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The Astrophysical Journal (ApJ)

Resumen/Descripción – provisto por la editorial en inglés
The Astrophysical Journal is an open access journal devoted to recent developments, discoveries, and theories in astronomy and astrophysics. Publications in ApJ constitute significant new research that is directly relevant to astrophysical applications, whether based on observational results or on theoretical insights or modeling.
Palabras clave – provistas por la editorial

astronomy; astrophysics

Disponibilidad
Institución detectada Período Navegá Descargá Solicitá
No detectada desde jul. 1995 / hasta dic. 2023 IOPScience

Información

Tipo de recurso:

revistas

ISSN impreso

0004-637X

ISSN electrónico

1538-4357

Editor responsable

American Astronomical Society (AAS)

Idiomas de la publicación

  • inglés

País de edición

Reino Unido

Información sobre licencias CC

https://creativecommons.org/licenses/by/4.0/

Cobertura temática

Tabla de contenidos

Visible Opacity of M Dwarfs and Hot Jupiters: The TiO B 3Π−X 3Δ Band System

W. Doug Cameron; Peter BernathORCID

<jats:title>Abstract</jats:title> <jats:p>The TiO <jats:italic>B</jats:italic> <jats:sup>3</jats:sup>Π − <jats:italic>X</jats:italic> <jats:sup>3</jats:sup>Δ electronic transition (<jats:inline-formula> <jats:tex-math> <?CDATA ${\gamma }^{{\prime} }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac49f0ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> system) is an important opacity source in the atmospheres of M dwarfs and hot Jupiter exoplanets. The 0–0, 1–0, and 2–1 bands of the <jats:italic>B</jats:italic> <jats:sup>3</jats:sup>Π − <jats:italic>X</jats:italic> <jats:sup>3</jats:sup>Δ band system have been analyzed using a TiO emission spectrum recorded at the McMath-Pierce Solar Telescope, operated by the National Solar Observatory at Kitt Peak, Arizona. Improved spectroscopic and equilibrium constants were determined. Line strengths were calculated from an ab initio transition-dipole moment function scaled using an experimental lifetime. A new line list for <jats:inline-formula> <jats:tex-math> <?CDATA $v^{\prime} =0\mbox{--}2$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>v</mml:mi> <mml:mo accent="false">′</mml:mo> <mml:mo>=</mml:mo> <mml:mn>0</mml:mn> <mml:mo>–</mml:mo> <mml:mn>2</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac49f0ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>v</jats:italic>″ = 0–4 of the <jats:italic>B</jats:italic> <jats:sup>3</jats:sup>Π − <jats:italic>X</jats:italic> <jats:sup>3</jats:sup>Δ band system is provided.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 39

Estimations and Scaling Laws for Stellar Magnetic Fields

Xing WeiORCID

<jats:title>Abstract</jats:title> <jats:p>In rapidly rotating turbulence (i.e., a Rossby number much less than unity), the standard mixing length theory for turbulent convection breaks down. However, the Coriolis force enters the force balance such that the magnetic field eventually depends on rotation. By simplifying the self-sustained magnetohydrodynamics dynamo equations of electrically conducting fluid motion, with the aid of the theory of isotropic nonrotating or anisotropic rotating turbulence driven by thermal convection, we make estimations and derive scaling laws for stellar magnetic fields with slow and fast rotation. Our scaling laws are in good agreement with the observations.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 40

Geminga SNR: Possible Candidate of the Local Cosmic-Ray Factory

Bing Zhao; Wei LiuORCID; Qiang Yuan; Hong-Bo Hu; Xiao-Jun BiORCID; Han-Rong Wu; Xun-Xiu Zhou; Yi-Qing GuoORCID

