adsabs/SciX_UAT_keywords huggingface dataset:
Debiased Galaxy Cluster Pressure Profiles from X-Ray Observations and Simulations

We present an updated model for the average cluster pressure profile, adjusted for hydrostatic mass bias by combining results from X-ray observations with cosmological simulations. Our model estimates this bias by fitting a power law to the relation between the "true" halo mass and X-ray cluster mass in hydrodynamic simulations (IllustrisTNG, BAHAMAS, and MACSIS). As an example application, we consider the REXCESS X-ray cluster sample and the universal pressure profile derived from scaled and stacked pressure profiles. We find adjusted masses, M500c, that are ≲15% higher and scaled pressures P/P500c that have ≲35% lower normalization than previously inferred. Our debiased pressure profile (DPP) is well-fit by a generalized Navarro-Frenk-White function, with parameters [P0, c500, α, β, γ] = [5.048, 1.217, 1.192, 5.490, 0.433] and does not require a mass-dependent correction term. When the DPP is used to model the Sunyaev-Zel'dovich (SZ) effect, we find that the integrated Compton Y-M relation has only minor deviations from self-similar scaling. The thermal SZ angular power spectrum is lower in amplitude by approximately 30%, assuming nominal cosmological parameters (e.g., Ωm = 0.3, σ8 = 0.8), and is broadly consistent with recent Planck results without requiring additional bias corrections.

Keywords: galaxy clusters; large-scale structure of the universe; observational cosmology; cosmology; intracluster medium
Carnegie Supernova Project-II: Near-infrared Spectroscopy of Stripped-envelope Core-collapse Supernovae

We present 75 near-infrared (NIR; 0.8-2.5 μm) spectra of 34 stripped-envelope core-collapse supernovae (SESNe) obtained by the Carnegie Supernova Project-II (CSP-II), encompassing optical spectroscopic Types IIb, Ib, Ic, and Ic-BL. The spectra range in phase from pre-maximum to 80 days past maximum. This unique data set constitutes the largest NIR spectroscopic sample of SESNe to date. NIR spectroscopy provides observables with additional information that is not available in the optical. Specifically, the NIR contains the strong lines of He I and allows a more detailed look at whether Type Ic supernovae are completely stripped of their outer He layer. The NIR spectra of SESNe have broad similarities, but closer examination through statistical means reveals a strong dichotomy between NIR "He-rich" and "He-poor" SNe. These NIR subgroups correspond almost perfectly to the optical IIb/Ib and Ic/Ic-BL types, respectively. The largest difference between the two groups is observed in the 2 μm region, near the He I λ2.0581 μm line. The division between the two groups is not an arbitrary one along a continuous sequence. Early spectra of He-rich SESNe show much stronger He I λ2.0581 μm absorption compared to the He-poor group, but with a wide range of profile shapes. The same line also provides evidence for trace amounts of He in half of our SNe in the He-poor group. *This paper includes data gathered with the 6.5 m Magellan Telescopes at Las Campanas Observatory, Chile.

Keywords: galactic and extragalactic astronomy; core-collapse supernovae; type ib supernovae; type ic supernovae; supernovae
Long-term Period Changes and Brightness Variations for the Deeply Eclipsing Cataclysmic Variable SW Sex

SW Sex is a deeply eclipsing cataclysmic variable with an orbital period of 0.1349 days. Based on the new photometric observations together with the data collected in the literature, we find that the orbital period shows a period wiggle from 1980 to 2015, and then decreases severely until 2020, when our observations end. If the oscillation with an amplitude of 0.000973 days and a period of 36.57 yr is due to the presence of a third body, the mass of this component can be determined as M3sini' = 0.014 M⊙. Supposing the companion and the central binary are coplanar, its mass would correspond to a giant planet. However, Applegate's mechanism can also provide enough energy to force such variation and more data will distinguish the reason. The rapid decline of the orbital period at a rate of -4.24 × 10-10 s s-1 in 2015-2020 cannot be attributed to magnetic braking. Also, Applegate's mechanism fails to produce such a fast decrease. It can be explained as the angular momentum loss caused by a strong disk wind, which declares its existence by synchronizing the period decrease with the brightness increase. In addition, the long-term brightness oscillation with an amplitude of 0.6 mag and a timescale of about 9.7 yr is discovered. This is the first it has been detected for nova-like cataclysmic variables (CVs). It will provide valuable information for understanding the disk activity and the evolution of the CVs.

