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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

Isochronic Evolution and the Radioactive Decay of r-process Nuclei

T. M. SprouseORCID; G. Wendell MischORCID; M. R. MumpowerORCID

<jats:title>Abstract</jats:title> <jats:p>We report on the creation and application of a novel decay network that uses the latest data from experiment and evaluation. We use the network to simulate the late-time phase of the rapid neutron capture (<jats:italic>r</jats:italic>) process. In this epoch, the bulk of nuclear reactions, such as radiative capture, have ceased, and nuclear decays are the dominant transmutation channels. We find that the decay from short-lived to long-lived species naturally leads to an isochronic evolution in which nuclei with similar half-lives are populated at the same time. We consider random perturbations along each isobaric chain to initial solar-like <jats:italic>r</jats:italic>-process compositions to demonstrate the isochronic nature of the late-time phase of the <jats:italic>r</jats:italic>-process. Our analysis shows that detailed knowledge of the final isotopic composition allows for the prediction of late-time evolution with a high degree of confidence despite uncertainties that exist in astrophysical conditions and the nuclear physics properties of the most neutron-rich nuclei. We provide the time-dependent nuclear composition in the Appendix as supplemental material.</jats:p>

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

Pp. 22

Polycyclic Aromatic Hydrocarbons, Anomalous Microwave Emission, and their Connection to the Cold Neutral Medium

Brandon S. HensleyORCID; Claire E. MurrayORCID; Mark DodiciORCID

<jats:title>Abstract</jats:title> <jats:p>Using new large-area maps of the cold neutral medium (CNM) fraction, <jats:italic>f</jats:italic> <jats:sub>CNM</jats:sub>, we investigate the relationship between the CNM, the abundance of polycyclic aromatic hydrocarbons (PAHs), and the anomalous microwave emission (AME). We first present our <jats:italic>f</jats:italic> <jats:sub>CNM</jats:sub> map based on full-sky HI4PI data, using a convolutional neural network to convert the spectroscopic H <jats:sc>i</jats:sc> data to <jats:italic>f</jats:italic> <jats:sub>CNM</jats:sub>. We demonstrate that <jats:italic>f</jats:italic> <jats:sub>CNM</jats:sub> is strongly correlated with the fraction of dust in PAHs as estimated from mid- and far-infrared dust emission. In contrast, we find no correlation between <jats:italic>f</jats:italic> <jats:sub>CNM</jats:sub> and the amount of AME per dust emission and no to weakly negative correlation between <jats:italic>f</jats:italic> <jats:sub>CNM</jats:sub> and the AME peak frequency. These results suggest PAHs preferentially reside in cold, relatively dense gas, perhaps owing to enhanced destruction in more diffuse media. The lack of positive correlation between <jats:italic>f</jats:italic> <jats:sub>CNM</jats:sub> and AME peak frequency is in tension with expectations from theoretical models positing different spectral energy distributions of AME in the cold versus warm neutral medium. We suggest that different PAH abundances and emission physics in different interstellar environments may explain the weaker-than-expected correlation between 12 <jats:italic>μ</jats:italic>m PAH emission and AME even if PAHs are the AME carriers.</jats:p>

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

Pp. 23

Fluorine Abundances in the Galactic Nuclear Star Cluster

Rafael GuerçoORCID; Solange Ramírez; Katia CunhaORCID; Verne V. SmithORCID; Nikos PrantzosORCID; Kris SellgrenORCID; Simone DaflonORCID

