adsabs/SciX_UAT_keywords huggingface dataset:
The Second Discovery from the COCONUTS Program: A Cold Wide-orbit Exoplanet around a Young Field M Dwarf at 10.9 pc

We present the identification of the second discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) program, the COCONUTS-2 system, composed of the M3 dwarf L 34-26 and the T9 dwarf WISEPA J075108.79-763449.6. Given their common proper motions and parallaxes, these two field objects constitute a physically bound pair with a projected separation of 594″ (6471au). The primary star COCONUTS-2A has strong stellar activity (Hα, X-ray, and ultraviolet emission) and is rapidly rotating (Prot = 2.83 days), from which we estimate an age of 150-800 Myr. Comparing equatorial rotational velocity derived from the Transiting Exoplanet Survey Satellite (TESS) light curve to spectroscopic vsini, we find that COCONUTS-2A has a nearly edge-on inclination. The wide exoplanet COCONUTS-2b has an effective temperature of Teff = 434 ± 9 K, a surface gravity of $\mathrm{log}g={4.11}_{-0.18}^{+0.11}$ dex, and a mass of M = ${6.3}_{-1.9}^{+1.5}$ MJup based on hot-start evolutionary models, leading to a mass ratio of ${0.016}_{-0.005}^{+0.004}$ for the COCONUTS-2 system. COCONUTS-2b is the second coldest (after WD 0806-661B), and the second widest (after TYC 9486-927-1 b) exoplanet imaged to date. Comparison of COCONUTS-2b's infrared photometry with ultracool model atmospheres suggests the presence of both condensate clouds and non-equilibrium chemistry in its photosphere. Similar to 51 Eri b, COCONUTS-2b has a sufficiently low luminosity ($\mathrm{log}({L}_{\mathrm{bol}}/{L}_{\odot })=-6.384\pm 0.028$ dex) to be consistent with the cold-start process that may form gas-giant (exo)planets, though its large separation means that such formation would not have occurred in situ. Finally, at a distance of 10.9 pc, COCONUTS-2b is the nearest imaged exoplanet to Earth known to date.

Keywords: exoplanets; t dwarfs; extrasolar gaseous giant planets
An Extreme Ultraviolet Wave Associated with a Solar Filament Activation

Extreme ultraviolet (EUV) waves are impressive coronal propagating disturbances. They are closely associated with various eruptions and can be used for global coronal seismology and the acceleration of solar energetic particles. Hence, the study of EUV waves plays an important role in solar eruptions and space weather. Here we present an EUV wave associated with a filament activation that did not evolve into any eruption. Due to the continuous magnetic flux emergence and cancellation around its one end, the filament rose with untwisting motion, and the filament mass flowed toward another end along the rising fields. Intriguingly, following the filament activation, an EUV wave formed with a fast constant speed (∼500 km s-1) ahead of the mass flow, and the overlying coronal loops expanded in both lateral and radial directions. Excluding the possibility of a remote flare and an absent coronal mass ejection, we suggest that the EUV wave was only closely associated with the filament activation. Furthermore, their intimate spatial and temporal relationship indicates that the EUV wave was likely directly triggered by the lateral expansion of overlying loops. We propose that the EUV wave can be interpreted as a linear fast-mode wave, and the most vital key for the successful generation of the EUV wave is the impulsive early phase lateral expansion of overlying loops that was driven by the activated filament mass flow without any eruption.

Keywords: solar filaments; solar coronal waves; solar coronal loops; solar magnetic flux emergence
Tianwen-1 and MAVEN Observations of the Response of Mars to an Interplanetary Coronal Mass Ejection