<jats:title>Abstract</jats:title> <jats:p>The precise measurements of energy spectra and anisotropy could help us uncover the local cosmic-ray accelerators. Our recent works have shown that spectral hardening above 200 GeV in the energy spectra and transition of large-scale anisotropy at ∼100 TeV are of local source origin. Less than 100 TeV, both spectral hardening and anisotropy explicitly indicate the dominant contribution from nearby sources. In this work, we further investigate the parameter space of sources allowed by the observational energy spectra and anisotropy amplitude. To obtain the best-fit source parameters, a numerical package to compute the parameter posterior distributions based on Bayesian inference, which is applied to perform an elaborate scan of parameter space. We find that by combining the energy spectra and anisotropy data, the permissible range of location and age of the local source is considerably reduced. When comparing with the current local supernova remnant (SNR) catalog, only Geminga SNR could be the proper candidate of the local cosmic-ray source.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 41

Synchronization of Small-scale Magnetic Features, Blinkers, and Coronal Bright Points

Zahra Shokri; Nasibe AlipourORCID; Hossein SafariORCID; Pradeep KayshapORCID; Olena Podladchikova; Giuseppina NigroORCID; Durgesh TripathiORCID

<jats:title>Abstract</jats:title> <jats:p>We investigate the relationship between different transients such as blinkers detected in images taken at 304 Å, extreme ultraviolet coronal bright points (ECBPs) at 193 Å, X-ray coronal bright points (XCBPs) at 94 Å on the Atmospheric Imaging Assembly, and magnetic features observed by the Helioseismic and Magnetic Imager during 10 yr of solar cycle 24. An automatic identification method is applied to detect transients, and the YAFTA algorithm is used to extract the magnetic features. Using 10 yr of data, we detect in total 7,483,827 blinkers, 2,082,162 ECBPs, and 1,188,839 XCBPs, respectively, with their birth rate of about 1.1 × 10<jats:sup>−18</jats:sup> m<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>, 3.8 × 10<jats:sup>−19</jats:sup> m<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>, and 1.5 × 10<jats:sup>−19</jats:sup> m<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>. We find that about 80% of blinkers are observed at the boundaries of supergranules, and 57% (34%) are associated with ECBPs (XCBPs). We further find that about 61%–80% of transients are associated with the isolated magnetic poles in the quiet Sun and that the normalized maximum intensities of the transients are correlated with the photospheric magnetic flux of poles via a power law. These results conspicuously show that these transients have a magnetic origin and their synchronized behavior provides further clues toward the understanding of the coupling among the different layers of the solar atmosphere. Our study further reveals that the appearance of these transients is strongly anticorrelated with the sunspots’ cycle. This finding can be relevant for a better understanding of solar dynamo and magnetic structures at different scales during the solar cycle.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 42

The Critical Core Mass of Rotating Planets

Wei Zhong; Cong YuORCID

<jats:title>Abstract</jats:title> <jats:p>The gravitational harmonics measured from the Juno and Cassini spacecraft help us specify the internal structure and chemical elements of Jupiter and Saturn, respectively. However, we still do not know much about the impact of rotation on the planetary internal structure as well as on their formation. The centrifugal force induced by the rotation deforms the planetary shape and partially counteracts the gravitational force. Thus, rotation will affect the critical core mass of the exoplanet. Once the atmospheric mass becomes comparable to the critical core mass, the planet will enter the runaway accretion phase and become a gas giant. We have confirmed that the critical core masses of rotating planets depend on the stiffness of the polytrope, the outer boundary conditions, and the thickness of the isothermal layer. The critical core mass with the Bondi boundary condition is determined by the surface properties. The critical core mass of a rotating planet will increase with the core gravity (i.e., the innermost density). For the Hill boundary condition, the soft polytrope shares the same properties as planets with the Bondi boundary condition. Because the total mass for planets with the Hill boundary condition increases with the decrease of the polytropic index, a higher core gravity is required for rotating planets. As a result, the critical core mass in the stiff Hill model sharply increases. The rotational effects become more important when the radiative and convective regions coexist. Further, the critical core mass of planets with the Hill (Bondi) boundary increases noticeably as the radiative layer becomes thinner (thicker).</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 43

