adsabs/SciX_UAT_keywords huggingface dataset:
Awakening of Two Gamma-Ray High-redshift, Flat-spectrum Radio Quasars in the Southern Hemisphere

High-redshift blazars are valuable tools to study the early universe. So far, only a handful of γ-ray blazars have been found at redshifts above 3. Gamma-ray signals are detected in the direction of PMN J2219-2719 (z = 3.63) and PMN J2321-0827 (z = 3.16) by analyzing the 10 yr Fermi-LAT Pass 8 data. PMN J2219-2719 is not distinguished from the background in the global analysis. During the 5 month epoch, the TS value is 47.8 and the flux is more than 10 times that of the 10 yr averaged flux. In addition, the angular distance between the γ-ray position and the radio position of PMN J2219-2719 is only 0°04. Moreover, the long timescale γ-ray and infrared light curves are very similar, which supports the association between the γ-ray source and PMN J2219-2719. The global analysis of PMN J2321-0827 suggest a new γ-ray source; during the flare phase, the TS value is 61.4 and the γ-ray flux increased significantly. The association probability suggests that PMN J2321-0827 may be the counterpart of the new γ-ray source. In the future, the number of high-redshift γ-ray sources will increase by combining Fermi-LAT and the upcoming Large Synoptic Survey Telescope.

Keywords: galaxy jets; quasars; gamma-ray sources; non-thermal radiation sources; high-redshift galaxies
Probing the Star Formation Main Sequence Down to 108 M ⊙ at 1.0 < z < 3.0

We investigate the star formation main sequence (MS; SFR-M ⋆) down to 108-9 M ⊙ using a sample of 34,061 newly discovered ultrafaint (27 mag ≲ i ≲ 30 mag) galaxies at 1 < z < 3 detected in the GOODS-N field. Virtually none of these galaxies are contained in previous public catalogs, effectively doubling the number of known sources in the field. The sample was constructed by stacking the optical broadband observations taken by the HST/GOODS-CANDELS surveys, as well as the 25 ultradeep medium-band images gathered by the GTC/SHARDS project. Our sources are faint (average observed magnitudes ~ 28.2 and <H> ~ 27.9 mag), blue (UV slope <β> ~ -1.9), star-forming (rest-frame colors <U - V> ~ 0.10 and <V - J> ~ 0.17 mag) galaxies. These observational characteristics are identified with young (mass-weighted age <t M-w > ~ 0.014 Gyr) stellar populations subject to low attenuations (<A(V)> ~ 0.30 mag). Our sample allows us to probe the MS down to 108.0 M ⊙ at z = 1 and 108.5 M ⊙ at z = 3, around 0.6 dex deeper than previous analyses. In the low-mass galaxy regime, we find an average value for the slope of 0.97 at 1 < z < 2 and 1.12 at 2 < z < 3. Nearly 60% of our sample presents stellar masses in the range 106-8 M ⊙ at 1 < z <G 3. If the slope of the MS remained constant in this regime, the sources populating the low-mass tail of our sample would qualify as starburst galaxies.

Keywords: high-redshift galaxies; dwarf galaxies; galaxy formation; galaxy evolution; galaxies; star formation; catalogs
Impact of NICER's Radius Measurement of PSR J0740+6620 on Nuclear Symmetry Energy at Suprasaturation Densities

By directly inverting several neutron star (NS) observables in the three-dimensional parameter space for the equation of state of super-dense neutron-rich nuclear matter, we show that the lower radius limit for PSR J0740+6620 of mass 2.08 ± 0.07 M⊙ from Neutron Star Interior Composition Explorer (NICER)'s very recent observation sets a much tighter lower boundary than previously known for nuclear symmetry energy in the density range of (1.0 ~ 3.0) times the saturation density ρ0 of nuclear matter. The super-soft symmetry energy leading to the formation of proton polarons in this density region of NSs is clearly disfavored by the first radius measurement for the most massive NS observed reliably so far.