Interplanetary coronal mass ejections (ICMEs) are solar transients that have significant effects on the upper atmosphere and ionosphere of Mars. The simultaneous spacecraft observations from Tianwen-1/MOMAG in solar wind and multiple instruments on board the Mars Atmosphere and Volatile Evolution (MAVEN) in the Martian upper atmosphere are used to study the response of Mars to an ICME. The ICME was observed at Mars by Tianwen-1 and MAVEN at 00:00 UT on 2021 December 10, which was earlier observed by BepiColombo upstream of Mars at 22:32 UT on 2021 December 6. During 2021 December 6-15, MAVEN measured the nightside ionosphere and Tianwen-1 measured the dayside ionosphere while both were inside the Martian bow shock. The rapid drop in densities of ionospheric ions and electrons, which is typically identified as the end of the ionosphere at altitudes between 300-800 km, is known as the ionopause. The altitude of the Martian ionopause location was lowered by the high dynamic pressure of the solar wind during the ICME passage. The depletion of the plasma density in the topside Martian ionosphere on the nightside reveals the presence of substantial ion and electron escape to space through the interaction between the ICME and Mars. The column abundance of plasma dramatically decreased, with 34% e-, 61% ${{\rm{O}}}_{2}^{+}$ , and 73% O+ reduced. This study highlights the significant impact of the space weather associated with the intense magnetic field and high dynamic pressure of the ICME on Mars's atmosphere, which is particularly important for future human exploration missions to Mars.

Keywords: solar coronal mass ejections; solar system terrestrial planets
Shock Cooling and Breakout Emission for Optical Flares Associated with Gravitational-wave Events

The astrophysical origin of stellar-mass black hole (BH) mergers discovered through gravitational waves (GWs) is widely debated. Mergers in the disks of active galactic nuclei (AGNs) represent promising environments for at least a fraction of these events, with possible observational clues in the GW data. An additional clue to unveil AGN merger environments is provided by possible electromagnetic emission from postmerger accreting BHs. Associated with BH mergers in AGN disks, emission from shocks emerging around jets launched by accreting merger remnants is expected. Here we compute the properties of the emission produced during breakout and the subsequent adiabatic expansion phase of the shocks, and we then apply this model to optical flares suggested to be possibly associated with GW events. We find that the majority of the reported flares can be explained by breakout and shock cooling emission. If the optical flares are produced by shock cooling emission, they would display moderate color evolution, possibly color variations among different events, and a positive correlation between delay time and flare duration and would be preceded by breakout emission in X-rays. If the breakout emission dominates the observed lightcurve, we predict the color to be distributed in a narrow range in the optical band and the delay time from GW to electromagnetic emission to be longer than ∼2 days. Hence, further explorations of delay time distributions, flare color evolution, and associated X-ray emission will be useful to test the proposed emission model for the observed flares.

Keywords: astrophysical black holes; gravitational wave sources; active galactic nuclei; transient sources; jets
SZ Scaling Relations of Galaxy Groups and Clusters Near the North Ecliptic Pole

Sunyaev-Zel'dovich (SZ) scaling relations have been used to test the self-similar prediction for massive galaxy clusters, but little attention has been given to individual galaxy groups. We investigate the scaling relations of galaxy groups and clusters near the North Ecliptic Pole using X-ray and SZ observations. This region of the sky is where both the ROSAT and Planck satellites achieved their deepest observations, permitting the investigation of lower mass systems. Our sample consists of 62 X-ray detected groups and clusters, spanning a mass range of ${10}^{13.4}{M}_{\odot }\lt \,{M}_{500}\lt {10}^{15}{M}_{\odot }$ and redshifts of 0.03 ≲ z ≲ 0.82. We extract the total SZ flux from unresolved Planck data and estimate the fraction of the SZ flux within R500 assuming two different pressure profiles. The SZ scaling relations were derived using a Bayesian technique that accounts for censored data. We find a power law slope of ${1.73}_{-0.18}^{+0.19}$ for the YSZ-M500 relation that is consistent with the self-similar prediction of 5/3. The slope of ${0.89}_{-0.08}^{+0.09}$ for the ${Y}_{\mathrm{SZ}}\mbox{--}{L}_{{\rm{X}},500}$ relation is in agreement with other observational studies but not the self-similar prediction of 5/4, and the ${Y}_{\mathrm{SZ}}\mbox{--}{Y}_{{\rm{X}}}$ relation lies below the 1:1 relation when the slope is fixed to unity. The determined scaling relations are dependent on the selected pressure profile, so resolved data are needed to determine the effects of active galactic nucleus feedback. In addition, we find a number of potential cluster candidates in the Planck Compton maps that were not identified in our X-ray sample.

