adsabs/SciX_UAT_keywords huggingface dataset:
Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b

We present Keck Planet Imager and Characterizer (KPIC) high-resolution (R ~35,000) K-band thermal emission spectroscopy of the ultrahot Jupiter WASP-33b. The use of KPIC's single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We retrieve the dayside emission spectrum with a nested-sampling pipeline, which fits for orbital parameters, the atmospheric pressure-temperature profile, and the molecular abundances. We strongly detect the thermally inverted dayside and measure mass-mixing ratios for CO ( ${\mathrm{logCO}}_{\mathrm{MMR}}=-{1.1}_{-0.6}^{+0.4}$ ), H2O ( ${\mathrm{logH}}_{2}{{\rm{O}}}_{\mathrm{MMR}}\,=-{4.1}_{-0.9}^{+0.7}$ ), and OH ( ${\mathrm{logOH}}_{\mathrm{MMR}}=-{2.1}_{-1.1}^{+0.5}$ ), suggesting near-complete dayside photodissociation of H2O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of ${0.8}_{-0.2}^{+0.1}$ , consistent with the accretion of high-metallicity gas near the CO2 snow line and post-disk migration or with accretion between the soot and H2O snow lines. We also find tentative evidence for 12CO/13CO ~ 50, consistent with values expected in protoplanetary disks, as well as tentative evidence for a metal-enriched atmosphere (2-15 × solar). These observations demonstrate KPIC's ability to characterize close-in planets and the utility of KPIC's improved instrumental stability for cross-correlation techniques.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; hot jupiters; high resolution spectroscopy
Analytical Modeling of Exoplanet Transit Spectroscopy with Dimensional Analysis and Symbolic Regression

The physical characteristics and atmospheric chemical composition of newly discovered exoplanets are often inferred from their transit spectra, which are obtained from complex numerical models of radiative transfer. Alternatively, simple analytical expressions provide insightful physical intuition into the relevant atmospheric processes. The deep-learning revolution has opened the door for deriving such analytical results directly with a computer algorithm fitting to the data. As a proof of concept, we successfully demonstrate the use of symbolic regression on synthetic data for the transit radii of generic hot-Jupiter exoplanets to derive a corresponding analytical formula. As a preprocessing step, we use dimensional analysis to identify the relevant dimensionless combinations of variables and reduce the number of independent inputs, which improves the performance of the symbolic regression. The dimensional analysis also allowed us to mathematically derive and properly parameterize the most general family of degeneracies among the input atmospheric parameters that affect the characterization of an exoplanet atmosphere through transit spectroscopy.

Keywords: exoplanet atmospheres; radiative transfer equation; hot jupiters; transmission spectroscopy; dimensionality reduction; regression
A Deep Census of Outlying Star Formation in the M101 Group

We present deep, narrowband imaging of the nearby spiral galaxy M101 and its group environment to search for star-forming dwarf galaxies and outlying H II regions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, Hα, Hβ, and [O III], to detect potential outlying star-forming regions. Our survey covers ~6 deg2 around M101, and we detect objects in emission down to an Hα flux level of 5.7 × 10-17 erg s-1 cm-2 (equivalent to a limiting star formation rate of 1.7 × 10-6 M⊙ yr-1 at the distance of M101). After careful removal of background contaminants and foreground M stars, we detect 19 objects in emission in all three bands and 8 objects in emission in Hα and [O III]. We compare the structural and photometric properties of the detected sources to Local Group dwarf galaxies and star-forming galaxies in the 11HUGS and SINGG surveys. We find no large population of outlying H II regions or undiscovered star-forming dwarfs in the M101 Group, as most sources (93%) are consistent with being M101 outer-disk H II regions. Only two sources were associated with other galaxies: a faint star-forming satellite of the background galaxy NGC 5486 and a faint outlying H II region near the M101 companion NGC 5474. We also find no narrowband emission associated with recently discovered ultradiffuse galaxies and starless H I clouds near M101. The lack of any hidden population of low-luminosity star-forming dwarfs around M101 suggests a rather shallow faint-end slope (as flat as α ~ -1.0) for the star-forming luminosity function in the M101 Group. We discuss our results in the context of tidally triggered star formation models and the interaction history of the M101 Group.