Keywords: neutron stars; nuclear astrophysics
Towards a Comprehensive View of Accretion, Inner Disks, and Extinction in Classical T Tauri Stars: An ODYSSEUS Study of the Orion OB1b Association

The coevolution of T Tauri stars and their surrounding protoplanetary disks dictates the timescales of planet formation. In this paper, we present magnetospheric accretion and inner disk wall model fits to near-UV (NUV) to near-IR (NIR) spectra of nine classical T Tauri stars in Orion OB1b as part of the Outflows and Disks around Young Stars: Synergies for the Exploration of ULLYSES Spectra (ODYSSEUS) survey. Using NUV-optical spectra from the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Director's Discretionary Program and optical-NIR spectra from the PENELLOPE VLT Large Programme, we find that the accretion rates of these targets are relatively high for the region's intermediate age of 5.0 Myr; rates are in the range of (0.5-17.2) × 10-8 M ☉ yr-1, with a median value of 1.2 × 10-8 M ☉ yr-1. The NIR excesses can be fit with 1200-1800 K inner disk walls located at 0.05-0.10 au from the host stars. We discuss the significance of the choice in extinction law, as the measured accretion rate depends strongly on the adopted extinction value. This analysis will be extended to the complete sample of T Tauri stars being observed through ULLYSES to characterize accretion and inner disks in star-forming regions of different ages and stellar populations.

Keywords: pre-main sequence stars; stellar accretion; stellar accretion disks; protoplanetary disks; reddening law; interstellar extinction; hubble space telescope; very large telescope
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: CO Excitation and Atomic Carbon in Star-forming Galaxies at z = 1-3

We investigate the CO excitation and interstellar medium (ISM) conditions in a cold gas mass-selected sample of 22 star-forming galaxies at z = 0.46-3.60, observed as part of the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). Combined with Very Large Array follow-up observations, we detect a total of 34 CO $J\to J-1$ transitions with J = 1 up to 8 (and an additional 21 upper limits, up to J = 10) and 6 $[{\rm{C}}\,{\rm\small{I}}]$ ${}^{3}{P}_{1}{\to }^{3}\,{P}_{0}$ and ${}^{3}{P}_{2}{\to }^{3}\,{P}_{1}$ transitions (and 12 upper limits). The CO(2-1) and CO(3-2)-selected galaxies, at $\langle z\rangle =1.2$ and 2.5, respectively, exhibit a range in excitation in their mid-J = 4, 5 and high-J = 7, 8 lines, on average lower than ( ${L}_{\mathrm{IR}}$ -brighter) BzK-color- and submillimeter-selected galaxies at similar redshifts. The former implies that a warm ISM component is not necessarily prevalent in gas mass-selected galaxies at $\langle z\rangle =1.2$ . We use stacking and Large Velocity Gradient models to measure and predict the average CO ladders at z < 2 and z ≥ 2, finding ${r}_{21}=0.75\pm 0.11$ and ${r}_{31}=0.77\pm 0.14$ , respectively. From the models, we infer that the galaxies at z ≥ 2 have intrinsically higher excitation than those at z < 2. This fits a picture in which the global excitation is driven by an increase in the star formation rate surface density of galaxies with redshift. We derive a neutral atomic carbon abundance of $(1.9\pm 0.4)\times {10}^{-5}$ , comparable to the Milky Way and main-sequence galaxies at similar redshifts, and fairly high densities (≥104 cm-3), consistent with the low-J CO excitation. Our results imply a decrease in the cosmic molecular gas mass density at z ≥ 2 compared to previous ASPECS measurements.

Keywords: co line emission; dust continuum emission; interstellar medium; galaxy formation; galaxy evolution; high-redshift galaxies; millimeter astronomy
Radio Spectra of SN 2020oi: Effects of Radiative Cooling on the Deduced Source Properties

Observations of radiative cooling in a synchrotron source offer a possibility to further constrain its properties. Inverse Compton cooling is indicated in the radio spectra during the early phases of SN 2020oi. It is shown that contrary to previous claims, observations are consistent with equipartition between relativistic electrons and magnetic field as well as a constant mass-loss rate of the progenitor star prior to the supernova explosion. The reason for this difference is the need to include cooling directly in the fitting procedure rather than estimating its effects afterward. It is emphasized that the inferred properties of the supernova ejecta are sensitive to the time evolution of the synchrotron self-absorption frequency; hence, great care should be taken when modeling spectra for which cooling and/or inhomogeneities are indicated. Furthermore, it is noted that the energies of the relativistic electrons in the radio emission regions in supernovae are likely too low for first-order Fermi acceleration to be effective.