Dynamical Friction and Tidal Interactions

Mahmood RoshanORCID; Bahram MashhoonORCID

<jats:title>Abstract</jats:title> <jats:p>We discuss dynamical friction in an <jats:italic>N</jats:italic>-body system in the presence of tidal interactions caused by a distant external source. Using the distant tide approximation, we develop a perturbation scheme for the calculation of dynamical friction that takes tidal effects into account in linear order. In this initial analytic approach to the problem, we neglect the influence of tides on the distribution function of stars in the background stellar system. Our result for the dynamical friction force in the appropriate limit is in agreement with Chandrasekhar’s formula in the absence of tides. We provide preliminary estimates for the tidal contributions to the dynamical friction force. The astrophysical implications of our results are briefly discussed.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 44

The Importance of Being Interpretable: Toward an Understandable Machine Learning Encoder for Galaxy Cluster Cosmology

Michelle NtampakaORCID; Alexey VikhlininORCID

<jats:title>Abstract</jats:title> <jats:p>We present a deep machine-learning (ML) approach to constraining cosmological parameters with multiwavelength observations of galaxy clusters. The ML approach has two components: an encoder that builds a compressed representation of each galaxy cluster and a flexible convolutional neural networks to estimate the cosmological model from a cluster sample. It is trained and tested on simulated cluster catalogs built from the <jats:monospace>Magneticum</jats:monospace> simulations. From the simulated catalogs, the ML method estimates the amplitude of matter fluctuations, <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub>, at approximately the expected theoretical limit. More importantly, the deep ML approach can be interpreted. We lay out three schemes for interpreting the ML technique: a leave-one-out method for assessing cluster importance, an average saliency for evaluating feature importance, and correlations in the terse layer for understanding whether an ML technique can be safely applied to observational data. These interpretation schemes led to the discovery of a previously unknown self-calibration mode for flux- and volume-limited cluster surveys. We describe this new mode, which uses the amplitude and peak of the cluster mass probability density function as anchors for mass calibration. We introduce the term <jats:italic>overspecialized</jats:italic> to describe a common pitfall in astronomical applications of ML in which the ML method learns simulation-specific details, and we show how a carefully constructed architecture can be used to check for this source of systematic error.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 45

Using Computational Models to Uncover the Parameters of Three Kepler Binaries: KIC 5957123, KIC 8314879, and KIC 10727668*

Padraic E. Odesse; Catherine LovekinORCID

<jats:title>Abstract</jats:title> <jats:p>Theories of stellar convective core overshoot can be examined through analysis of pulsating stars. Better accuracy can be achieved by obtaining external constraints such as those provided by observing pulsating stars in eclipsing binary systems, but this requires that the binary parameters be identified so photometric variations of the pulsating component may be isolated from the binary periodicity. This study aims to uncover the physical parameters of three binaries observed by the Kepler spacecraft. We also seek to evaluate the feasibility of accurately constraining binaries using only readily available time-series photometry and distance estimates. Binary models were constructed using the Physics of Eclipsing Binaries software package. Markov Chain Monte Carlo (MCMC) methods were used to sample the parameter space of these models and provide estimates of the posterior distributions for these systems. An initial run using binned light-curve data was performed to identify general parameter trends and provide initializing distributions for a subsequent analysis incorporating the full data set. We present theoretical models for all three binaries, along with posterior distributions from our MCMC analyses. Models for KIC 8314879 and KIC 10727668 produced a good match to the observed data, while the model of KIC 5957123 failed to generate an appropriate synthetic light curve. For the two successful models, we interpret the posterior distributions and discuss confidence in our parameter estimates and uncertainties. We also evaluate the feasibility of this procedure in various contexts and propose several modifications to improve the success of future studies.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 46

Stars Crushed by Black Holes. II. A Physical Model of Adiabatic Compression and Shock Formation in Tidal Disruption Events

