Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Mini-EUSO is a telescope observing the Earth in the ultraviolet band from the International Space Station. It is a part of the JEM-EUSO program, paving the way to future larger missions, such as K-EUSO and POEMMA, devoted primarily to the observation of ultrahigh-energy cosmic rays from space. Mini-EUSO is capable of observing extensive air showers generated by ultrahigh-energy cosmic rays with an energy above 10<jats:sup>21</jats:sup> eV and to detect artificial showers generated with lasers from the ground. Other main scientific objectives of the mission are the search for nuclearites and strange quark matter, the study of atmospheric phenomena such as transient luminous events, meteors, and meteoroids, the observation of sea bioluminescence and of artificial satellites and man-made space debris. Mini-EUSO will map the nighttime Earth in the UV range (290–430 nm), with a spatial resolution of about 6.3 km and a temporal resolution of 2.5 <jats:italic>μ</jats:italic>s, through a nadir-facing UV-transparent window in the Russian Zvezda module. The instrument, launched on 2019 August 22, from the Baikonur Cosmodrome, is based on an optical system employing two Fresnel lenses and a focal surface composed of 36 multianode photomultiplier tubes, 64 channels each, for a total of 2304 channels with single-photon counting sensitivity and an overall field of view of 44°. Mini-EUSO also contains two ancillary cameras to complement measurements in the near-infrared and visible ranges. In this paper, we describe the detector and present the various phenomena observed in the first months of operations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Observations of positional offsets between the location of X-ray and radio features in many resolved, extragalactic jets indicates that the emitting regions are not cospatial, an important piece of evidence in the debate over the origin of the X-ray emission on kiloparsec scales. The existing literature is nearly exclusively focused on jets with sufficiently deep Chandra observations to yield accurate positions for X-ray features, but most of the known X-ray jets are detected with tens of counts or fewer, making detailed morphological comparisons difficult. Here we report the detection of X-ray-to-radio positional offsets in 15 extragalactic jets from an analysis of 22 sources with low-count Chandra observations, where we utilized the Low-count Image Reconstruction Algorithm. This algorithm has allowed us to account for effects such as Poisson background fluctuations and nearby point sources which have previously made the detection of offsets difficult in shallow observations. Using this method, we find that in 55% of knots with detectable offsets, the X-rays peak upstream of the radio, questioning the applicability of one-zone models, including the IC/CMB model for explaining the X-ray emission. We also report the nondetection of two previously claimed X-ray jets. Many, but not all, of our sources follow a loose trend of increasing offset between the X-ray and radio emission, as well as a decreasing X-ray-to-radio flux ratio along the jet.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Reliable fundamental parameters of star clusters such as distance modulus, metallicity, age, extinction, and binary fraction are of key importance for astrophysical studies. Although a lot of new star clusters were identified from the data of, e.g., Gaia Data Release 2 (Gaia DR2), the fundamental parameters of many clusters were not determined reliably. This work makes use of the photometry data of Gaia DR2 and a good color–magnitude diagram (CMD) analysis tool, Powerful CMD, to determine the fundamental parameters of 49 new star clusters in detail. All CMDs are fitted carefully by both statistics and by eye, to make sure the CMDs are reproduced as well as possible. As a result, the fundamental parameters of 22 clusters are determined reliably, and those of the others are also determined as well as we can. Because the width of the main sequence in the color direction is used, combined with other widely used CMD features to constrain the fundamental parameters, the results of this work are more reliable than those reported by single-star isochrone fits. As a feature of this work, the primordial binary fractions and rotating star fractions of star clusters have been reported, which are useful for many works, in particular for some simulation research.