adsabs/SciX_UAT_keywords huggingface dataset:
Collapsar Black Holes Are Likely Born Slowly Spinning

Collapsing stars constitute the main black hole (BH) formation channel, and are occasionally associated with the launch of relativistic jets that power γ-ray bursts (GRBs). Thus, collapsars offer an opportunity to infer the natal (before spin-up/down by accretion) BH spin directly from observations. We show that once the BH saturates with a large-scale magnetic flux, the jet power is dictated by the BH spin and mass accretion rate. Core-collapse simulations by Halevi et al. and GRB observations favor stellar density profiles that yield an accretion rate of $\dot{m}\approx {10}^{-2}\,{M}_{\odot }\,{{\rm{s}}}^{-1}$ , weakly dependent on time. This leaves the spin as the main factor that governs the jet power. By comparing the jet power to characteristic GRB luminosities, we find that the majority of BHs associated with jets are likely born slowly spinning with a dimensionless spin of a ≃ 0.2, or a ≃ 0.5 for wobbling jets, with the main uncertainty originating in the unknown γ-ray radiative efficiency. This result could be applied to the entire core-collapse BH population, unless an anticorrelation between the stellar magnetic field and angular momentum is present. In a companion paper, Jacquemin-Ide et al., we show that regardless of the natal spin, the extraction of BH rotational energy leads to spin-down to a ≲ 0.2, consistent with gravitational-wave observations. We verify our results by performing the first 3D general-relativistic magnetohydrodynamic simulations of collapsar jets with characteristic GRB energies, powered by slowly spinning BHs. We find that jets of typical GRB power struggle to escape from the star, providing the first numerical indication that many jets fail to generate a GRB.

Keywords: stellar mass black holes; black hole physics; astrophysical black holes; gamma-ray bursts; core-collapse supernovae; magnetohydrodynamical simulations
AT 2019avd: A Tidal Disruption Event with a Two-phase Evolution

Tidal disruption events (TDEs) can uncover the quiescent supermassive black holes (SMBHs) at the center of galaxies and also offer a promising method to study them. After the disruption of a star by an SMBH, the highly elliptical orbit of the debris stream will be gradually circularized due to the self-crossing, and then the circularized debris will form an accretion disk. The recent TDE candidate AT 2019avd has double peaks in its optical light curve, and the X-ray emerges near the second peak. The durations of the peaks are ~400 and 600 days, respectively, and the separation between them is ~700 days. We fit its spectral energy distribution and analyze its light curves in the optical/UV, mid-infrared, and X-ray bands. We find that this source can be interpreted as a two-phase scenario in which the first phase is dominated by the stream circularization, and the second phase is the delayed accretion. We use the succession of the self-crossing model and delayed accretion model to fit the first and second peaks, respectively. The fitting result implies that AT 2019avd can be interpreted by the partial disruption of a 0.9 M ⊙ star by a 7 × 106 M ⊙ SMBH, but this result is sensitive to the stellar model. Furthermore, we find that the large-amplitude (by factors up to ~5) X-ray variability in AT 2019avd can be interpreted as the rigid-body precession of the misaligned disk due to the Lense-Thirring effect of a spinning SMBH, with a precession period of 10-25 days.

Keywords: accretion; black hole physics; galaxy nuclei; tidal disruption
The Multilayer Nature of Molecular Gas toward the Cygnus Region

We study the physical properties and 3D distribution of molecular clouds (MCs) toward the Cygnus region using the MWISP CO survey and Gaia DR3 data. Based on Gaussian decomposition and clustering for 13CO lines, over 70% of the fluxes are recovered. With the identification result of 13CO structures, two models are designed to measure the distances of the molecular gas in velocity crowding regions. The distances of more than 200 large 13CO structures are obtained toward the 150 deg2 region. Additionally, tens of the identified MC structures coincide well with masers and/or intense mid-IR emission. We find multiple gas layers toward the region: (1) the extensive gas structures composing the Cygnus Rift from 700 pc to 1 kpc across the whole region; (2) the ∼1.3 kpc gas layer mainly in the Cygnus X South region; and (3) the 1.5 kpc dense filament at the Cygnus X North region and many cometary clouds shaped by Cygnus OB2. We also note that the spatial distribution of young stellar object candidates is generally consistent with the molecular gas structures. The total molecular mass of the Cygnus region is estimated to be ∼2.7 × 106 M ⊙ assuming an X-factor ratio ${X}_{\mathrm{CO}}=2\times {10}^{20}\,{\mathrm{cm}}^{-2}{\,({\rm{K}}\,\mathrm{km}\,{{\rm{s}}}^{-1})}^{-1}$ . The foreground Cygnus Rift contributes ∼25% of the molecular mass in the whole region. Our work presents a new 3D view of the MCs' distribution toward the Cygnus X region, as well as the exact molecular gas mass distribution in the foreground Cygnus Rift.