Keywords: narrow band photometry; galaxy environments; star formation
Clumpy Accretion in Pre-main-sequence Stars as a Source of Perturbations in Circumstellar Disks

The development of perturbations in the circumstellar disks of pre-main-sequence stars caused by clumpy accretion was investigated. Here we perform 3D smoothed particle hydrodynamics simulations of disks perturbed by a recent clump accretion event. These simulations are further explored by radiative transfer calculations to quantify the observational appearance of such disks. It was shown that the density waves in the disks were formed at the fall of the clump. After several revolutions they can transform into spirals and ring structures. Their images in millimeter wavelengths are very similar to those observed with Atacama Large Millimeter/submillimeter Array in some protoplanetary disks. We assume that clumpy accretion may be the source of such structures.

Keywords: accretion; protoplanetary disks; pre-main sequence stars; hydrodynamical simulations; radiative transfer simulations
Gas-phase Metallicity of Local Active Galactic Nuclei in the GASP and MaNGA Surveys: The Role of Ram Pressure Stripping

Growing evidence in support of a connection between active galactic nuclei (AGN) activity and the ram pressure stripping (RPS) phenomenon has been found both observationally and theoretically in the past decades. In this work, we further explore the impact of RPS on the AGN activity by estimating the gas-phase metallicity of nuclear regions and the mass–metallicity relation of galaxies at z ≤ 0.07 and with stellar masses $\mathrm{log}{M}_{* }/{M}_{\odot }\geqslant 9.0$ , either experiencing RPS or not. To measure oxygen abundances, we exploit Integral Field Spectroscopy data from the GASP and MaNGA surveys, photoionization models generated with the code CLOUDY and the code NEBULABAYES to compare models and observations. In particular, we build CLOUDY models to reproduce line ratios induced by photoionization from stars, AGN, or a contribution of both. We find that the distributions of metallicity and [O III] λ5007 luminosity of galaxies undergoing RPS are similar to the ones of undisturbed galaxies. Independently of the RPS, we do not find a correlation between stellar mass and AGN metallicity in the mass range $\mathrm{log}{M}_{* }/{M}_{\odot }\geqslant 10.4$ , while for the star-forming galaxies we observe the well-known mass–metallicity relation between $9.0\leqslant \mathrm{log}\ {M}_{* }/{M}_{\odot }\leqslant 10.8$ with a scatter mainly driven by the star formation rate and a plateau around $\mathrm{log}{M}_{* }/{M}_{\odot }\sim 10.5$ . The gas-phase metallicity in the nuclei of AGN hosts is enhanced with respect to those of star-forming galaxies by a factor of ∼ 0.05 dex regardless of the RPS.

Keywords: galaxy environments; active galactic nuclei; galaxy chemical evolution
No Redshift Evolution in the Broad-line-region Metallicity up to z = 7.54: Deep Near-infrared Spectroscopy of ULAS J1342+0928

We present deep (9 hr) Gemini-N/Gemini Near-InfraRed Spectrograph near-infrared spectroscopic observations of ULAS J1342+0928, a luminous quasar at z = 7.54. Various broad emission lines were detected, as well as the underlying continuum and iron forests over the rest-frame wavelength 970-2930 Å. There is a clear trend that higher-ionization emission lines show larger blueshifts with C IV $\lambda 1549$ exhibiting ${5510}_{-110}^{+240}$ km s-1 blueshift with respect to the systematic redshift from the far-infrared [C II] $158\,\mu {\rm{m}}$ emission line. Those high-ionization lines have wide profiles with FWHM more than 10,000 km s-1. A modest blueshift of ${340}_{-80}^{+110}$ km s-1 is also seen in Mg II, the lowest-ionization line identified in the spectrum. The updated Mg II-based black hole mass of ${M}_{\mathrm{BH}}={9.1}_{-1.3}^{+1.4}\times {10}^{8}{M}_{\odot }$ and the Eddington ratio of ${L}_{\mathrm{bol}}/{L}_{\mathrm{Edd}}={1.1}_{-0.2}^{+0.2}$ confirm that ULAS J1342+0928 is powered by a massive and actively accreting black hole. There is no significant difference in the emission-line ratios such as Si IV/C IV and Al III/C IV when compared to lower-redshift quasars in a similar luminosity range, which suggests early metal pollution of the broad-line-region clouds. This trend also holds for the Fe II/Mg II line ratio, known as a cosmic clock that traces the iron enrichment in the early universe. Different iron templates and continuum fitting ranges were used to explore how the Fe II/Mg II measurement changes as a function of spectral modeling. Quasars at even higher redshift or at fainter luminosity range ( ${L}_{\mathrm{bol}}\lesssim {10}^{46}$ erg s-1) are needed to probe the sites of early metal enrichment and a corresponding change in the Fe II/Mg II ratio.

