adsabs/SciX_UAT_keywords huggingface dataset:
Second Timescale Photometry of the Very Fast Nova V1674 Her with Palomar Gattini-IR

We report second-timescale infrared photometry of the nova V1674 Her using Palomar Gattini-IR (PGIR). These observations constitute the first infrared and highest temporal resolution data (resolution of ≈0.84 s) of the nova reported to date. PGIR observed in this fast readout mode for more than an hour on three nights between 3 and 6 days after discovery. We searched for periodic variability using a Lomb-Scargle periodogram and did not detect anything down to a three sigma upper limit of 0.093 mag. This suggests that the periodic variability detected in the nova by Patterson et al. was lower by at least a factor of about 1.65 in the first week of the eruption.

Keywords: classical novae; light curves; time domain astronomy
Optical Transmission Spectroscopy of the Terrestrial Exoplanet LHS 3844b from 13 Ground-based Transit Observations

Atmospheric studies of spectroscopically accessible terrestrial exoplanets lay the groundwork for comparative planetology between these worlds and the solar system terrestrial planets. LHS 3844b is a highly irradiated terrestrial exoplanet (R = 1.303 ± 0.022R⊕) orbiting a mid-M dwarf 15 parsecs away. Work based on near-infrared Spitzer phase curves ruled out atmospheres with surface pressures ≥10 bars on this planet. We present 13 transit observations of LHS 3844b taken with the Magellan Clay telescope and the LDSS3C multi-object spectrograph covering 620-1020 nm. We analyze each of the 13 data sets individually using a Gaussian process regression, and present both white and spectroscopic light curves. In the combined white light curve we achieve an rms precision of 65 ppm when binning to 10 minutes. The mean white light-curve value of (Rp/Rs)2 is 0.4170 ± 0.0046%. To construct the transmission spectrum, we split the white light curves into 20 spectrophotometric bands, each spanning 20 nm, and compute the mean values of (Rp/Rs)2 in each band. We compare the transmission spectrum to two sets of atmospheric models. We disfavor a clear, solar composition atmosphere (μ = 2.34) with surface pressures ≥0.1 bar to 5.2σ confidence. We disfavor a clear, H2O steam atmosphere (μ = 18) with surface pressures ≥0.1 bar to low confidence (2.9σ). Our observed transmission spectrum favors a flat line. For solar composition atmospheres with surface pressures ≥1 bar we rule out clouds with cloud-top pressures of 0.1 bar (5.3σ), but we cannot address high-altitude clouds at lower pressures. Our results add further evidence that LHS 3844b is devoid of an atmosphere.

Keywords: exoplanet astronomy; exoplanet atmospheres; ground-based astronomy
Activity Complexes and a Prominent Poleward Surge during Solar Cycle 24

Long-lasting activity complexes (ACs), characterized as a series of closely located, continuously emerging solar active regions (ARs), are considered generating prominent poleward surges from observations. The surges lead to significant variations of the polar field, which are important for the modulation of solar cycles. We aim to study a prominent poleward surge during solar cycle 24 on the southern hemisphere, and analyze its originating ACs and the effect on the polar field evolution. We automatically identify and characterize ARs based on synoptic magnetograms from the Solar Dynamics Observatory. We assimilate these ARs with realistic magnetic configuration into a surface flux transport model, and simulate the creation and migration of the surge. Our simulations well reproduce the characteristics of the surge and show that the prominent surge is mainly caused by the ARs belonging to two ACs during Carrington rotations 2145-2159 (2013 December-2015 January). The surge has a strong influence on the polar field evolution of the southern hemisphere during the latter half of cycle 24. Without the about one-year-long flux emergence in the form of ACs, the polar field around the cycle minimum would have remained at a low level and even reversed to the polarity at cycle 23 minimum. Our study also shows that the long-lived unipolar regions due to the decay of the earlier emerging ARs cause an intrinsic difficulty of automatically identifying and precisely quantifying later emerging ARs in ACs.

