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<jats:title>Abstract</jats:title> <jats:p>Simultaneous monitoring observations of H<jats:sub>2</jats:sub>O 6<jats:sub>1,6</jats:sub> − 5<jats:sub>2,3</jats:sub> and SiO <jats:italic>v</jats:italic> = 1, 2, <jats:italic>J</jats:italic> = 1 → 0, <jats:italic>v</jats:italic> = 1, <jats:italic>J</jats:italic> = 2 → 1, <jats:italic>J</jats:italic> = 3 → 2 masers were performed toward the suspected D-type symbiotic star V627 Cas from 2011 October to 2020 March using the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) single-dish telescopes. All spectra of the H<jats:sub>2</jats:sub>O masers showed highly redshifted emissions with respect to the stellar velocity of −52 km s<jats:sup>−1</jats:sup> with high asymmetries. In addition, the spectra of the H<jats:sub>2</jats:sub>O maser showed three components which varied according to observational dates. On the other hand, the SiO <jats:italic>v</jats:italic> = 1, 2, <jats:italic>J</jats:italic> = 1 → 0 and <jats:italic>v</jats:italic> = 1, <jats:italic>J</jats:italic> = 2 → 1 masers exhibited a predominantly blueshifted emission in most epochs. The SiO <jats:italic>v</jats:italic> = 1, <jats:italic>J</jats:italic> = 3 → 2 maser has arisen around the stellar velocity from 2016 November 19 and shows a predominantly redshifted emission from 2018 June 15. We analyze time variations of the H<jats:sub>2</jats:sub>O and SiO maser intensities, their intensity ratios, peak and mean velocities, and full width zero power. Based on these analyses, the asymmetries of the H<jats:sub>2</jats:sub>O and SiO masers’ spectra in V627 Cas and the variation characteristics of the maser properties of the different maser lines are discussed. As a possible cause of asymmetries, the influence of a hot component located at the eastern part of the red giant can be suggested based on the KVN VLBI results. The differences in the variation characteristics of the maser properties may originate from the differences in their locations and excitation conditions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Light curves and color evolutions of two classical novae can be largely overlapped if we properly squeeze or stretch the timescale of a target nova against that of a template nova by <jats:inline-formula> <jats:tex-math> <?CDATA $t^{\prime} =t/{f}_{{\rm{s}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabd31eieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. Then, the brightness of the target nova is related to the brightness of the template nova by <jats:inline-formula> <jats:tex-math> <?CDATA ${(M[t])}_{\mathrm{template}}={(M[t/{f}_{{\rm{s}}}]-2.5\mathrm{log}{f}_{{\rm{s}}})}_{\mathrm{target}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabd31eieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, where <jats:italic>M</jats:italic>[<jats:italic>t</jats:italic>] is the absolute magnitude and a function of time <jats:italic>t</jats:italic>, and <jats:italic>f</jats:italic> <jats:sub>s</jats:sub> is the ratio of timescales between the target and template novae. In the previous papers of this series, we show that many novae broadly overlap in the time-stretched (<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>)<jats:sub>0</jats:sub>–<jats:inline-formula> <jats:tex-math> <?CDATA $({M}_{V}-2.5\mathrm{log}{f}_{{\rm{s}}})$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabd31eieqn3.gif" xlink:type="simple" /> </jats:inline-formula> color–magnitude diagram. In the present paper, we propose two other (<jats:italic>U</jats:italic> − <jats:italic>B</jats:italic>)<jats:sub>0</jats:sub>–<jats:inline-formula> <jats:tex-math> <?CDATA $({M}_{B}-2.5\mathrm{log}{f}_{{\rm{s}}})$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabd31eieqn4.gif" xlink:type="simple" /> </jats:inline-formula> and (<jats:italic>V</jats:italic> − <jats:italic>I</jats:italic>)<jats:sub>0</jats:sub>–<jats:inline-formula> <jats:tex-math> <?CDATA $({M}_{I}-2.5\mathrm{log}{f}_{{\rm{s}}})$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabd31eieqn5.gif" xlink:type="simple" /> </jats:inline-formula> diagrams and show that their tracks overlap for 16 and 52 novae, respectively. Here (<jats:italic>U</jats:italic> − <jats:italic>B</jats:italic>)<jats:sub>0</jats:sub>, (<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>)<jats:sub>0</jats:sub>, and (<jats:italic>V</jats:italic> − <jats:italic>I</jats:italic>)<jats:sub>0</jats:sub> are the intrinsic <jats:italic>U</jats:italic> − <jats:italic>B</jats:italic>, <jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>, and <jats:italic>V</jats:italic> − <jats:italic>I</jats:italic> colors and not changed by the time stretch, and <jats:italic>M</jats:italic> <jats:sub> <jats:italic>B</jats:italic> </jats:sub>, <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub>, and <jats:italic>M</jats:italic> <jats:sub> <jats:italic>I</jats:italic> </jats:sub> are the absolute <jats:italic>B</jats:italic>, <jats:italic>V</jats:italic>, and <jats:italic>I</jats:italic> magnitudes. Using these properties, we considerably refine the previous estimates of their distance and reddening. The obtained distances are in reasonable agreement with those of the Gaia Data Release 2 catalog.