Keywords: supermassive black holes; quasars
Premaximum Spectroscopic Diversity of Hydrogen-poor Superluminous Supernovae

We search for the reasons behind the spectroscopic diversity of hydrogen-poor superluminous supernovae (SLSNe-I) in the premaximum phase. Our analysis is a continuation of the paper of Könyves-Tóth & Vinkó, who disclosed two new subtypes of SLSNe-I characterized by the presence/absence of a W-shaped absorption feature in their premaximum spectra between 4000 and 5000 Å (called Type W and Type 15bn, respectively). However, the physical cause of this bimodality is still uncertain. Here we present premaximum spectral synthesis of 27 SLSNe-I with special attention to the photospheric temperature (T phot) and velocity (v phot) evolution. We find that a T phot limit of 12,000 K separates the Type W and Type 15bn SLSNe-I: Type W objects tend to show T phot ≥ 12,000 K, while Type 15bn ones have T phot ≤ 12,000 K. This is consistent with the chemical composition of the studied objects. Another difference between these groups may be found in their ejecta geometry: Type W SLSNe-I may show null polarization, implying spherical symmetry, while the polarization of Type 15bn objects may increase in time. This suggests a two-component model with a spherical outer carbon-oxygen layer and an asymmetric inner layer containing heavier ions. The two subgroups may have different light-curve evolution as well, since six Type W objects show early bumps, unlike Type 15bn SLSNe-I. This feature, however, needs further study, as it is based on only a few objects at present.

Keywords: supernovae
High-level Ab Initio Studies of the Spectroscopic Properties of Triatomic [Al, S, O]x (x = 0, +1) and Its Potential for Detection in Space

Highly reliable molecular properties have been computed for the [Al, S, O]x (x = 0, +1) molecular system. Spectroscopic parameters are predicted from analysis of each isomer&'s 3D potential energy surface calculated using the explicitly correlated multireference configuration interaction method, including the Davidson correction (MRCI-F12+Q). These parameters provide an accurate prediction of spectroscopic data that can be used in laboratory and observational studies of these molecules. Linear-SAlO is expected to have a large permanent dipole moment suitable for detection in the circumstellar envelopes of large, evolved, oxygen-rich stars such as VY Canis Majoris, IK Tauri, and R Doradus. Frequencies are provided for rotational transitions originating from the most highly populated rotational state based on a Boltzmann distribution. Additionally, both linear isomers exhibit a flat potential along the bending angle and are predicted to have very low bending mode frequencies (<200 cm-1), complicating the spectra of these molecules.

Keywords: astrochemistry; molecular spectroscopy; red supergiant stars; radio spectroscopy; line positions
Photometric Signature of Ultraharmonic Resonances in Barred Galaxies

Bars may induce morphological features, such as rings, through their resonances. Previous studies suggested that the presence of "dark gaps," or regions of a galaxy where the difference between the surface brightness along the bar major axis and that along the bar minor axis is maximal, can be attributed to the location of bar corotation. Here, using GALAKOS, a high-resolution N-body simulation of a barred galaxy, we test this photometric method's ability to identify the bar corotation resonance. Contrary to previous work, our results indicate that "dark gaps" are a clear sign of the location of the 4:1 ultraharmonic resonance instead of bar corotation. Measurements of the bar corotation can indirectly be inferred using kinematic information, e.g., by measuring the shape of the rotation curve. We demonstrate our concept on a sample of 578 face-on barred galaxies with both imaging and integral field observations and find that the sample likely consists primarily of fast bars.

Keywords: barred spiral galaxies; galaxy structure; galaxy evolution; disk galaxies; galaxy kinematics; galaxy dynamics
The Reactivation of Main-belt Comet 259P/Garradd (P/2008 R1)

