Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Accurately estimating of diffuse X-ray background (DXB) is essential for the investigation of sources in the Galactic plane observed with Insight-HXMT/LE, which is a collimated telescope in the soft X-ray energy band with a relatively large field of view. In the high-Galactic-latitude region, DXB is dominated by the cosmic X-ray background, which is almost uniform, but DXB in the Galactic plane region is more complex due to the Galactic H <jats:sc>i</jats:sc> absorption and the contribution of the Galactic ridge X-ray emission. This study, as a part of background estimation of LE, focuses on estimating the contribution of DXB in the Galactic plane to Insight-HXMT/LE observations. We calculate DXB confined in a region of 0° &lt; <jats:italic>l</jats:italic> &lt; 360° and ∣<jats:italic>b</jats:italic>∣ &lt; 10°, where <jats:italic>l</jats:italic> and <jats:italic>b</jats:italic> denote Galactic longitude and latitude, respectively, with the first 3 yr of Galactic-plane-scanning survey data of Insight-HXMT/LE. The Galactic plane is divided into 360 × 20 small pixels (1° × 1° per pixel), and a DXB spectrum is obtained for each pixel. An indirect method is developed for the pixels of the bright source regions, which brings a systematic error of ∼10%. The systematic error brought by the satellite attitude is ∼7% on average for all the pixels in the Galactic plane. The LE DXB spectrum obtained in this study is consistent with that reported by RXTE’s Proportional Counter Array.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The vast size of the Sun’s heliosphere, combined with sparse spacecraft measurements over that large domain, makes numerical modeling a critical tool to predict solar wind conditions where there are no measurements. This study models the solar wind propagation in 2D using the BATSRUS MHD solver to form the MSWIM2D data set of solar wind in the outer heliosphere. Representing the solar wind from 1 to 75 au in the ecliptic plane, a continuous model run from 1995–present has been performed. The results are available for free at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://csem.engin.umich.edu/mswim2d/" xlink:type="simple">http://csem.engin.umich.edu/mswim2d/</jats:ext-link>. The web interface extracts output at desired locations and times. In addition to solar wind ions, the model includes neutrals coming from the interstellar medium to reproduce the slowing of the solar wind in the outer heliosphere and to extend the utility of the model to larger radial distances. The inclusion of neutral hydrogen is critical to recreating the solar wind accurately outside of ∼4 au. The inner boundary is filled by interpolating and time-shifting in situ observations from L1 and STEREO spacecraft when available. Using multiple spacecraft provides a more accurate boundary condition than a single spacecraft with time shifting alone. Validations of MSWIM2D are performed using MAVEN and New Horizons observations. The results demonstrate the efficacy of this model to propagate the solar wind to large distances and obtain practical, useful solar wind predictions. For example, the rms error of solar wind speed prediction at Mars is only 66 km s<jats:sup>−1</jats:sup> and at Pluto is a mere 25 km s<jats:sup>−1</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Estimating the cross-correlation power spectra of the cosmic microwave background, in particular, the <jats:italic>TB</jats:italic> and <jats:italic>EB</jats:italic> spectra, is important for testing parity symmetry in cosmology and diagnosing insidious instrumental systematics. The quadratic maximum-likelihood (QML) estimator provides optimal estimates of the power spectra, but it is computationally very expensive. The hybrid pseudo-<jats:italic>C</jats:italic> <jats:sub> <jats:italic>ℓ</jats:italic> </jats:sub> estimator is computationally fast but performs poorly on large scales. As a natural extension of previous work, in this article, we present a new unbiased estimator based on the Smith–Zaldarriaga (SZ) approach of <jats:italic>E</jats:italic>–<jats:italic>B</jats:italic> separation and the scalar QML approach to reconstruct the cross-correlation power spectrum, called the QML-SZ estimator. Our new estimator relies on the ability to construct scalar maps, which allows us to use a scalar QML estimator to obtain the cross-correlation power spectrum. By reducing the pixel number and algorithm complexity, the computational cost is nearly one order of magnitude smaller and the running time is nearly two orders of magnitude faster in the test situations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low Resolution Spectroscopic Survey (LRS) provides massive spectroscopic data on M-type stars, and the derived stellar parameters could