Keywords: solar magnetic fields; solar cycle; solar active regions
Impact of 3D Structure on Magnetic Reconnection

Results from 2.5D and 3D studies of the onset and development of the tearing instability are presented, using high-fidelity resistive MHD simulations. A limited parameter study of the strength of the reconnecting field (or shear angle) was performed. An initially simple 1D equilibrium was used, consisting of a modified force-free current sheet, with periodic boundary conditions in all directions. In all cases, the linear and nonlinear evolution led to a primary current sheet between two large flux ropes. The global reconnection rate during this later stage was analyzed in all simulations. It was found that in 2.5D the primary current sheet fragmented owing to plasmoids, and as expected, the global reconnection rate, calculated using multiple methods, increases with the strength of the reconnecting field owing to a stronger Alfvén speed. In 3D, the presence of interacting oblique modes of the tearing instability complicates the simple 2.5D picture, entangling the magnetic field of the inflow and introducing a negative effect on the reconnection rate. The two competing effects of stronger Alfvén speed and entangling, which both increase with the strength of the reconnecting field, resulted in a decrease in the reconnection rate with increasing reconnecting field. For all simulations, the 3D rates were less than in 2.5D but suggest that as one goes to weak reconnecting field (or strong guide field) the system becomes more 2.5D-like and the 2.5D and 3D rates converge. These results have relevance to situations like nanoflare heating and flare current sheets in the corona.

Keywords: solar corona; solar atmosphere; solar magnetic reconnection; solar magnetic fields; solar physics; solar flares; magnetohydrodynamics
The Messy Nature of Fiber Spectra: Star-Quasar Pairs Masquerading as Dual Type 1 AGNs

Theoretical studies predict that the most significant growth of supermassive black holes (SMBHs) occurs in late-stage mergers, coinciding with the manifestation of dual active galactic nuclei (AGNs), and both major and minor mergers are expected to be important for dual AGN growth. In fact, dual AGNs in minor mergers should be signposts for efficient minor-merger-induced SMBH growth for both the more and less massive progenitor. We identified two candidate dual AGNs residing in apparent minor mergers with mass ratios of ~1:7 and ~1:30. Sloan Digital Sky Survey (SDSS) fiber spectra show broad and narrow emission lines in the primary nuclei of each merger while only a narrow [O III] emission line and a broad and prominent Hα/[N II] complex is observed in the secondary nuclei. The FWHMs of the broad Hα lines in the primary and secondary nuclei are inconsistent in each merger, suggesting that each nucleus in each merger hosts a Type 1 AGN. However, spatially resolved Large Binocular Telescope optical spectroscopy reveals rest-frame stellar absorption features, indicating the secondary sources are foreground stars and that the previously detected broad lines are likely the result of fiber spillover effects induced by the atmospheric seeing at the time of the SDSS observations. This study demonstrates for the first time that optical spectroscopic searches for Type 1/Type 1 pairs similarly suffer from fiber spillover effects as has been observed previously for Seyfert 2 dual AGN candidates. The presence of foreground stars may not have been clear if an instrument with more limited wavelength range or limited sensitivity had been used.

Keywords: active galactic nuclei; active galaxies
Neutral Metals in the Atmosphere of HD 149026b

Recent progress in high-dispersion spectroscopy has revealed the presence of vaporized heavy metals and ions in the atmosphere of hot Jupiters whose dayside temperature is larger than 2000 K, categorized as ultrahot Jupiters (UHJs). Using the archival data of high-resolution transmission spectroscopy obtained with the Subaru telescope, we searched for neutral metals in HD 149026b, a hot Jupiter cooler than UHJs. By removing stellar and telluric absorption and using a cross-correlation technique, we report a tentative detection of neutral titanium with 4.4σ and a marginal signal of neutral iron with 2.8σ in the atmosphere. This is the first detection of neutral titanium in an exoplanetary atmosphere. In this temperature range, titanium tends to form titanium oxide (TiO). The fact that we did not detect any signal from TiO suggests that the C/O ratio in the atmosphere is higher than the solar value. The detection of metals in the atmosphere of hot Jupiters cooler than UHJs will be useful for understanding the atmospheric structure and formation history of hot Jupiters.