We present observations of main-belt comet (MBC) 259P/Garradd from 4 months prior to its 2017 perihelion passage to 5 months after perihelion using the Gemini North and South telescopes. The object was confirmed to be active during this period, placing it among seven MBCs confirmed to have recurrent activity. We find an average net pre-perihelion dust production rate for 259P in 2017 of ${\dot{M}}_{d}=(4.6\pm 0.2)$ kg s-1 (assuming grain densities of ρ = 2500 kg m-3 and a mean effective particle size of ${\bar{a}}_{d}=2$ mm) and a best-fit start date of detectable activity of 2017 April 22 ± 1, when the object was at a heliocentric distance of rh = 1.96 ∓ 0.03 au and a true anomaly of ν = 313°9 ± 0°4. We estimate the effective active fraction of 259P's surface area to be from fact ∼ 7 × 10-3 to fact ∼ 6 × 10-2 (corresponding to effective active areas of Aact ∼ 8 × 103 m2 to Aact ∼ 7 × 104 m2) at the start of its 2017 active period. A comparison of estimated total dust masses measured for 259P in 2008 and 2017 shows no evidence of changes in activity strength between the two active apparitions. The heliocentric distance of 259P's activity onset point is much smaller than those of other MBCs, suggesting that its ice reservoirs may be located at greater depths than on MBCs farther from the Sun, increasing the time needed for a solar-irradiation-driven thermal wave to reach subsurface ice. We suggest that deeper ice on 259P could be a result of more rapid ice depletion caused by the object's closer proximity to the Sun compared to other MBCs.

Keywords: comets; main-belt comets; main belt asteroids
The Twins Embedding of Type Ia Supernovae. I. The Diversity of Spectra at Maximum Light

We study the spectral diversity of Type Ia supernovae (SNe Ia) at maximum light using high signal-to-noise spectrophotometry of 173 SNe Ia from the Nearby Supernova Factory. We decompose the diversity of these spectra into different extrinsic and intrinsic components, and we construct a nonlinear parameterization of the intrinsic diversity of SNe Ia that preserves pairings of "twin" SNe Ia. We call this parameterization the "Twins Embedding." Our methodology naturally handles highly nonlinear variability in spectra, such as changes in the photosphere expansion velocity, and uses the full spectrum rather than being limited to specific spectral line strengths, ratios, or velocities. We find that the time evolution of SNe Ia near maximum light is remarkably similar, with 84.6% of the variance in common to all SNe Ia. After correcting for brightness and color, the intrinsic variability of SNe Ia is mostly restricted to specific spectral lines, and we find intrinsic dispersions as low as ∼0.02 mag between 6600 and 7200 Å. With a nonlinear three-dimensional model plus one dimension for color, we can explain 89.2% of the intrinsic diversity in our sample of SNe Ia, which includes several different kinds of "peculiar" SNe Ia. A linear model requires seven dimensions to explain a comparable fraction of the intrinsic diversity. We show how a wide range of previously established indicators of diversity in SNe Ia can be recovered from the Twins Embedding. In a companion article, we discuss how these results can be applied to the standardization of SNe Ia for cosmology.

Keywords: type ia supernovae; standard candles; observational cosmology
Correlation of the Sunspot Number and the Waiting-time Distribution of Solar Flares, Coronal Mass Ejections, and Solar Wind Switchback Events Observed with the Parker Solar Probe

Waiting-time distributions of solar flares and coronal mass ejections (CMEs) exhibit power-law-like distribution functions with slopes in the range of ατ ≈ 1.4-3.2, as observed in annual data sets during four solar cycles (1974-2012). We find a close correlation between the waiting-time power-law slope ατ and the sunspot number (SN), i.e., ατ = 1.38 + 0.01 × SN. The waiting-time distribution can be fitted with a Pareto-type function of the form N(τ) = N0 ${({\tau }_{0}+\tau )}^{-{\alpha }_{\tau }}$ , where the offset τ0 depends on the instrumental sensitivity, the detection threshold of events, and pulse pileup effects. The time-dependent power-law slope ατ(t) of waiting-time distributions depends only on the global solar magnetic flux (quantified by the sunspot number) or flaring rate, which is not predicted by self-organized criticality or magnetohydrodynamic turbulence models. Power-law slopes of ατ ≈ 1.2-1.6 were also found in solar wind switchback events, as observed with the Parker Solar Probe during the solar minimum, while steeper slopes are predicted during the solar maximum. We find that the annual variability of switchback events in the heliospheric solar wind and solar flare and CME rates (originating in the photosphere and lower corona) are highly correlated.

