Hasil untuk "astro-ph.HE"

Hui Yang, Jeremy Hare, Oleg Kargaltsev et al.

The rapid increase in serendipitous X-ray source detections requires the development of novel approaches to efficiently explore the nature of X-ray sources. If even a fraction of these sources could be reliably classified, it would enable population studies for various astrophysical source types on a much larger scale than currently possible. Classification of large numbers of sources from multiple classes characterized by multiple properties (features) must be done automatically and supervised machine learning (ML) seems to provide the only feasible approach. We perform classification of Chandra Source Catalog version 2.0 (CSCv2) sources to explore the potential of the ML approach and identify various biases, limitations, and bottlenecks that present themselves in these kinds of studies. We establish the framework and present a flexible and expandable Python pipeline, which can be used and improved by others. We also release the training data set of 2941 X-ray sources with confidently established classes. In addition to providing probabilistic classifications of 66,369 CSCv2 sources (21% of the entire CSCv2 catalog), we perform several narrower-focused case studies (high-mass X-ray binary candidates and X-ray sources within the extent of the H.E.S.S. TeV sources) to demonstrate some possible applications of our ML approach. We also discuss future possible modifications of the presented pipeline, which are expected to lead to substantial improvements in classification confidences.

Tyler Parsotan, Davide Lazzati

Although Gamma Ray Bursts (GRBs) have been detected for many decades, the lack of knowledge regarding the radiation mechanism that produces the energetic flash of radiation, or prompt emission, from these events has prevented the full use of GRBs as probes of high energy astrophysical processes. While there are multiple models that attempt to describe the prompt emission, each model can be tuned to account for observed GRB characteristics in the gamma and X-ray energy bands. One energy range that has not been fully explored for the purpose of prompt emission model comparison is that of the optical band, especially with regards to polarization. Here, we use an improved MCRaT code to calculate the expected photospheric optical and gamma-ray polarization signatures ($Π_\mathrm{opt}$ and $Π_γ$, respectively) from a set of two relativistic hydrodynamic long GRB simulations, which emulate a constant and variable jet. We find that time resolved $Π_\mathrm{opt}$ can be large ($\sim 75\%$) while time-integrated $Π_\mathrm{opt}$ can be smaller due to integration over the asymmetries in the GRB jet where optical photons originate; $Π_γ$ follows a similar evolution as $Π_\mathrm{opt}$ with smaller polarization degrees. We also show that $Π_\mathrm{opt}$ and $Π_γ$ agree well with observations in each energy range. Additionally, we make predictions for the expected polarization of GRBs based on their location within the Yonetoku relationship. While improvements can be made to our analyses and predictions, they exhibit the insight that global radiative transfer simulations of GRB jets can provide with respect to current and future observations.

Tyler Parsotan, Davide Lazzati

A complete understanding of Gamma Ray Bursts (GRBs) has been difficult to achieve due to our incomplete knowledge of the radiation mechanism that is responsible for producing the prompt emission. This emission, which is detected in the first tens of seconds of the GRB, is typically dominated by hard X-ray and gamma ray photons although, there have also been a few dozen prompt optical detections. These optical detections have the potential to discriminate between plausible prompt emission models, such as the photospheric and synchrotron shock models. In this work we use an improved MCRaT code, which includes cyclo-synchrotron emission and absorption, to conduct radiative transfer calculations from optical to gamma ray energies under the photospheric model. The calculations are conducted using a set of two dimensional relativistic hydrodynamic long GRB jet simulations, consisting of a constant and variable jet. We predict the correlations between the optical and gamma ray light curves as functions of observer angle and jet variability and find that there should be extremely dim optical prompt precursors for large viewing angles. Additionally, the detected optical emission originates from dense regions of the outflow such as shock interfaces and the jet-cocoon interface. Our results also show that the photospheric model is not able to account for the current set of optical prompt detections that have been made and additional radiative mechanisms are needed to explain these prompt optical observations. These findings show the importance of conducting global radiative transfer simulations using hydrodynamically calculated jet structures.

