Context. The second Gaia data release (Gaia DR2) provides precise five-parameter astrometric data (positions, proper motions, and parallaxes) for an unprecedented number of sources (more than 1.3 billion, mostly stars). This new wealth of data will enable the undertaking of statistical analysis of many astrophysical problems that were previously infeasible for lack of reliable astrometry, and in particular because of the lack of parallaxes. However, the use of this wealth of astrometric data comes with a specific challenge: how can the astrophysical parameters of interest be properly inferred from these data? Aims. The main focus of this paper, but not the only focus, is the issue of the estimation of distances from parallaxes, possibly combined with other information. We start with a critical review of the methods traditionally used to obtain distances from parallaxes and their shortcomings. Then we provide guidelines on how to use parallaxes more efficiently to estimate distances by using Bayesian methods. In particular we also show that negative parallaxes, or parallaxes with relatively large uncertainties still contain valuable information. Finally, we provide examples that show more generally how to use astrometric data for parameter estimation, including the combination of proper motions and parallaxes and the handling of covariances in the uncertainties. Methods. The paper contains examples based on simulated Gaia data to illustrate the problems and the solutions proposed. Furthermore, the developments and methods proposed in the paper are linked to a set of tutorials included in the Gaia archive documentation that provide practical examples and a good starting point for the application of the recommendations to actual problems. In all cases the source code for the analysis methods is provided. Results. Our main recommendation is to always treat the derivation of (astro-)physical parameters from astrometric data, in particular when parallaxes are involved, as an inference problem which should preferably be handled with a full Bayesian approach. Conclusions. Gaia will provide fundamental data for many fields of astronomy. Further data releases will provide more data, and more precise data. Nevertheless, to fully use the potential it will always be necessary to pay careful attention to the statistical treatment of parallaxes and proper motions. The purpose of this paper is to help astronomers find the correct approach.
Menurut WHO (2017) kekerasan seksual didefenisikan sebagai setiap tindakan seksual, usaha melakukan tindakan seksual, komentar atau menyarankan untuk berperilaku seksual yang tidak disengaja ataupun sebaliknya, tindakan pelanggaran untuk melakukan hubungan seksual dengan paksaan kepada seseorang. Kekerasan seksual mengacu pada perilaku dimana seseorang mengontrol atau memanipulasi orang lain melalui kata-kata atau tindakan dan membuat mereka terlibat dalam perilaku seksual yang berbahaya. Semua informan korban adalah anak yang berusia dibawah 18 tahun dan mengalami kekerasan seksual. Kekerasan seksual pada anak yang dilakukan pelaku adalah pencabulan (pedofilia) sebanyak 4 orang dan kekerasan seksual dalam berpacaran sebanyak 2 orang. Hal ini dapat disebabkan oleh faktor internal maupun faktor eksternal, serta berdampak emosional dan fisik pada korban kekerasan seksual. Beberapa faktor lain, yaitu posisi anak yang dianggap lemah dan tidak berdaya, rendahnya moralitas masyarakat khusunya pelaku kekerasan seksual, kurangnya kesadaran dan partisipasi orangtua dalam mengantisipasi tindak kekerasan seksual pada anak, program edukasi dari pihak pemerintah yang sulit diakses masyarakat, dan masih banyak faktor lainnya. Kekerasan seksual yang terjadi di Indonesia dapat di minimalisasi dengan FGD (Focus Group Discussion) dan peningkatan peran kepolisian, maupun pihak-pihak yang berwenang. Berkaitan dengan teori gunung es, istilah ini cocok dijadikan metamorfosa kasus kekerasan seksual di Indonesia. Ibarat gunung es, kasus kekerasan seksual yang diketahui dan dilaporkan hanya terlihat sedikit atau pada puncaknya saja. Padahal ada banyak yang tak tampak dan tak terlapor. Dapat disimpulkan bahwa kekerasan seksual terjadi karena kurangnya pengawasan orangtua terhadap anak serta minimnya pengetahuan tentang seks, dan anggapan bahwa seks tabu di masyarakat.