Keywords: interstellar medium; distance measure; molecular clouds; molecular gas
The Magnificent Five Images of Supernova Refsdal: Time Delay and Magnification Measurements

In late 2014, four images of supernova (SN) "Refsdal," the first known example of a strongly lensed SN with multiple resolved images, were detected in the MACS J1149 galaxy-cluster field. Following the images' discovery, the SN was predicted to reappear within hundreds of days at a new position ~8″ away in the field. The observed reappearance in late 2015 makes it possible to carry out Refsdal's original proposal to use a multiply imaged SN to measure the Hubble constant H 0, since the time delay between appearances should vary inversely with H 0. Moreover, the position, brightness, and timing of the reappearance enable a novel test of the blind predictions of galaxy-cluster models, which are typically constrained only by the positions of multiply imaged galaxies. We have developed a new photometry pipeline that uses DOLPHOT to measure the fluxes of the five images of SN Refsdal from difference images. We apply four separate techniques to perform a blind measurement of the relative time delays and magnification ratios between the last image SX and the earlier images S1-S4. We measure the relative time delay of SX-S1 to be $\displaystyle {376.0}_{-5.5}^{+5.6}$ days and the relative magnification to be $\displaystyle {0.30}_{-0.3}^{+0.5}$ . This corresponds to a 1.5% precision on the time delay and 17% precision for the magnification ratios and includes uncertainties due to millilensing and microlensing. In an accompanying paper, we place initial and blind constraints on the value of the Hubble constant.

Keywords: hubble constant; gravitational lensing; type ii supernovae; cosmology
Fitting Optical Light Curves of Tidal Disruption Events with TiDE

A Tidal Disruption Event (TDE) occurs when a supermassive black hole tidally disrupts a nearby passing star. The fallback accretion rate of the disrupted star may exceed the Eddington limit, which induces a supersonic outflow and a burst of luminosity, similar to an explosive event. Thus, TDEs can be detected as very luminous transients, and the number of observations for such events is increasing rapidly. In this paper we fit 20 TDE light curves with TiDE, a new public, object-oriented code designed to model optical TDE light curves. We compare our results with those obtained by the popular MOSFiT and the recently developed TDEmass codes, and discuss the possible sources of differences.

Keywords: supermassive black holes; accretion; tidal disruption
Bridging Scales in Black Hole Accretion and Feedback: Magnetized Bondi Accretion in 3D GRMHD

Fueling and feedback couple supermassive black holes (SMBHs) to their host galaxies across many orders of magnitude in spatial and temporal scales, making this problem notoriously challenging to simulate. We use a multi-zone computational method based on the general relativistic magnetohydrodynamic (GRMHD) code KHARMA that allows us to span 7 orders of magnitude in spatial scale, to simulate accretion onto a non-spinning SMBH from an external medium with a Bondi radius of R B ≈ 2 × 105 GM •/c 2, where M • is the SMBH mass. For the classic idealized Bondi problem, spherical gas accretion without magnetic fields, our simulation results agree very well with the general relativistic analytic solution. Meanwhile, when the accreting gas is magnetized, the SMBH magnetosphere becomes saturated with a strong magnetic field. The density profile varies as ~r -1 rather than r -3/2 and the accretion rate $\dot{M}$ is consequently suppressed by over 2 orders of magnitude below the Bondi rate ${\dot{M}}_{{\rm{B}}}$ . We find continuous energy feedback from the accretion flow to the external medium at a level of $\sim {10}^{-2}\dot{M}{c}^{2}\sim 5\,\times \,{10}^{-5}{\dot{M}}_{{\rm{B}}}{c}^{2}$ . Energy transport across these widely disparate scales occurs via turbulent convection triggered by magnetic field reconnection near the SMBH. Thus, strong magnetic fields that accumulate on horizon scales transform the flow dynamics far from the SMBH and naturally explain observed extremely low accretion rates compared to the Bondi rate, as well as at least part of the energy feedback.