Keywords: galaxy clusters; intracluster medium; galaxy groups; sunyaev-zeldovich effect
The Magellan M2FS Spectroscopic Survey of High-redshift Galaxies: A Sample of 260 Lyα Emitters at Redshift z ≈ 5.7

We present a spectroscopic survey of Lyα emitters (LAEs) at z ≈ 5.7 using the multiobject spectrograph M2FS on the Magellan Clay telescope. This is part of a high-redshift galaxy survey carried out in several well-studied deep fields. These fields have deep images in multiple UV/optical bands, including a narrow NB816 band that has allowed an efficient selection of LAE candidates at z ≈ 5.7. Our sample consists of 260 LAEs and covers a total effective area of more than 2 deg2 on the sky. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We use the secure redshifts and narrowband photometry to measure Lyα luminosities. We find that these LAEs span a Lyα luminosity range of $\sim 2\times {10}^{42}\mbox{--}5\times {10}^{43}$ erg s-1 and include some of the most luminous galaxies known at $z\geqslant 5.7$ in terms of Lyα luminosity. Most of them have rest-frame equivalent widths between 20 and 300 Å, and more luminous Lyα emission lines tend to have broader line widths. We detect a clear offset of ∼20 Å between the observed Lyα wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Lyα in the high-redshift spectra. This sample is being used to study the Lyα luminosity function and galaxy properties at z ≈ 5.7.

Keywords: high-redshift galaxies; galaxy properties
X-Ray Redshifts for Obscured AGN: A Case Study in the J1030 Deep Field

We present a procedure to constrain the redshifts of obscured ( ${N}_{H}\gt {10}^{22}\,{\mathrm{cm}}^{-2}$ ) active galactic nuclei (AGN) based on low count statistics X-ray spectra, which can be adopted when photometric and/or spectroscopic redshifts are unavailable or difficult to obtain. We selected a sample of 54 obscured AGN candidates on the basis of their X-ray hardness ratio, ${\rm{HR}}\gt -0.1$ , in the Chandra deep field (∼479 ks, 335 arcmin2) around the z = 6.3 QSO SDSS J1030+0524. The sample has a median value of ≈80 net counts in the 0.5-7 keV energy band. We estimate reliable X-ray redshift solutions taking advantage of the main features in obscured AGN spectra, like the Fe 6.4 keV ${\rm{K}}\alpha $ emission line, the 7.1 keV Fe absorption edge, and the photoelectric absorption cutoff. The significance of such features is investigated through spectral simulations, and the derived X-ray redshift solutions are then compared with photometric redshifts. Both photometric and X-ray redshifts are derived for 33 sources. When multiple solutions are derived by any method, we find that combining the redshift solutions of the two techniques improves the rms by a factor of 2. Using our redshift estimates ( $0.1\lesssim z\lesssim 4$ ), we derived absorbing column densities in the range $\sim {10}^{22}\mbox{--}{10}^{24}\,{\mathrm{cm}}^{-2}$ and absorption-corrected, 2-10 keV rest-frame luminosities between $\sim {10}^{42}$ and 1045 erg s-1, with median values of ${N}_{H}=1.7\times {10}^{23}\,{\mathrm{cm}}^{-2}$ and ${L}_{2-10\mathrm{keV}}=8.3\times {10}^{43}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ , respectively. Our results suggest that the adopted procedure can be applied to current and future X-ray surveys for sources detected only in X-rays or that have uncertain photometric or single-line spectroscopic redshifts.

Keywords: active galactic nuclei; x-ray active galactic nuclei; spectral energy distribution; x-ray surveys; redshift surveys; agn host galaxies
Early Results from GLASS-JWST. XIV. A Spectroscopically Confirmed Protocluster 650 Million Years after the Big Bang