Keywords: nova-like variable stars; stellar evolution; stellar winds; stellar accretion disks; ccd photometry
The Parallax of ω Centauri Measured from Gaia EDR3 and a Direct, Geometric Calibration of the Tip of the Red Giant Branch and the Hubble Constant

We use data from the ESA Gaia mission Early Data Release 3 (EDR3) to measure the trigonometric parallax of ω Cen, the first high-precision parallax measurement for the most massive globular cluster in the Milky Way. We use a combination of positional and high-quality proper motion data from EDR3 to identify over 100,000 cluster members, of which 67,000 are in the magnitude and color range where EDR3 parallaxes are best calibrated. We find the estimated parallax to be robust, demonstrating good control of systematics within the color-magnitude diagram of the cluster. We find a parallax for the cluster of 0.191 ± 0.001 (statistical) ±0.004 (systematic) mas (2.2% total uncertainty) corresponding to a distance of 5.24 ± 0.11 kpc. The parallax of ω Cen provides a unique opportunity to directly and geometrically calibrate the luminosity of the tip of the red giant branch (TRGB) because it is the only cluster with sufficient mass to provide enough red giant stars, more than 100 one magnitude below the tip, for a precise, model-free measurement of the tip. Combined with the preexisting and most widely used measurements of the tip and foreground Milky Way extinction, we find MI,TRGB =-3.97 ± 0.06 mag for the I-band luminosity of the blue edge. Using the TRGB luminosity calibrated from the Gaia EDR3 parallax of ω Cen to calibrate the luminosity of Type Ia supernovae results in a value for the Hubble constant of H0 = 72.1 ± 2.0 km s-1 Mpc-1. We make the data for the stars in ω Cen available electronically and encourage independent analyses of the results presented here.

Keywords: red giant tip; hubble constant; distance measure; globular star clusters; distance indicators
Forward Modeling of Solar Coronal Magnetic-field Measurements Based on a Magnetic-field-induced Transition in Fe X

It was recently proposed that the intensity ratios of several extreme ultraviolet spectral lines from Fe X ions can be used to measure the solar coronal magnetic field based on magnetic-field-induced transition (MIT) theory. To verify the suitability of this method, we performed forward modeling with a three-dimensional radiation magnetohydrodynamic model of a solar active region. Intensities of several spectral lines from Fe X were synthesized from the model. Based on MIT theory, the intensity ratios of the MIT line Fe X 257 Å to several other Fe X lines were used to derive magnetic-field strengths, which were then compared with the field strengths in the model. We also developed a new method to simultaneously estimate the coronal density and temperature from the Fe X 174/175 and 184/345 Å line ratios. Using these estimates, we demonstrated that the MIT technique can provide reasonably accurate measurements of the coronal magnetic field in both on-disk and off-limb solar observations. Our investigation suggests that a spectrometer that can simultaneously observe the Fe X 174, 175, 184, 257, and 345 Å lines and allow an accurate radiometric calibration for these lines is highly desired to achieve reliable measurements of the coronal magnetic field. We have also evaluated the impact of the uncertainty in the Fe x 3p4 3d 4D5/2 and 4D7/2 energy difference on the magnetic-field measurements.

Keywords: magnetohydrodynamics; solar magnetic fields; solar corona
Formation of Polar Terrestrial Circumbinary Planets

All circumbinary planets (CBPs) currently detected are in orbits that are almost coplanar to the binary orbit. While misaligned CBPs are more difficult to detect, observations of polar-aligned circumbinary gas and debris disks around eccentric binaries suggest that polar planet formation may be possible. A polar-aligned planet has a stable orbit that is inclined by 90° to the orbital plane of the binary with an angular momentum vector that is aligned to the binary eccentricity vector. With n-body simulations we model polar terrestrial planet formation using hydrodynamic gas disk simulations to motivate the initial particle distribution. Terrestrial planet formation around an eccentric binary is more likely in a polar alignment than in a coplanar alignment. Similar planetary systems form in a polar alignment around an eccentric binary and a coplanar alignment around a circular binary. The polar planetary systems are stable even with the effects of general relativity. Planetary orbits around an eccentric binary exhibit tilt and eccentricity oscillations at all inclinations; however, the oscillations are larger in the coplanar case than the polar case. We suggest that polar-aligned terrestrial planets will be found in the future.

