90 research outputs found
Massive stars exploding in a He-rich circumstellar medium - VII. The metamorphosis of ASASSN-15ed from a narrow line Type Ibn to a normal Type Ib Supernova
We present the results of the spectroscopic and photometric monitoring campaign of ASASSN-15ed. The transient was discovered quite young by the All Sky Automated Survey for SuperNovae (ASAS-SN) survey. Amateur astronomers allowed us to sample the photometric SN evolution around maximum light, which we estimate to have occurred on JD = 2457087.4 ± 0.6 in the r band. Its apparent r-band magnitude at maximum was r = 16.91 ± 0.10, providing an absolute magnitude Mr â â20.04 ± 0.20, which is slightly more luminous than the typical magnitudes estimated for Type Ibn SNe. The post-peak evolution was well monitored, and the decline rate (being in most bands around 0.1 mag dâ1 during the first 25 d after maximum) is marginally slower than the average decline rates of SNe Ibn during the same time interval. The object was initially classified as a Type Ibn SN because early-time spectra were characterized by a blue continuum with superimposed narrow P-Cygni lines of HeâI, suggesting the presence of a slowly moving (1200â1500 km sâ1), He-rich circumstellar medium. Later on, broad P-Cygni HeâI lines became prominent. The inferred velocities, as measured from the minimum of the broad absorption components, were between 6000 and 7000 km sâ1. As we attribute these broad features to the SN ejecta, this is the first time we have observed the transition of a Type Ibn SN to a Type Ib SN
2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation: executive summary.
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The influence of seasonality on fish life stages and residence in surf zones: a case of study in a tropical region
A methodology for simultaneous retrieval of ice and liquid water cloud properties. Part I: Information content and case study
International audienceThis article presents a novel methodology dedicated to retrieving the optical and microphysical properties of ice and liquid water clouds simultaneously. An optimal estimation method is used to retrieve the ice water path of one iceâcloud layer and the optical thickness and droplet effective radius of up to two liquidâwater cloud layers, along with rigorous uncertainties. In order to perform the retrievals, radiometric measurements in five channels ranging from the visible to the thermal infrared are utilized. The position of cloud layers is currently provided by lidar information, which narrows the retrievals to its track. In the first part of this article, theoretical information content analyses are performed under different atmospheric conditions, over an oceanic surface. This type of analysis quantifies prior to the retrievals the amount of information that should be available regarding each parameter to be retrieved and helps to identify which set of channels provides this information. It is observed that strong information can be expected for retrieving each parameter in doubleâlayer cases, while yet stronger limitations appear in tripleâlayer cases. In the second part of this article, our methodology is applied to a case study. In agreement with a priori expectations, accurate retrievals of ice and liquid cloud properties are obtained. These results are later compared with the products of a singleâlayer retrieval method, CloudâAerosol Lidar with Orthogonal Polarization (CALIOP) operational products and in situ estimates. We show that a much better consistency with the latter two is found when retrieving the properties of each layer simultaneously. However, further statistical analyses and comparisons with various operational products should be undertaken for validation of the methodology. Such results will be presented in the second part of this study
A methodology for simultaneous retrieval of ice and liquid water cloud properties. Part I: Information content and case study
Evaluation of branched DNA signal amplification for the detection of hepatitis C virus RNA
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