Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Photometric monitoring by the Transiting Exoplanet Survey Satellite (TESS) has discovered not only periodic signals by transiting exoplanets but also episodic or quasiperiodic dimming around young stellar objects. The dimming mechanisms of these objects, the so-called “dippers,” are thought to be related to either the accretion property or the structure of protoplanetary disks especially in regions close to the host star. Recently, we have created a catalog of dippers from one year of TESS full-frame image data. In this paper, we report on the spectral features of four newly found dippers in that catalog and show that they potentially shed light on the dimming mechanisms. We found that all of the targets exhibit the H<jats:italic>α</jats:italic> emission line, which is an indicator of ongoing accretion. Based on their line profiles and/or their variability, we characterized the properties of the disks of each source, which can support dimming mechanisms via a dusty disk wind or an accretion-driven inner-disk warp. Also, we found an interesting dipper (TIC 317873721), a “close-in binary dipper,” showing a complex variability of the line profile and a large radial velocity variation. Because the dimming intervals are similar to the orbital period of the binary, we suggest that the dips are caused by dust in the accretion warp from a circumbinary disk onto stars. Such a close-in (&lt;0.1 au) binary dipper has been rarely reported thus far; further investigation will reveal new aspects of disk evolution and planetary formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a near-complete catalog of the metal-rich population of thermally pulsing asymptotic giant branch (AGB) stars in the northwest quadrant of M31. This metal-rich sample complements the equally complete metal-poor Magellanic Cloud AGB catalogs produced by the SAGE program. Our catalog includes Hubble Space Telescope (HST) wide-band photometry from the Panchromatic Hubble Andromeda Treasury survey, HST medium-band photometry used to chemically classify a subset of the sample, and Spitzer mid- and far-IR photometry that we have used to isolate dust-producing AGB stars. We have detected 346,623 AGB stars; these include 4802 AGB candidates producing considerable dust, and 1356 AGB candidates that lie within clusters with measured ages, and in some cases metallicities. Using the Spitzer data and chemical classifications made with the medium-band data, we have identified both carbon- and oxygen-rich AGB candidates producing significant dust. We have applied color–mass-loss relations based on dusty-AGB stars from the LMC to estimate the dust injection by AGB stars in the PHAT footprint. Applying our color relations to a subset of the chemically classified stars producing the bulk of the dust, we find that ∼97.8% of the dust is oxygen-rich. Using several scenarios for the dust lifetime, we have estimated the contribution of AGB stars to the global dust budget of M31 to be 0.9%–35.5%, which is in line with previous estimates in the Magellanic Clouds. Follow-up observations of the M31 AGB candidates with the JWST will allow us to further constrain stellar and chemical evolutionary models, and the feedback and dust production of metal-rich evolved stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The IBEX-Lo instrument on board the Interstellar Boundary Explorer (IBEX) mission samples interstellar neutral (ISN) helium atoms penetrating the heliosphere from the very local interstellar medium (VLISM). In this study, we analyze the IBEX-Lo ISN helium observations covering a complete solar cycle, from 2009 through 2020 using a comprehensive uncertainty analysis including statistical and systematic sources. We employ the Warsaw Test Particle Model to simulate ISN helium fluxes at IBEX, which are subsequently compared with the observed count rate in the three lowest energy steps of IBEX-Lo. The <jats:italic>χ</jats:italic> <jats:sup>2</jats:sup> analysis shows that the ISN helium flows from ecliptic <jats:inline-formula> <jats:tex-math> <?CDATA $\left(\lambda ,\beta \right)=(255\buildrel{\circ}\over{.} 59\pm 0\buildrel{\circ}\over{.} 23,5\buildrel{\circ}\over{.} 14\pm 0\buildrel{\circ}\over{.} 08)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>λ</mml:mi> <mml:mo>,</mml:mo> <mml:mi>β</mml:mi> </mml:mrow> </mml:mfenced> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mn>255</mml:mn> <mml:mo>.