adsabs/SciX_UAT_keywords huggingface dataset:
Detection of an Extremely Large Impact Flash on Jupiter by High-cadence Multiwavelength Observations

We report the detection of an optical impact flash on Jupiter on 2021 October 15 by a dedicated telescope, Planetary ObservatioN Camera for Optical Transient Surveys, for the first time. Our temporally resolved three-band observations of the flash allowed investigations of its optical energy without the need for approximations on the impact brightness temperature. The kinetic energy of the impactor was equivalent to approximately two megatons of TNT, an order of magnitude greater than that of previously detected flashes on Jupiter and comparable with the Tunguska impact on Earth in 1908. This detection indicates that Tunguska-like impact events on Jupiter occur approximately once per year, two to three orders of magnitude more frequently than terrestrial impacts. The observed flash displayed a single-temperature blackbody spectrum with an effective temperature of approximately 8300 K without clear temporal variation, possibly representing common radiative features of terrestrial Tunguska-class superbolides.

Keywords: jupiter; impact phenomena; time domain astronomy; planetary atmospheres; solar system astronomy
Enhancing Stellar Temperature Estimation through Machine Learning and Multifaceted Data Exploration

This paper employs machine learning to estimate stellar temperatures using photometric data, focusing on the GAIA ESA Archive Data Release 3 data set. The study underscores the effectiveness of neural networks in deciphering intricate relationships within the data. Notably, the addition of metallicity improves model accuracy in characterizing stellar properties. The study also investigates outlier removal techniques, specifically favoring the Isolation Forest method, showcasing its efficacy in refining model performance. Automated machine learning, facilitated by PyCaret Regressor, emerges as a valuable tool, identifying top-performing models and highlighting feature importance. The implications of this research extend beyond the specifics of stellar temperature estimation. In contemplating future directions, this study suggests the exploration of diverse data sources to ensure balanced distributions of stellar temperatures and the potential incorporation of deep learning architectures for heightened accuracy in addressing astrophysical inquiries.

Keywords: photometric systems; photometry; stellar effective temperatures; neural networks; outlier detection
A Low-mass Binary Neutron Star: Long-term Ejecta Evolution and Kilonovae with Weak Blue Emission

We study the long-term evolution of ejecta formed in a binary neutron star (NS) merger that results in a long-lived remnant NS by performing a hydrodynamics simulation with the outflow data of a numerical relativity simulation as the initial condition. At the homologously expanding phase, the total ejecta mass reaches ≈ 0.1 M⊙ with an average velocity of ≈ 0.1 c and lanthanide fraction of ≈ 0.005. We further perform the radiative transfer simulation employing the obtained ejecta profile. We find that, contrary to a naive expectation from the large ejecta mass and low lanthanide fraction, the optical emission is not as bright as that in GW170817/AT2017gfo, while the infrared emission can be brighter. This light-curve property is attributed to preferential diffusion of photons toward the equatorial direction due to the prolate ejecta morphology; large opacity contribution of Zr, Y, and lanthanides; and low specific heating rate of the ejecta. Our results suggest that these light-curve features could be used as an indicator for the presence of a long-lived remnant NS. We also found that the bright optical emission broadly consistent with GW170817/AT2017gfo is realized for the case in which the high-velocity ejecta components in the polar region are suppressed. These results suggest that the remnant in GW170817/AT2017gfo is unlikely to be a long-lived NS but might have collapsed to a black hole within ${ \mathcal O }(0.1)$ s.

Keywords: gravitational wave astronomy; neutron stars; radiative transfer simulations
Improved Upper Limit on Degree-scale CMB B-mode Polarization Power from the 670 Square-degree POLARBEAR Survey

We report an improved measurement of the degree-scale cosmic microwave background B-mode angular-power spectrum over 670 deg2 sky area at 150 GHz with POLARBEAR. In the original analysis of the data, errors in the angle measurement of the continuously rotating half-wave plate, a polarization modulator, caused significant data loss. By introducing an angle-correction algorithm, the data volume is increased by a factor of 1.8. We report a new analysis using the larger data set. We find the measured B-mode spectrum is consistent with the ΛCDM model with Galactic dust foregrounds. We estimate the contamination of the foreground by cross-correlating our data and Planck 143, 217, and 353 GHz measurements, where its spectrum is modeled as a power law in angular scale and a modified blackbody in frequency. We place an upper limit on the tensor-to-scalar ratio r < 0.33 at 95% confidence level after marginalizing over the foreground parameters.