We present the spectroscopic confirmation of a protocluster at z = 7.88 behind the galaxy cluster Abell 2744 (hereafter A2744-z7p9OD). Using JWST NIRSpec, we find seven galaxies within a projected radius of 60 kpc. Although the galaxies reside in an overdensity around ≳20× greater than a random volume, they do not show strong Lyα emission. We place 2σ upper limits on the rest-frame equivalent width <16-28 Å. Based on the tight upper limits to the Lyα emission, we constrain the volume-averaged neutral fraction of hydrogen in the intergalactic medium to be x HI > 0.45 (68% C I). Using an empirical M UV-M halo relation for individual galaxies, we estimate that the total halo mass of the system is ≳4 × 1011 M ⊙. Likewise, the line-of-sight velocity dispersion is estimated to be 1100 ± 200 km s-1. Using an empirical relation, we estimate the present-day halo mass of A2744-z7p9OD to be ~2 × 1015 M ⊙, comparable to the Coma cluster. A2744-z7p9OD is the highest redshift spectroscopically confirmed protocluster to date, demonstrating the power of JWST to investigate the connection between dark-matter halo assembly and galaxy formation at very early times with medium-deep observations at <20 hr total exposure time. Follow-up spectroscopy of the remaining photometric candidates of the overdensity will further refine the features of this system and help characterize the role of such overdensities in cosmic reionization.

Keywords: galaxies; galaxy clusters; reionization; protoclusters
Implications of Atmospheric Nondetections for Trappist-1 Inner Planets on Atmospheric Retention Prospects for Outer Planets

JWST secondary eclipse observations of Trappist-1b seemingly disfavor atmospheres >~1 bar since heat redistribution is expected to yield dayside emission temperature below the ~500 K observed. Given the similar densities of Trappist-1 planets, and the theoretical potential for atmospheric erosion around late M dwarfs, this observation might be assumed to imply substantial atmospheres are also unlikely for the outer planets. However, the processes governing atmosphere erosion and replenishment are fundamentally different for inner and outer planets. Here, an atmosphere-interior evolution model is used to show that an airless Trappist-1b (and c) only weakly constrains stellar evolution, and that the odds of outer planets e and f retaining substantial atmospheres remain largely unchanged. This is true even if the initial volatile inventories of planets in the Trappist-1 system are highly correlated. The reason for this result is that b and c sit unambiguously interior to the runaway greenhouse limit, and so have potentially experienced ~8 Gyr of X-ray and extreme ultraviolet-driven hydrodynamic escape; complete atmospheric erosion in this environment only weakly constrains stellar evolution and escape parameterizations. In contrast, e and f reside within the habitable zone, and likely experienced a comparatively short steam atmosphere during Trappist-1's pre-main sequence, and consequently complete atmospheric erosion remains unlikely across a broad swath of parameter space (e and f retain atmospheres in ~98% of model runs). Naturally, it is still possible that all Trappist-1 planets formed volatile-poor and are all airless today. But the airlessness of b (and c) does not require this, and as such, JWST transit spectroscopy of e and f remains the best near-term opportunity to characterize the atmospheres of habitable zone terrestrial planets.

Keywords: exoplanets; habitable planets; exoplanet astronomy
The Mean Underabundances of Carbon and Aluminum Over the Surface of 21 Com from Its Far-ultraviolet Spectra Recorded by IUE

The comparison of a coadded International Ultraviolet Explorer (IUE) far-ultraviolet spectrum of 21 Com (A3p SrCr) to that of the standard star α Psa (A3V) reveals large differences in the resonance and low-excitation lines of C I and Al II. All the lines of these species are significantly weaker in the mean spectrum of 21 Com. The synthesis of these lines consistently yields sizable underabundances for 21 Com of about 0.5 times the solar carbon, and 0.20 times solar for aluminum. Inspection of 10 individual spectra taken over the 24 hr monitoring of 21 Com with IUE on 1991 April 17 does not reveal convincing variations of the lines analyzed here between rotational phases 0.18 and 0.65 of the 2 days period, suggesting a uniform repartition of these 2 elements over the hemisphere of 21 Com observed then.

Keywords: chemically peculiar stars; chemical abundances
Benchmarking Dust Emission Models in M101

We present a comparative study of four physical dust models and two single-temperature modified blackbody models by fitting them to the resolved WISE, Spitzer, and Herschel photometry of M101 (NGC 5457). Using identical data and a grid-based fitting technique, we compare the resulting dust and radiation field properties derived from the models. We find that the dust mass yielded by the different models can vary by up to a factor of 3 (factor of 1.4 between physical models only), although the fits have similar quality. Despite differences in their definition of the carriers of the mid-IR aromatic features, all physical models show the same spatial variations for the abundance of that grain population. Using the well-determined metallicity gradient in M101 and resolved gas maps, we calculate an approximate upper limit on the dust mass as a function of radius. All physical dust models are found to exceed this maximum estimate over some range of galactocentric radii. We show that renormalizing the models to match the same Milky Way high-latitude cirrus spectrum and abundance constraints can reduce the dust mass differences between models and bring the total dust mass below the maximum estimate at all radii.