°</mml:mo> <mml:mn>59</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.°</mml:mo> <mml:mn>23</mml:mn> <mml:mo>,</mml:mo> <mml:mn>5</mml:mn> <mml:mo>.°</mml:mo> <mml:mn>14</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.°</mml:mo> <mml:mn>08</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjsac4bdeieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, with speed <jats:italic>v</jats:italic> <jats:sub>HP</jats:sub> = 25.86 ± 0.21 km s<jats:sup>−1</jats:sup> and temperature <jats:italic>T</jats:italic> <jats:sub>HP</jats:sub> = 7450 ±140 K at the heliopause. Accounting for gravitational attraction and elastic collisions, the ISN helium speed and temperature in the pristine VLISM far from the heliopause are <jats:italic>v</jats:italic> <jats:sub>VLISM</jats:sub> = 25.9 km s<jats:sup>−1</jats:sup> and <jats:italic>T</jats:italic> <jats:sub>VLISM</jats:sub> = 6150 K, respectively. The time evolution of the ISN helium fluxes at 1 au over 12 yr suggests significant changes in the IBEX-Lo detection efficiency, higher ionization rates of ISN helium atoms in the heliosphere than assumed in the model, or an additional unaccounted for signal source in the analyzed observations. Nevertheless, we do not find any indication of the evolution of the derived parameters of ISN helium over the period analyzed. Finally, we argue that the continued operation of IBEX-Lo to overlap with the Interstellar Mapping and Acceleration Probe will be pivotal in tracking possible physical changes in the VLISM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Virgo is the nearest galaxy cluster; it is thus ideal for studies of galaxy evolution in dense environments in the local universe. It is embedded in a complex filamentary network of galaxies and groups, which represents the skeleton of the large-scale Laniakea supercluster. Here we assemble a comprehensive catalog of galaxies extending up to ∼12 virial radii in projection from Virgo to revisit the cosmic-web structure around it. This work is the foundation of a series of papers that will investigate the multiwavelength properties of galaxies in the cosmic web around Virgo. We match spectroscopically confirmed sources from several databases and surveys including HyperLeda, NASA Sloan Atlas, NASA/IPAC Extragalactic Database, and ALFALFA. The sample consists of ∼7000 galaxies. By exploiting a tomographic approach, we identify 13 filaments, spanning several megaparsecs in length. Long &gt;17 <jats:italic>h</jats:italic> <jats:sup>–1</jats:sup> Mpc filaments, tend to be thin (&lt;1 <jats:italic>h</jats:italic> <jats:sup>–1</jats:sup> Mpc in radius) and with a low-density contrast (&lt;5), while shorter filaments show a larger scatter in their structural properties. Overall, we find that filaments are a transitioning environment between the field and cluster in terms of local densities, galaxy morphologies, and fraction of barred galaxies. Denser filaments have a higher fraction of early-type galaxies, suggesting that the morphology–density relation is already in place in the filaments, before galaxies fall into the cluster itself. We release the full catalog of galaxies around Virgo and their associated properties.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Experimental radiative lifetimes for 34 odd-parity levels belonging to 4<jats:italic>d</jats:italic> <jats:sup>3</jats:sup>5<jats:italic>p</jats:italic> and 4<jats:italic>d</jats:italic> <jats:sup>2</jats:sup>5<jats:italic>s</jats:italic>5<jats:italic>s</jats:italic> configurations of Nb <jats:sc>ii</jats:sc> were measured by the time-resolved laser-induced fluorescence method. The results range from 2.2 to 11.5 ns, and 30 of them were reported for the first time, as far as we know. The theoretical radiative lifetimes for these levels were also calculated by the pseudorelativistic Hartree–Fock method including core-polarization contributions (HFR+CPOL) and the fully relativistic multiconfiguration Dirac–Hartree–Fock method, and branching fractions for these levels were also calculated by HFR+CPOL. By combining the experimental lifetimes and the calculated branching fraction values, the semiempirical transition probabilities and oscillator strengths for 389 Nb <jats:sc>ii</jats:sc> lines were obtained.