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The study of narrow-line Seyfert 1 galaxies (NLS1s) is now mostly limited to low redshift (<jats:italic>z</jats:italic> &lt; 0.8) because their definition requires the presence of the H<jats:italic>β</jats:italic> emission line, which is redshifted out of the spectral coverage of major ground-based spectroscopic surveys at <jats:italic>z</jats:italic> &gt; 0.8. We studied the correlation between the properties of H<jats:italic>β</jats:italic> and Mg <jats:sc>ii</jats:sc> lines of a large sample of SDSS DR14 quasars to find high-<jats:italic>z</jats:italic> NLS1 candidates. Based on the strong correlation of FWHM(Mg <jats:sc>II</jats:sc>) = (0.880 ± 0.005) × FWHM(H<jats:italic>β</jats:italic>) + (0.438 ± 0.018), we present a sample of high-<jats:italic>z</jats:italic> NLS1 candidates having FWHM of Mg <jats:sc>ii</jats:sc> &lt; 2000 km s<jats:sup>−1</jats:sup>. The high-<jats:italic>z</jats:italic> sample contains 2684 NLS1s with redshift <jats:italic>z</jats:italic> = 0.8–2.5 with a median logarithmic bolometric luminosity of 46.16 ± 0.42 erg s<jats:sup>−1</jats:sup>, logarithmic black hole mass of 8.01 ± 0.35 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, and logarithmic Eddington ratio of 0.02 ± 0.27. The fraction of radio-detected high-<jats:italic>z</jats:italic> NLS1s is similar to that of the low-<jats:italic>z</jats:italic> NLS1s and SDSS DR14 quasars at a similar redshift range, and their radio luminosity is found to be strongly correlated with their black hole mass.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Lyman-alpha (Ly<jats:italic>α</jats:italic>) line of neutral hydrogen at 121.6 nm is by far the brightest emission line in the vacuum ultraviolet spectral range of the Sun. The emission at this line could be a major energy input to the upper layers of the Earth’s atmosphere, strongly impacting the geospace environment. The Geostationary Operational Environmental Satellite (GOES) series, starting with GOES-13, began to carry a multichannel Extreme UltraViolet Sensor (EUVS) with one channel (E-channel) targeting the Ly<jats:italic>α</jats:italic> line. In the present work, we produce a Ly<jats:italic>α</jats:italic> flare catalog from the GOES-15/EUVS-E data between 2010 April 8 and 2016 June 6 with an automatic flare detection algorithm. This algorithm is designed to search events at various scales and find their real start and end times. Based on the obtained flare list, statistics on the temporal behavior such as the duration, rise, and decay times, and the event asymmetries of Ly<jats:italic>α</jats:italic> flares is presented. On average (defined by the median of the distributions), the duration, rise and decay times of the flares were estimated to be 20.8 minutes, 5.6 minutes, and 14.2 minutes, respectively. We also discuss the frequency distributions of the peak flux and the fluence of Ly<jats:italic>α</jats:italic> flares, both of which reveal power-law behaviors with power-law indices of 2.71 ± 0.06 and 2.42 ± 0.06, respectively, implying that more flares are accumulated at small scales and these small-scale events play an important role in explaining the violent solar energy release.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Computing and using opacities is a key part of modeling and interpreting data of exoplanetary atmospheres. Since the underlying spectroscopic line lists are constantly expanding and currently include up to ∼10<jats:sup>10</jats:sup>–10<jats:sup>11</jats:sup> transition lines, the opacity calculator codes need to become more powerful. Here we present major upgrades to the <jats:monospace>HELIOS-K</jats:monospace> GPU-accelerated opacity calculator and describe the necessary steps to process large line lists within a reasonable amount of time. Besides performance improvements, we include more capabilities and present a toolbox for handling different atomic and molecular data sets, from downloading and preprocessing the data to performing the opacity calculations in a user-friendly