Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We describe 238 mid-infrared detections of supernovae and 195 possible supernovae in co-added images of the NEOWISE mission. We find one type Ia supernova (SN 2015cp), which has a mid-infrared evolution that is similar to known type Ia with long-lived mid-infrared detections. We also find long-lived mid-infrared detections in one type Ic (SN 2017dio) and one type Ib (SN 2016ajo). Additionally we provide measured magnitudes for most of our detections. We also find two transients, which we suspect to be TDEs: ASASSN-18ap and ATLAS17jrp.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Evidence is reported for the first time for the presence of the Hg <jats:sc>ii</jats:sc> line in a Narval I profile of Maia, the fourth brightest member of the Pleiades open cluster. The Hg <jats:sc>ii</jats:sc> line in Maia absorbs about 2% of the local continuum and can be reproduced with an overabundance of mercury of about 4000 times the solar mercury abundance. This line is probably variable suggesting that mercury might be distributed in spot(s) over the surface of Maia. Maia is currently classified as a He-weak Mn star, it should probably be reclassified as a HgMn star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Astrometric positions of radio-emitting active galactic nuclei (AGNs) can be determined with sub-milliarcsec accuracy using very long baseline interferometry (VLBI). The usually small apparent proper motion of distant extragalactic targets allow us to realize the fundamental celestial reference frame with VLBI observations. However, long-term astrometric monitoring may reveal extreme changes in some AGN positions. We present the case of CTA 21 whose position gradually shifted by ∼0.″04 over two decades. By comparing archival VLBI images from 1996 and 2018, we show that its radio structure changed substantially, likely causing the apparent positional shift.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The “Breakthrough” proposal for laser acceleration of spacecraft to semi-relativistic speeds has insuperable problems. It is not even self-consistent.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We recently discovered an extragalactic transient, AT2020caa, from the Zwicky Transient Facility alert stream using the community broker ANTARES. This transient apparently exhibited two outbursts within one year (between 2020 and 2021). Based on a decade-long historical light curve of the candidate host galaxy, we rule out activity from the galaxy nucleus to explain these outbursts. The measured peak magnitudes (assuming the known spectroscopic redshift of the candidate host galaxy) put AT2020caa in the realm of thermonuclear supernovae (SNe) or luminous core-collapse SNe. A handful of the latter are known to show prior outbursts (POs), thought to be linked to mass loss in massive stars. Using Gemini/GMOS, we obtained a spectrum of the current outburst that shows it to be a Type Ia supernova. We examine the nature of AT2020caa’s PO seen a year earlier and conclude that it is likely a separate SN within the same galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present deep, narrowband imaging of the nearby spiral galaxy M101 to search for star-forming dwarf galaxies and isolated H <jats:sc>ii</jats:sc> regions in the group environment. Isolated star-forming regions, unassociated with spiral arms, probe star formation (SF) at the lowest masses and environmental densities. Such objects may be isolated star-forming events or ongoing evidence of tidal interactions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, H<jats:italic>α</jats:italic>, H<jats:italic>β</jats:italic>, and [O <jats:sc>iii</jats:sc>], to detect potential isolated regions. Great care was taken to remove potential source contaminants, such as high-redshift objects and Galactic M stars, from our source list. For each detected source, we compare the emission line fluxes and equivalent widths, along with structural and photometric properties, to samples of Local Group dwarfs and star-forming galaxies in the SINGG/11HUGS samples. We discuss our findings in the context of SF in low-density environments and evolution of the M101 Group.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The process by which stars accumulate their mass is episodic, characterized by long-duration low-accretion phases punctuated with intense accretion bursts. The bursts are several orders of magnitude greater in accretion rate and contribute a significant fraction of the total mass. In this article we present results of performing a time series analysis using the Fourier transform on a computer simulation of the burst mode of mass accretion. We find that the most prominent peaks in the power spectrum correspond to characteristic timescales of several thousand years.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>I have studied the variability of the FeK<jats:italic>α</jats:italic> emission line flux in response to changes in the 2–10 keV unabsorbed flux in a sample of Compton thin type-II active galactic nuclei. All of the 20 sources in the sample studied by Laha et al., exhibit the presence of a narrow FeK<jats:italic>α</jats:italic> emission line. Except for one source (NGC 2992), all other sources show no correlations between the FeK<jats:italic>α</jats:italic> emission line flux and 2–10 keV unabsorbed flux. This implies that although most of the sources have shown significant variations in their 2–10 keV flux, the FeK<jats:italic>α</jats:italic> emission line did not get enough time to respond to those changes. This helps us put lower limits on the distance of the FeK<jats:italic>α</jats:italic> emitters to &gt;10 lt-yr from the central engine, equivalent to ∼3 pc which is consistent with the standard torus/narrow-line-region distance. I conclude that the FeK<jats:italic>α</jats:italic> emission lines of these sources arise from reflection of the hard X-ray photons off neutral materials located beyond  pcscale.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>One of the Roman Space Telescopes principal science objectives is to measure dark energy's equation-of-state using a strategic combination of imaging and spectroscopic surveys at high galactic latitude. Type Ia Supernovae survey requirements demand 0.3% photometric accuracy and calibration of key systematic effects. One of these is count rate dependent nonlinearity (CRNL) that if uncorrected affects the accuracy of SNe Ia distance measurements. Romans Relative Calibration System (RCS) enables on-orbit measurement and tracking of CRNL, through a direct illumination mode and a simultaneous lamp plus scene mode. We present results on the impact of CRNL calibration on the dark energy figure of merit (FoM), for a specific reduction of RCS capabilities. We examined many combinations of illumination and passbands, finding that only six meet the requirements. No RCS at all results in a factor of 5 degradation in the FoM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have spectroscopically identified 600 new E+A galaxies and candidates across 16 fields totaling roughly 480 square degrees in the Sloan Digital Sky Survey. E+A galaxies are post-starburst systems that have undergone a significant burst of star formation within the past 1–2 Gyr and are now fully quenched. They comprise a small population that is key to understanding the transition from star-forming to quiescent galaxies. Our survey focused on four nearby rich clusters of galaxies and their surroundings: Virgo, Coma, Leo, and Hercules. 356 candidates were identified in the clusters, and an additional 244 were identified in control fields or otherwise outside cluster bounds. Understanding the distribution and dynamics of the E+As has the potential to shed light on the evolutionary mechanisms present within nearby cluster environments. In this note, we give a brief overview of our selection processes and locations, and report on ongoing analyses of the sample.</jats:p>