Keywords: cosmic microwave background radiation; observational cosmology; cosmological parameters; cosmic inflation
Investigating the Relative Gas and Small Dust Grain Surface Heights in Protoplanetary Disks

Dust evolution in protoplanetary disks from small dust grains to pebbles is key to the planet formation process. The gas in protoplanetary disks should influence the vertical distribution of small dust grains (∼1 μm) in the disk. Utilizing archival near-infrared polarized light and millimeter observations, we can measure the scale height and flare parameter β of the small dust grain scattering surface and 12CO gas emission surface for three protoplanetary disks: IM Lup, HD 163296, and HD 97048 (CU Cha). For two systems, IM Lup and HD 163296, the 12CO gas and small dust grains at small radii from the star have similar heights, but at larger radii (>100 au), the dust grain scattering surface height is lower than the 12CO gas emission surface height. In the case of HD 97048, the small dust grain scattering surface has similar heights to the 12CO gas emission surface at all radii. We ran a protoplanetary disk radiative transfer model of a generic protoplanetary disk with TORUS and showed that there is no difference between the observed scattering surface and 12CO emission surface. We also performed analytical modeling of the system and found that gas-to-dust ratios larger than 100 could explain the observed difference in IM Lup and HD 163296. This is the first direct comparison of observations of gas and small dust grain height distribution in protoplanetary disks. Future observations of gas emission and near-infrared scattered-light instruments are needed to look for similar trends in other protoplanetary disks.

Keywords: protoplanetary disks; direct imaging
Modeling the Infrared Reverberation Response of the Circumnuclear Dusty Torus in AGNs: An Investigation of Torus Response Functions

The size and structure of the dusty circumnuclear torus in active galactic nuclei (AGNs) can be investigated by analyzing the temporal response of the torus's infrared (IR) dust emission to variations in the AGN ultraviolet/optical luminosity. This method, reverberation mapping, is applicable over a wide redshift range, but the IR response is sensitive to several poorly constrained variables relating to the dust distribution and its illumination, complicating the interpretation of measured reverberation lags. We have used an enhanced version of our torus reverberation mapping code (TORMAC) to conduct a comprehensive exploration of the torus response functions at selected wavelengths, for the standard interstellar medium grain composition. The shapes of the response functions vary widely over the parameter range covered by our models, with the largest variations occurring at shorter wavelengths (≤4.5 μm). The reverberation lag, quantified as the response-weighted delay (RWD), is most affected by the radial depth of the torus, the steepness of the radial cloud distribution, the degree of anisotropy of the AGN radiation field, and the volume filling factor. Nevertheless, we find that the RWD provides a reasonably robust estimate, to within a factor of ∼3, of the luminosity-weighted torus radius, confirming the basic assumption underlying reverberation mapping. However, overall, the models predict radii at 2.2 μm that are typically a factor of ∼2 larger than those derived from K-band reverberation mapping. This is likely an indication that the innermost region of the torus is populated by clouds dominated by large graphite grains.

Keywords: active galactic nuclei; accretion; infrared galaxies; reverberation mapping; astrophysical dust processes; radiative transfer; active galaxies
Real-time Experimental Demonstrations of a Photonic Lantern Wave-front Sensor

