Statistical Re-examination of Reported Emission Lines in the X-ray Afterglow of GRB 011211

(abridged) A 0.2-12 keV spectrum obtained with the XMM EPIC/pn instrument of GRB 011211 was found by Reeves et al. (2002) to contain emission lines which were interpreted to be from Mg XI, Si XIV, S XVI, Ar XVIII, and Ca XX, at a lower redshift (z_{obs}=1.88) than the host galaxy (z_{host}=2.14). We examine the spectrum independently, and find that the claimed lines would not be discovered in a blind search. Specifically, Monte Carlo simulations show that they would be observed in 10% of featureless spectra with the same signal-to-noise. Imposing a model in which the two brightest lines would be Si XIV and S XVI K-alpha emission possibly velocity shifted to between z=1.88--2.40, such features would be found in between ~1.2-2.6% of observed featureless spectra. We find the detection significances to be insufficient to justify the claim of detection and the model put forth to explain them. K-alpha line complexes are also found at z=1.2 and z=2.75 of significance equal to or greater than that at z=1.88. If one adopts the z=1.88 complex as significant, one must also adopt the other two complexes to be significant. The interpretation of these data in the context of the model proposed by Reeves et al. is therefore degenerate, and cannot be resolved by these data alone.Comment: 23 pages, 4 figures. MNRAS, accepted. Expanded discussio

The SNAP Strong Lens Survey

Basic considerations of lens detection and identification indicate that a wide field survey of the types planned for weak lensing and Type Ia SNe with SNAP are close to optimal for the optical detection of strong lenses. Such a ``piggy-back'' survey might be expected even pessimistically to provide a catalogue of a few thousand new strong lenses, with the numbers dominated by systems of faint blue galaxies lensed by foreground ellipticals. After sketching out our strategy for detecting and measuring these galaxy lenses using the SNAP images, we discuss some of the scientific applications of such a large sample of gravitational lenses: in particular we comment on the partition of information between lens structure, the source population properties and cosmology. Understanding this partitioning is key to assessing strong lens cosmography's value as a cosmological probe.Comment: 6 pages, 4 figures. To appear in the conference proceedings of "Wide Field Imaging from Space" (published in New Astronomy Reviews), eds. T. McKay, A. Fruchter, and E. Linde

Photo-zSNthesis: Converting Type Ia Supernova Lightcurves to Redshift Estimates via Deep Learning

Upcoming photometric surveys will discover tens of thousands of Type Ia supernovae (SNe Ia), vastly outpacing the capacity of our spectroscopic resources. In order to maximize the science return of these observations in the absence of spectroscopic information, we must accurately extract key parameters, such as SN redshifts, with photometric information alone. We present Photo-zSNthesis, a convolutional neural network-based method for predicting full redshift probability distributions from multi-band supernova lightcurves, tested on both simulated Sloan Digital Sky Survey (SDSS) and Vera C. Rubin Legacy Survey of Space and Time (LSST) data as well as observed SDSS SNe. We show major improvements over predictions from existing methods on both simulations and real observations as well as minimal redshift-dependent bias, which is a challenge due to selection effects, e.g. Malmquist bias. The PDFs produced by this method are well-constrained and will maximize the cosmological constraining power of photometric SNe Ia samples.Comment: submitted to Ap

Soft X-Ray Absorption by Fe0+^{0+} to Fe15+^{15+} in Active Galactic Nuclei

A full set of calculations is presented for inner-shell n = 2 to 3 photoexcitation of the 16 iron charge states: Fe I through Fe XVI. The blend of the numerous absorption lines arising from these excitations (mainly 2p - 3d) forms an unresolved transition array (UTA), which has been recently identified as a prominent feature between 16 - 17 \AA in the soft X-ray spectra of active galactic nuclei (AGN). Despite the blending within charge-states, the ample separation between the individual-ion features enables precise diagnostics of the ionization range in the absorbing medium. Column density and turbulent velocity diagnostics are also possible, albeit to a lesser accuracy. An abbreviated set of atomic parameters useful for modeling the Fe 2p - 3d UTA is given. It is shown that the effects of accompanying photoexcitation to higher levels ($n \ge$ 4), as well as the associated photoionization edges, may also be relevant to AGN spectra.Comment: Accepted for publication in The Astrophysical Journa

