other than radioactive decay. Either shock cooling or magnetar spin-down could provide the requisite luminosity. Finally, we find that even with our improved measurements, the
M
Ni
values of SESNe are still a factor of ∼3 larger than those of hydrogen-rich Type II SNe, indicating that these supernovae are inherently different in terms of the initial mass distributions of their progenitors or their explosion mechanisms.
Abstract
We present AT2020mrf (SRGe J154754.2+443907), an extra-galactic (
z
= 0.1353) fast blue optical transient (FBOT) with a rise time of
t
g
,rise
= 3.7 days and a peak luminosity of
M
g
,peak
= ...−20.0. Its optical spectrum around peak shows a broad (
v
∼ 0.1
c
) emission feature on a blue continuum (
T
∼ 2 × 10
4
K), which bears a striking resemblance to AT2018cow. Its bright radio emission (
ν
L
ν
= 1.2 × 10
39
erg s
−1
;
ν
rest
= 7.4 GHz; 261 days) is similar to four other AT2018cow-like events, and can be explained by synchrotron radiation from the interaction between a sub-relativistic (≳0.07–0.08c) forward shock and a dense environment (
M
̇
≲
10
−
3
M
⊙
yr
−
1
for
v
w
= 10
3
km s
−1
). AT2020mrf occurs in a galaxy with
M
*
∼ 10
8
M
⊙
and specific star formation rate ∼10
−10
yr
−1
, supporting the idea that AT2018cow-like events are preferentially hosted by dwarf galaxies. The X-ray luminosity of AT2020mrf is the highest among FBOTs. At 35–37 days, SRG/eROSITA detected luminous (
L
X
∼ 2 × 10
43
erg s
−1
; 0.3–10 keV) X-ray emission. The X-ray spectral shape (
f
ν
∝
ν
−0.8
) and erratic intraday variability are reminiscent of AT2018cow, but the luminosity is a factor of ∼20 greater than AT2018cow. At 328 days, Chandra detected it at
L
X
∼ 10
42
erg s
−1
, which is >200 times more luminous than AT2018cow and CSS161010. At the same time, the X-ray emission remains variable on the timescale of ∼1 day. We show that a central engine, probably a millisecond magnetar or an accreting black hole, is required to power the explosion. We predict the rates at which events like AT2018cow and AT2020mrf will be detected by SRG and Einstein Probe.
We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 0.1 mag hr−1) and luminous ( mag) transient. ...It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity ( ), the short rise time ( in g band), and the blue colors at peak ( ) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature ( ) spectra of a stripped-envelope SN. A retrospective search revealed luminous ( mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release , a limit on X-ray emission , and a limit on radio emission . Taken together, we find that the early ( ) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 ) at large radii ( ) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time ( ) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.
Simplified analytic methods are frequently used to model the light curves of supernovae and other energetic transients and to extract physical quantities, such as the ejecta mass and amount of ...radioactive heating. The applicability and quantitative accuracy of these models, however, have not been clearly delineated. Here we carry out a systematic study comparing certain analytic models to numerical radiation transport calculations. We show that the neglect of time-dependent diffusion limits the accuracy of common Arnett-like analytic models, and that the widely-applied Arnett's rule for inferring radioactive mass does not hold in general, with an error that increases for models with longer diffusion times or more centralized heating. We present new analytic relations that accurately relate the peak time and luminosity of an observed light curve to the physical ejecta and heating parameters. We further show that recombination and the spatial distribution of heating modify the peak of the light curve and that these effects can be accounted for by varying a single dimensionless parameter in the new relations. The results presented should be useful for estimating the physical properties of a wide variety of transient phenomena.
Purpose
177
Lu-Dotatate is an emerging treatment modality for patients with unresectable or metastatic well-differentiated NETs. This study examines survival predictors in patients who received
177
...Lu-Dotatate.
Methods
A retrospective single-center review was conducted, examining 47 individuals with progressive well-differentiated NETs treated with
177
Lu-Dotatate (four induction cycles of 5.5 GBq at 10-week intervals followed by eight maintenance cycles of 3.7 GBq at 6-month intervals).
Results
Median follow-up was 63.1 months with a median progression-free survival (PFS) of 34.1 months. However, median overall survival (OS) was not reached at the time of analysis. The presence of ≥ 5 bone metastases (hazard ratio HR 4.33;
p
= 0.015), non-gastroenteropancreatic (non-GEP) NETs (HR 3.22;
p
= 0.025) and development of interim ascites (HR 3.15;
p
= 0.047) independently predicted a worse OS. Patients with chromogranin A of ≥ 4 × upper limit of normal (ULN) had shorter OS (
p
< 0.001) and PFS (
p
= 0.004). Similarly, those with pre-existing ascites demonstrated a worse OS (
p
= 0.009) and PFS (
p
= 0.026). Liver metastases involving greater than 50% liver volume and the existence of unusual metastatic locations had a negative impact on OS (
p
= 0.033) and PFS (
p
= 0.026), respectively.
Conclusion
High burden of skeletal and hepatic metastases, non-GEP-NETs, chromogranin A of ≥ 4 × ULN, unusual metastatic sites, pre-existing and interim ascites are predictors of poor outcomes in patients treated with
177
Lu-Dotatate. These common indicators can be used for the risk stratification and identification of patients most likely to benefit from PRRT.