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In fulfilling the aims of the planetary and asteroseismic research missions, such as that of the NASA Transiting Exoplanet Survey Satellite (TESS) space telescope, accurate stellar atmospheric parameters and a detailed chemical composition are required as inputs. We have observed high-resolution spectra for all 848 bright (<jats:italic>V</jats:italic> &lt; 8 mag) stars that are cooler than F5 spectral class in the area up to 12 deg surrounding the northern TESS continuous viewing zone and uniformly determined the main atmospheric parameters, ages, orbital parameters, velocity components, and precise abundances of up to 24 chemical species (C(C<jats:sub>2</jats:sub>), N(CN), [O <jats:sc>i</jats:sc>], Na <jats:sc>i</jats:sc>, Mg <jats:sc>i</jats:sc>, Al <jats:sc>i</jats:sc>, Si <jats:sc>i</jats:sc>, Si <jats:sc>ii</jats:sc>, Ca <jats:sc>i</jats:sc>, Ca <jats:sc>ii</jats:sc>, Sc <jats:sc>i</jats:sc>, Sc <jats:sc>ii</jats:sc>, Ti <jats:sc>i</jats:sc>, Ti <jats:sc>ii</jats:sc>, V <jats:sc>i</jats:sc>, Cr <jats:sc>i</jats:sc>, Cr <jats:sc>ii</jats:sc>, Mn <jats:sc>i</jats:sc>, Fe <jats:sc>i</jats:sc>, Fe <jats:sc>ii</jats:sc>, Co <jats:sc>i</jats:sc>, Ni <jats:sc>i</jats:sc>, Cu <jats:sc>i</jats:sc>, and Zn <jats:sc>i</jats:sc>) for 740 slowly rotating stars. The analysis of 25 planet-hosting stars in our sample drove us to the following conclusions: the dwarf stars hosting high-mass planets are more metal rich than those with low-mass planets. We find slightly negative C/O and Mg/Si slopes toward the stars with high-mass planets. All the low-mass planet hosts in our sample show positive Δ[El/Fe] versus condensation temperature slopes, in particular, the star with the largest number of various planets. The high-mass planet hosts have a diversity of slopes, but in more metal-rich, older, and cooler stars, the positive elemental abundance slopes are more common.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Hard X-ray Modulation Telescope (Insight-HXMT) is China’s first X-ray astronomy satellite. It was launched on 2017 June 15. The anticoincidence CsI detectors of the High Energy X-ray telescope (HE) on board Insight-HXMT could serve as an all-sky gamma-ray monitor in about 0.2–3 MeV. In its first four years of operation, Insight-HXMT has detected 322 gamma-ray bursts (GRBs) by the offline search pipeline, including blind search and targeted search. For the GOLDEN sample of Insight-HXMT GRBs, joint analyses were performed with other GRB missions, including the Fermi Gamma-ray Burst Monitor (Fermi/GBM), the Swift Burst Alert Telescope (Swift/BAT), and the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM). The analyses showed that Insight-HXMT can provide a better constraint on the GRB spectrum at a higher-energy band. The properties of Insight-HXMT GRBs are reported in detail, including their trigger time, duration, spectral parameters, peak fluxes of different timescales, and fluence. This catalog is an official product of the Insight-HXMT GRB team.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper reports computational results on hydrogen Lyman <jats:italic>β</jats:italic>, <jats:italic>γ</jats:italic>, and Balmer <jats:italic>β</jats:italic> spectral lines in the presence of parallel magnetic and electric fields. A two-dimensional B-spline approach is adopted in the current calculations. This approach was originally developed to treat high-lying states but was found to be also effective for low-lying states. Wavelengths and oscillator strengths are presented for a total of 31 transitions in magnetic and electric fields with field strengths ranging, respectively, from 23.5 to 2350 MG and from 0 to 10<jats:sup>8</jats:sup> V m<jats:sup>−1</jats:sup>. These spectral data are compared to available results from other theoretical methods, and good agreement is clearly visible. Our calculations show that in the scope of field strengths we are concerned with, Lyman <jats:italic>β</jats:italic> and <jats:italic>γ</jats:italic> spectral lines lie in the ultraviolet region, while the Balmer <jats:italic>β</jats:italic> lines lie in the ultraviolet and visible-light regions. Furthermore, Zeeman spectral lines related to atomic states in the <jats:italic>n</jats:italic> = 4 manifold may be blue- or redshifted by a strong electric field, dependent on the transitions as well as on magnetic field strengths. Atomic spectral data of the 31 transitions listed are applicable for modeling discrete spectra of magnetic white dwarfs when a strong electric field exists in the hydrogen-dominated atmospheres of these celestial objects.