The direct imaging of an Earth-like exoplanet will require sub-nanometric wave-front control across large light-collecting apertures to reject host starlight and detect the faint planetary signal. Current adaptive optics systems, which use wave-front sensors that reimage the telescope pupil, face two challenges that prevent this level of control: non-common-path aberrations, caused by differences between the sensing and science arms of the instrument; and petaling modes: discontinuous phase aberrations caused by pupil fragmentation, especially relevant for the upcoming 30 m class telescopes. Such aberrations drastically impact the capabilities of high-contrast instruments. To address these issues, we can add a second-stage wave-front sensor to the science focal plane. One promising architecture uses the photonic lantern (PL): a waveguide that efficiently couples aberrated light into single-mode fibers (SMFs). In turn, SMF-confined light can be stably injected into high-resolution spectrographs, enabling direct exoplanet characterization and precision radial velocity measurements; simultaneously, the PL can be used for focal-plane wave-front sensing. We present a real-time experimental demonstration of the PL wave-front sensor on the Subaru/SCExAO testbed. Our system is stable out to around ±400 nm of low-order Zernike wave-front error and can correct petaling modes. When injecting ~30 nm rms of low-order time-varying error, we achieve ~10× rejection at 1 s timescales; further refinements to the control law and lantern fabrication process should make sub-nanometric wave-front control possible. In the future, novel sensors like the PL wave-front sensor may prove to be critical in resolving the wave-front control challenges posed by exoplanet direct imaging.

Keywords: adaptive optics; astronomical instrumentation
Observing Supernova Neutrino Light Curves with Super-Kamiokande. IV. Development of SPECIAL BLEND: A New Public Analysis Code for Supernova Neutrinos

Supernova neutrinos are invaluable signals that offer information about the interior of supernovae. Because a nearby supernova can occur at any time, preparing for future supernova neutrino observation is an urgent task. For the prompt analysis of supernova neutrinos, we have developed a new analysis code, the "Supernova Parameter Estimation Code based on Insight on Analytic Late-time Burst Light curve at Earth Neutrino Detector" (SPECIAL BLEND). This code estimates the parameters of supernovae based on an analytic model of supernova neutrinos from the proto-neutron star cooling phase. For easy availability to the community, this code is public and easily runs in web environments. SPECIAL BLEND can estimate the parameters better than the analysis pipeline we developed in a previous paper. By using SPECIAL BLEND, we can estimate the supernova parameters within 10% precision up to ~20 and ~60 kpc (Large Magellanic Cloud contained) with Super-Kamiokande and Hyper-Kamiokande, respectively.

Keywords: core-collapse supernovae; supernova neutrinos; neutrino astronomy; neutrino telescopes; neutron stars
Rise of the Phoenix Giants: A Rich History of Dusty Post-merger Stellar Remnants

Hoadley et al. present an exceptional star system hosting orbiting dust and gas and a detached shell of material presumably generated in a stellar merger event. While they claim it to be "the only known merger system not enshrouded by dust," the reality is that this system is a new addition to a remarkable collection of stars first recognized decades ago as likely post-merger stellar remnants. In this note we give an abridged history of evidence for dusty stellar merger remnants in the the Milky Way.

Keywords: circumstellar matter; stellar evolution
An Optical Search for New Outbursting Low Mass X-Ray Binaries

Transient low-mass X-ray binaries (LMXBs) are discovered largely by X-ray and gamma-ray all-sky monitors. The X-ray outburst is also accompanied by an optical brightening, which empirically can precede the detection of X-rays. Newly sensitive optical synoptic surveys may offer a complementary pathway for discovery and potential for insight into the initial onset and propagation of the thermal instability that leads to the ionization of the accretion disk. We use the Zwicky Transient Facility (ZTF) alert stream to perform a comprehensive search at optical wavelengths for previously undiscovered outbursting LMXBs. Our pipeline first crossmatches the positions of the alerts to cataloged X-ray sources, and then analyzes the 30 day lightcurve of matched alerts by thresholding on differences with an 8 day exponentially weighted moving average. In addition to a 19 month long live search, we ran our pipeline over 4 yr of ZTF archival data, recovering four known LMXBs. We also independently detected an outburst of MAXI J1957+032 in the live search and found the first outburst of Swift J1943.4+0228, an unclassified X-ray transient, in 10 yr. Using Monte Carlo simulations of the Galactic LMXB population, we estimate that 29% of outbursting LMXBs are detectable by ZTF and that 4.4% of LMXBs would be present in the crossmatched X-ray catalogs, giving an estimated Galactic population of ${3390}_{-1930}^{+3980}$ . We estimate that our current pipeline can detect 1.3% of all outbursting LMXBs, including those previously unknown, but that Rubin Observatory's Legacy Survey of Space and Time will be able to detect 43% of outbursting LMXBs.