Keywords: exoplanet atmospheres; high resolution spectroscopy; transmission spectroscopy; hot jupiters
Rapid Quenching of Galaxies at Cosmic Noon

The existence of massive quiescent galaxies at high redshift seems to require rapid quenching, but it is unclear whether all quiescent galaxies have gone through this phase and what physical mechanisms are involved. To study rapid quenching, we use rest-frame colors to select 12 young quiescent galaxies at z ~ 1.5. From spectral energy distribution fitting, we find that they all experienced intense starbursts prior to rapid quenching. We confirm this with deep Magellan/FIRE spectroscopic observations for a subset of seven galaxies. Broad emission lines are detected for two galaxies, and are most likely caused by active galactic nucleus (AGN) activity. The other five galaxies do not show any emission features, suggesting that gas has already been removed or depleted. Most of the rapidly quenched galaxies are more compact than normal quiescent galaxies, providing evidence for a central starburst in the recent past. We estimate an average transition time of 300 Myr for the rapid quenching phase. Approximately 4% of quiescent galaxies at z = 1.5 have gone through rapid quenching; this fraction increases to 23% at z = 2.2. We identify analogs in the TNG100 simulation and find that rapid quenching for these galaxies is driven by AGNs, and for half of the cases, gas-rich major mergers seem to trigger the starburst. We conclude that these young massive quiescent galaxies are not just rapidly quenched, but also rapidly formed through a major starburst. We speculate that mergers drive gas inflow toward the central regions and grow supermassive black holes, leading to rapid quenching by AGN feedback.

Keywords: galaxy formation; galaxy evolution; galaxy quenching
A New Catalog of Am-type Chemically Peculiar Stars Based on LAMOST

A total of about 21,600 Am candidates were detected with the MKCLASS code based on the low-resolution spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope Data Releases 8 (v1.0), 9 (v0), and 10 (v0), which greatly expands the database of Am-type stars. By crossmatching the known catalogs of Am stars and our Am candidates with the AAVSO International Variable Star Index catalog, a catalog of the largest eclipsing Am binaries was obtained, which includes 754 binaries and provides a substantial sample with which to study Am stars. Fundamental information, including atmospheric parameters of the two kinds of candidates, are collected and listed in the catalogs, such as temperature, log g, and metallicity. We further carried out statistical analysis of the types of parameters. In our new catalog, there are some Am candidates with a temperature lower than 7000 K and some eclipsing Am binary candidates with a period of less than 1 day, which poses challenges to the slow rotation of stars classified as type Am observed in previous research. These candidates are significant and provide a great opportunity to explore the real relationship between Am-type stars' peculiarity and slow stellar rotation. The Hertzsprung-Russell diagram of Am stars and the primary stars of eclipsing Am binary candidates indicate that a majority of the Am stars and almost all primary stars of binaries are in or around the main-sequence evolution stage.

Keywords: chemically peculiar stars; am stars; multiple stars; astrometric binary stars; eclipsing binary stars
Interaction of Magnetic Fields with a Vortex Tube at Solar Subgranular Scale

Using high-resolution spectropolarimetric data recorded with the Swedish 1 m Solar Telescope, we have identified several instances of granular lanes traveling into granules. These are believed to be the observational signature of underlying tubes of vortical flow with their axis oriented parallel to the solar surface. Associated with these horizontal vortex tubes, we detect in some cases a significant signal in linear polarization, located at the trailing dark edge of the granular lane. The linear polarization appears at a later stage of the granular lane development, and is flanked by patches of circular polarization. Stokes inversions show that the elongated patch of linear polarization signal arises from the horizontal magnetic field aligned with the granular lane. We analyze snapshots of a magnetohydrodynamic numerical simulation and find cases in which the horizontal vortex tube of the granular lane redistributes and transports the magnetic field to the solar surface causing a polarimetric signature similar to what is observed. We thus witness a mechanism capable of transporting magnetic flux to the solar surface within granules. This mechanism is probably an important component of the small-scale dynamo supposedly acting at the solar surface and generating the quiet-Sun magnetic field.