bring vital help to various studies. We adopt the ULySS package to perform <jats:italic>χ</jats:italic> <jats:sup>2</jats:sup> minimization with model spectra generated from the MILES interpolator and determine the stellar atmospheric parameters for the M-type stars from LAMOST LRS Data Release 8. Comparison with the stellar parameters from the APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP) suggests that most of our results have good consistency. For M dwarfs, we achieve dispersions better than 74 K, 0.19 dex, and 0.16 dex for <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub>, <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}g$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac6754ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, and [Fe/H], while for M giants, the internal uncertainties are 58 K, 0.32 dex, and 0.26 dex, respectively. Compared to ASPCAP we also find a systematic underestimation of Δ<jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> = −176 K for M dwarfs and a systematic overestimation of <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\Delta }}\mathrm{log}g$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac6754ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> = 0.30 dex for M giants. However, such differences are less significant when we make a comparison with common stars from other literature, which indicates that systematic biases exist in the difference between ASPCAP and other measurements. A catalog of 763,136 spectra corresponding to 616,314 M-type stars with derived stellar parameters is presented. We determine the stellar parameters for stars with <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> higher than 2900 K, with <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}g$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac6754ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> from −0.24 dex to 5.9 dex. The typical precisions are 45 K, 0.25 dex, and 0.22 dex, for <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub>, <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}g$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac6754ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, and [Fe/H], respectively, which are estimated from duplicate observations of the same stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a collection of 65,981 Mira-type variable stars found in the Optical Gravitational Lensing Experiment (OGLE) project database. Two-thirds of our sample (40,356 objects) are located in the Galactic bulge fields, whereas 25,625 stars are in the Galactic disk. The vast majority of the collection (47,532 objects) comprises new discoveries. We provide basic observational parameters of the Mira variables: equatorial coordinates, pulsation periods, <jats:italic>I</jats:italic>-band and <jats:italic>V</jats:italic>-band mean magnitudes, <jats:italic>I</jats:italic>-band brightness amplitudes, and identifications in other catalogs of variable stars. We also provide the <jats:italic>I</jats:italic>-band and <jats:italic>V</jats:italic>-band time-series photometry collected since 1997 during the OGLE-II, OGLE-III, and OGLE-IV phases. The classical selection process, i.e., being mostly based on the visual inspection of light curves by experienced astronomers, has led to the high purity of the catalog. As a result, this collection can be used as a training set for machine-learning classification algorithms. Using overlapping areas of adjacent OGLE fields, we estimate the completeness of the catalog to be about 96%. We compare and discuss the statistical features of Miras located in different regions of the Milky Way. We show examples of stars that change their type over time, from a semiregular variable to Mira and vice versa. This data set is perfectly suited to studying the three-dimensional structure of the Milky Way, and it may help to explain the puzzle of the X-shaped bulge.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Variability is one of the main observational characteristics of blazars. Studying variability is an efficient method to reveal the nature of active galactic nuclei. In the present work, we report optical <jats:italic>R</jats:italic>-band photometry observations of a TeV blazar, 1ES 2344 + 514, carried out with a 70 cm telescope in the period of 1998 July–2017 November at Abastumani Observatory, Georgia. Based on the optical <jats:italic>R</jats:italic>-band observations, the optical variation behaviors on both short timescales and long timescales are investigated. Three methods (Jurkevich, discrete correlation function, and power spectrum analysis) are used to investigate periodicity in the light curve. In addition, combined with multiwavelength data, the jet physical properties are discussed. The following