<jats:title>Abstract</jats:title> <jats:p>Abundances of fluorine (<jats:sup>19</jats:sup>F), as well as isotopic ratios of <jats:sup>16</jats:sup>O/<jats:sup>17</jats:sup>O, are derived in a sample of luminous young (∼10<jats:sup>7</jats:sup>–10<jats:sup>8</jats:sup> yr) red giants in the Galactic center (with galactocentric distances ranging from 0.6–30 pc), using high-resolution infrared spectra and vibration-rotation lines of H<jats:sup>19</jats:sup>F near <jats:italic>λ</jats:italic>2.3 <jats:italic>μ</jats:italic>m. Five of the six red giants are members of the Nuclear star cluster that orbits the central supermassive black hole. Previous investigations of the chemical evolution of <jats:sup>19</jats:sup>F in Galactic thin and thick-disk stars have revealed that the nucleosynthetic origins of <jats:sup>19</jats:sup>F may be rather complex, resulting from two, or more, astrophysical sites; fluorine abundances behave as a primary element with respect to Fe abundances for thick-disk stars and as a secondary element in thin-disk stars. The Galactic center red giants analyzed fall within the thin-disk relation of F with Fe, having near-solar, to slightly larger, abundances of Fe (〈[Fe/H]〉 = +0.08 ± 0.04), with a slight enhancement of the F/Fe abundance ratio (〈[F/Fe]〉 = +0.28 ± 0.17). In terms of their F and Fe abundances, the Galactic center stars follow the thin-disk population, which requires an efficient source of <jats:sup>19</jats:sup>F that could be the winds from core-He burning Wolf–Rayet stars, or thermally pulsing AGB stars, or a combination of both. The observed increase of [F/Fe] with increasing [Fe/H] found in thin-disk and Galactic center stars is not predicted by any published chemical evolution models that are discussed, thus a quantitative understanding of yields from the various possible sources of <jats:sup>19</jats:sup>F remains unknown.</jats:p>

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

Pp. 24

The Primary Proton Spectrum of the Hadronic PeVatron Candidate HAWC J1825-134

Timur DzhatdoevORCID; Egor PodlesnyiORCID; Igor VaimanORCID

<jats:title>Abstract</jats:title> <jats:p>The <jats:italic>γ</jats:italic>-ray spectrum of the source HAWC J1825-134 measured with the High Altitude Water Cherenkov (HAWC) observatory extends beyond 200 TeV without any evidence for a steepening or cutoff. There are some indications that the <jats:italic>γ</jats:italic>-rays detected with HAWC were produced by cosmic-ray protons or nuclei colliding with the ambient gas. Assuming primary protons, we inquire which shape of the primary proton spectrum is compatible with the HAWC measurements. We find that the primary proton spectrum with the power-law shape of <jats:italic>γ</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> = 2.2 and the cutoff energy <jats:italic>E</jats:italic> <jats:sub> <jats:italic>c</jats:italic>−<jats:italic>p</jats:italic> </jats:sub> &gt; 500 TeV describes the data well. However, much harder spectra with <jats:italic>γ</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> down to 1.3 and <jats:italic>E</jats:italic> <jats:sub> <jats:italic>c</jats:italic>−<jats:italic>p</jats:italic> </jats:sub> as low as 200 TeV also do not contradict the HAWC measurements. The former option might be realized if the accelerator is inside or very near to the <jats:italic>γ</jats:italic>-ray production zone. The latter option is viable for the case of a cosmic-ray source that effectively confines low-energy (<jats:italic>E</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> &lt; 10 TeV) accelerated protons. Using publicly available data of the Fermi-LAT space <jats:italic>γ</jats:italic>-ray telescope, we derive upper limits on the intensity of the <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="object" xlink:href="HAWC J1825-134" xlink:type="simple">HAWC J1825-134</jats:named-content> source in the 1 GeV–1 TeV energy range. We show that the account of these upper limits drastically changes the interpretation: only hard (<jats:italic>γ</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub> &lt; 1.7) spectra describe the combined HAWC and Fermi-LAT data sets well.</jats:p>

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

Pp. 25

Improving White Dwarfs as Chronometers with Gaia Parallaxes and Spectroscopic Metallicities

Adam MossORCID; Ted von HippelORCID; Elliot Robinson; Kareem El-BadryORCID; David C. Stenning; David van DykORCID; Morgan FouesneauORCID; Coryn A. L. Bailer-Jones; Elizabeth Jeffery; Jimmy Sargent; Isabelle Kloc; Natalie Moticska