Keywords: solar wind; solar flares
Kinematic Analysis of a Protostellar Multiple System: Measuring the Protostar Masses and Assessing Gravitational Instability in the Disks of L1448 IRS3B and L1448 IRS3A

We present new Atacama Large Millimeter/submillimeter Array observations toward a compact (∼230 au separation) triple protostar system, L1448 IRS3B, at 879 μm with 0"11 × 0"05 resolution. Spiral arm structure within the circum-multiple disk is well resolved in dust continuum toward IRS3B, and we detect the known wide (∼2300 au) companion, IRS3A, also resolving possible spiral substructure. Using dense gas tracers, C17O (J = 3 $\to $ 2), H13CO+ (J = 4 $\to $ 3), and H13CN (J = 4 $\to $ 3), we resolve the Keplerian rotation for both the circum-triple disk in IRS3B and the disk around IRS3A. Furthermore, we use the molecular line kinematic data and radiative transfer modeling of the molecular line emission to confirm that the disks are in Keplerian rotation with fitted masses of ${1.19}_{-0.07}^{+0.13}$ M⊙ for IRS3B-ab and ${1.51}_{-0.07}^{+0.06}$ M⊙ for IRS3A and place an upper limit on the central protostar mass for the tertiary IRS3B-c of 0.2 M⊙. We measure the mass of the fragmenting disk of IRS3B to be ∼0.29 M⊙ from the dust continuum emission of the circum-multiple disk and estimate the mass of the clump surrounding IRS3B-c to be 0.07 M⊙. We also find that the disk around IRS3A has a mass of ∼0.04 M⊙. By analyzing the Toomre Q parameter, we find the IRS3A circumstellar disk is gravitationally stable (Q > 5), while the IRS3B disk is consistent with a gravitationally unstable disk (Q < 1) between the radii ∼200-500 au. This coincides with the location of the spiral arms and the tertiary companion IRS3B-c, supporting the hypothesis that IRS3B-c was formed in situ via fragmentation of a gravitationally unstable disk.

Keywords: protostars; young stellar objects
Solar Radio Spikes and Type IIIb Striae Manifestations of Subsecond Electron Acceleration Triggered by a Coronal Mass Ejection

Understanding electron acceleration associated with magnetic energy release at subsecond scales presents major challenges in solar physics. Solar radio spikes observed as subsecond, narrow-bandwidth bursts with Δf/f ~ 10-3-10-2 are indicative of a subsecond evolution of the electron distribution. We present a statistical analysis of frequency- and time-resolved imaging of individual spikes and Type IIIb striae associated with a coronal mass ejection (CME). LOFAR imaging reveals that the cotemporal (<2 s) spike and striae intensity contours almost completely overlap. On average, both burst types have a similar source size with a fast expansion at millisecond scales. The radio source centroid velocities are often superluminal and independent of frequency over 30-45 MHz. The CME perturbs the field geometry, leading to increased spike emission likely due to frequent magnetic reconnection. As the field restores itself toward the prior configuration, the observed sky-plane emission locations drift to increased heights over tens of minutes. Combined with previous observations above 1 GHz, the average decay time and source size estimates follow a ~1/f dependence over three decades in frequency, similar to radio-wave scattering predictions. Both time and spatial characteristics of the bursts between 30 and 70 MHz are consistent with radio-wave scattering with a strong anisotropy of the density fluctuation spectrum. Consequently, the site of the radio-wave emission does not correspond to the observed burst locations and implies acceleration and emission near the CME flank. The bandwidths suggest intrinsic emission source sizes <1″ at 30 MHz and magnetic field strengths a factor of two larger than average in events that produce decameter spikes.

Keywords: solar corona; solar radio emission
Hinode/EIS Measurements of Active-region Magnetic Fields

The present work illustrates the potential of a new diagnostic technique that allows the measurement of the coronal magnetic field strength in solar active regions by utilizing a handful of bright Fe X and Fe XI lines commonly observed by the high-resolution Hinode/EUV Imaging Spectrometer (EIS). The importance of this new diagnostic technique is twofold: (1) the coronal magnetic field is probably the most important quantity in coronal physics, being at the heart of the processes regulating space weather and the properties of the solar corona, and (2) this technique can be applied to the existing EIS archive spanning from 2007 to 2020, including more than one full solar cycle and covering a large number of active regions, flares, and even coronal mass ejections. This new diagnostic technique opens the door to a whole new field of studies, complementing the magnetic field measurements from the upcoming DKIST and UCoMP ground-based observatories, and extending our reach to active regions observed on the disk and until now only sampled by radio measurements. In this work, we present a few examples of the application of this technique to EIS observations taken at different times during the EIS mission, and we discuss its current limitations and the steps to improve its accuracy. We also present a list of EIS observing sequences whose data include all of the lines necessary for the application of this diagnostic technique, to help the solar community navigate the immense set of EIS data and to find observations suitable for measuring the coronal magnetic field.

Keywords: solar magnetic fields; solar corona