ABSTRACT We present a Hubble Space Telescope Space Telescope Imaging Spectrograph spectrum of ASASSN-14li, the first rest-frame ultraviolet (UV) spectrum of a tidal disruption flare (TDF). The ...underlying continuum is well fit by a blackbody with K, an order of magnitude smaller than the temperature inferred from X-ray spectra (and significantly more precise than previous efforts based on optical and near-UV photometry). Superimposed on this blue continuum, we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (∼2000-8000 km s−1) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by Δv = −(250-400) km s−1. Due both to this velocity offset and the lack of common low-ionization features (Mg ii, Fe ii), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N iii, N iv, and He ii are quite prominent, while the common quasar emission lines of C iii and Mg ii are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and "N-rich" quasars.
Gas accretion onto some massive black holes (MBHs) at the centers of galaxies actively powers luminous emission, but most MBHs are considered dormant. Occasionally, a star passing too near an MBH is ...torn apart by gravitational forces, leading to a bright tidal disruption flare (TDF). Although the high-energy transient Sw 1644+57 initially displayed none of the theoretically anticipated (nor previously observed) TDF characteristics, we show that observations suggest a sudden accretion event onto a central MBH of mass about 10 6 to 10 7 solar masses. There is evidence for a mildly relativistic outflow, jet collimation, and a spectrum characterized by synchrotron and inverse Compton processes; this leads to a natural analogy of Sw 1644+57 to a temporary smaller-scale blazar.
We present multiwavelength modeling of the afterglow from the long γ-ray burst (GRB) 160625B using Markov Chain Monte Carlo techniques of the afterglowpy Python package. GRB 160625B is an extremely ...bright burst with a rich set of observations spanning from radio to γ-ray frequencies. These observations range from ∼0.1 days to >1000 days, thus making this event extremely well suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best-fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7 -5.3 ) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 1 26 to 3 90, depending on jet-shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation a fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of ∼1053 erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity; thus, this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment.
Purpose
To support the wellbeing of both patients and their families, our aim was to investigate the satisfaction of non-COVID in- and out-patients regarding safety measures implemented at our ...radiology unit of a transplant institute against COVID infection.
Materials and Methods
Over a five-month period, adult patients’ feedback was obtained by a questionnaire on the fear of contracting COVID-19 during a radiology examination, the perceived delay in treatment, and the following safety measures implemented: modified schedules to limit the number of patients in the waiting area and to maximize social distancing; assistance by staff when visitors were not admitted; cleaning and disinfection of machines; mask wearing and hand hygiene of staff; and staff advice on hand hygiene and infection control precautions.
Results
Over a five-month period, our preliminary results (387 patients) showed general patient satisfaction (99.1%) with safety measures applied at our radiology unit. Patients were satisfied with distancing and assistance by staff (100%), cleaning and disinfection (91%), mask wearing and hand hygiene of the staff (97%), and staff advice (94%). There was some criticism of the perceived delay in treatment (7.3%) and in the scheduling of the waiting list (5.4%), with 5.4% fearing contracting the virus. Patients’ awareness of safety measures and confidence in the hospital preparedness policy was perceived by all interviewers, and 100% appreciated being questioned.
Conclusion
The feedback given by the non-COVID patient helps to measure the quality in health care, to improve the quality service, and to protect and satisfy more vulnerable patients, also during the COVID-19 pandemic.
Radionuclides are unstable isotopes that mainly emit alpha (α), beta (β) or gamma (γ) radiation through radiation decay. Therefore, they are used in the biomedical field to label biomolecules or ...drugs for diagnostic imaging applications, such as positron emission tomography (PET) and/or single-photon emission computed tomography (SPECT). A growing field of research is the development of new radiopharmaceuticals for use in cancer treatments. Preclinical studies are the gold standard for translational research. Specifically, in vitro radiopharmaceutical studies are based on the use of radiopharmaceuticals directly on cells. To date, radiometric β- and γ-counters are the only tools able to assess a preclinical in vitro assay with the aim of estimating uptake, retention, and release parameters, including time- and dose-dependent cytotoxicity and kinetic parameters. This review has been designed for researchers, such as biologists and biotechnologists, who would like to approach the radiobiology field and conduct in vitro assays for cellular radioactivity evaluations using radiometric counters. To demonstrate the importance of in vitro radiopharmaceutical assays using radiometric counters with a view to radiogenomics, many studies based on 64Cu-, 68Ga-, 125I-, and 99mTc-labeled radiopharmaceuticals have been revised and summarized in this manuscript.