<jats:title>Abstract</jats:title> <jats:p>White dwarfs (WDs) offer unrealized potential in solving two problems in astrophysics: stellar age accuracy and precision. WD cooling ages can be inferred from surface temperatures and radii, which can be constrained with precision by high-quality photometry and parallaxes. Accurate and precise Gaia parallaxes along with photometric surveys provide information to derive cooling and total ages for vast numbers of WDs. Here we analyze 1372 WDs found in wide binaries with main-sequence (MS) companions and report on the cooling and total age precision attainable in these WD+MS systems. The total age of a WD can be further constrained if its original metallicity is known because the MS lifetime depends on metallicity at fixed mass, yet metallicity is unavailable via spectroscopy of the WD. We show that incorporating spectroscopic metallicity constraints from 38 wide binary MS companions substantially decreases internal uncertainties in WD total ages compared to a uniform constraint. Averaged over the 38 stars in our sample, the total (internal) age uncertainty improves from 21.04% to 16.77% when incorporating the spectroscopic constraint. Higher mass WDs yield better total age precision; for eight WDs with zero-age MS masses ≥2.0 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, the mean uncertainty in total ages improves from 8.61% to 4.54% when incorporating spectroscopic metallicities. We find that it is often possible to achieve 5% total age precision for WDs with progenitor masses above 2.0 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> if parallaxes with ≤1% precision and Pan-STARRS <jats:italic>g</jats:italic>, <jats:italic>r</jats:italic>, and <jats:italic>i</jats:italic> photometry with ≤0.01 mag precision are available.</jats:p>

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

Pp. 26

Studying Magnetic Fields and Dust in M17 Using Polarized Thermal Dust Emission Observed by SOFIA/HAWC+

Thuong Duc HoangORCID; Nguyen Bich NgocORCID; Pham Ngoc DiepORCID; Le Ngoc TramORCID; Thiem HoangORCID; Kate PattleORCID; Wanggi LimORCID; Ngan LeORCID; Dieu D. NguyenORCID; Nguyen Thi Phuong; Nguyen FudaORCID; Tuan Van Bui; Gia Bao Truong LeORCID; Hien PhanORCID; Nguyen Chau GiangORCID

<jats:title>Abstract</jats:title> <jats:p>We report on the highest spatial resolution measurement to date of magnetic fields (B-fields) in M17 using thermal dust polarization measurements taken by SOFIA/HAWC+ centered at a wavelength of 154 <jats:italic>μ</jats:italic>m. Using the Davis–Chandrasekhar–Fermi method, in which the polarization angle dispersion calculated using the structure function technique is the quantity directly observed by SOFIA/HAWC+, we found the presence of strong B-fields of 980 ± 230 and 1665 ± 885 <jats:italic>μ</jats:italic>G in the lower-density M17-N and higher-density M17-S regions, respectively. The B-field morphology in M17-N possibly mimics the fields in gravitationally collapsing molecular cores, while in M17-S the fields run perpendicular to the density structure. M17-S also displays a pillar feature and an asymmetric large-scale hourglass-shaped field. We use the mean B-field strengths to determine Alfvénic Mach numbers for both regions, finding that B-fields dominate over turbulence. We calculate the mass-to-flux ratio, <jats:italic>λ</jats:italic>, finding <jats:italic>λ</jats:italic> = 0.07 for M17-N and 0.28 for M17-S. These subcritical <jats:italic>λ</jats:italic> values are consistent with the lack of massive stars formed in M17. To study dust physics, we analyze the relationship between dust polarization fraction, <jats:italic>p</jats:italic>, emission intensity, <jats:italic>I</jats:italic>, gas column density, <jats:italic>N</jats:italic>(H<jats:sub>2</jats:sub>), polarization angle dispersion function, <jats:italic>S</jats:italic>, and dust temperature, <jats:italic>T</jats:italic> <jats:sub>d</jats:sub>. <jats:italic>p</jats:italic> decreases with intensity as <jats:italic>I</jats:italic> <jats:sup>−<jats:italic>α</jats:italic> </jats:sup> with <jats:italic>α</jats:italic> = 0.51. <jats:italic>p</jats:italic> tends to first increase with <jats:italic>T</jats:italic> <jats:sub>d</jats:sub>, but then decreases at higher <jats:italic>T</jats:italic> <jats:sub>d</jats:sub>. The latter feature, seen in M17-N at high <jats:italic>T</jats:italic> <jats:sub>d</jats:sub> when <jats:italic>N</jats:italic>(H<jats:sub>2</jats:sub>) and <jats:italic>S</jats:italic> decrease, is evidence of the radiative torque disruption effect.</jats:p>