Keywords: x-ray binary stars
A Study of Stellar Spins in 15 Open Clusters

We analyze spectroscopic and photometric data to determine the projected inclinations of stars in 11 open clusters, placing constraints on the spin-axis distributions of six clusters. We combine these results with four additional clusters studied by Healy & McCullough and Healy et al. to perform an ensemble analysis of their spins. We find that eight out of 10 constrained clusters (80%) have spin-axis orientations consistent with isotropy, and we establish a lower limit of four out of 10 (40%) isotropic clusters at 75% confidence, assuming no correlation of spins between clusters. We also identify two clusters whose spin-axis distributions can be better described by a model consisting of an aligned fraction of stars combined with an isotropic distribution. However, the inclination values of these stars may be influenced by systematic error, and the small number of stars modeled as aligned in these two clusters precludes the interpretation that their stellar subsets are physically aligned. Overall, no cluster displays an unambiguous signature of spin alignment, and 97% of the stars in our sample are consistent with isotropic orientations in their respective clusters. Our results offer support for the dominance of turbulence over ordered rotation in clumps and do not suggest the alignment of rotation axes and magnetic fields in protostars.

Keywords: open star clusters; inclination; stellar rotation; star formation
Self-similar Outflows at the Source of the Fast Solar Wind: A Smoking Gun of Multiscale Impulsive Reconnection?

We present results of a quantitative analysis of structured plasma outflows above a polar coronal hole observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) spacecraft. In a 6 hr interval of continuous high-cadence SDO/AIA images, we identified more than 2300 episodes of small-scale plasma flows in the polar corona. The mean upward flow speed measured by the surfing transform technique is estimated to be 122 ± 34 km s-1, which is comparable to the local sound speed. The typical recurrence period of the flow episodes is 10-30 minutes, and the mean duration and transverse size of each episode are about 3-5 minutes and 3-4 Mm, respectively. The largest identifiable episodes last for tens of minutes and reach widths up to 40 Mm. For the first time, we demonstrate that the polar coronal-hole outflows obey a family of power-law probability distributions characteristic of impulsive interchange magnetic reconnection. Turbulent photospheric driving may play a crucial role in releasing magnetically confined plasma onto open field. The estimated occurrence rate of the detected self-similar coronal outflows is sufficient for them to make a dominant contribution to the fast-wind mass and energy fluxes and to account for the wind's small-scale structure.

Keywords: plasma jets; solar magnetic reconnection; fast solar wind; extreme ultraviolet astronomy
The Evryscope Fast Transient Engine: Real-time Detection for Rapidly Evolving Transients

Astrophysical transients with rapid developments on subhour timescales are intrinsically rare. Due to their short durations, events like stellar superflares, optical flashes from gamma-ray bursts, and shock breakouts from young supernovae are difficult to identify on timescales that enable spectroscopic follow-up. This paper presents the Evryscope Fast Transient Engine (EFTE), a new data reduction pipeline that is designed to provide low-latency transient alerts from the Evryscopes-a north-south pair of ultra-wide-field telescopes with an instantaneous footprint covering 38% of the entire sky-and tools for building long-term light curves from Evryscope data. EFTE leverages the optical stability of the Evryscopes by using a simple direct image subtraction routine that is suited to continuously monitoring the transient sky at a cadence of a minute. Candidates are produced within the base Evryscope 2 minute cadence for 98.5% of images, and internally filtered using VETNET, a convolutional neural network real-bogus classifier. EFTE provides an extensible and robust architecture for transient surveys probing similar timescales, and serves as the software test bed for the real-time analysis pipelines and public data distribution systems for the Argus Array, a next-generation all-sky observatory with a data rate 62 times higher than that of Evryscope.