A Convolutional Neural Network Approach to Supernova Time-Series Classification

One of the brightest objects in the universe, supernovae (SNe) are powerful explosions marking the end of a star's lifetime. Supernova (SN) type is defined by spectroscopic emission lines, but obtaining spectroscopy is often logistically unfeasible. Thus, the ability to identify SNe by type using time-series image data alone is crucial, especially in light of the increasing breadth and depth of upcoming telescopes. We present a convolutional neural network method for fast supernova time-series classification, with observed brightness data smoothed in both the wavelength and time directions with Gaussian process regression. We apply this method to full duration and truncated SN time-series, to simulate retrospective as well as real-time classification performance. Retrospective classification is used to differentiate cosmologically useful Type Ia SNe from other SN types, and this method achieves >99% accuracy on this task. We are also able to differentiate between 6 SN types with 60% accuracy given only two nights of data and 98% accuracy retrospectively.Comment: Accepted at the ICML 2022 Workshop on Machine Learning for Astrophysic

Apoyo público a la energía eólica en España

El presente trabajo pretende describir y valorar brevemente el régimen jurídico-económico de la energía eólica en España. Nos referimos en concreto al sistema de apoyo público a la producción de electricidad a partir de las energías renovables mediante el sistema denominado “de primas”. El fijarnos en la energía eólica en particular se justifica por la sencilla razón de que España ocupa el tercer puesto a nivel mundial en potencia eólica instalada, después de Alemania y EE. UU, hecho que va unido a la circunstancia de la importancia a todos los niveles que ha cobrado este sector en España. Por otra parte, conviene recordar que el uso de energía (su producción y consumo) es el principal factor de emisiones de gases de efecto invernadero y las energías renovables suponen una pieza clave en la lucha contra el cambio climático. Y también que España se encuentra entre los países más alejados del cumplimiento del Protocolo de Kyoto. Desde esta perspectiva, el protagonismo de la energía eólica es también patente: en nuestro país, dentro de las energías renovables, la energía eólica en particular es la que más está aportando al mix de generación eléctrica, convirtiéndose en la contribución más segura a dicha lucha ambiental de carácter global. En este sentido, la proporción de energía eléctrica aportada por la eólica se encuentra –con más del 11% en 2008– en la segunda posición mundial; aquí España solo es superada por Dinamarca. Es importante, por tanto, mantener una buena política de fomento de esta tecnología renovable.This paper briefly attempts to describe and assess the legal and economic wind energy in Spain. We refer specifically to the system of public support for the production of electricity from renewables through the system called “premium.” The focus on wind energy in particular is justified simply for the reason that, as you know, Spain is ranked third worldwide in installed wind power second only to Germany and the U.S., which is coupled with the fact of significance for all levels that has taken the wind power sector in our country. It should also be remembered that on the one hand, energy use (production and consumption) is the main factor in emissions of greenhouse gases and on the other hand, renewables are a key element in combating Climate Change. And also that Spain is among the countries furthest away from compliance with the Kyoto Protocol. From this perspective, the role of wind energy is also evident in our country in renewable energy, wind energy in particular is what is making the most of electricity generation mix, making it the most secure in this fight environmental and global. In this sense, the proportion of electricity produced by wind-is over 11% in 2008 - the second in the world, second only to Denmark. It is therefore important to maintain a good policy to promote this renewable technology.Trabajo realizado en el marco del Proyecto de Investigación I+D del Ministerio de Ciencia e Innovación SEJ2006-15178 “Problemas jurídicos-ambientales y de ordenación del territorio de la implantación de parques eólicos”

High-Resolution X-Ray Spectroscopy of the Accretion Disk Corona Source 4U 1822-37

We present a preliminary analysis of the X-ray spectrum of the accretion disk corona source, 4U 1822-37, obtained with the High Energy Transmission Grating Spectrometer onboard the Chandra X-ray Observatory. We detect discrete emission lines from photoionized iron, silicon, magnesium, neon, and oxygen, as well as a bright iron fluorescence line. Phase-resolved spectroscopy suggests that the recombination emission comes from an X-ray illuminated bulge located at the predicted point of impact between the disk and the accretion stream. The fluorescence emission originates in an extended region on the disk that is illuminated by light scattered from the corona.Comment: 12 pages, 6 figures; Accepted for publication in ApJ Letter