Keywords: accretion; active galactic nuclei; bondi accretion; schwarzschild black holes; supermassive black holes; hydrodynamical simulations
On the X-Ray Spectral Energy Distributions of Star-forming Galaxies: The 0.3-30 keV Spectrum of the Low-metallicity Starburst Galaxy VV 114

Binary population synthesis combined with cosmological models suggests that X-ray emission from star-forming galaxies, consisting primarily of emission from X-ray binaries (XRBs) and the hot interstellar medium (ISM), could be an important, and perhaps dominant, source of heating of the intergalactic medium prior to the epoch of reionization. However, such models rely on empirical constraints for the X-ray spectral energy distributions (SEDs) of star-forming galaxies, which are currently lacking for low-metallicity galaxies. Using a combination of Chandra, XMM-Newton, and NuSTAR observations, we present new constraints on the 0.3-30 keV SED of the low-metallicity starburst galaxy VV 114, which is known to host several ultraluminous X-ray sources (ULXs) with luminosities above 1040 erg s-1. We use an archival Chandra observation of VV 114 to constrain the contributions to the X-ray SED from the major X-ray-emitting components of the galaxy and newly acquired, nearly simultaneous XMM-Newton and NuSTAR observations to extend the spectral model derived from Chandra to cover the 0.3-30 keV range. Using our best-fit galaxy-wide spectral model, we derive the 0.3-30 keV SED of VV 114, which we find is dominated by emission from the XRB population, and in particular ULXs, at energies >1.5 keV, and which we find to have an elevated galaxy-integrated X-ray luminosity per unit star formation rate relative to higher-metallicity star-forming galaxies. We discuss our results in terms of the effect of metallicity on XRB populations and the hot ISM, as well as the importance of X-ray emission from star-forming galaxies in the high-redshift universe.

Keywords: x-ray binary stars; starburst galaxies; interstellar medium
A Stream of Hypervelocity Stars from the Galactic Center

Recent observations have found a 1700 km s-1 star [S5-HVS1] that was ejected from the Galactic center approximately five million years ago. This star was likely produced by the tidal disruption of a binary. In particular, the Galactic center contains a few million year old stellar disk that could excite binaries to nearly radial orbits via a secular gravitational instability. Such binaries would be disrupted by the central supermassive black hole, and would also explain the observed cluster of B stars ∼0.01 pc from the Galactic center. In this paper we predict S5-HVS1 is part of a larger stream, and use observationally motivated N-body simulations to predict its spatial and velocity distributions.

Keywords: hypervelocity stars; galactic center; binary stars
Physically Motivated Deep Learning to Superresolve and Cross Calibrate Solar Magnetograms

Superresolution (SR) aims to increase the resolution of images by recovering detail. Compared to standard interpolation, deep learning-based approaches learn features and their relationships to leverage prior knowledge of what low-resolution patterns look like in higher resolution. Deep neural networks can also perform image cross-calibration by learning the systematic properties of the target images. While SR for natural images aims to create perceptually convincing results, SR of scientific data requires careful quantitative evaluation. In this work, we demonstrate that deep learning can increase the resolution and calibrate solar imagers belonging to different instrumental generations. We convert solar magnetic field images taken by the Michelson Doppler Imager (resolution ∼2″ pixel‑1; space based) and the Global Oscillation Network Group (resolution ∼2.″5 pixel‑1; ground based) to the characteristics of the Helioseismic and Magnetic Imager (resolution ∼0.″5 pixel‑1; space based). We also establish a set of performance measurements to benchmark deep-learning-based SR and calibration for scientific applications.