Recent studies have revealed a dynamic interplay between the galaxy ecosystem and circumgalactic medium (CGM). We investigate the CGM at high redshifts (z 2) by using bright afterglows of gamma-ray ...bursts (GRBs) as background sources. We compiled a sample of medium-resolution (Δv < 50 km s−1) and high signal-to-noise ratio (typical S/N ∼ 10) spectra from 27 GRB afterglows covering z ∼ 2-6, with six of them at z 4. We analyzed the high- and low-ionization absorption features within 400 km s−1 to extract the CGM and interstellar medium (ISM) kinematics. In the stacked spectra, high-ionization absorption profiles (e.g., C iv, Si iv) present significant absorption excess in their blue wings (v < −100 km s−1) relative to the red wings (v > 100 km s−1). The stronger blue wings in high-ionization species are indicative of the presence of ubiquitous warm outflows in the GRB hosts at high redshifts. We used simple toy models to kinematically distinguish the CGM and ISM absorption and estimate the CGM mass and outflow velocity. We find tentative evidence of the evolution of the CGM metal mass by ∼0.5 dex between two redshift bins, each spanning 1 Gyr, z1: 2-2.7 and z2: 2.7-5. By comparing with past studies, we find that over the course of evolution of present-day galaxies with M* > 1010 M , the ratio of C iv mass in the CGM to the stellar mass remains fairly uniform, with log(MC iv/M*) ∼ −4.5 within 0.5 dex from z ∼ 4 to z ∼ 0, suggesting CGM-galaxy coevolution.
Abstract
The current data acquisition rate of astronomical transient surveys and the promise for significantly higher rates in the next decade necessitate the development of novel approaches to ...analyze astronomical data sets and promptly detect objects of interest. The Deeper, Wider, Faster (DWF) program is a survey focused on the identification of fast-evolving transients, such as fast radio bursts, gamma-ray bursts, and supernova shock breakouts. It employs multifrequency simultaneous coverage of the same part of the sky over several orders of magnitude. Using the Dark Energy Camera mounted on the 4 m Blanco telescope, DWF captures a 20 s
g
-band exposure every minute, at a typical seeing of ∼1″ and an air mass of ∼1.5. These optical data are collected simultaneously with observations conducted over the entire electromagnetic spectrum—from radio to
γ
-rays—as well as cosmic-ray observations. In this paper, we present a novel real-time light-curve analysis algorithm, designed to detect transients in the DWF optical data; this algorithm functions independently from, or in conjunction with, image subtraction. We present a sample of fast transients detected by our algorithm, as well as a false-positive analysis. Our algorithm is customizable and can be tuned to be sensitive to transients evolving over different timescales and flux ranges.
GRBs as Probes of the IGM Cucchiara, Antonino; Totani, Tonomori; Tanvir, Nial
Space science reviews,
12/2016, Letnik:
202, Številka:
1-4
Journal Article
Recenzirano
Odprti dostop
Gamma-ray Bursts (GRBs) are the most powerful explosions known, capable of outshining the rest of gamma-ray sky during their short-lived prompt emission. Their cosmological nature makes them the best ...tool to explore the final stages in the lives of very massive stars up to the highest redshifts. Furthermore, studying the emission from their low-energy counterparts (optical and infrared) via rapid spectroscopy, we have been able to pin down the exact location of the most distant galaxies as well as placing stringent constraints on their host galaxies and intervening systems at low and high-redshift (e.g. metallicity and neutral hydrogen fraction). In fact, each GRB spectrum contains absorption features imprinted by metals in the host interstellar medium (ISM) as well as the intervening intergalactic medium (IGM) along the line of sight. In this chapter we summarize the progress made using a large dataset of GRB spectra in understanding the nature of both these absorbers and how GRBs can be used to study the early Universe, in particular to measure the neutral hydrogen fraction and the escape fraction of UV photons before and during the epoch of re-ionization.
Abstract Astronomical research is often made possible by the utilization of different resources that support members of the community in their research endeavors (e.g., telescopes access, or funds). ...Often, the entities that provide these resources establish a competitive process, which include the submission, by interested parties, of research proposals describing the research objectives and how the resources will be used to reach them. These proposals are evaluated by “ad hoc” panels of researchers, that provide a ranked list of the proposals based on their scientific relevance and other factors. This is also true for many NASA funding opportunities. In this article we present an open-sourced tool, the Expertise Finder , that simplifies the reviewers identification process. Expertise Finder provides NASA officials ways to scout prospective reviewers at small, less resourced, institutions that may have fewer opportunities to present and publish their research work with respect to colleagues at larger institutions.
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