E. Troost, U. Nestle, P. Putora et al.

M. Trombetta, A. Dragun, N. Mayr et al.

PURPOSE To develop a summary of recommendations regarding locoregional management of patients with breast cancer and germline mutations in breast cancer susceptibility genes based on the American Society of Clinical Oncology/American Society for Radiation Oncology/Society of Surgical Oncology Guideline on Management of Hereditary Breast Cancer. METHODS The American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology convened an expert panel to develop recommendations based on a systematic review of the literature and a formal consensus process. A total of 58 articles met the eligibility criteria and formed the evidentiary basis for the locoregional therapy recommendations. Additionally, 6 randomized controlled trials of systemic therapy also met eligibility criteria. RESULTS A joint evidence-based guideline was developed by a multidisciplinary panel, which has been separately published. From this guideline, the radiation-oncologist authors of the panel extracted pertinent surgical and radiation-specific recommendations of findings that are hereby presented. CONCLUSIONS Patients with newly diagnosed breast cancer and BRCA1/2 mutations may be considered for breast conserving therapy (BCT), expecting similar rates of local control of the index cancer as noncarriers. The significant risk of contralateral breast cancer in these women (especially younger women), coupled with the higher risk of new cancers in the ipsilateral breast, warrant discussion of bilateral mastectomy. For women with mutations in BRCA1/2 or moderate-penetrance genes who are eligible for mastectomy, nipple-sparing mastectomy is a reasonable approach. There is no evidence of increased toxicity or contralateral breast cancer events from radiation exposure in BRCA1/2 carriers. Patients with mutations in moderate-risk genes should be offered BCT as one choice after appropriate counseling. Radiation therapy should not be withheld in ATM carriers if BCT is planned. For patients with germline TP53 mutations, mastectomy is advised and radiation therapy is contraindicated except for those with a significant risk of locoregional recurrence.

M. Hurwitz, J. Buscombe, H. Jacene et al.

Aim/Objectives/Background: The goal of therapy with unsealed radiopharmaceutical sources is to provide either cure or significant prolongation of disease-specific survival, and effective reduction and/or prevention of adverse disease-related symptoms or untoward events while minimizing treatment-associated side effects and complications. Radium-223 dichloride (radium-223) is an alpha particle–emitting isotope used for targeted bone therapy. This practice parameter is intended to guide appropriately trained and licensed physicians performing therapy with radium-223. Such therapy requires close cooperation and communication between the physicians who are responsible for the clinical management of the patient and those who administer radiopharmaceutical therapy and manage the attendant side effects. Adherence to this parameter should help to maximize the efficacious use of radium-223, maintain safe conditions, and ensure compliance with applicable regulations. Methods: This practice parameter was developed according to the process described on the American College of Radiology (ACR) website (“The Process for Developing ACR Practice Parameters and Technical Standards,” www.acr.org/ClinicalResources/Practice-Parameters-and-Technical-Standards) by the Committee on Practice Parameters of the ACR Commission on Radiation Oncology in collaboration with the American College of Nuclear Medicine (ACNM), the American Society for Radiation Oncology (ASTRO), and the Society of Nuclear Medicine and Molecular Imaging (SNMMI). All these societies contributed to the development of the practice parameter and approved the final document. Results: This practice parameter addresses the many factors which contribute to appropriate, safe, and effective clinical use of radium-223. Topics addressed include qualifications and responsibilities of personnel, specifications of patient examination and treatment; documentation, radiation safety, quality control/improvement, infection control, and patient education. Conclusions: This practice parameter is intended as a tool to guide clinical use of radium-223 with the goal of facilitating safe and effective medical care based on current knowledge, available resources and patient needs. The sole purpose of this document is to assist practitioners in achieving this objective.

H. Shih, R. Rengan, S. Apisarnthanarax et al.

Aim/Objectives/Background: The American College of Radiology (ACR) and the American Society for Radiation Oncology (ASTRO) have jointly developed the following practice parameter for proton beam radiation therapy. Proton radiotherapy is the application of a high-energy proton beam to a patient in a clinical setting with therapeutic intent. Proton radiotherapy may permit improved therapeutic ratios with lower doses to sensitive normal structures and greater dose to target tumor tissues. Methods: A literature search was performed to identify published articles regarding clinical outcomes, reviews, quality assurance methodologies, and guidelines and standards for proton radiation therapy. Selected articles are referenced in the text. The following recommendations are based on firsthand experiences of multiple clinical authorities who employ proton therapy and have been peer reviewed by experts at different practicing institutions. Results: This practice parameter is developed to serve as a tool in the appropriate application of this evolving technology in the care of cancer patients or other patients with conditions where radiation therapy is indicated. It addresses clinical implementation of proton radiation therapy, including personnel qualifications, quality assurance standards, indications, and suggested documentation. Conclusions: This practice parameter is a tool to guide technical use of proton therapy and does not assess the relative clinical indication of proton radiotherapy when compared with other forms of radiotherapy, but to focus on the best practices required to deliver proton therapy safely and effectively, when clinically indicated. Costs of proton treatments are high, and the economic costs of proton radiotherapy may also need to be considered.