Keywords: solar magnetic fields; the sun; solar physics; solar active regions
A Chondritic Solar Neighborhood

A persistent question in exoplanet demographics is whether exoplanetary systems form from similar compositional building blocks to our own. Polluted white dwarf stars offer a unique way to address this question, as they provide measurements of the bulk compositions of exoplanetary material. We present a statistical analysis of the rocks polluting oxygen-bearing white dwarfs and compare their compositions to rocks in the solar system. We find that the majority of the extrasolar rocks are consistent with the composition of typical chondrites. Measurement uncertainties prevent distinguishing between chondrites and bulk Earth but do permit detecting the differences between chondritic compositions and basaltic or continental crust. We find no evidence of crust among the polluted white dwarfs. We show that the chondritic nature of extrasolar rocks is also supported by the compositions of local stars. While galactic chemical evolution results in variations in the relative abundances of rock-forming elements spatially and temporally on galaxy-wide scales, the current sample of polluted white dwarfs are sufficiently young and close to Earth that they are not affected by this process. We conclude that exotic compositions are not required to explain the majority of observed rock types around polluted white dwarfs and that variations between exoplanetary compositions in the stellar neighborhood are generally not due to significant differences in the initial composition of protoplanetary disks. Nonetheless, there is evidence from stellar observations that planets formed in the first several billion years in the Galaxy have lower metal core fractions compared with Earth on average.

Keywords: white dwarf stars
Proton and Helium Heating by Cascading Turbulence in a Low-beta Plasma

How ions are energized and heated is a fundamental problem in the study of energy dissipation in magnetized plasmas. In particular, the heating of heavy ions (including 4He2+, 3He2+, and others) has been a constant concern for understanding the microphysics of impulsive solar flares. In this article, via two-dimensional hybrid-kinetic particle-in-cell simulations, we study the heating of helium ions (4He2+) by turbulence driven by cascading waves launched at large scales from the left-handed polarized helium ion cyclotron wave branch of a multi-ion plasma composed of electrons, protons, and helium ions. We find significant parallel (to the background magnetic field) heating for both helium ions and protons due to the formation of beams and plateaus in their velocity distribution functions along the background magnetic field. The heating of helium ions in the direction perpendicular to the magnetic field starts with a lower rate than that in the parallel direction, but overtakes the parallel heating after a few hundreds of the proton gyro-periods due to cyclotron resonances with mainly obliquely propagating waves induced by the cascade of injected helium ion cyclotron waves at large scales. There is, however, little evidence for proton heating in the perpendicular direction due to the absence of left-handed polarized cyclotron waves near the proton cyclotron frequency. Our results are useful for understanding the preferential heating of 3He and other heavy ions in the 3He-rich solar energetic particle events, in which helium ions play a crucial role as a species of background ions regulating the kinetic plasma behavior.

Keywords: solar energetic particles; solar flares; plasma physics; space plasmas
First Phase Space Portrait of a Hierarchical Stellar Structure in the Milky Way

We present the first detailed observational picture of a possible ongoing massive cluster hierarchical assembly in the Galactic disk as revealed by the analysis of the stellar full phase space (3D positions and kinematics and spectro-photometric properties) of an extended area (6° diameter) surrounding the well-known h and χ Persei double stellar cluster in the Perseus Arm. Gaia-EDR3 shows that the area is populated by seven comoving clusters, three of which were previously unknown, and by an extended and quite massive (M ∼ 105 M⊙) halo. All stars and clusters define a complex structure with evidence of possible mutual interactions in the form of intra-cluster overdensities and/or bridges. They share the same chemical abundances (half-solar metallicity) and age (t ∼ 20 Myr) within a small confidence interval and the stellar density distribution of the surrounding diffuse stellar halo resembles that of a cluster-like stellar system. The combination of these pieces of evidence suggests that stars distributed within a few degrees from h and χ Persei are part of a common, substructured stellar complex that we named LISCA I. Comparison with results obtained through direct N-body simulations suggest that LISCA I may be at an intermediate stage of an ongoing cluster assembly that can eventually evolve in a relatively massive (a few times 105 M⊙) stellar system. We argue that such a cluster formation mechanism may be quite efficient in the Milky Way and disk-like galaxies and, as a consequence, it has a relevant impact on our understanding of cluster formation efficiency as a function of the environment and redshift.