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Measurements of starlight polarized by aligned interstellar dust grains are used to probe the relation between the orientation of the ambient interstellar magnetic field (ISMF) and the ISMF traced by the ribbons of energetic neutral atoms discovered by the Interstellar Boundary Explorer spacecraft. We utilize polarization data, many acquired specifically for this study, to trace the configuration of the ISMF within 40 pc. A statistical analysis yields a best-fit ISMF orientation, <jats:italic>B</jats:italic> <jats:sub>magpol</jats:sub>, aligned with Galactic coordinates <jats:italic>ℓ</jats:italic> = 42°, <jats:italic>b</jats:italic> = 49°. Further analysis shows the ISMF is more orderly for “downfield” stars located over 90° from <jats:italic>B</jats:italic> <jats:sub>magpol</jats:sub>. The data subset of downfield stars yields an orientation for the nearby ISMF at ecliptic coordinates <jats:italic>λ</jats:italic>, <jats:italic>β</jats:italic> ≈ 219° ± 15°, 43° ± 9° (Galactic coordinates <jats:italic>l</jats:italic>, <jats:italic>b</jats:italic> ≈ 40°, 56°, ±17°). This best-fit ISMF orientation from polarization data is close to the field direction obtained from ribbon models. This agreement suggests that the ISMF shaping the heliosphere belongs to an extended ordered magnetic field. Extended filamentary structures are found throughout the sky. A previously discovered filament traversing the heliosphere nose region, “Filament A,” extends over 300° of the sky, and crosses the upwind direction of interstellar dust flowing into the heliosphere. Filament A overlaps the locations of the Voyager kilohertz emissions, three quasar intraday variables, cosmic microwave background (CMB) components, and the inflow direction of interstellar grains sampled by Ulysses and Galileo. These features are likely located in the upstream outer heliosheath where ISMF drapes over the heliosphere, suggesting Filament A coincides with a dusty magnetized plasma. A filament 55° long is aligned with a possible shock interface between local interstellar clouds. A dark spot in the CMB is seen within 5° of the filament and within 10° of the downfield ISMF direction. Two large magnetic arcs are centered on the directions of the heliotail. The overlap between CMB components and the aligned dust grains forming Filament A indicates the configuration of dust entrained in the ISMF interacting with the heliosphere provides a measurable foreground to the CMB.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have investigated the optical spectral behavior of a large sample of Fermi blazars (40 flat-spectrum radio quasars (FSRQs) and 13 BL Lacertae objects (BL Lacs)), and found two new universal optical spectral behaviors. In the low state the optical spectrum gradually becomes softer (steeper) or harder (flatter), but more and more slowly as the brightness increases, and then tends to stabilize in the high state. These are briefly named the redder-stable-when-brighter (RSWB) and bluer-stable-when-brighter (BSWB) behaviors, respectively. Thirty-four FSRQs and 7 BL Lacs exhibit clear RSWB behavior, and 2 FSRQs and 5 BL Lacs show distinct BSWB behavior, which means that FSRQs favor more RSWB than BSWB behavior, while BL Lacs have no clear preference between both behaviors. We have put forward a unified nonlinear formula to quantitatively characterize the optical spectral behaviors of FSRQs and BL Lacs, which can fit both kinds of behaviors very well. We argue that the RSWB and BSWB behaviors originate from the same mechanism, and that they are the universal optical spectral behaviors for blazars. The frequently observed redder-when-brighter and bluer-when-brighter trends can be considered to be the approximations of the RSWB and BSWB behaviors, respectively. The rarely observed stable-when-brighter trend can also be viewed as an approximation or a special case of the RSWB or BSWB behaviors. We have developed a model with two constant-spectral-index components, which cannot only explain the two kinds of optical spectral behaviors well, but also successfully interpret the differential behaviors between FSRQs and BL Lacs.</jats:p>