Keywords: supernovae; radio continuum emission; magnetic fields; non-thermal radiation sources; shocks
Constraining the Orbit and Mass of epsilon Eridani b with Radial Velocities, Hipparcos IAD-Gaia DR2 Astrometry, and Multiepoch Vortex Coronagraphy Upper Limits

ϵ Eridani is a young planetary system hosting a complex multibelt debris disk and a confirmed Jupiter-like planet orbiting at 3.48 au from its host star. Its age and architecture are thus reminiscent of the early Solar System. The most recent study of Mawet et al., which combined radial-velocity data and Ms-band direct imaging upper limits, started to constrain the planet's orbital parameters and mass, but are still affected by large error bars and degeneracies. Here we make use of the most recent data compilation from three different techniques to further refine ϵ Eridani b's properties: RVs, absolute astrometry measurements from the Hipparcos and Gaia missions, and new Keck/NIRC2 Ms-band vortex coronagraph images. We combine this data in a Bayesian framework. We find a new mass, ${M}_{b}={0.66}_{-0.09}^{+0.12}$ MJup, and inclination, $i=78.{81}_{-22.41\mathop{}\limits^{^\circ }}^{+29.34}$ , with at least a factor 2 of improvement over previous uncertainties. We also report updated constraints on the longitude of the ascending node, the argument of the periastron, and the time of periastron passage. With these updated parameters, we can better predict the position of the planet at any past and future epoch, which can greatly help define the strategy and planning of future observations and with subsequent data analysis. In particular, these results can assist the search for a direct detection with JWST and the Nancy Grace Roman Space Telescope's coronagraph instrument.

Keywords: exoplanet astronomy; exoplanets; radial velocity; astrometry; direct imaging; debris disks
A Possible Cyclotron Feature of the Gamma-Ray Binary 4FGL J1405.1–6119

We reanalyzed the X-ray observations of the γ-ray binary candidate 4FGL J1405.1‑6119 using the XMM-Newton observations. In the X-ray spectra, we find a weak absorption feature around 2 keV in the XMM-Newton observations, which could be the cyclotron resonant scattering feature (CRSF) or so called cyclotron line of the possible neutron star (NS) in the binary. The line energy of the CRSF is ∼2 keV, implying that the magnetic field on the surface of the NS is about B ≈ 1011 G or B ≈ 1014 G depending on the cyclotron line being generated by electron or proton, respectively. This suggest that 4FGL J1405.1‑6119 hosts a weakly magnetized NS or a magnetar.

Keywords: high mass x-ray binary stars; gamma-ray astronomy; neutron stars; magnetic fields
Physical Parameters of Late-type Contact Binaries in the Northern Catalina Sky Survey

We present the physical parameters of 2335 late-type contact binary (CB) systems extracted from the Catalina Sky Survey (CSS). Our sample was selected from the CSS Data Release 1 by strictly limiting the prevailing temperature uncertainties and light-curve fitting residuals, allowing us to almost eliminate any possible contaminants. We developed an automatic Wilson-Devinney-type code to derive the relative properties of CBs based on their light-curve morphology. By adopting the distances derived from CB (orbital) period-luminosity relations (PLRs), combined with the well-defined mass-luminosity relation for the systems' primary stars and assuming solar metallicity, we calculated the objects' masses, radii, and luminosities. Our sample of fully eclipsing CBs contains 1530 W-, 710 A-, and 95 B-type CBs. A comparison with literature data and with the results from different surveys confirms the accuracy and coherence of our measurements. The period distributions of the various CB subtypes are different, hinting at a possible evolutionary sequence. W-type CBs are clearly located in a strip in the total mass versus mass-ratio plane, while A-type CBs may exhibit a slightly different dependence. There are no significant differences among the PLRs of A- and W-type CBs, but the PLR zero-points are affected by their mass ratios and fill-out factors. Determination of zero-point differences for different types of CBs may help us improve the accuracy of the resulting PLRs. We demonstrate that automated approaches to deriving CB properties could be a powerful tool for application to the much larger CB samples expected to result from future surveys.