Keywords: binary stars; solar system terrestrial planets; extrasolar rocky planets; exoplanet formation
The Dynamics and Gravitational-wave Signal of a Binary Flying Closely by a Kerr Supermassive Black Hole

Recent astrophysical models predict that stellar-mass binary black holes (BBHs) could form and coalesce within a few gravitational radii of a supermassive black hole (SMBH). Detecting the gravitational waves (GWs) from such systems requires numerical tools that can track the dynamics of the binaries while capturing all the essential relativistic effects. This work develops upon our earlier study of a BBH moving along a circular orbit in the equatorial plane of a Kerr SMBH. Here we modify the numerical method to simulate a BBH falling toward the SMBH along a parabolic orbit of arbitrary inclination with respect to the equator. By tracking the evolution in a frame freely falling alongside the binary, we find that the eccentricity of the BBH is more easily excited than it is in the previous equatorial case, and that the cause is the asymmetry of the tidal tensor imposed on the binary when the binary moves out of the equatorial plane. Since the eccentricity reaches maximum around the same time as the BBH becomes the closest to the SMBH, multiband GW bursts could be produced that are simultaneously detectable by space- and ground-based detectors. We show that the effective spin parameters of such GW events also undergo significant variation due to the rapid reorientation of the inner BBHs during their interaction with SMBHs. These results demonstrate the richness of three-body dynamics in the region of strong gravity, and highlight the necessity of building new numerical tools to simulate such systems.

Keywords: astrophysical black holes; gravitational wave sources; stellar mass black holes; supermassive black holes
A Fully Explicit Integrator for Modeling Astrophysical Reactive Flows

Simulating complex astrophysical reacting flows is computationally expensive-reactions are stiff and typically require implicit integration methods. The reaction update is often the most expensive part of a simulation, which motivates the exploration of more economical methods. In this research note, we investigate how the explicit Runge-Kutta-Chebyshev (RKC) method performs compared to an implicit method when applied to astrophysical reactive flows. These integrators are applied to simulations of X-ray bursts arising from unstable thermonuclear burning of accreted fuel on the surface of neutron stars. We show that the RKC method performs with similar accuracy to our traditional implicit integrator, but is more computationally efficient when run on CPUs.

Keywords: computational methods; gpu computing; hydrodynamical simulations; hydrodynamics; open source software; x-ray bursts
Globular Cluster Systems of Massive Compact Elliptical Galaxies in the Local Universe: Evidence for Relic Red Nuggets?

Nearby massive compact elliptical galaxies (MCEGs) are strong candidates for relic galaxies (i.e., local analogs of red nuggets at high redshifts). It is expected that the globular cluster (GC) systems of relic galaxies are dominated by red (metal-rich) GCs. NGC 1277 is known as a unique example of such a galaxy in the previous study. In this study, we search for GCs in 12 nearby MCEGs at distances of ≲100 Mpc from the Hubble Space Telescope/Wide Field Camera 3 F814W(I814)/F160W(H160) archival images. We find that most of these MCEGs host a rich population of GCs with a color range of $0.0\lt {({I}_{814}-{H}_{160})}_{0}\lt 1.1$ . The fractions of their red GCs range from fRGC = 0.2 to 0.7 with a mean of fRGC = 0.48 ± 0.14. We divide the MCEG sample into two groups: one in clusters and the other in groups/fields. The mean red GC fraction of the cluster MCEGs is 0.60 ± 0.06, which is 0.2 larger than the value of the group/field MCEGs, 0.40 ± 0.10. The value for the cluster MCEGs is ~0.3 larger than the mean value of giant early-type galaxies with similar stellar mass in the Virgo Cluster (fRGC = 0.33 ± 0.13). Our results show that most of the MCEGs in our sample are indeed relic galaxies. This further implies that a majority of the red GCs in MCEGs are formed early in massive galaxies and that most MCEGs in the local universe have rarely undergone mergers after they became red nuggets about 10 Gyr ago.