D. Slater

Diego F. Torres, Shuang-Nan Zhang

Insight-HXMT is the first Chinese X-ray astronomical mission, launched successfully on June 15, 2017, from China's Jiuquan Satellite Launch Center. Insight-HXMT was designed to have a broad energy coverage in X-rays, from 1-250 keV, with excellent timing and adequate energy resolution at soft X-rays, and the largest effective area at hard X-rays. Here, we present a collection of papers of the Journal of High Energy Astrophysics on the Early Results of China's 1st X-ray Astronomy Satellite Insight-HXMT. These papers cover the in-orbit performance, the background model, and all calibration results, together with several first results on observations of binaries and details on the Galactic plane survey.

H. Ji, A. Alt, S. Antiochos et al.

This white paper summarizes major scientific challenges and opportunities in understanding magnetic reconnection and related explosive phenomena as a fundamental plasma process.

C. Joblin, G. Wenzel, S. R. Castillo et al.

Polycyclic aromatic hydrocarbons (PAHs) are key species in astrophysical environments in which vacuum ultraviolet (VUV) photons are present, such as star-forming regions. The interaction with these VUV photons governs the physical and chemical evolution of PAHs. Models show that only large species can survive. However, the actual molecular properties of large PAHs are poorly characterized and the ones included in models are only an extrapolation of the properties of small and medium-sized species. We discuss here experiments performed on trapped ions including some at the SOLEIL VUV beam line DESIRS. We focus on the case of the large dicoronylene cation, C48H20+ , and compare its behavior under VUV processing with that of smaller species. We suggest that C2 H2 is not a relevant channel in the fragmentation of large PAHs. Ionization is found to largely dominate fragmentation. In addition, we report evidence for a hydrogen dissociation channel through excited electronic states. Although this channel is minor, it is already effective below 13.6 eV and can significantly influence the stability of astro-PAHs. We emphasize that the competition between ionization and dissociation in large PAHs should be further evaluated for their use in astrophysical models.

Dawit Tegbaru, Lisa C. Braverman, A. Zietman et al.

Transparency, openness, and reproducibility are important characteristics in scientific publishing. Although many researchers embrace these characteristics, data sharing has yet to become common practice. Nevertheless, data sharing is becoming an increasingly important topic among societies, publishers, researchers, patient advocates, and funders, especially as it pertains to data from clinical trials. In response, ASTRO developed a data policy and guide to best practices for authors submitting to its journals. ASTRO's data sharing policy is that authors should indicate, in data availability statements, if the data are being shared and if so, how the data may be accessed.

M. Roach, T. Thomas, A. Paravati et al.

PURPOSE Insurance payers in the United States vary in the indications for which they consider stereotactic body radiation therapy (SBRT) "medically necessary." We compared changes in policies after the last update to the American Society for Radiation Oncology's (ASTRO) SBRT model policy. METHODS AND MATERIALS We identified 77 payers with SBRT policies in 2015 from a policy aggregator, as well as 4 national benefits managers (NBMs). Of these, 65 payers and 3 NBMs had publicly available updates since 2015. For each of the indications in ASTRO's model policy, we calculated the proportion of payers that considered SBRT medically necessary. We used Fisher's exact test to compare these proportions between 2015 and now, between policies updated in the past 12 months and those updated less often, and between national and regional payers currently. RESULTS Payers consider SBRT medically necessary most often for primary lung cancer (97%), reirradiation to the spine (91%), prostate cancer (68%), primary liver cancer (66%), and spinal metastases with radioresistant histologies (66%). Policies have become more aligned with ASTRO's model policy over time. National payers and NBMs cover indications in higher proportions than regional payers. CONCLUSIONS Although there have been improvements over time, more work is needed to align payer policies with ASTRO's model SBRT policy, especially at the regional level.

B. S. Sathyaprakash, Alessandra Buonanno, Luis Lehner et al.

Future gravitational-wave observations will enable unprecedented and unique science in extreme gravity and fundamental physics answering questions about the nature of dynamical spacetimes, the nature of dark matter and the nature of compact objects.