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the fourth catalog of serendipitously discovered compact extragalactic emission-line sources—H<jats:italic>α</jats:italic> Dots. A total of 454 newly discovered objects are included in the current survey list. These objects have been detected in searches of moderately deep narrowband images acquired for the ALFALFA H<jats:italic>α</jats:italic> project. The catalog of H<jats:italic>α</jats:italic> Dots presented in the current paper was derived from searches carried out using ALFALFA H<jats:italic>α</jats:italic> images obtained with the KPNO 2.1 m telescope. This results in a substantially deeper sample of Dots compared to our previous lists, which were all discovered in images taken with the WIYN 0.9 m telescope. The median <jats:italic>R</jats:italic>-band magnitude of the current catalog is 21.59, more than 1.6 mag fainter than the median for the 0.9 m sample (a factor of 4.4× fainter). Likewise, the median emission-line flux of the detected sources is a factor of 4.3× fainter. The line flux completeness limit of the current sample is ~3 × 10<jats:sup>−16</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup>. We present accurate coordinates, apparent magnitudes, and narrowband line fluxes for each object in the sample. Unlike our previous lists of H<jats:italic>α</jats:italic> Dots, the current sample does not include follow-up spectroscopy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Glycolaldehyde (GA) has been observed toward several different sources, with a broad range of rotational temperatures (8–300 K). At the high end, the temperature is comparable to the energy of the lowest vibrational states of GA, making the vibrational contribution to the partition function significant. Here, we report an analysis of the high-resolution far-infrared spectrum of GA, which features a plethora of well-resolved lines from 170–430 cm<jats:sup>−1</jats:sup> (13–5 THz). We focus on the three fundamental vibrational bands in this range, i.e., the symmetric <jats:italic>ν</jats:italic> <jats:sub>12</jats:sub> bend at 282 cm<jats:sup>−1</jats:sup>, and the asymmetric <jats:italic>ν</jats:italic> <jats:sub>17</jats:sub> and <jats:italic>ν</jats:italic> <jats:sub>18</jats:sub> torsions at 360 and 208 cm<jats:sup>−1</jats:sup>, respectively. We assigned 23,266 transitions to 13,999 lines within these bands, which, when combined with the previously reported microwave and millimeter-wave spectra, allowed for refinement of the vibrationally excited rotational constants, and accurate determination of their band origins. Additionally, the assignment of a number of lines in several hot bands that are significantly populated at 300 K allowed for determination of their band origins. The rotational constants reported here should be useful in searches of vibrationally excited GA toward warm sources, and the accurately determined band origins allow for refinement of the vibrational partition function, and therefore column density, for a given excitation temperature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the discovery of 33 oxygen-anomalous grains from the CH3/CB<jats:sub>b</jats:sub>3 chondrite Isheyevo and the CR2 chondrite Northwest Africa (NWA) 801. Oxygen isotopic compositions indicate the origin of the majority grains in stellar outflows of low-mass (∼1.2 to ∼2.2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), solar-metallicity red giant or asymptotic giant branch stars, while highly <jats:sup>17</jats:sup>O-enriched grains probably have nova origins. Isotopic compositions of the eight <jats:sup>18</jats:sup>O-rich grains, including an extremely <jats:sup>18</jats:sup>O-rich grain (∼16 times solar <jats:sup>18</jats:sup>O/<jats:sup>16</jats:sup>O ratio), are reproduced by zone mixing of SNe II ejecta. Close-to-normal silicon, magnesium, and calcium isotopic compositions of grains are consistent with the isotope exchange in the interstellar medium or the meteorite parent body, while two grains with Si isotopic anomalies and one grain with Mg isotopic anomalies reflect the Galactic chemical evolution. An Isheyevo clast showed several hot spots with moderate to high <jats:sup>15</jats:sup>N enrichments, including a hot spot with an extreme <jats:sup>15</jats:sup>N excess of (7225 ± 316)‰. However, no correlation between <jats:sup>15</jats:sup>N enrichment and presolar oxygen-rich grain abundance is found. Grains with elliptical shapes probably indicate primary condensation feature. Two complex grains possibly display decoupling of the isotopic and elemental compositions in the grain formation environments. The low silicate-to-oxide abundance ratio for the fine-grained chondrule rims in NWA 801 likely reflects the preferential destruction of silicates due to terrestrial weathering. In NWA 801, the presolar O-rich grain abundance in fine-grained chondrule rims is higher than in the interchondrule matrix, similar to the trend observed for some aqueously altered chondrites of petrologic type 2.