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

Pp. 27

Simple Analytic Formula Relating the Mass and Spin of Accreting Compact Objects to Their Rapid X-Ray Variability

Gabriel TörökORCID; Andrea KotrlováORCID; Monika MatuszkováORCID; Kateřina KlimovičováORCID; Debora LančováORCID; Gabriela UrbancováORCID; Eva ŠrámkováORCID

<jats:title>Abstract</jats:title> <jats:p>Following the previous research on epicyclic oscillations of accretion disks around black holes (BHs) and neutron stars (NSs), a new model of high-frequency quasiperiodic oscillations (QPOs) has been proposed, so-called cusp torus (CT) model, which deals with oscillations of fluid in marginally overflowing accretion tori (i.e., tori terminated by cusps). According to preliminary investigations, the model provides better fits of the NS QPO data compared to the relativistic precession (RP) model. It also implies a significantly higher upper limit on the Galactic microquasar BH spins. A short analytic formula has been noticed to well reproduce the model’s predictions on the QPO frequencies in Schwarzschild spacetimes. Here we derive an extended version of this formula that applies to rotating compact objects. We start with the consideration of Kerr spacetimes and derive a formula that is not restricted to a particular specific angular momentum distribution of the inner accretion flow, such as a Keplerian or constant one. Finally, we consider Hartle–Thorne spacetimes and include corrections implied by the NS oblateness. For a particular choice of a single parameter, our relation provides frequencies predicted by the CT model. For another value, it provides frequencies predicted by the RP model. We conclude that the formula is well applicable to rotating oblate NSs and both models. We briefly illustrate the application of our simple formula on several NS sources and confirm the expectation that the CT model is compatible with realistic values of the NS mass and provides better fits of data than the RP model.</jats:p>

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

Pp. 28

Detection of Gravitational Redshift in Open Cluster Nondegenerate Stars

Carlos M. GutiérrezORCID; Nataliya Ramos-Chernenko

<jats:title>Abstract</jats:title> <jats:p>A key observational prediction of Einstein’s Equivalence Principle is that light undergoes redshift when it escapes from a gravitational field. Although astrophysics provides a wide variety of physical conditions in which this redshift should be significant, until very recently the observational evidence for this gravitational effect was limited to the light emitted by the Sun and white dwarfs. Gaia-DR2 astrometric and kinematic data, in combination with other spectroscopic observations, provides a test bench to validate such predictions in statistical terms. The aim of this paper is to analyze several thousand main-sequence and giant stars in open clusters (OCs) in order to measure the gravitational redshift effect. Observationally, a spectral shift will depend on the stellar mass-to-radius ratio as expected from the theoretical estimation of relativity. After the analysis, the obtained correlation coefficient between theoretical predictions and observations for 28 (51) OCs is <jats:italic>a</jats:italic> = 0.977 ± 0.218 (0.899 ± 0.137). The result has proven to be statistically robust and with little dependence on the details of the methodology or sample selection criteria. This study represents one of the more extensive validations of a fundamental prediction of gravity theories.</jats:p>

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

Pp. 29

On Estimating the Cosmic Molecular Gas Density from CO Line Intensity Mapping Observations