conclusions are drawn: (1) A variability of Δ<jats:italic>R</jats:italic> = 0.155 mag (15.356 − 15.201 mag) over a timescale of Δ<jats:italic>T</jats:italic> = 12.99 minutes is detected during our 628 days of monitoring. (2) According to the Kelvin–Helmholtz thermal instability, if the magnetic field intensity (<jats:italic>B</jats:italic>) for the source is greater than a critical value (<jats:italic>B</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub>), it will reduce the incidence of intraday variations in the light curves. (3) The physical parameters of the dissipation region are obtained by fitting the spectral energy distribution with a one-zone synchrotron self-Compton model for the average and flare states. (4) The three methods show that there are periods of <jats:italic>P</jats:italic> = 2.72 ± 0.47 yr, <jats:italic>P</jats:italic> = 1.61 ± 0.18 yr, <jats:italic>P</jats:italic> = 1.31 ± 0.17 yr, and <jats:italic>P</jats:italic> = 1.05 ± 0.07 yr. When a binary black hole system is adopted with a period of <jats:italic>P</jats:italic> = 2.72 ± 0.41 yr, we obtain the orbital parameters for the binary black hole system as follows: <jats:italic>M</jats:italic> = 8.08 × 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, the sum of the semiaxes is <jats:italic>r</jats:italic> = 7.18 × 10<jats:sup>16</jats:sup> cm, and the lifetime of the binary black hole is <jats:italic>τ</jats:italic> <jats:sub>merge</jats:sub> = 6.24 × 10<jats:sup>2</jats:sup> yr.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Blazar CTA 102 experienced an intense multiwavelength activity phase from 2015 to 2018; in particular, an unprecedented outburst was observed from 2016 October to 2017 February. In this work, we extract a 7 day binned <jats:italic>γ</jats:italic>-ray light curve from 2008 August to 2018 March in the energy range 0.1–300 GeV and identify three main outbursts. We study in detail the short-timescale variability of these three outbursts via an exponential function with parameterized rise and decay timescales. The obtained shortest rise and decay timescales are 0.70 ± 0.05 hr and 0.79 ± 0.27 hr, respectively. Based on these variability timescales, the physical parameters of the flaring region (e.g., the minimum Doppler factor and the emission region size) are constrained. The short-timescale flares exhibit a symmetric temporal profile within the error bars, implying that the rise and decay timescales are dominated by the light-crossing timescale or by disturbances caused by dense plasma blobs passing through the standing shock front in the jet region. We also find that the best-fitting form of the <jats:italic>γ</jats:italic>-ray spectra during the flare period is a power law with an exponential cutoff. The derived jet parameters from the spectral behavior and the temporal characteristics of the individual flares suggest that the <jats:italic>γ</jats:italic>-ray emission region is located upstream of the radio core. The extreme <jats:italic>γ</jats:italic>-ray flare of CTA 102 is likely to have been caused by magnetic reconnection.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-redshift radio sources provide plentiful opportunities for studying the formation and evolution of early galaxies and supermassive black holes. However, the number of known radio-loud active galactic nuclei (AGN) above redshift 4 is rather limited. At high redshifts, it appears that blazars, with relativistically beamed jets pointing toward the observer, are in the majority compared to the radio-loud sources with jets misaligned with respect to the line of sight. To find more of these misaligned AGN, milliarcsecond-scale imaging studies carried out with very long baseline interferometry (VLBI) are needed, as they allow us to distinguish between compact-core–jet radio sources and those with more extended emission. Previous high-resolution VLBI studies revealed that some of the radio sources among blazar candidates in fact show unbeamed radio emission on milliarcsecond scales. The most accurate optical coordinates determined with the Gaia astrometric space mission are also useful in the classification process. Here, we report on dual-frequency imaging observations of 13 high-redshift (4 &lt; <jats:italic>z</jats:italic> &lt; 4.5) quasars at 1.7 and 5 GHz with the European VLBI Network. This sample increases the number of <jats:italic>z</jats:italic> &gt; 4 radio sources for which VLBI observations are available by about a quarter. Using structural and physical properties, such as radio morphology, spectral index, variability, brightness temperature, as well as optical coordinates, we identified six blazars and six misaligned radio AGNs, with the remaining one tentatively identified as blazar.