way. <jats:monospace>HELIOS-K</jats:monospace> supports line lists from ExoMol, HITRAN, HITEMP, NIST, Kurucz, and VALD3. By matching the resolution of 0.1 cm<jats:sup>−1</jats:sup> and cutting length of 25 cm<jats:sup>−1</jats:sup> used by the <jats:monospace>ExoCross</jats:monospace> code for timing performance (251 s excluding data read-in time), <jats:monospace>HELIOS-K</jats:monospace> can process the ExoMol BT2 water line list in 12.5 s. Using a resolution of 0.01 cm<jats:sup>−1</jats:sup>, it takes 45 s, equivalent to about 10<jats:sup>7</jats:sup> lines s<jats:sup>−1</jats:sup>. As a wavenumber resolution of 0.01 cm<jats:sup>−1</jats:sup> suffices for most exoplanetary atmosphere spectroscopic calculations, we adopt this resolution in calculating opacity functions for several hundred atomic and molecular species and make them freely available on the open-access DACE database. For the opacity calculations of the database, we use a cutting length of 100 cm<jats:sup>−1</jats:sup> for molecules and no cutting length for atoms. Our opacities are available for downloading from <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://dace.unige.ch/opacityDatabase" xlink:type="simple">https://dace.unige.ch/opacityDatabase</jats:ext-link> and may be visualized using <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://dace.unige.ch/opacity" xlink:type="simple">https://dace.unige.ch/opacity</jats:ext-link>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We describe the simulated sky survey underlying the second data challenge (DC2) carried out in preparation for analysis of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) by the LSST Dark Energy Science Collaboration (LSST DESC). Significant connections across multiple science domains will be a hallmark of LSST; the DC2 program represents a unique modeling effort that stresses this interconnectivity in a way that has not been attempted before. This effort encompasses a full end-to-end approach: starting from a large <jats:italic>N</jats:italic>-body simulation, through setting up LSST-like observations including realistic cadences, through image simulations, and finally processing with Rubin’s LSST Science Pipelines. This last step ensures that we generate data products resembling those to be delivered by the Rubin Observatory as closely as is currently possible. The simulated DC2 sky survey covers six optical bands in a wide-fast-deep area of approximately 300 deg<jats:sup>2</jats:sup>, as well as a deep drilling field of approximately 1 deg<jats:sup>2</jats:sup>. We simulate 5 yr of the planned 10 yr survey. The DC2 sky survey has multiple purposes. First, the LSST DESC working groups can use the data set to develop a range of DESC analysis pipelines to prepare for the advent of actual data. Second, it serves as a realistic test bed for the image processing software under development for LSST by the Rubin Observatory. In particular, simulated data provide a controlled way to investigate certain image-level systematic effects. Finally, the DC2 sky survey enables the exploration of new scientific ideas in both static and time domain cosmology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Modeling binary star populations is critical to linking the theories of star formation and stellar evolution with observations. In order to test these theories, we need accurate models of observable binary populations. The Kepler Eclipsing Binary Catalog (KEBC), with its estimated &gt;90% completeness, provides an observational anchor on binary population models. In this work we present the results of a new forward model of the binary star population in the Kepler field. The forward model takes a single star population from a model of the Galaxy and pairs the stars into binaries by applying the constraints on the population from the results of observational binary population surveys such as Raghavan et al. and Duchêne &amp; Kraus. A synthetic binary population is constructed from the initial distributions of orbital parameters. We identify the eclipsing binary sample from the generated binary star population and compare this with the observed sample of eclipsing binaries contained in the KEBC. Finally, we update the distributions of the synthetic population and repeat the process until the synthetic eclipsing binary sample agrees with the KEBC. The end result of this process is a model of the underlying binary star population that has been fit to observations. We find that for fixed flat mass ratio and eccentricity input distributions, the binary period distribution is logarithmically flat above ∼3.2 days. With additional constraints on distributions