Keywords: compact galaxies; elliptical galaxies; galaxy evolution; globular star clusters
Determination of Solar Wind Angular Momentum and Alfvén Radius from Parker Solar Probe Observations

As fundamental parameters of the Sun, the Alfvén radius and angular momentum loss determine how the solar wind changes from sub-Alfvénic to super-Alfvénic and how the Sun spins down. We present an approach to determining the solar wind angular momentum flux based on observations from Parker Solar Probe (PSP). A flux of about 0.15 × 1030 dyn cm sr-1 near the ecliptic plane and 0.7:1 partition of that flux between the particles and magnetic field are obtained by averaging data from the first four encounters within 0.3 au from the Sun. The angular momentum flux and its particle component decrease with the solar wind speed, while the flux in the field is remarkably constant. A speed dependence in the Alfvén radius is also observed, which suggests a "rugged" Alfvén surface around the Sun. Substantial diving below the Alfvén surface seems plausible only for relatively slow solar wind given the orbital design of PSP. Uncertainties are evaluated based on the acceleration profiles of the same solar wind streams observed at PSP and a radially aligned spacecraft near 1 au. We illustrate that the "angular momentum paradox" raised by Réville et al. can be removed by taking into account the contribution of the alpha particles. The large proton transverse velocity observed by PSP is perhaps inherent in the solar wind acceleration process, where an opposite transverse velocity is produced for the alphas with the angular momentum conserved. Preliminary analysis of some recovered alpha parameters tends to agree with the results.

Keywords: fundamental parameters of stars; solar rotation; solar wind
Is the High-energy Neutrino Event IceCube-200530A Associated with a Hydrogen-rich Superluminous Supernova?

The Zwicky Transient Facility follow-up campaign of alerts released by the IceCube Neutrino Observatory has led to the likely identification of the transient AT2019fdr as the source of the neutrino event IC200530A. AT2019fdr was initially suggested to be a tidal disruption event in a Narrow-Line Seyfert 1 galaxy. However, the combination of its spectral properties, color evolution, and feature-rich light curve suggests that AT2019fdr may be a Type IIn superluminous supernova. In the latter scenario, IC200530A may have been produced via inelastic proton-proton collisions between the relativistic protons accelerated at the forward shock and the cold protons of the circumstellar medium. Here, we investigate this possibility and find that at most 4.6 × 10-2 muon neutrino and antineutrino events are expected to be detected by the IceCube Neutrino Observatory within 394 days of discovery in the case of excellent discrimination of the atmospheric background. After correcting for the Eddington bias, which occurs when a single cosmic neutrino event is adopted to infer the neutrino emission at the source, we conclude that IC200530A may originate from the hydrogen-rich superluminous supernova AT2019fdr.

Keywords: type ii supernovae; neutrino astronomy; particle astrophysics
Experimental and Computational Studies on the Physicochemical Behavior of Phosphine Induced by Reactions with H and D Atoms on Interstellar Ice Grains

Phosphine (PH3) is an important molecule in the chemistry of phosphorus (P)-bearing species in the interstellar medium. Interstellar PH3 is thought to primarily form on icy grains, where several surface processes may occur during and after its formation. To better understand the physicochemical behavior of PH3 on icy grains in dense molecular clouds, we performed experimental and computational studies on the reactions of phosphine with H and D atoms at low temperatures. We found that phosphine and its deuterated isotopologue PD3 are released into the gas phase from icy surfaces (porous amorphous, compact amorphous, and crystalline ice) via chemical desorption. Even though the effective desorption cross section did not vary between the different icy surfaces, the desorption fraction was smallest for porous amorphous ice. We confirmed that, at 10 K on icy surfaces, H-D substitution reactions of PH3 and D-H substitution reactions of PD3 occurred following reactions with D and H atoms, respectively. Because the activation barrier for the abstraction of H or D atoms from phosphine is ~1500 K, quantum tunneling should play a role at low temperatures. Under the present experimental conditions, the H-D substitution reaction of PH3 was slightly slower than the D-H substitution reaction of PD3. Therefore, the rates of the H-D and D-H substitution reactions should not be constrained by tunneling reactions but rather by other elementary processes such as atom diffusion on ice. Our experimental results suggest the possible presence of a deuterated phosphine isotopologue (PH2D) in PH3-rich interstellar environments.

Keywords: astrochemistry; dense interstellar clouds; interstellar dust processes; pre-biotic astrochemistry
Black Hole Mass and Eddington-ratio Distributions of Less-luminous Quasars at z ∼ 4 in the Subaru Hyper Suprime-Cam Wide Field