A nucleossíntese primordial é o tema central deste artigo que descreve a evolução do universo desde a sua origem até os 3 primeiros minutos após o big bang. O universo é caracterizado como um caldeirão de partículas. À medida em que o universo se expande e a temperatura diminui, ocorre uma competição entre a criação e a aniquilação das partículas, levando à formação dos primeiros núcleos leves, como hidrogênio, deutério, trítio, lítio, berílio e boro. A formação destes núcleos de massas leves é apresentada sob o ponto de vista da Física Nuclear.
O objetivo deste artigo é descrever, de forma sucinta, o início da cosmologia moderna bem como destacar a contribuição fundamental de Friedmann no seu desenvolvimento.
Nesta nota, apresentamos brevemente os principais fatos da biografia de Alexander Friedmann, o matemático e físico russo que previu a expansão do Universo há cem anos. O papel desta previsão para a ciência moderna e para nossa imagem do mundo é discutido com uma ênfase na mudança radical em nossos conceitos básicos introduzidos pela previsão de Friedmann e sua confirmação experimental.
Este trabalho apresenta uma visão da Geofísica no que diz respeito à algumas manifestações físicas que trazem informações sobre a estrutura interna da Terra. Desta forma, são abordados alguns conceitos básicos sobre sismologia, o estudo das ondas elásticas liberadas por terremotos, geomagnetismo, o estudo do campo magnético gerado no interior da Terra, e gravimetria, a interpretação das anomalias gravimétricas produzidas pelas heterogeneidades nas estruturas internas da Terra.
We present the latest results of our ongoing multiplicity study of (Community) TESS Objects of Interest, using astro- and photometric data from the ESA-Gaia mission, to detect stellar companions of these stars and to characterize their properties. In total, 113 binary, 5 hierarchical triple star systems, as well as one quadruple system were detected among 585 targets surveyed, which are all located at distances closer than about 500pc around the Sun. As proven with their accurate Gaia EDR3 astrometry the companions and the targets are located at the same distance and share a common proper motion, as it is expected for components of gravitationally bound stellar systems. The companions exhibit masses in the range between about 0.09$M_\odot$ and 4.5$M_\odot$ and are most frequently found in the mass range between 0.15 and 0.6$M_{\odot}$. The companions are separated from the targets by about 120 up to 9500au and their frequency is the highest and constant within about 500au while it continually decreases for larger separations. Beside mainly early to mid M dwarfs, also 5 white dwarf companions were identified in this survey, whose true nature was revealed by their photometric properties.
Searches for gravitational wave echoes in the aftermath of mergers and/or formation of astrophysical black holes have recently opened a novel and surprising window into the quantum nature of their horizons. Similar to astro- and helioseismology, study of the spectrum of quantum black holes provides a promising method to understand their inner structure, what we call $\textit{quantum black hole seismology}$. We provide a detailed numerical and analytic description of this spectrum in terms of the properties of the Kerr spacetime and quantum black hole horizons, showing that it drastically differs from their classical counterparts. Our most significant findings are the following: (1) If the temperature of quantum black hole is $\lesssim 2 \times$ Hawking temperature, then it will not suffer from ergoregion instability (although the bound is looser at smaller spins). (2) We find how quantum black hole spectra pinpoint the microscopic properties of quantum structure. For example, the detailed spacing of spectral lines can distinguish whether quantum effects appear through compactness (i.e., exotic compact objects) or frequency (i.e., modified dispersion relation). (3) We find out that the overtone quasinormal modes may strongly enhance the amplitude of echo in the low-frequency region. (4) We show the invariance of the spectrum under the generalized Darboux transformation of linear perturbations, showing that it is a genuine covariant observable.
PURPOSE The American Society for Radiation Oncology (ASTRO) annual meeting is the most prominent international conference in radiation oncology. It represents one of the greatest time efforts for ASTRO volunteers, and the quality of the annual meeting is a high priority. Measures of diversity have been linked with quality of academic efforts. We conducted a study of gender diversity of the ASTRO invited speakers, focusing on speaker and panel characteristics, and associations of these characteristics with measures of audience satisfaction. METHODS AND MATERIALS We created a database of all invited speakers (n = 1499 cumulative speaking positions, n = 725 individual speakers) and panels (n = 381) in the ASTRO annual meetings from 2012 to 2016. Speaker characteristics were acquired using publically available online search tools (including Scopus for citation metrics). SAS software was used for statistical analysis. RESULTS Of the 725 individual speakers, 27% were women. Men had higher median Hirsch index (H-index) (27 vs 20, P 50% female (metric: request for session repeat). Female conveners were associated with greater panel gender diversity. CONCLUSION Given observations that women constitute a minority of invited speakers and that greater female representation correlates with a key panel success metric, efforts to ensure greater diversity of those included in AM speaking invitations merit serious attention.