from observations, we can further adjust the synthetic binary population by relaxing other input constraints, such as mass ratio and eccentricity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Earth’s magnetosphere represents a natural plasma laboratory that allows us to study the behavior of particle distribution functions in the absence of Coulomb collisions, typically described by the kappa distributions. We have investigated the properties of these functions for ions and electrons in different magnetospheric regions, thereby making it possible to reveal the <jats:italic>κ</jats:italic>-parameters for a wide range of plasma beta (<jats:italic>β</jats:italic>) values (from 10<jats:sup>−3</jats:sup> to 10<jats:sup>2</jats:sup>). This was done using simultaneous ion and electron measurements from the five Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft spanning the years 2008–2018. It was found that for a fixed plasma <jats:italic>β</jats:italic>, the <jats:italic>κ</jats:italic>-index and core energy (<jats:italic>E</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub>) of the distribution can be modeled by the power law <jats:inline-formula> <jats:tex-math> <?CDATA $\kappa ={{AE}}_{c}^{\gamma }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabdec9ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> for both species, and the relation between <jats:italic>β</jats:italic>, <jats:italic>κ</jats:italic>, and <jats:italic>E</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> is much more complex than earlier reported: both <jats:italic>A</jats:italic> and <jats:italic>γ</jats:italic> exhibit systematic dependencies with <jats:italic>β</jats:italic>. Our results indicate that <jats:italic>β</jats:italic> ∼ 0.1–0.3 is a range where the plasma is more dynamic, since it is influenced by both the magnetic field and temperature fluctuations, which suggests that the transition between magnetically and kinetically dominated plasmas occurs at these values of <jats:italic>β</jats:italic>. For <jats:italic>β</jats:italic> &gt; 1, both <jats:italic>A</jats:italic> and <jats:italic>γ</jats:italic> take nearly constant values, a feature that is especially notable for the electrons and might be related to their demagnetization. The relation between <jats:italic>β</jats:italic>, <jats:italic>κ</jats:italic>, and <jats:italic>E</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub> that we present is an important result that can be used by theoretical models in the future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, 1272 superflares on 311 stars are collected from 22,539 solar-type stars from the second-year observation of the Transiting Exoplanet Survey Satellite (TESS), which almost covered the northern hemisphere of the sky. Three superflare stars contain hot Jupiter candidates or ultrashort-period planet candidates. We obtain <jats:italic>γ</jats:italic> = −1.76 ± 0.11 of the correlation between flare frequency and flare energy (<jats:inline-formula> <jats:tex-math> <?CDATA ${dN}/{dE}\propto {E}^{-\gamma }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabda3cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) for all superflares and get <jats:italic>β</jats:italic> = 0.42 ± 0.01 of the correlation between superflare duration and energy (<jats:italic>T</jats:italic> <jats:sub>duration</jats:sub> ∝ <jats:italic>E</jats:italic> <jats:sup> <jats:italic>β</jats:italic> </jats:sup>), which supports that a similar mechanism is shared by stellar superflares and solar flares. Stellar photometric variability (<jats:italic>R</jats:italic> <jats:sub>var</jats:sub>) is estimated for all solar-type stars, and the relation of <jats:inline-formula> <jats:tex-math> <?CDATA $E\propto {R}_{\mathrm{var}}^{3/2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsabda3cieqn2.gif" xlink:type="simple" /> </jats:inline-formula> is included. An indicator of chromospheric activity (<jats:italic>S</jats:italic>-index) is obtained by using data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) for 7454 solar-type stars. Distributions of these two properties indicate that the Sun is generally less active than superflare stars. We find that saturation-like feature of <jats:italic>R</jats:italic> <jats:sub>var</jats:sub> ∼ 0.1 may be the reason for superflare energy saturating around 10<jats:sup>36</jats:sup> erg. Object TIC 93277807 was captured by the TESS first-year mission and generated the most energetic superflare. This superflare is valuable and unique in that it can be treated as an extreme event, which may be generated by different mechanisms than other superflares.</jats:p>