X-ray Localization of the Globular Cluster G1 with XMM-Newton

We present an accurate X-ray position of the massive globular cluster G1 by using XMM-Newton and the Hubble Space Telescope (HST). The X-ray emission of G1 has been detected recently with XMM-Newton. There are two possibilities for the origin of the X-ray emission. It can be either due to accretion of the central intermediate-mass black hole, or by ordinary low-mass X-ray binaries. The precise location of the X-ray emission might distinguish between these two scenarios. By refining the astrometry of the XMM-Newton and HST data, we reduced the XMM-Newton error circle to 1.5". Despite the smaller error circle, the precision is not sufficient to distinguish an intermediate-mass black hole and luminous low-mass X-ray binaries. This result, however, suggests that future Chandra observations may reveal the origin of the X-ray emission.Comment: 4 pages, 2 figures; accepted for publication in Ap

X-ray Spectral Signatures of the Photon Bubble Model for Ultraluminous X-ray Sources

The nature of ultraluminous X-ray sources in nearby galaxies is one of the major open questions in modern X-ray astrophysics. One possible explanation for these objects is an inhomogeneous, radiation dominated accretion disk around a $\sim 10 M_{\odot}$ black hole -- the so-called ``photon bubble'' model. While previous studies of this model have focused primarily on its radiation-hydrodynamics aspects, in this paper, we provide an analysis of its X-ray spectral (continuum and possible edge and line) characteristics. Compton reflection between high and low density regions in the disk may provide the key to distinguishing this model from others, such as accretion onto an intermediate mass black hole. We couple a Monte Carlo/Fokker-Planck radiation transport code with the XSTAR code for reflection to simulate the photon spectra produced in a photon bubble model for ULXs. We find that reflection components tend to be very weak and in most cases not observable, and make predictions for the shape of the high-energy Comptonizing spectra. In many cases the Comptonization dominates the spectra even down to $\sim$ a few keV. In one simulation, a \sim 9 \kev feature was found, which may be considered a signature of photon bubbles in ULXs; furthermore, we make predictions of high energy power-laws which may be observed by future instruments.Comment: Accepted for publication in the Astrophysical Journa

The dependence of the estimated luminosities of ULX on spectral models

Data from {\it Chandra} observations of thirty nearby galaxies were analyzed and 365 X-ray point sources were chosen whose spectra were not contaminated by excessive diffuse emission and not affected by photon pile up. The spectra of these sources were fitted using two spectral models (an absorbed power-law and a disk blackbody) to ascertain the dependence of estimated parameters on the spectral model used. It was found that the cumulative luminosity function depends on the choice of the spectral model, especially for luminosities $> 10^{40}$ ergs/s. In accordance with previous results, a large number ($\sim 80$) of the sources have luminosities $> 10^{39}$ ergs/s (Ultra-Luminous X-ray sources) with indistinguishable average spectral parameters (inner disk temperature $\sim 1$ keV and/or photon index $\Gamma \sim 2$) with those of the lower luminosities ones. After considering foreground stars and known background AGN,we identify four sources whose minimum luminosity exceed $10^{40}$ ergs/s, and call them Extremely Luminous X-ray sources (ELX). The spectra of these sources are in general better represented by the disk black body model than the power-law one. These ELX can be grouped into two distinct spectral classes. Two of them have an inner disk temperature of $< 0.5$ keV and hence are called ``supersoft'' ELX, while the other two have temperatures $\gtrsim 1.3$ keV and are called ``hard'' ELX. The estimated inner disk temperatures of the supersoft ELX are compatible with the hypothesis that they harbor intermediate size black holes, which are accreting at $\sim 0.5$ times their Eddington Luminosity. The radiative mechanism for hard ELX, seems to be Inverse Comptonization, which in contrast to standard black holes systems, is probably saturated.Comment: Accepted for publication in Astrophysical Journal. 9 pages. Complete long Tables 4 and 5 are given as tab4.tex and tab5.tex separatel