Eric R. CoughlinORCID; C. J. NixonORCID

<jats:title>Abstract</jats:title> <jats:p>We develop a Newtonian model of a deep tidal disruption event (TDE), for which the pericenter distance of the star, <jats:italic>r</jats:italic> <jats:sub>p</jats:sub>, is well within the tidal radius of the black hole, <jats:italic>r</jats:italic> <jats:sub>t</jats:sub>, i.e., when <jats:italic>β</jats:italic> ≡ <jats:italic>r</jats:italic> <jats:sub>t</jats:sub>/<jats:italic>r</jats:italic> <jats:sub>p</jats:sub> ≫ 1. We find that shocks form for <jats:italic>β</jats:italic> ≳ 3, but they are weak (with Mach numbers ∼1) for all <jats:italic>β</jats:italic>, and that they reach the center of the star prior to the time of maximum adiabatic compression for <jats:italic>β</jats:italic> ≳ 10. The maximum density and temperature reached during the TDE follow much shallower relations with <jats:italic>β</jats:italic> than the previously predicted <jats:inline-formula> <jats:tex-math> <?CDATA ${\rho }_{\max }\propto {\beta }^{3}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ρ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mi>β</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3fb9ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${T}_{\max }\propto {\beta }^{2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mi>β</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3fb9ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> scalings. Below <jats:italic>β</jats:italic> ≃ 10, this shallower dependence occurs because the pressure gradient is dynamically significant before the pressure is comparable to the ram pressure of the free-falling gas, while above <jats:italic>β</jats:italic> ≃ 10, we find that shocks prematurely halt the compression and yield the scalings <jats:inline-formula> <jats:tex-math> <?CDATA ${\rho }_{\max }\propto {\beta }^{1.62}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ρ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mi>β</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1.62</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3fb9ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${T}_{\max }\propto {\beta }^{1.12}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mi>β</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1.12</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3fb9ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>. We find excellent agreement between our results and high-resolution simulations. Our results demonstrate that, in the Newtonian limit, the compression experienced by the star is completely independent of the mass of the black hole. We discuss our results in the context of existing (affine) models, polytropic versus non-polytropic stars, and general relativistic effects, which become important when the pericenter of the star nears the direct capture radius, at <jats:italic>β</jats:italic> ∼ 12.5 (2.7) for a solar-like star disrupted by a 10<jats:sup>6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> (10<jats:sup>7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) supermassive black hole.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 47

Class I Methanol Masers Related to Shocks Induced by Bar Rotation in the Nearby Starburst Galaxy Maffei 2

Xi ChenORCID; Tian Yang; Simon P. EllingsenORCID; Tiege P. McCarthyORCID; Zhi-Yuan Ren

<jats:title>Abstract</jats:title> <jats:p>We report the detection of class I methanol maser at the 36.2 GHz transition toward the nearby starburst galaxy Maffei 2 with the Karl G. Jansky Very Large Array. Observations of the 36.2 GHz transition at two epochs separated by ∼4 yr show consistencies in both the spatial distribution and flux density of the methanol emission in this transition. Similar to the detections in other nearby starbursts the class I methanol masers sites are offset by a few hundred pc from the center of the galaxy and appear to be associated with the bar edges of Maffei 2. Narrow spectral features with line widths of a few km s<jats:sup>−1</jats:sup> are detected, supporting the hypothesis that they are masing. Compared to other nearby galaxies with the detections in the 36.2 GHz methanol maser transition, the maser detected in Maffei 2 has about an order of magnitude higher isotropic luminosity, and thus represents the first confirmed detection of class I methanol megamasers. The spatial distribution of the 36.2 GHz maser spot clusters may trace the rotational gas flow of the galactic bar, providing direct evidence that the class I methanol maser is related to shocks induced by galactic bar rotation. A tentative detection in the 6.7 GHz class II methanol maser (at a 5<jats:italic>σ</jats:italic> level) is also reported. This is comparable in luminosity to some of the 6.7 GHz maser sources detected in Galactic star-forming regions. The 6.7 GHz methanol emission appears to be associated with star formation activity in a smaller volume, rather than related to the larger-scale galactic activities.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 48