Keywords: solar photosphere; solar granulation; solar magnetic fields; magnetohydrodynamical simulations; magnetohydrodynamics
The Thermal Equilibrium Mass-loss Model and Its Applications in Binary Evolution

Binary evolution is indispensable in stellar evolution to understand the formation and evolution of most peculiar and energetic objects, such as binary compact objects, Type Ia supernovae, X-ray binaries, cataclysmic variables, blue stragglers, hot subdwarfs, and central binaries in planetary nebulae. Mass transfer in binary stars can change the evolutionary path and fate of the components compared to what is expected from single stellar evolution. The critical mass ratio at which unstable mass transfer occurs is an unsolved fundamental problem in binary evolution. To resolve this issue, we construct the thermal equilibrium mass-loss model and derive critical mass ratios for both thermal-timescale mass transfer and unstable mass transfer, the latter of which occurs when the outer Lagrangian point, L2, is overfilled. Using several 3.2 M⊙ stellar models as examples, we study the stellar response to thermal equilibrium mass loss and present the thresholds for thermal-timescale mass transfer. We study the possible mass-transfer channels of binary systems containing a 3.2 M⊙ donor star, taking into account thermal-timescale mass transfer, unstable mass transfer through L2, and dynamical-timescale mass transfer. We repeat this simulation for a grid of donor stars with different masses (from 0.1 to 100 M⊙ with Z = 0.02) and at different evolutionary stages, and present our results. The results show that unstable mass transfer due to the overfilling of the outer Lagrangian point may also play an essential role in the formation of common envelopes for late red giant branch and asymptotic giant branch donors.

Keywords: stellar evolution; stellar mass loss; close binary stars; common envelope evolution; stellar interiors; stellar structures
Simultaneous Dependence of Matter Clustering on Scale and Environment

In this work, we propose new statistical tools that are capable of characterizing the simultaneous dependence of dark matter and gas clustering on the scale and the density environment, and these are the environment-dependent wavelet power spectrum (env-WPS), the environment-dependent bias function (env-bias), and the environment-dependent wavelet cross-correlation function (env-WCC). These statistics are applied to the dark matter and baryonic gas density fields of the TNG100-1 simulation at redshifts of z=3.0-0.0, and to Illustris-1 and SIMBA at z = 0. The measurements of the env-WPSs suggest that the clustering strengths of both the dark matter and the gas increase with increasing density, while that of a Gaussian field shows no density dependence. By measuring the env-bias and env-WCC, we find that they vary significantly with the environment, scale, and redshift. A noteworthy feature is that at z = 0.0, the gas is less biased in denser environments of Δ ≳ 10 around 3 h Mpc-1, due to the gas reaccretion caused by the decreased AGN feedback strength at lower redshifts. We also find that the gas correlates more tightly with the dark matter in both the most dense and underdense environments than in other environments at all epochs. Even at z = 0, the env-WCC is greater than 0.9 in Δ ≳ 200 and Δ ≲ 0.1 at scales of k ≲ 10 h Mpc-1. In summary, our results support the local density environment having a non-negligible impact on the deviations between dark matter and gas distributions up to large scales.

Keywords: large-scale structure of the universe; dark matter; intergalactic medium; wavelet analysis
Rotational Fingerprints of Vinylketene for Astronomical Observations

A high degree of isomerism in the realm of interstellar molecules stimulates systematic astronomical investigations of members of different families of isomers. Among them, vinyl-bearing compounds have kindled considerable interest due to recent detections of vinylamine, vinylacetylene, and vinylcyanoacetylene. Herein, we open the possibility to search for vinylketene in the interstellar space by means of its rotational transitions. The pure rotational spectrum of the title molecule was recorded in the frequency regions 195-218 and 293-324 GHz and an improved and extended set of spectroscopic parameters has been obtained for the most stable trans conformer. In addition, rotational signatures and molecular constants for the less stable cis form are reported for the first time. We provide a catalog of precise transition frequencies and intensities of vinylketene to the astronomical community and pave the way toward interstellar explorations of C4H4O isomer family.