Trial registration
ClinicalTrials.gov identifier: NCT02236910, Retrospectively registered on September, 2014.
We present AT2020mrf (SRGe J154754.2\(+\)443907), an extra-galactic (\(z=0.1353\)) fast blue optical transient (FBOT) with a rise time of \(t_{g,\rm rise}=3.7\) days and a peak luminosity of ...\(M_{g,\rm peak}=-20.0\). Its optical spectrum around peak shows a broad (\(v\sim0.1c\)) emission feature on a blue continuum (\(T\sim2\times10^4\) K), which bears a striking resemblance to AT2018cow. Its bright radio emission (\(\nu L_\nu = 1.2\times 10^{39}\,{\rm erg\,s^{-1}}\); \(\nu_{\rm rest}= 7.4\) GHz; 261 days) is similar to four other AT2018cow-like events, and can be explained by synchrotron radiation from the interaction between a sub-relativistic (\(\gtrsim0.07\)-\(0.08c\)) forward shock and a dense environment (\(\dot M \lesssim 10^{-3}\,M_\odot \,{\rm yr^{-1}}\) for \(v_{\rm w}=10^3\,{\rm km\,s^{-1}}\)). AT2020mrf occurs in a galaxy with \(M_\ast \sim 10^8\,M_\odot\) and specific star formation rate \(\sim 10^{-10}\, {\rm yr^{-1}}\), supporting the idea that AT2018cow-like events are preferentially hosted by dwarf galaxies. The X-ray luminosity of AT2020mrf is the highest among FBOTs. At 35-37 days, SRG/eROSITA detected luminous (\(L_{\rm X}\sim 2\times 10^{43}\,{\rm erg\,s^{-1}}\); 0.3-10 keV) X-ray emission. The X-ray spectral shape (\(f_\nu \propto \nu^{-0.8}\)) and erratic intraday variability are reminiscent of AT2018cow, but the luminosity is a factor of \(\sim20\) greater than AT2018cow. At 328 days, Chandra detected it at \(L_{\rm X}\sim10^{42}\,{\rm erg\,s^{-1}}\), which is \(>200\) times more luminous than AT2018cow and CSS161010. At the same time, the X-ray emission remains variable on the timescale of \(\sim1\) day. We show that a central engine, probably a millisecond magnetar or an accreting black hole, is required to power the explosion. We predict the rates at which events like AT2018cow and AT2020mrf will be detected by SRG and Einstein Probe.
This work demonstrates the design, fabrication, packaging, characterization, and functionality of an electrically and fluidically active three-dimensional micro-electrode array (3D MEA) for use with ...neuronal cell cultures. The successful function of the device implies that this basic concept-construction of a 3D array with a layered approach-can be utilized as the basis for a new family of neural electrode arrays. The 3D MEA prototype consists of a stack of individually patterned thin films that form a cell chamber conducive to maintaining and recording the electrical activity of a long-term three-dimensional network of rat cortical neurons. Silicon electrode layers contain a polymer grid for neural branching, growth, and network formation. Along the walls of these electrode layers lie exposed gold electrodes which permit recording and stimulation of the neuronal electrical activity. Silicone elastomer micro-fluidic layers provide a means for loading dissociated neurons into the structure and serve as the artificial vasculature for nutrient supply and aeration. The fluidic layers also serve as insulation for the micro-electrodes. Cells have been shown to survive in the 3D MEA for up to 28 days, with spontaneous and evoked electrical recordings performed in that time. The micro-fluidic capability was demonstrated by flowing in the drug tetrotodoxin to influence the activity of the culture.
Peptide receptor radionuclide therapy (PRRT) has been recently established as a treatment option for progressive gastro-entero-pancreatic neuroendocrine tumors (NETs) including four 200 mCi induction ...cycles. The purpose of this phase 2 trial is to expand use of PRRT to different types of NETs with the application of dose adjustment and evaluate value of maintenance therapy in patients who had disease control on induction therapy. Forty-seven PRRT naïve NET patients with different primary origin received 177Lu-DOTATATE induction therapy, ranging from 75 to 150 mCi per cycle, based on patients’ clinical status such as liver and renal function, extent of metastases, and previous therapies. Thirty-four patients underwent additional maintenance therapy (50–100 mCi per cycle) following induction course until they developed disease progression. The estimated median progression-free survival (PFS) was 36.1 months. The median PFS in our MNET subgroup was 47.7 months, which is markedly longer than NETTER-1 trial with median PFS of 28.4 months. The median PFS was significantly longer in patients who received PRRT as first-line treatment after disease progression on somatostatin analogs compared to patients who received other therapies first (p-value = 0.04). The total disease response rate (DRR) and disease control rate (DCR) was 32% and 85% based on RECIST 1.1 and 45% and 83% based on Choi criteria. This trial demonstrates longer PFS with the addition of low dose maintenance therapy to induction therapy compared to NETTER-1 trial that only included induction therapy. Also, we observed considerable efficacy of PRRT in various types of advanced NETs.
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