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Deep near-infrared (NIR) <jats:italic>J</jats:italic>- and <jats:italic>K</jats:italic>-band photometry of three Local Group dwarf spheroidal galaxies—Fornax, Carina, and Sculptor—is made available for the community. Until now, these data have only been used by the Araucaria Project to determine distances using the tip of the red giant branch and RR Lyrae stars. Now, we present the entire data collection in the form of a database, consisting of accurate <jats:italic>J</jats:italic>- and <jats:italic>K</jats:italic>-band magnitudes, sky coordinates, ellipticity measurements, and timestamps of observations, complemented by stars’ loci in their reference images. The depth of our photometry reaches about 22 mag at the 5<jats:italic>σ</jats:italic> level, and is comparable to NIR surveys, such as the UKIRT Infrared Deep Sky Survey (UKIDSS) or the VISTA Hemisphere Survey (VHS). Small overlap with VHS and no overlap with UKIDSS makes our database a unique source of quality photometry.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>When a gamma-ray burst (GRB) emitter stops emission abruptly, the observer receives rapidly fading emission from high latitudes with respect to the line of sight, known as the “curvature effect.” Identifying such emission from GRB prompt-emission lightcurves would constrain the radius of prompt emission from the central engine and the composition of GRB jets. We perform a dedicated search of high-latitude emission (HLE) through spectral and temporal analyses of a sample of single-pulse bursts detected by the Gamma-ray Burst Monitor on board the Fermi satellite. We identify HLE from a subsample of bursts and constrain the emission radius to be <jats:italic>R</jats:italic> <jats:sub>GRB</jats:sub> ∼ (10<jats:sup>15</jats:sup>–10<jats:sup>16</jats:sup>) cm from the central engine. Some bursts have the HLE decay faster than predicted by a constant Lorentz factor jet, suggesting that the emission region is undergoing acceleration during prompt emission. This supports the Poynting-flux-dominated jet composition for these bursts. The conclusion is consistent with previous results drawn from spectral-lag modeling of prompt emission and HLE analysis of X-ray flares.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Circumstellar environments of oxygen-rich stars are among the strongest SiO maser emitters. Physical processes such as collisions, infrared pumping, and overlaps favor the inversion of level population and produce maser emission at different vibrational states. Despite numerous observational and theoretical efforts, we still do not have a unified picture including all of the physical processes involved in SiO maser emission. The aim of this work is to provide homogeneous data in a large sample of oxygen-rich stars. We present a survey of 67 oxygen-rich stars from 7 to 1 mm, in their rotational transitions from <jats:italic>J</jats:italic> = 1 → 0 to <jats:italic>J</jats:italic> = 5 → 4, for vibrational numbers <jats:italic>v</jats:italic> from 0 to 6 in the three main SiO isotopologs. We have used one of the 34 m NASA antennas at Robledo and the IRAM 30 m radio telescope. The first tentative detection of a <jats:italic>v</jats:italic> = 6 line is reported, as well as the detection of new maser lines. The highest vibrational levels seem confined to small volumes, presumably close to the stars. The <jats:italic>J</jats:italic> = 1 → 0, <jats:italic>v</jats:italic> = 2 line flux is greater than the corresponding <jats:italic>v</jats:italic> = 1 in almost half of the sample, which may confirm a predicted dependence on the pulsation cycle. This database is potentially useful in models which should consider most of the physical agents, time dependency, and mass-loss rates. As a by-product, we report detections of 27 thermal rotational lines from other molecules, including isotopologs of SiS, H<jats:sub>2</jats:sub>S, SO, SO<jats:sub>2</jats:sub>, and NaCl.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The M dwarf stars are the most common stars in the Galaxy, dominating the population of the Galaxy at faint magnitudes. Precise and accurate stellar parameters for M dwarfs are of crucial importance for many studies. However, the atmospheric parameters of M dwarf stars are difficult to determine. In this paper, we present a catalog of the spectroscopic stellar parameters (<jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> and [M/H]) of ∼300,000 M dwarf stars observed by both LAMOST and Gaia using the Stellar LAbel Machine (SLAM). We train a SLAM model using LAMOST spectra with APOGEE Data Release 16 labels with 2800 K &lt; <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> &lt; 4500K and −2 dex &lt; [M/H] &lt; 0.5 dex. The SLAM <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> is in agreement to within ∼50 K compared to the previous study determined by APOGEE observations, and the SLAM [M/H] agrees within 0.12 dex compared to the APOGEE observation. We also set up a SLAM model trained by the BT-Settl atmospheric model with random uncertainties (in cross validation) to 60 K and agreeing within ∼90 K compared to previous studies.</jats:p>