We investigate the black hole mass function (BHMF) and Eddington-ratio distribution function (ERDF) of broad-line active galactic nuclei (AGNs) at z = 4, based on a sample of 52 quasars with i < 23.2 at 3.50 ≤ z ≤ 4.25 from the Hyper Suprime-Cam Subaru Strategic Program S16A-Wide2 data set, and 1462 quasars with i < 20.2 in the same redshift range from the Sloan Digital Sky Survey data release 7 quasar catalog. Virial black hole (BH) masses of quasars are estimated using the width of the CIV 1549 Å line and the continuum luminosity at 1350 Å. To obtain the intrinsic broad-line AGN BHMF and ERDF, we correct for the incompleteness in the low-mass and/or low-Eddington-ratio ranges caused by the flux-limited selection. The resulting BHMF is constrained down to $\mathrm{log}{M}_{\mathrm{BH}}/{M}_{\odot }\sim 7.5$ . In comparison with broad-line AGN BHMFs at z ∼ 2 in the literature, we find that the number density of massive SMBHs peaks at higher redshifts, consistent with the downsizing evolutionary scenario. Additionally, the resulting ERDF shows a negative dependence on BH mass, suggesting more massive SMBHs tend to accrete at lower-Eddington ratios at z = 4. With the derived intrinsic broad-line AGN BHMF, we also evaluate the active fraction of broad-line AGNs among the entire SMBH population at z = 4. The resulting active fraction may suggest a positive dependence on BH mass. Finally, we examine the time evolution of broad-line AGN BHMF between z = 4 and 6 through solving the continuity equation. The results suggest that the broad-line AGN BHMFs at z = 4–6 only show evolution in their normalization, but with no significant changes in their shape.

Keywords: supermassive black holes; galaxy evolution; high-redshift galaxies; active galaxies
Mapping the Chemodynamics of the Galactic Disk Using the LAMOST and APOGEE Red Clump Stars

A detailed measurement is made of the metallicity distributions, kinematics, and dynamics of the thin and thick disks across a large disk volume (5.0 ≤ R ≤ 15.0 kpc and ∣Z∣ ≤ 3.0 kpc) by using the LAMOST–APOGEE red clump stars. The metallicity distribution results show that the radial metallicity gradient Δ[Fe/H]/ΔR of the thin disk weakens with ∣Z∣ from ‑0.06 dex kpc‑1 at around ∣Z∣ < 0.25 kpc to ‑0.02 dex kpc‑1 at around ∣Z∣ > 2.75 kpc, while the thick disk displays a global weak positive Δ[Fe/H]/ΔR that is generally weaker than 0.01 dex kpc‑1. The vertical metallicity gradient Δ[Fe/H]/Δ∣Z∣ steadily weakened from ‑0.36 dex kpc‑1 at R ∼ 5.5 kpc to ‑0.05 dex kpc‑1 at around R > 11.5 kpc for the thin disk, while the thick disk presents an almost constant value (nearly ‑0.06∼‑0.08 dex kpc‑1) for all the R bins. These results indicate the contribution of the radial migration to the disk evolution, and the obvious north–south asymmetry in [Fe/H] may be linked to disk warp and/or disk perturbation events. The oscillations in the corrected Δ[Fe/H]/Δ∣Z∣ with R likely arise from the resonances with the Galactic bar. Our detailed measurements of ΔV ϕ /Δ[Fe/H] indicate an inside-out and upside-down star formation scenario for the thick disk. The results of eccentricity distributions and [α/Fe]–velocity dispersion relations are likely to suggest that thick-disk stars require an obvious contribution from other heating mechanisms, such as mergers and accretion, or are born in the chaotic mergers of gas-rich systems and/or the turbulent interstellar medium.

Keywords: stellar abundances; stellar kinematics; milky way dynamics; milky way disk; milky way formation; milky way evolution
Discovery of Magnetically Guided Metal Accretion onto a Polluted White Dwarf

Dynamically active planetary systems orbit a significant fraction of white dwarf stars. These stars often exhibit surface metals accreted from debris disks, which are detected through infrared excess or transiting structures. However, the full journey of a planetesimal from star-grazing orbit to final dissolution in the host star is poorly understood. Here, we report the discovery that the cool metal-polluted star WD 0816–310 has cannibalized heavy elements from a planetary body similar in size to Vesta, and where accretion and horizontal mixing processes have clearly been controlled by the stellar magnetic field. Our observations unveil periodic and synchronized variations in metal line strength and magnetic field intensity, implying a correlation between the local surface density of metals and the magnetic field structure. Specifically, the data point to a likely persistent concentration of metals near a magnetic pole. These findings demonstrate that magnetic fields may play a fundamental role in the final stages of exoplanetary bodies that are recycled into their white dwarf hosts.

Keywords: white dwarf stars; debris disks; stellar magnetic fields; exoplanet systems