Keywords: spectral energy distribution; interstellar dust; dust continuum emission; gas-to-dust ratio; metallicity
Accelerated Electrons Observed Down to <7 keV in a NuSTAR Solar Microflare

We report the detection of emission from a nonthermal electron distribution in a small solar microflare (GOES class A5.7) observed by the Nuclear Spectroscopic Telescope Array, with supporting observation by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The flaring plasma is well accounted for by a thick-target model of accelerated electrons collisionally thermalizing within the loop, akin to the "coronal thick-target" behavior occasionally observed in larger flares. This is the first positive detection of nonthermal hard X-rays from the Sun using a direct imager (as opposed to indirectly imaging instruments). The accelerated electron distribution has a spectral index of 6.3 ± 0.7, extends down to at least 6.5 keV, and deposits energy at a rate of ∼2 × 1027 erg s-1, heating the flare loop to at least 10 MK. The existence of dominant nonthermal emission in X-rays down to <5 keV means that RHESSI emission is almost entirely nonthermal, contrary to what is usually assumed in RHESSI spectroscopy. The ratio of nonthermal to thermal energies is similar to that of large flares, in contrast to what has been found in previous studies of small RHESSI flares. We suggest that a coronal thick target may be a common property of many small microflares based on the average electron energy and collisional mean free path. Future observations of this kind will enable understanding of how flare particle acceleration changes across energy scales, and will aid the push toward the observational regime of nanoflares, which are a possible source of significant coronal heating.

Keywords: active sun; the sun; solar flare spectra; solar x-ray flares; flare stars; non-thermal radiation sources
Extended Point-spread Functions for Deep Astronomical Imaging Surveys

The low surface brightness (LSB) universe is one of the last frontiers in observational astronomy. However, uncovering the information contained in ultra-deep imaging is technically challenging. In this contribution, we present one of the fundamental tools of LSB astronomers: correcting for the extended Point-Spread Function (PSF), which is critical to characterize the LSB properties of astronomical images. We show how to build the extended PSF (approximately 5' in radius), in 5 bands (grizY), of one of the most important modern deep surveys: the Hyper-Suprime Camera (HSC) one on the 8.2 m Subaru telescope. These PSFs have been obtained by sampling individual point-like sources at different brightness. The techniques used here can be applied to the next generation of deep astronomical imaging surveys as the LSST.

Keywords: catalogs; surveys; galaxy formation; galaxy evolution
Multiwavelength Observations of Multiple Eruptions of the Recurrent Nova M31N 2008-12a

We report the optical, UV, and soft X-ray observations of the 2017–2022 eruptions of the recurrent nova M31N 2008-12a. We find a cusp feature in the $r^{\prime} $ - and $i^{\prime} $ -band light curves close to the peak, which could be related to jets. The geometry of the nova ejecta based on morpho-kinematic modeling of the Hα emission line indicates an extended jet-like bipolar structure. Spectral modeling indicates an ejecta mass of 10‑7–10‑8 M ⊙ during each eruption and an enhanced helium abundance. The supersoft source phase shows significant variability, which is anticorrelated to the UV emission, indicating a common origin. The variability could be due to the reformation of the accretion disk. We infer a steady decrease in the accretion rate over the years based on the intereruption recurrence period. A comparison of the accretion rate with different models on the ${M}_{\mathrm{WD}}\mbox{--}\dot{M}$ plane yields the mass of a CO white dwarf, powering the H-shell flashes every ∼1 yr, to be >1.36 M ⊙ and growing with time, making M31N 2008-12a a strong candidate for the single degenerate scenario of the Type Ia supernovae progenitor.

Keywords: recurrent novae; andromeda galaxy; cataclysmic variable stars; transient sources; photometry; spectroscopy; ultraviolet astronomy; x-ray astronomy