I. H. Park, K. -Y. Choi, J. Hwang et al.

We propose a new method to detect gravitational waves, based on spatial coherence interferometry with stellar light, as opposed to the conventional temporal coherence interferometry with laser sources. The proposed method detects gravitational waves by using two coherent beams of light from a single distant star measured at separate space-based detectors with a long baseline. This method can be applied to either the amplitude or intensity interferometry. This experiment allows for the search of gravitational waves in the lower frequency range of $10^{-6}$ to $10^{-4}$ Hz. In this work, we present the detection sensitivity of the proposed stellar interferometer by taking the detector response and shot and acceleration noises into account. Furthermore, the proposed experimental setup is capable of searching for primordial black holes and studying the size of the target neutron star, which are also discussed in the paper.

Takaaki Tanaka, H. Uchida, H. Nakajima et al.

Abstract. The Soft X-ray Imager (SXI) is an imaging spectrometer using charge-coupled devices (CCDs) aboard the Hitomi x-ray observatory. The SXI sensor has four CCDs with an imaging area size of 31  mm×31  mm arranged in a 2×2 array. Combined with the x-ray mirror, the Soft X-ray Telescope, the SXI detects x-rays between 0.4 and 12 keV and covers a 38′×38′ field of view. The CCDs are P-channel fully depleted, back-illumination type with a depletion layer thickness of 200  μm. Low operation temperature down to −120°C as well as charge injection is employed to reduce the charge transfer inefficiency (CTI) of the CCDs. The functionality and performance of the SXI are verified in on-ground tests. The energy resolution measured is 161 to 170 eV in full width at half maximum for 5.9-keV x-rays. In the tests, we found that the CTI of some regions is significantly higher. A method is developed to properly treat the position-dependent CTI. Another problem we found is pinholes in the Al coating on the incident surface of the CCDs for optical light blocking. The Al thickness of the contamination blocking filter is increased to sufficiently block optical light.

M. Knoll, B. Kavanagh, M. Katz

In June 2017, the board of directors of the American Society of Radiation Oncology (ASTRO) revised and updated the organization’s strategic plan. The directors reiterated that the core purpose of the organization is to advance the field of radiation oncology, and the overarching vision is that the field should be a recognized leader in quality, innovation, and value in multidisciplinary cancer care. The strategic plan would be operationalized through 4 major areas of focus, the first of which was to “elevate the profile of the field” for the purpose of establishing radiation oncology as an equal partner in the field of cancer. One barometer of public exposure of the field of radiation oncology is the depth of penetration into social media, defined as tools for electronic communication. The aspirational goals of a national medical conference are to provide education, networking opportunities, and access to the latest technology for improving patient care. Professional medical societies have begun to explore how best to incorporate social media to augment these missions, and metrics of social media activity related to a society’s meetings might provide insights into the quantity of communications connecting attendees and other interested stakeholders in the general public. In the present report, we offer preliminary subjective and objective observations about the extent of the social media activity generated in association with the 2017 Annual Meeting of ASTRO and compare findings with prior ASTRO Annual Meetings and with the activity generated by selected other annual medical conferences.

Amanda Schulman, Jennifer A. Mirrielees, G. Leverson et al.

J. Boggio, T. Fremberg, D. Bodenmüller et al.

Ariyam Das, Sahil M. Gandhi, C. Zaniolo

The rise of the Internet of Things (IoT) and the recent focus on a gamut of 'Smart City' initiatives world-wide have pushed for new advances in data stream systems to (1) support complex analytics and evolving graph applications as continuous queries, and (2) deliver fast and scalable processing on large data streams. Unfortunately current continuous query languages (CQL) lack the features and constructs needed to support the more advanced applications. For example recursive queries are now part of SQL, Datalog, and other query languages, but they are not supported by most CQLs, a fact that caused a significant loss of expressive power, which is further aggravated by the limitation that only non-blocking queries can be supported. To overcome these limitations we have developed an a dvanced st ream r easo ning system ASTRO that builds on recent advances in supporting aggregates in recursive queries. In this demo, we will briefly elucidate the formal Streamlog semantics, which combined with the Pre-Mappability (PreM) concept, allows the declarative specification of many complex continuous queries, which are then efficiently executed in real-time by the portable ASTRO architecture. Using different case studies, we demonstrate (i) the ease-of-use, (ii) the expressive power and (iii) the robustness of our system, as compared to other state-of-the-art declarative CQL systems.