Keywords: astronomy data analysis; contact binary stars; fundamental parameters of stars
Solar Energetic Electrons Entering the Earth's Cusp/Lobe

We present a comprehensive study of three solar energetic electron events observed in the Earth's cusp/lobe regions by the BeiDa Image Electron Spectrometer (BD-IES) on board a BeiDou satellite in an inclined (55°) geosynchronous orbit in 2015 October, 2015 November, and 2016 January, respectively. In all three events at energies above 50 keV, the electron omnidirectional differential fluxes from BD-IES show a strong (∼0.7-0.9) correlation with the simultaneous electron fluxes from the Wind 3DP instrument in the interplanetary medium, but generally with a smaller intensity. Compared to the Wind 3DP spectra of electron flux versus energy, the BD-IES electron spectra also fit well to a power-law function, ${J}_{\mathrm{IES}}\propto {E}^{-{\gamma }_{\mathrm{IES}}}$ , but the power-law spectral index appears to be mostly smaller than the 3DP spectral index, for all three events. These measurements provide the first observational evidence that solar/interplanetary energetic electrons can directly and continuously enter the planet's cusp/lobe regions and get trapped there, probably leading to a contribution to the energetic electrons and/or seed particles for acceleration in the planetary magnetosphere.

Keywords: solar energetic particles
Model Spectrum of Ultrahigh-energy Cosmic Rays Accelerated in FR-I Radio Galaxy Jets

Nearby radio galaxies (RGs) of Fanaroff–Riley Class I (FR-I) are considered possible sites for the production of observed ultrahigh-energy cosmic rays (UHECRs). Among those, some exhibit blazar-like inner jets, while others display plume-like structures. We reproduce the flow dynamics of FR-I jets using relativistic hydrodynamic simulations. Subsequently, we track the transport and energization of cosmic ray (CR) particles within the simulated jet flows using Monte Carlo simulations. The key determinant of flow dynamics is the mean Lorentz factor of the jet-spine flow, <Γ>spine. When <Γ>spine ≳ 6, the jet spine remains almost unimpeded, but for <Γ>spine ≲ 3, substantial jet deceleration occurs. CRs gain energy mainly through diffusive shock acceleration for E ≲ 1 EeV and shear acceleration for E ≳ 1 EeV. The time-asymptotic energy spectrum of CRs escaping from the jet can be modeled by a double power law, transitioning from ∼E ‑0.6 to ∼E ‑2.6 around a break energy, E break, with an exponential cutoff at ${E}_{\mathrm{break}}\langle {\rm{\Gamma }}{\rangle }_{\mathrm{spine}}^{2}$ . E break is limited either by the Hillas confinement condition or by particle escape from the cocoon via fast spatial diffusion. The spectral slopes primarily arise from multiple episodes of shock and relativistic shear acceleration, and the confinement–escape processes within the cocoon. The exponential cutoff is determined by nongradual shear acceleration that boosts the energy of high-energy CRs by a factor of $\sim \langle {\rm{\Gamma }}{\rangle }_{\mathrm{spine}}^{2}$ . We suggest that the model spectrum derived in this work could be employed to investigate the contribution of RGs to the observed population of UHECRs.

Keywords: cosmic rays; fanaroff-riley radio galaxies; relativistic jets
Ensemble Simulations of the 2012 July 12 Coronal Mass Ejection with the Constant-turn Flux Rope Model

Flux-rope-based magnetohydrodynamic modeling of coronal mass ejections (CMEs) is a promising tool for prediction of the CME arrival time and magnetic field at Earth. In this work, we introduce a constant-turn flux rope model and use it to simulate the 2012 July 12 16:48 CME in the inner heliosphere. We constrain the initial parameters of this CME using the graduated cylindrical shell (GCS) model and the reconnected flux in post-eruption arcades. We correctly reproduce all the magnetic field components of the CME at Earth, with an arrival time error of approximately 1 hr. We further estimate the average subjective uncertainties in the GCS fittings by comparing the GCS parameters of 56 CMEs reported in multiple studies and catalogs. We determined that the GCS estimates of the CME latitude, longitude, tilt, and speed have average uncertainties of 5.°74, 11.°23, 24.°71, and 11.4%, respectively. Using these, we have created 77 ensemble members for the 2012 July 12 CME. We found that 55% of our ensemble members correctly reproduce the sign of the magnetic field components at Earth. We also determined that the uncertainties in GCS fitting can widen the CME arrival time prediction window to about 12 hr for the 2012 July 12 CME. On investigating the forecast accuracy introduced by the uncertainties in individual GCS parameters, we conclude that the half-angle and aspect ratio have little impact on the predicted magnetic field of the 2012 July 12 CME, whereas the uncertainties in longitude and tilt can introduce relatively large spread in the magnetic field predicted at Earth.

