Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Radiation contributes to the acceleration of large-scale flows in various astrophysical environments because of strong opacity in the spectral lines. Quantification of the associated force is crucial to understanding these line-driven flows, and a large number of lines (due to the full set of elements and ionization stages) must be taken into account. Here we provide new calculations of the dimensionless line strengths and associated opacity-dependent force multipliers for an updated list of approximately 4.5 million spectral lines compiled from the NIST, CHIANTI, CMFGEN, and TOPbase databases. To maintain generality of application to different environments, we assume local thermodynamic equilibrium, illumination by a Planck function, and the Sobolev approximation. We compute the line forces in a two-dimensional grid of temperatures (i.e., values between 5200 and 70,000 K) and densities (varying over 11 orders of magnitude). Historically, the force multiplier function has been described by a power-law function of optical depth. We revisit this assumption by fitting alternate functions that include saturation to a constant value (Gayley’s <jats:inline-formula> <jats:tex-math> <?CDATA $\bar{Q}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdf52ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> parameter) in the optically thin limit. This alternate form is a better fit than the power-law form, and we use it to calculate example mass-loss rates for massive main-sequence stars. Because the power-law force multiplier does not continue to arbitrarily small optical depths, we find a sharp decrease, or quenching, of line-driven winds for stars with effective temperatures less than about 15,000 K.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The second Gaia data release (DR2) delivers accurate and homogeneous photometry data of the whole sky of an exquisite quality, reaching down to the unprecedented millimagnitude (mmag) level for the <jats:italic>G</jats:italic>, <jats:italic>G</jats:italic> <jats:sub>RP</jats:sub>, and <jats:italic>G</jats:italic> <jats:sub>BP</jats:sub> passbands. However, the presence of magnitude-dependent systematic effects at the 10 mmag level limits its power in scientific exploitation. In this work, using about a half million stars in common with the LAMOST DR5, we apply the spectroscopy-based stellar color regression method to calibrate the Gaia <jats:italic>G</jats:italic> − <jats:italic>G</jats:italic> <jats:sub>RP</jats:sub> and <jats:italic>G</jats:italic> <jats:sub>BP</jats:sub> − <jats:italic>G</jats:italic> <jats:sub>RP</jats:sub> colors. With an unprecedented precision of about 1 mmag, systematic trends with <jats:italic>G</jats:italic> magnitude are revealed for both colors in great detail, reflecting changes in instrument configurations. Color-dependent trends are found for the <jats:italic>G</jats:italic> <jats:sub>BP</jats:sub> − <jats:italic>G</jats:italic> <jats:sub>RP</jats:sub> color and for stars brighter than <jats:italic>G</jats:italic> ∼ 11.5 mag. The maximum correction term of the calibration is about 20 mmag in general and varies by a few mmag/mag. A revised color–color diagram of Gaia DR2 is given, and some applications are briefly discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A fraction of the electromagnetic radiation emitted from the surface of a geometrically thin and optically thick accretion disk of a black hole returns to the disk because of the strong light bending in the vicinity of the compact object (returning radiation). While such radiation clearly affects the observed spectrum of the source, it is often neglected in theoretical models. In the present paper, we study the impact of the returning radiation on relativistic reflection spectra. Assuming neutral material in the disk, we estimate the systematic uncertainties on the measurement of the properties of the system when we fit the data with a theoretical model that neglects the returning radiation. Our NICER simulations show that the inclination angle of the disk and the black hole spin parameter tend to be overestimated for low viewing angles, while no clear bias is observed for high viewing angles. The iron abundance of the disk is never overestimated. In the most extreme cases (in particular, for maximally rotating black holes), the returning radiation flattens the radial emissivity beyond a few gravitational radii. In such cases, it also produces residuals that cannot be compensated for by adjusting the parameters of models that neglect the returning radiation. This may be an important issue for the interpretation of data from future X-ray missions (e.g., Athena). When we simulate some observations with NuSTAR and fit data above 10 keV, we find that some conclusions that are valid for the NICER simulations are no longer true (e.g., we can obtain a high iron abundance).