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Large-scale multiconfiguration Dirac–Hartree–Fock calculations are provided for the <jats:italic>n</jats:italic> ≤ 5 states in C-like ions from O <jats:sc>iii</jats:sc> to Mg <jats:sc>vii</jats:sc>. Electron correlation effects are accounted for by using large configuration state function expansions, built from sets of orbitals with principal quantum numbers <jats:italic>n</jats:italic> ≤ 10. An accurate and complete data set of excitation energies, wavelengths, radiative transition parameters, and lifetimes is offered for the 156 (196, 215, 272, 318) lowest states of the 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>3</jats:sup>, 2<jats:italic>p</jats:italic> <jats:sup>4</jats:sup>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>3<jats:italic>s</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>3<jats:italic>p</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>3<jats:italic>d</jats:italic>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>3<jats:italic>s</jats:italic>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>3<jats:italic>p</jats:italic>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>3<jats:italic>d</jats:italic>, 2<jats:italic>p</jats:italic> <jats:sup>3</jats:sup>3<jats:italic>s</jats:italic>, 2<jats:italic>p</jats:italic> <jats:sup>3</jats:sup>3<jats:italic>p</jats:italic>, 2<jats:italic>p</jats:italic> <jats:sup>3</jats:sup>3<jats:italic>d</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>4<jats:italic>s</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>4<jats:italic>p</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>4<jats:italic>d</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>4<jats:italic>f</jats:italic>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>4<jats:italic>s</jats:italic>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>4<jats:italic>p</jats:italic>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>4<jats:italic>d</jats:italic>, 2<jats:italic>s</jats:italic>2<jats:italic>p</jats:italic> <jats:sup>2</jats:sup>4<jats:italic>f</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>5<jats:italic>s</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>5<jats:italic>p</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>5<jats:italic>d</jats:italic>, 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>5<jats:italic>f</jats:italic>, and 2<jats:italic>s</jats:italic> <jats:sup>2</jats:sup>2<jats:italic>p</jats:italic>5<jats:italic>g</jats:italic> configurations in O <jats:sc>iii</jats:sc> (F <jats:sc>iv</jats:sc>, Ne <jats:sc>v</jats:sc>, Na <jats:sc>vi</jats:sc>, Mg <jats:sc>vii</jats:sc>). By comparing available experimental wavelengths with the MCDHF results, the previous line identifications for the <jats:italic>n</jats:italic> = 5, 4, 3 → <jats:italic>n</jats:italic> = 2 transitions of Na <jats:sc>vi</jats:sc> in the X-ray and EUV wavelength range are revised. For several previous identifications discrepancies are found, and tentative new (or revised) identifications are proposed. A consistent atomic data set including both energy and transition data with spectroscopic accuracy is provided for the lowest hundreds of states for C-like ions from O <jats:sc>iii</jats:sc> to Mg <jats:sc>vii</jats:sc>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report a survey of excited-state hydroxyl (ex-OH) masers at the 4.7 and 6.0 GHz transitions toward a sample consisting of 3348 massive star-forming region candidates selected from the all-sky Wide-field Infrared Survey Explorer point-source catalog. The survey was conducted with the Shanghai Tianma Radio Telescope. In total, 6, 9, and 30 sources were detected with the ex-OH masers at the 4766, 6031, and 6035 MHz transitions, respectively. Among them, one 4766 MHz, one 6031 MHz, and five 6035 MHz ex-OH maser sources are newly identified. A series of statistical analyses derived that the ex-OH masers were detected efficiently toward the subsamples associated with both the 6.7 GHz CH<jats:sub>3</jats:sub>OH maser and radio recombination lines (RRLs), whereas compared to the CH<jats:sub>3</jats:sub>OH masers, the ex-OH masers are more likely to be produced toward the sources with stronger 22 <jats:italic>μ</jats:italic>m band emission. A significant luminosity correlation is found between the ex-OH masers and RRLs. In addition, we found that the magnetic field strength of most sources with the 6.7 GHz CH<jats:sub>3</jats:sub>OH maser was stronger relative to that of sources without the CH<jats:sub>3</jats:sub>OH maser. Combined with these, it demonstrates that the ex-OH maser is associated with more evolved star-forming regions, likely associated with thicker dust envelopes. Meanwhile, the ex-OH masers might be a potential tracer for measuring the Galactic magnetic field information on the large-scale views using their Zeeman pairs.</jats:p>