X-ray reflection in a sample of X-ray bright Ultraluminous X-ray sources

We apply a reflection-based model to the best available XMM-Newton spectra of X-ray bright UltraLuminous X-ray (ULX) sources (NGC 1313 X-1, NGC 1313 X-2, M 81 X-6, Holmberg IX X-1, NGC 5408 X-1 and Holmberg II X-1). A spectral drop is apparent in the data of all the sources at energies 6-7 keV. The drop is interpreted here in terms of relativistically-blurred ionized reflection from the accretion disk. A soft-excess is also detected from these sources (as usually found in the spectra of AGN), with emission from O K and Fe L, in the case of NGC 5408 X-1 and Holmberg II X-1, which can be understood as features arising from reflection of the disk. Remarkably, ionized disk reflection and the associated powerlaw continuum provide a good description of the broad-band spectrum, including the soft-excess. There is no requirement for thermal emission from the inner disk in the description of the spectra. The black holes of these systems must then be highly spinning, with a spin close to the maximum rate of a maximal spinning black hole. The results require the action of strong light bending in these sources. We suggest that they could be strongly accreting black holes in which most of the energy is extracted from the flow magnetically and released above the disc thereby avoiding the conventional Eddington limit.Comment: Accepted for publication in MNRA

"Everything about him was just perfect. And I fell in love instantly":Life and love in welcome to Night Vale

Despite, or even because of, its surreal and fantastical characters, Night Vale is an open and accepting place for most of its residents, and using the podcasts and the 2015 novel, this chapter explores Night Vale's ability to accept diversity. Focusing on representations of gender, sexuality, and disability, I show Night Vale to be an open-minded, progressive town, and that the podcast actively endorses attitudes of acceptance and understanding, not only through the actions of the characters affected by these issues, but by the actions of the inhabitants themselves, particularly radio host Cecil, and how they treat each other. © The Author(s) 2018

Searching for Massive Outflows in Holmberg IX X-1 and NGC 1313 X-1: The Iron K Band

We have analysed all the good quality XMM-Newton data publicly available for the bright ULXs Holmberg IX X-1 and NGC 1313 X-1, with the aim of searching for discrete emission or absorption features in the Fe K band that could provide observational evidence for the massive outflows predicted if these sources are accreting at substantially super-Eddington rates. We do not find statistically compelling evidence for any atomic lines, and the limits that are obtained have interesting consequences. Any features in the immediate Fe K energy band (6-7 keV) must have equivalent widths weaker than ~30 eV for Holmberg IX X-1, and weaker than ~50 eV for NGC 1313 X-1 (at 99 per cent confidence). In comparison to the sub-Eddington outflows observed in GRS 1915+105, which imprint iron absorption features with equivalent widths of ~30 eV, the limits obtained here appear quite stringent, particularly when Holmberg IX X-1 and NGC 1313 X-1 must be expelling at least 5-10 times as much material if they host black holes of similar masses. The difficulty in reconciling these observational limits with the presence of strong line-of-sight outflows suggests that either these sources are not launching such outflows, or that they must be directed away from our viewing angle.Comment: 11 pages, 5 figures, accepted for publication in MNRA

Multi-band study of NGC 7424 and its two newly-discovered ULXs

We have studied the face-on, barred spiral NGC 7424 (site of the rare Type IIb SN 2001ig) with Chandra, Gemini and the Australia Telescope Compact Array. After giving revised X-ray colours and luminosity of the supernova, here we focus on some other interesting sources in the galaxy: in particular, our serendipitous discovery of two ultraluminous X-ray sources (ULXs). The brighter one (~ 10^{40} erg/s) has a power-law-like spectrum with photon index Gamma ~ 1.8. The other ULX shows a spectral state transition or outburst between the two Chandra observations, 20 days apart. Optical data show that this ULX is located in a young (age ~ 7-10 Myr), bright complex rich with OB stars and clusters. An exceptionally bright, unresolved radio source (0.14 mJy at 4.79 GHz, implying a radio luminosity twice as high as Cas A) is found slightly offset from the ULX (~ 80 pc). Its radio spectral index alpha ~ -0.7 suggests optically-thin synchrotron emission, either from a young supernova remnant or from a radio lobe powered by a ULX jet. An even brighter, unresolved radio source (0.22 mJy at 4.79 GHz) is found in another young, massive stellar complex, not associated with any X-ray sources: based on its flatter radio spectral index (alpha ~ -0.3), we suggest that it is a young pulsar wind nebula, a factor of 10 more radio luminous than the Crab.Comment: 12 pages, 11 figures. Accepted by MNRAS. High-resolution colour images of NGC 7424 from the Gemini observations are available at http://www.gemini.edu/2001igp