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Luminous compact blue galaxies (LCBGs) are compact, star-forming galaxies that are rarely observed in the local universe but abundant at <jats:italic>z</jats:italic> = 1. This increase in LCBG number density over cosmic lookback time roughly follows the increase in the star formation rate density of the universe over the same period. We use publicly available data in the COSMOS field to study the evolution of the largest homogeneous sample of LCBGs to date by deriving their luminosity function in four redshift bins over the range 0.1 ≤ <jats:italic>z</jats:italic> ≤ 1. We find that over this redshift range, the characteristic luminosity (<jats:italic>M</jats:italic>*) increases by ∼0.2 mag, and the number density increases by a factor of 4. While LCBGs make up only about 18% of galaxies more luminous than <jats:italic>M</jats:italic> <jats:sub> <jats:italic>B</jats:italic> </jats:sub> = −18.5 at <jats:italic>z</jats:italic> ∼ 0.2, they constitute roughly 54% at <jats:italic>z</jats:italic> ∼ 0.9. The strong evolution in number density indicates that LCBGs are an important population of galaxies to study in order to better understand the decrease in the star formation rate density of the universe since <jats:italic>z</jats:italic> ∼ 1.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We focus on the connection between the internal dynamo magnetic field and the stellar wind. If the star has a cyclic dynamo, the modulations of the magnetic field can affect the wind, which, in turn, can back-react on the boundary conditions of the star, creating a feedback loop. We have developed a 2.5D numerical setup to model this essential coupling. We have implemented an alpha–omega mean-field dynamo in the PLUTO code and then coupled it to a spherical polytropic wind model via an interface composed of four grid layers with dedicated boundary conditions. We present here a dynamo model close to a young Sun with cyclic magnetic activity. First, we show how this model allows one to track the influence of the dynamo activity on the corona by displaying the correlation between the activity cycle, the coronal structure, and the time evolution of integrated quantities. Then we add the feedback of the wind on the dynamo and discuss the changes observed in the dynamo symmetry and wind variations. We explain these changes in terms of dynamo modes; in this parameter regime, the feedback loop leads to a coupling between the dynamo families via a preferred growth of the quadrupolar mode. We also study our interface in terms of magnetic helicity and show that it leads to a small injection in the dynamo. This model confirms the importance of coupling physically internal and external stellar layers, as it has a direct impact on both the dynamo and the wind.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the temporal properties of the ultraluminous X-ray (ULX) pulsar M51 ULX-7 inferred from the analysis of the 2018–2020 Swift/X-ray Telescope monitoring data and archival Chandra data obtained over a period of 33 days in 2012. We find an extended low flux state, which might be indicative of propeller transition, lending further support to the interpretation that the neutron star is rotating near equilibrium. Alternatively, this off-state could be related to a variable superorbital period. Moreover, we report the discovery of periodic dips in the X-ray light curve that are associated with the binary orbital period. The presence of the dips implies a configuration where the orbital plane of the binary is closer to an edge-on orientation, and thus demonstrates that favorable geometries are not necessary in order to observe ULX pulsars. These characteristics are similar to those seen in prototypical X-ray pulsars such as Her X-1 and SMC X-1 or other ULX pulsars such as NGC 5907 ULX1.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent multiwavelength observations suggest that inner parts of protoplanetary disks (PPDs) have shorter lifetimes for heavier host stars. Since PPDs around high-mass stars are irradiated by strong ultraviolet radiation, photoevaporation may provide an explanation for the observed trend. We perform radiation hydrodynamics simulations of photoevaporation of PPDs for a wide range of host star mass of <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> = 0.5–7.0 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We derive disk mass-loss rate <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe2afieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, which has strong stellar dependence as <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}\approx 7.30\times {10}^{-9}{({M}_{* }/{\text{}}{M}_{\odot })}^{2}\,{\text{}}{M}_{\odot }\,{\mathrm{yr}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> <mml:mo>≈</mml:mo> <mml:mn>7.30</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>9</mml:mn> </mml:mrow> </mml:msup> <mml:msup> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mspace width="0.25em" /> <mml:mtext mathvariant="italic" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:mtext mathvariant="italic" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>yr</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe2afieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. The