Keywords: star clusters; dynamical evolution; photometry; astrometry
Optical to X-Ray Signatures of Dense Circumstellar Interaction in Core-collapse Supernovae

Progenitors of core-collapse supernovae (SNe) can shed significant mass to circumstellar material (CSM) in the months to years preceding core collapse. The ensuing SN explosion launches ejecta that may subsequently collide with this CSM, producing shocks that can power emissions across the electromagnetic spectrum. In this work we explore the thermal signatures of dense CSM interaction when the CSM density profile is truncated at some outer radius. CSM with optical depth >c/v (where v is the shock velocity) will produce primarily ~blackbody optical/UV emission, whereas lower optical depth CSM will power bremsstrahlung X-ray emission. Focusing on the latter, we derive light curves and spectra of the resulting X-ray transients that include a detailed treatment of Comptonization. Due to strong photoelectric absorption, the X-ray light curve is dominated by the postinteraction phase that occurs after the shock reaches the CSM truncation radius. We treat this regime here for the first time. Using these results, we present the phase space of optical, UV, and X-ray transients as a function of CSM properties, and discuss detectability prospects. We find that ROSAT would not have been sensitive to CSM X-ray transients but that eROSITA is expected to detect many such events. Future wide-field UV missions such as the Ultraviolet Transient Astronomy Satellite will dramatically enhance sensitivity to large optical depth CSM configurations. Finally, we present a framework within which CSM properties may be directly inferred from observable features of X-ray transients. This can serve as an important tool for studying stellar mass loss using SN X-ray detections.

Keywords: time domain astronomy; x-ray transient sources; high energy astrophysics; ultraviolet transient sources; core-collapse supernovae
DKIST Unveils the Serpentine Topology of Quiet Sun Magnetism in the Photosphere

We present the first quiet Sun spectropolarimetric observations obtained with the Visible SpectroPolarimeter at the 4 m Daniel K. Inouye Solar Telescope. We recorded observations in a wavelength range that includes the magnetically sensitive Fe I 6301.5/6302.5 Å doublet. With an estimated spatial resolution of 0.″08, this represents the highest spatial resolution full-vector spectropolarimetric observations ever obtained of the quiet Sun. We identified 53 small-scale magnetic elements, including 47 magnetic loops and four unipolar magnetic patches, with linear and circular polarization detected in all of them. Of particular interest is a magnetic element in which the polarity of the magnetic vector appears to change three times in only 400 km and which has linear polarization signals throughout. We find complex Stokes V profiles at the polarity inversion lines of magnetic loops and discover degenerate solutions, as we are unable to conclusively determine whether these arise due to gradients in the atmospheric parameters or smearing of opposite-polarity signals. We analyze a granule that notably has linear and circular polarization signals throughout, providing an opportunity to explore its magnetic properties. On this small scale, we see the magnetic field strength range from 25 G at the granular boundary to 2 kG in the intergranular lane (IGL) and sanity-check the values with the weak and strong field approximations. A value of 2 kG in the IGL is among the highest measurements ever recorded for the internetwork.

Keywords: quiet sun; solar photosphere; spectropolarimetry; solar magnetic fields; solar physics; the sun
IOP4, the Interactive Optical Photo-Polarimetric Python Pipeline

IOP4 is a pipeline to perform photometry and polarimetry analysis of optical data from Calar Alto (CAHA) and Sierra Nevada (OSN) observatories. IOP4 implements Object Relational Mapping to seamlessly integrate all information about the reduction and results in a database that can be used to query and plot results, flag data, and inspect the reduction process in an integrated fashion with the whole pipeline. It also ships with an already built-in web interface that can be used out of the box to browse the database and supervise all pipeline processes. It is built to ease debugging and inspection of data. Reduction from five different instruments are already implemented: RoperT90, AndorT90, DIPOL (at OSN 0.9 m telescope), AndorT150 (OSN 1.5 m telescope), and CAFOS (CAHA 2.2 m telescope). IOP4's modular design allows for easy integration of new observatories and instruments, and its results have already featured in several high-impact refereed publications. In this paper we describe the implementation and characteristics of IOP4.

Keywords: astronomy data analysis; photometry; polarimetry; astronomy databases; open source software