Keywords: sky surveys; transient detection; stellar flares; convolutional neural networks; astronomy data reduction; astronomy image processing; artificial satellites; time domain astronomy; light curves; ccd photometry; flare stars; red dwarf flare stars
Confirmation and Characterization of the Eccentric, Warm Jupiter TIC 393818343 b with a Network of Citizen Scientists

NASA's Transiting Exoplanet Survey Satellite (TESS) has identified over 7000 candidate exoplanets via the transit method, with gas giants among the most readily detected due to their large radii. Even so, long intervals between TESS observations for much of the sky lead to candidates for which only a single transit is detected in one TESS sector, leaving those candidate exoplanets with unconstrained orbital periods. Here, we confirm the planetary nature of TIC 393818343 b, originally identified via a single TESS transit, using radial velocity data and ground-based photometric observations from citizen scientists with the Unistellar Network and Exoplanet Watch. We determine a period of P = 16.24921 days, a mass M P = 4.34 ± 0.15 M J, and semimajor axis a = 0.1291 au, placing TIC 393818343 b in the "warm Jupiter" population of exoplanets. With an eccentricity e = 0.6058 ± 0.0023, TIC 393818343 b is the most eccentric warm Jupiter to be discovered by TESS orbiting less than 0.15 au from its host star and therefore an excellent candidate for follow-up, as it may inform our future understanding of how hot and warm Jupiter populations are linked.

Keywords: extrasolar gaseous giant planets; transit photometry; exoplanet astronomy; amateur astronomers; amateur astronomy; radial velocity
Penetration of Nonenergetic Hydrogen Atoms into Amorphous Solid Water and their Reaction with Embedded Benzene and Naphthalene

Chemical processes on the surface of icy grains play an important role in the chemical evolution in molecular clouds. In particular, reactions involving nonenergetic hydrogen atoms accreted from the gaseous phase have been extensively studied. These reactions are believed to effectively proceed only on the surface of the icy grains; thus, molecules embedded in the ice mantle are not considered to react with hydrogen atoms. Recently, Tsuge et al. suggested that nonenergetic hydrogen atoms can react with CO molecules even in ice mantles via diffusive hydrogenation. This investigation was extended to benzene and naphthalene molecules embedded in amorphous solid water (ASW) in the present study, which revealed that a portion of these molecules could be fully hydrogenated in astrophysical environments. The penetration depths of nonenergetic hydrogen atoms into porous and nonporous ASW were determined using benzene molecules to be >50 and ~10 monolayers, respectively (1 monolayer ≈ 0.3 nm).

Keywords: astrochemistry; molecular clouds; dense interstellar clouds; interstellar molecules; interstellar dust; laboratory astrophysics
Search for Continuous Gravitational Waves from the Central Compact Objects in Supernova Remnants Cassiopeia A, Vela Jr., and G347.3-0.5

We perform a sub-threshold follow-up search for continuous nearly monochromatic gravitational waves from the central compact objects associated with the supernova remnants (SNRs) Vela Jr., Cassiopeia A, and SNR G347.3-0.5. Across the three targets, we investigate the most promising ≈10,000 combinations of gravitational-wave frequency and frequency derivative values, based on the results from an Einstein@Home search of the LIGO O1 observing run data, dedicated to these objects. The selection threshold is set so that a signal could be confirmed using the newly released O2 run LIGO data. In order to achieve best sensitivity we perform two separate follow-up searches, on two distinct stretches of the O2 data. Only one candidate survives the first O2 follow-up investigation, associated with the central compact object in SNR G347.3-0.5, but it is not conclusively confirmed. In order to assess a possible astrophysical origin we use archival X-ray observations and search for amplitude modulations of a pulsed signal at the putative rotation frequency of the neutron star and its harmonics. This is the first extensive electromagnetic follow-up of a continuous gravitational-wave candidate performed to date. No significant associated signal is identified. New X-ray observations contemporaneous with the LIGO O3 run will enable a more sensitive search for an electromagnetic counterpart. A focused gravitational-wave search in O3 data based on the parameters provided here should be easily able to shed light on the nature of this outlier. Noise investigations on the LIGO instruments could also reveal the presence of a coherent contamination.

Keywords: pulsars; supernova remnants; gravitational wave astronomy; gravitational waves; gravitational wave sources