absolute value of <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe2afieqn3.gif" xlink:type="simple" /> </jats:inline-formula> scales with the adopted far-ultraviolet and X-ray luminosities. We derive the surface mass-loss rates and provide polynomial function fits to them. We also develop a semianalytic model that well reproduces the derived mass-loss rates. The estimated inner-disk lifetime decreases as the host star mass increases, in agreement with the observational trend. We thus argue that photoevaporation is a major physical mechanism for PPD dispersal for a wide range of the stellar mass and can account for the observed stellar mass dependence of the inner-disk lifetime.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Intensity mapping of the H <jats:sc>i</jats:sc> 21 cm line and the CO 2.61 mm line from the epoch of reionization has emerged as powerful, complementary, probes of the high-redshift universe. However, both maps and their cross-correlation are dominated by foregrounds. We propose a new analysis by which the signal is unbiased by foregrounds, i.e., it can be measured without foreground mitigation. We construct the antisymmetric part of two-point cross-correlation between intensity maps of the H <jats:sc>i</jats:sc> 21 cm line and the CO 2.61 mm line, arising because the statistical fluctuations of two fields have different evolution in time. We show that the sign of this new signal can distinguish model independently whether inside-out reionization happens during some interval of time. More importantly, within the framework of the excursion-set model of reionization, we demonstrate that the slope of the dipole of H <jats:sc>i</jats:sc>–CO cross-power spectrum at large scales is linear to the rate of change of global neutral fraction of hydrogen in a manner independent of reionization parameters, until the slope levels out near the end of reionization, but this trend might possibly depend on the framework of reionization modeling. The H <jats:sc>i</jats:sc>–CO dipole may be a smoking-gun probe for the speed of reionization, or “standard speedometer” for cosmic reionization. Observations of this new signal will unveil the global reionization history from the midpoint to near the completion of reionization.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we first investigate the equatorial circular orbit structure of Kerr black holes with scalar hair (KBHsSH) and highlight their most prominent features, which are quite distinct from the exterior region of ordinary bald Kerr black holes, i.e., peculiarities that arise from the combined bound system of a hole with an off-center, self-gravitating distribution of scalar matter. Some of these traits are incompatible with the thin-disk approach; thus, we identify and map out various regions in parameter space. All of the solutions for which the stable circular orbital velocity (and angular momentum) curve is continuous are used for building thin and optically thick disks around them, from which we extract the radiant energy fluxes, luminosities, and efficiencies. We compare the results in batches with the same spin parameter <jats:italic>j</jats:italic> but different normalized charges, and the profiles are richly diverse. Because of the existence of a conserved scalar charge, <jats:italic>Q</jats:italic>, these solutions are nonunique in the (<jats:italic>M</jats:italic>, <jats:italic>J</jats:italic>) parameter space. Furthermore, <jats:italic>Q</jats:italic> cannot be extracted asymptotically from the metric functions. Nevertheless, by constraining the parameters through different observations, the luminosity profile could in turn be used to constrain the Noether charge and characterize the spacetime, should KBHsSH exist.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Motivated by the discovery of the ultra-strong emission-line starburst galaxies (EELGs) known as “green pea galaxies,” in this work we consider their contribution to the intergalactic flux of ionizing UV at high redshifts. Most galaxies that have been observed show a precipitous drop in the flux blueward of their Lyman limit. However, recent observations of EELGs have discovered that many more Lyman continuum photons escape from them into intergalactic space than previously suspected. We calculate their contribution to the extragalactic background light. We also calculate the effect of these photons on the absorption of high-energy <jats:italic>γ</jats:italic>-rays. For the more distant <jats:italic>γ</jats:italic>-ray sources, particularly at <jats:italic>z</jats:italic> ≥ 3, an intergalactic opacity above a few GeV is significantly higher than previous estimates which ignored the Lyman continuum photons. We calculate the results of this increased opacity on observed <jats:italic>γ</jats:italic>-ray spectra, which produce a high-energy turnover starting at lower energies than previously thought, and a gradual spectral steepening that may also be observable.</jats:p>