Keywords: catalogs; molecular spectroscopy; interstellar molecules; laboratory astrophysics; experimental data
Investigating the Correlation of Outflow Kinematics with Radio Activity. VII. Gas Outflows in AGNs

We explore the relationship between the ionized gas outflows and radio activity using a sample of ~6000 active galactic nuclei (AGNs) at z < 0.4 with the kinematical measurement based on the $\left[{\rm{O}}\,{\rm\small{III}}\right]$ line profile and the radio detection in the VLA FIRST Survey. To quantify radio activity, we divide our sample into a series of binary subclasses based on the radio properties, i.e., radio luminous/radio weak, AGN-dominated/star-formation contaminated, compact/extended, and radio loud/radio quiet. None of the binary subclasses exhibits a significant difference in the normalized $\left[{\rm{O}}\,{\rm\small{III}}\right]$ velocity dispersion at a given $\left[{\rm{O}}\,{\rm\small{III}}\right]$ luminosity once we correct for the influence of the host galaxy's gravitational potential. We only detect a significant difference in $\left[{\rm{O}}\,{\rm\small{III}}\right]$ kinematics between the high and low radio-Eddington ratio (L 1.4 GHz/L Edd) AGNs. In contrast, we find a remarkable difference in ionized gas kinematics between high and low bolometric-Eddington ratio AGNs. These results suggest that accretion rate is the primary mechanism in driving ionized gas outflows, while radio activity may play a secondary role providing additional influence on gas kinematics.

Keywords: active galactic nuclei; agn host galaxies; radio jets
Which Came First: Supermassive Black Holes or Galaxies? Insights from JWST

Insights from JWST observations suggest that active galactic nuclei feedback evolved from a short-lived, high-redshift phase in which radiatively cooled turbulence and/or momentum-conserving outflows stimulated vigorous early star formation ("positive" feedback), to late, energy-conserving outflows that depleted halo gas reservoirs and quenched star formation. The transition between these two regimes occurred at z ∼ 6, independently of galaxy mass, for simple assumptions about the outflows and star formation process. Observational predictions provide circumstantial evidence for the prevalence of massive black holes at the highest redshifts hitherto observed, and we discuss their origins.

Keywords: active galactic nuclei; quasars; black holes
Standing MHD Waves in a Magnetic Slab Embedded in an Asymmetric Plasma Environment: Slow Surface Waves

The field of solar magnetoseismology (SMS) is heavily reliant upon our understanding of magnetohydrodynamic (MHD) waves that occur in many solar features. Building on previous studies of propagating MHD waves in a magnetic slab embedded in a nonmagnetic asymmetric environment, in this study we assume a line-tying boundary condition and use analytical techniques to derive the dispersion relation for linear standing MHD oscillations. The slab is first assumed thin, with arbitrary asymmetry, in order to derive the frequencies of the standing harmonic modes for both slow quasi-sausage and slow quasi-kink waves. Besides this, the asymmetry is assumed to be weak in order to determine the frequency dependence on the width of the slab and the asymmetry of the system, to leading order. For both the quasi-sausage and quasi-kink modes, the derived eigenfrequencies show that the dependence on the asymmetry in the system is much weaker than the dependence on the width of the slab. Using the eigenfrequencies, other observable quantities are derived (such as, e.g., the frequency ratio) providing an opportunity to use SMS to infer background diagnostics of the system.

Keywords: the sun; magnetic fields; magnetohydrodynamics; solar physics; solar magnetic fields; solar oscillations; solar atmosphere; solar prominences