Patrick C. BreysseORCID; Shengqi YangORCID; Rachel S. Somerville; Anthony R. Pullen; Gergö PoppingORCID; Abhishek S. ManiyarORCID

<jats:title>Abstract</jats:title> <jats:p>The Millimeter-wave Intensity Mapping Experiment (mmIME) recently reported a detection of excess spatial fluctuations at a wavelength of 3 mm, which can be attributed to unresolved emission of several CO rotational transitions between <jats:italic>z</jats:italic> ∼ 1 and 5. We study the implications of these data for the high-redshift interstellar medium using a suite of state-of-the-art semianalytic simulations that have successfully reproduced many other submillimeter line observations across the relevant redshift range. We find that the semianalytic predictions are mildly in tension with the mmIME result, with a predicted CO power ∼3.5<jats:italic>σ</jats:italic> below what was observed. We explore some simple modifications to the models that could resolve this tension. Increasing the molecular gas abundance at the relevant redshifts to ∼10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> Mpc<jats:sup>−3</jats:sup>, a value well above that obtained from directly imaged sources, would resolve the discrepancy, as would assuming a CO–H<jats:sub>2</jats:sub> conversion factor <jats:italic>α</jats:italic> <jats:sub>CO</jats:sub> of ∼1.5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> K<jats:sup>−1</jats:sup> (km s<jats:sup>−1</jats:sup>)<jats:sup>−1</jats:sup> pc<jats:sup>2</jats:sup>, a value somewhat lower than is commonly assumed. We go on to demonstrate that these conclusions are quite sensitive to the detailed assumptions of our simulations, highlighting the need for more careful modeling efforts as more intensity mapping data become available.</jats:p>

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

Pp. 30

Relativistic Alfvén Waves Entering Charge-starvation in the Magnetospheres of Neutron Stars

Alexander Y. Chen; Yajie YuanORCID; Andrei M. BeloborodovORCID; Xinyu LiORCID

<jats:title>Abstract</jats:title> <jats:p>Instabilities in a neutron star can generate Alfvén waves in its magnetosphere. Propagation along the curved magnetic field lines strongly shears the wave, boosting its electric current <jats:italic>j</jats:italic> <jats:sub>A</jats:sub>. We derive an analytic expression for the evolution of the wavevector <jats:bold> <jats:italic>k</jats:italic> </jats:bold> and the growth of <jats:italic>j</jats:italic> <jats:sub>A</jats:sub>. In the strongly sheared regime, <jats:italic>j</jats:italic> <jats:sub>A</jats:sub> may exceed the maximum current <jats:italic>j</jats:italic> <jats:sub>0</jats:sub> that can be supported by the background <jats:italic>e</jats:italic> <jats:sup>±</jats:sup> plasma. We investigate these <jats:italic>charge-starved</jats:italic> waves, first using a simplified two-fluid analytic model, then with first-principles kinetic simulations. We find that the Alfvén wave is able to propagate successfully even when <jats:italic>κ</jats:italic> ≡ <jats:italic>j</jats:italic> <jats:sub>A</jats:sub>/<jats:italic>j</jats:italic> <jats:sub>0</jats:sub> ≫ 1. It sustains <jats:italic>j</jats:italic> <jats:sub>A</jats:sub> by compressing and advecting the plasma along the magnetic field lines with an increasing Lorentz factor, <jats:italic>γ</jats:italic> ≳ <jats:italic>κ</jats:italic> <jats:sup>1/2</jats:sup>. The simulations show how plasma instabilities lead to gradual dissipation of the wave energy. Our results suggest that an extremely high charge-starvation parameter <jats:italic>κ</jats:italic> ≳ 10<jats:sup>4</jats:sup> may be required in order for this mechanism to power the observed fast radio bursts (FRBs) from SGR 1935+2154. However, cosmological FRBs with much higher luminosities are unlikely to be a result of charge-starvation.</jats:p>

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

Pp. 31