The CosmicWatch Desktop Muon Detector is a self-contained, hand-held cosmic ray muon detector that is valuable for astro/particle physics research applications and outreach. The material cost of each detector is under $100 and it takes a novice student approximately four hours to build their first detector. The detectors are powered via a USB connection and the data can either be recorded directly to a computer or to a microSD card. Arduino- and Python-based software is provided to operate the detector and an online application to plot the data in real-time. In this paper, we describe the various design features, evaluate the performance, and illustrate the detectors capabilities by providing several example measurements.
Abstract. The soft x-ray spectrometer (SXS) was a cryogenic high-resolution x-ray spectrometer onboard the Hitomi (ASTRO-H) satellite that achieved energy resolution of 5 eV at 6 keV, by operating the detector array at 50 mK using an adiabatic demagnetization refrigerator (ADR). The cooling chain from room temperature to the ADR heat sink was composed of two-stage Stirling cryocoolers, a He4 Joule–Thomson cryocooler, and superfluid liquid helium and was installed in a dewar. It was designed to achieve a helium lifetime of more than 3 years with a minimum of 30 L. The satellite was launched on February 17, 2016, and the SXS worked perfectly in orbit, until March 26 when the satellite lost its function. It was demonstrated that the heat load on the helium tank was about 0.7 mW, which would have satisfied the lifetime requirement. This paper describes the design, results of ground performance tests, prelaunch operations, and initial operation and performance in orbit of the flight dewar and the cryocoolers.
In this paper, we discuss the characteristics and operation of Astro Space Center (ASC) software FX correlator that is an important component of space–ground interferometer for Radioastron project. This project performs joint observations of compact radio sources using 10m space radio telescope (SRT) together with ground radio telescopes at 92, 18, 6 and 1.3 cm wavelengths. In this paper, we describe the main features of space–ground VLBI data processing of Radioastron project using ASC correlator. Quality of implemented fringe search procedure provides positive results without significant losses in correlated amplitude. ASC Correlator has a computational power close to real time operation. The correlator has a number of processing modes: “Continuum”, “Spectral Line”, “Pulsars”, “Giant Pulses”,“Coherent”. Special attention is paid to peculiarities of Radioastron space–ground VLBI data processing. The algorithms of time delay and delay rate calculation are also discussed, which is a matter of principle for data correlation of space–ground interferometers. During five years of Radioastron SRT successful operation, ASC correlator showed high potential of satisfying steady growing needs of current and future ground and space VLBI science. Results of ASC software correlator operation are demonstrated.
This paper describes how semantic indexing can help to generate a contextual overview of topics and visually compare clusters of articles. The method was originally developed for an innovative information exploration tool, called Ariadne, which operates on bibliographic databases with tens of millions of records (Koopman et al. in Proceedings of the 33rd Annual ACM Conference Extended Abstracts on Human Factors in Computing Systems. doi:10.1145/2702613.2732781, 2015b). In this paper, the method behind Ariadne is further developed and applied to the research question of the special issue “Same data, different results”—the better understanding of topic (re-)construction by different bibliometric approaches. For the case of the Astro dataset of 111,616 articles in astronomy and astrophysics, a new instantiation of the interactive exploring tool, LittleAriadne, has been created. This paper contributes to the overall challenge to delineate and define topics in two different ways. First, we produce two clustering solutions based on vector representations of articles in a lexical space. These vectors are built on semantic indexing of entities associated with those articles. Second, we discuss how LittleAriadne can be used to browse through the network of topical terms, authors, journals, citations and various cluster solutions of the Astro dataset. More specifically, we treat the assignment of an article to the different clustering solutions as an additional element of its bibliographic record. Keeping the principle of semantic indexing on the level of such an extended list of entities of the bibliographic record, LittleAriadne in turn provides a visualization of the context of a specific clustering solution. It also conveys the similarity of article clusters produced by different algorithms, hence representing a complementary approach to other possible means of comparison.