| 1. |
- Ho, Anna Y. Q., et al.
(författare)
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SN 2020bvc : A Broad-line Type Ic Supernova with a Double-peaked Optical Light Curve and a Luminous X-Ray and Radio Counterpart
- 2020
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 902:1
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Tidskriftsartikel (refereegranskat)abstract
- We present optical, radio, and X-ray observations of SN 2020bvc (=ASASSN-20bs, ZTF 20aalxlis), a nearby (z = 0.0252; d.=.114Mpc) broad-line (BL) Type Ic supernova (SN) and the first double-peaked Ic-BL discovered without a gamma-ray burst (GRB) trigger. Our observations show that SN 2020bvc shares several properties in common with the Ic-BL SN 2006aj, which was associated with the low-luminosity gamma-ray burst (LLGRB) 060218. First, the 10 GHz radio luminosity (L-radio approximate to 10(37) erg s(-1)) is brighter than ordinary core-collapse SNe but fainter than LLGRB SNe such as SN 1998bw (associated with LLGRB 980425). We model our VLA observations (spanning 13-43 days) as synchrotron emission from a mildly relativistic (v greater than or similar to 0.3c) forward shock. Second, with Swift and Chandra, we detect X-ray emission (L-X approximate to 10(41) erg s(-1)) that is not naturally explained as inverse Compton emission or part of the same synchrotron spectrum as the radio emission. Third, high-cadence (6x night(-1)) data from the Zwicky Transient Facility (ZTF) show a double-peaked optical light curve, the first peak from shock cooling of extended low-mass material (mass M-e < 10(-2) M-circle dot at radius R-e > 10(12) cm) and the second peak from the radioactive decay of 56Ni. SN 2020bvc is the first double-peaked Ic-BL SN discovered without a GRB trigger, so it is noteworthy that it shows X-ray and radio emission similar to LLGRB SNe. For four of the five other nearby (z less than or similar to 0.05) Ic-BL SNe with ZTF high-cadence data, we rule out a first peak like that seen in SN 2006aj and SN 2020bvc, i.e., that lasts approximate to 1 day.and reaches a peak luminosity M approximate to -18. Follow-up X-ray and radio observations of Ic-BL SNe with well-sampled early optical light curves will establish whether double-peaked optical light curves are indeed predictive of LLGRB-like X-ray and radio emission.
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| 2. |
- Novotny, Susan A., et al.
(författare)
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Do Weightbearing Restrictions Cause Excess Weight Gain in Children With LEGG-Calve-Perthes Disease?
- 2023
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Ingår i: Journal of Pediatric Orthopaedics. - : Lippincott Williams & Wilkins. - 0271-6798 .- 1539-2570. ; 43:1, s. 31-36
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Tidskriftsartikel (refereegranskat)abstract
- Background: Restricted weight bearing is commonly prescribed in Legg-Calve-Perthes Disease (LCPD), raising concerns of causing overweight or obesity. This study utilizes prospectively collected data to address the following questions: (1) does body mass index (BMI) Z-score increase over the course of LCPD follow-up; (2) is having a BMI category of normal, overweight, or obese at baseline associated with BMI Z-score changes over the course of follow-up; and (3) is the duration of weight bearing restrictions (no restrictions, <3, 3 to <6, 6 to 9, or >9 mo) associated with BMI Z-score changes.Methods: Data of 130 children aged 5 to 12 years with unilateral early-stage LCPD were extracted from an international database. Nation-specific BMI Z-scores and percentile-based weight categories were determined, and the duration of follow-up and weight bearing restrictions were calculated. Longitudinal changes in BMI Z-scores were evaluated for the 3 study questions using mixed effects linear regression models with surgery as a covariate. Sensitivity analyses were used to determine the influence of socio-cultural background (USA vs. India) for each study question.Results: During the 35.5 +/- 15.9 months of follow-up, no statistically significant increase in BMI Z-scores was observed across the entire cohort, or following stratification by baseline weight categories or the duration of the weight bearing restriction. Sensitivity analyses indicated that patients in the USA had no change in their BMI Z-score. When stratified by weight categories, the normal weight of US children had a small increase in their BMI Z-score (0.005 per mo, 95% confidence interval: 0.0002, 0.009), but this was not seen in other BMI categories. The cohort of Indian children had a small but significant decrease in their BMI Z-score (-0.005/mo, 95% CI: -0.009, -0.0002). After stratification by weight categories, a small decrease of the BMI Z-score was observed only in the Indian overweight children (-0.016 per mo, 95% CI: -0.027, -0.005) and no other BMI category.Conclusions: Weightbearing restrictions over the course of follow-up for our cohort of children with early-stage LCPD were not associated with clinically meaningful increases of BMI Z-scores. Weight gain is multi-factorial and probably not caused by weight bearing restrictions alone.
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| 3. |
- Strotjohann, Nora L., et al.
(författare)
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Bright, Months-long Stellar Outbursts Announce the Explosion of Interaction-powered Supernovae
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 907:2
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Tidskriftsartikel (refereegranskat)abstract
- Interaction-powered supernovae (SNe) explode within an optically thick circumstellar medium (CSM) that could be ejected during eruptive events. To identify and characterize such pre-explosion outbursts, we produce forced-photometry light curves for 196 interacting SNe, mostly of Type IIn, detected by the Zwicky Transient Facility between early 2018 and 2020 June. Extensive tests demonstrate that we only expect a few false detections among the 70,000 analyzed pre-explosion images after applying quality cuts and bias corrections. We detect precursor eruptions prior to 18 Type IIn SNe and prior to the Type Ibn SN 2019uo. Precursors become brighter and more frequent in the last months before the SN and month-long outbursts brighter than magnitude -13 occur prior to 25% (5-69%, 95% confidence range) of all Type IIn SNe within the final three months before the explosion. With radiative energies of up to 10(49) erg, precursors could eject similar to 1 M of material. Nevertheless, SNe with detected precursors are not significantly more luminous than other SNe IIn, and the characteristic narrow hydrogen lines in their spectra typically originate from earlier, undetected mass-loss events. The long precursor durations require ongoing energy injection, and they could, for example, be powered by interaction or by a continuum-driven wind. Instabilities during the neon- and oxygen-burning phases are predicted to launch precursors in the final years to months before the explosion; however, the brightest precursor is 100 times more energetic than anticipated.
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