Keywords: solar coronal mass ejections; solar wind
Exoplanet Aeronomy: A Case Study of WASP-69 b's Variable Thermosphere

Aeronomy, the study of Earth's upper atmosphere and its interaction with the local space environment, has long traced changes in the thermospheres of Earth and other solar system planets to solar variability in the X-ray and extreme-ultraviolet (collectively, XUV) bands. Extending comparative aeronomy to the short-period extrasolar planets may illuminate whether stellar XUV irradiation powers atmospheric outflows that change planetary radii on astronomical timescales. In recent years, near-IR transit spectroscopy of metastable HeI has been a prolific tracer of high-altitude planetary gas. We present a case study of exoplanet aeronomy using metastable HeI transit observations from Palomar Observatory's Wide Field InfraRed Camera and follow-up high-energy data from the Neil Gehrels Swift Observatory that were taken within 1 month of the WASP-69 system, a K-type main-sequence star with a well-studied hot Jupiter companion. Supplemented by archival data, we find that WASP-69's X-ray flux in 2023 was less than 50% of what was recorded in 2016 and that the metastable HeI absorption from WASP-69 b was lower in 2023 versus past epochs from 2017 to 2019. Via atmospheric modeling, we show that this time-variable metastable HeI signal is in the expected direction given the observed change in stellar XUV, possibly stemming from WASP-69's magnetic activity cycle. Our results underscore the ability of multiepoch, multiwavelength observations to paint a cohesive picture of the interaction between an exoplanet's atmosphere and its host star.

Keywords: exoplanet atmospheres; exoplanet evolution; exoplanet astronomy; exoplanet atmospheric dynamics; exoplanet atmospheric variability; planetary atmospheres
Boron Abundances in Early B Dwarfs of the Galactic Open Cluster NGC 3293

New boron abundances or upper limits have been determined for eight early B stars in the young Galactic open cluster NGC 3293, using UV spectra obtained by the Hubble Space Telescope Cosmic Origins Spectrograph. With previous observations, there are now 18 early B stars in this cluster with boron measurements. Six of the newly observed stars have projected rotational velocities greater than 200 km s‑1, allowing new constraints on rotationally driven mixing in main-sequence stars. When comparing to synthetic model populations, we find that the majority of our sample stars agree well with the predicted trends of stronger boron depletion for larger rotation and for larger mass or luminosity. Based on those, a smaller than the canonical rotational mixing efficiency (f c ≈ 0.0165 versus the more standard value of 0.033) appears to be favored. In addition, the five mostly slowly rotating stars, when considered as a group, tend to show more boron depletion than expected from rotational mixing, and we speculate that most or all of these originate from binary mergers. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal GO-14673.

Keywords: stellar evolution; stellar populations; stellar rotation; stellar abundances; stellar physics
Constraints on Cosmological Parameters with a Sample of Type Ia Supernovae from JWST

We investigate the potential of using a sample of very high-redshift (2 ≲ z ≲ 6) (VHZ) Type Ia supernovae (SNe Ia) attainable by JWST on constraining cosmological parameters. At such high redshifts, the age of the universe is young enough that the VHZ SN Ia sample comprises the very first SNe Ia of the universe, with progenitors among the very first generation of low-mass stars that the universe has made. We show that the VHZ SNe Ia can be used to disentangle systematic effects due to the luminosity distance evolution with redshifts intrinsic to SN Ia standardization. Assuming that the systematic evolution can be described by a linear or logarithmic formula, we found that the coefficients of this dependence can be determined accurately and decoupled from cosmological models. Systematic evolution as large as 0.15 mag and 0.45 mag out to z = 5 can be robustly separated from popular cosmological models for linear and logarithmic evolution, respectively. The VHZ SNe Ia will lay the foundation for quantifying the systematic redshift evolution of SN Ia luminosity distance scales. When combined with SN Ia surveys at comparatively lower redshifts, the VHZ SNe Ia allow for the precise measurement of the history of the expansion of the universe from z ~ 0 to the epoch approaching reionization.

Keywords: cosmological parameters; cosmological constant; dark energy; type ia supernovae; hubble diagram; accelerating universe; cosmological models; expanding universe