Clinical research without consent in adults in the emergency setting: a review of patient and public views

<p>Abstract</p> <p>Background</p> <p>In emergency research, obtaining informed consent can be problematic. Research to develop and improve treatments for patients admitted to hospital with life-threatening and debilitating conditions is much needed yet the issue of research without consent (RWC) raises concerns about unethical practices and the loss of individual autonomy. Consistent with the policy and practice turn towards greater patient and public involvement in health care decisions, in the US, Canada and EU, guidelines and legislation implemented to protect patients and facilitate acute research with adults who are unable to give consent have been developed with little involvement of the lay public. This paper reviews research examining public opinion regarding RWC for research in emergency situations, and whether the rules and regulations permitting research of this kind are in accordance with the views of those who ultimately may be the most affected.</p> <p>Methods</p> <p>Seven electronic databases were searched: Medline, Embase, CINAHL, Cochrane Database of Systematic Reviews, Philosopher's Index, Age Info, PsychInfo, Sociological Abstracts and Web of Science. Only those articles pertaining to the views of the public in the US, Canada and EU member states were included. Opinion pieces and those not published in English were excluded.</p> <p>Results</p> <p>Considering the wealth of literature on the perspectives of professionals, there was relatively little information about public attitudes. Twelve studies employing a range of research methods were identified. In five of the six questionnaire surveys around half the sample did <it>not </it>agree generally with RWC, though paradoxically, a higher percentage would <it>personally </it>take part in such a study. Unfortunately most of the studies were not designed to investigate individuals' views in any depth. There also appears to be a level of mistrust of medical research and some patients were more likely to accept an experimental treatment 'outside' of a research protocol.</p> <p>Conclusion</p> <p>There are too few data to evaluate whether the rules and regulations permitting RWC protects – or is acceptable to – the public. However, any attempts to engage the public should take place in the context of findings from further basic research to attend to the apparently paradoxical findings of some of the current surveys.</p

The XMM-Newton Serendipitous Survey. V. The Second XMM-Newton Serendipitous Source Catalogue

Aims: Pointed observations with XMM-Newton provide the basis for creating catalogues of X-ray sources detected serendipitously in each field. This paper describes the creation and characteristics of the 2XMM catalogue. Methods: The 2XMM catalogue has been compiled from a new processing of the XMM-Newton EPIC camera data. The main features of the processing pipeline are described in detail. Results: The catalogue, the largest ever made at X-ray wavelengths, contains 246,897 detections drawn from 3491 public XMM-Newton observations over a 7-year interval, which relate to 191,870 unique sources. The catalogue fields cover a sky area of more than 500 sq.deg. The non-overlapping sky area is ~360 sq.deg. (~1% of the sky) as many regions of the sky are observed more than once by XMM-Newton. The catalogue probes a large sky area at the flux limit where the bulk of the objects that contribute to the X-ray background lie and provides a major resource for generating large, well-defined X-ray selected source samples, studying the X-ray source population and identifying rare object types. The main characteristics of the catalogue are presented, including its photometric and astrometric properties .Comment: 27 pages (plus 8 pages appendices), 15 figures. Minor changes following referee's comments; now accepted for publication in A & A. Note that this paper "V", not paper "VI" in the series. Previous posting was incorrect in this regar