Sazuna/UAT_keywords huggingface dataset:
Imaging of the Vega Debris System Using JWST/MIRI. We present images of the Vega planetary debris disk obtained at 15.5, 23, and 25.5 μm with the Mid-Infrared Instrument on JWST. The debris system is remarkably symmetric, smooth, and centered accurately on the star. There is a broad Kuiper-belt-analog ring at ∼80–170 au that coincides with the planetesimal belt detected with the Atacama Large Millimeter/submillimeter Array at 1.34 mm. The interior of the broad belt is filled with warm debris that shines most efficiently at mid-infrared, along with a shallow flux dip/gap at 60 au from the star. These qualitative characteristics argue against any Saturn-mass planets orbiting the star outside of about 10 au, assuming the unseen planet would be embedded in the very broad planetesimal disk from a few to hundreds of astronomical units. We find that the distribution of dust detected interior to the broad outer belt is consistent with grains being dragged inward by the Poynting–Robertson effect. Under the drag-dominated disk assumption, tighter constraints can be derived for planets in specific locations; for example, any planet shepherding the inner edge of the outer belt is likely to be less than six Earth masses. The disk surface brightness profile along with the available infrared photometry suggest a disk inner edge near ∼3‑5 au, disconnected from the sub-astronomical-unit region that gives rise to the hot near-infrared excess. The gap between the hot, sub-astronomical-unit zone and the inner edge of the warm debris might be shepherded by a modest-mass, Neptune-size planet.

Keywords: Planetesimals, Debris disks, Circumstellar disks
Icarus Revisited: An Ancient, Metal-poor Accreted Stellar Stream in the Disk of the Milky Way. The search for accreted satellites in the Galactic disk is a challenging task, to which Gaia plays a crucial role in synergy with ground-based spectroscopic surveys. In 2021, P. Re Fiorentin et al. discovered five substructures with disk kinematics including Icarus. To gain more insight into the origin of Icarus as a remnant of a dwarf galaxy rather than a signature of secular processes of disk formation, we complement astrometric Gaia DR3 data with spectroscopy from APOGEE DR17 and GALAH DR3, and explore the chemodynamical distributions within 3 kpc of the Sun. We select 622 stars in the accreted/unevolved regions of [Mg/Mn]–[Al/Fe] and [Mg/Fe]–[Fe/H], where we identify 81 and 376 stars with ‑2 &lt; [Fe/H] &lt; ‑0.7 belonging to Icarus and Gaia-Sausage-Enceladus (GSE), respectively. The revised properties of Icarus are: &lt;V + V LSR&gt; ≃ 171 km s‑1, σ  V  ≃ 37 km s‑1, &lt;e&gt; ≃ 0.36, &lt;[Fe/H]&gt; ≃ ‑1.35, &lt;[Mg/Fe]&gt; ≃ +0.27, &lt;[Al/Fe]&gt; ≃ ‑0.13, and &lt;[Mn/Fe]&gt; ≃ ‑0.39. From the color–magnitude diagram of its members, Icarus appears older than 12 Gyr. Such age and dynamical properties are reminiscent of the metal-weak thick disk. However, detailed chemical analysis in the diagnostic spaces [Ni/Fe]–[(C+N)/O], [Y/Eu]–[Fe/H], [Eu/Mg]–[Fe/H], [Ba/Y]–[Fe/H], and [Ba/Mg]–[Mg/H] evidences that Icarus and GSE occupy the accreted region, well separated from the bulk of in situ disk stars. Updated comparisons with N-body simulations confirm that Icarus's stars are consistent with the debris of a dwarf galaxy with a stellar mass of ∼109 M ☉ accreted onto a primordial disk on an initial prograde low-inclination orbit.

Keywords: Milky Way disk, Galaxy abundances, Milky Way dynamics, Milky Way formation
Gleeok's Fire-breathing: Triple Flares of AT 2021aeuk within Five Years from the Active Galaxy SDSS J161259.83+421940.3. We present a noteworthy transient AT 2021aeuk exhibiting three distinct optical flares between 2018 and 2023. It is hosted in a radio-loud narrow-line Seyfert 1 galaxy, with an optical image showing a minor tidal morphology and a red mid-infrared color (W1 ‑ W2 = 1.1). Flares II and III exhibit rapid rises, and long-term decays (≳1000 days) with recurring after-peak bumps. The g ‑ r color after subtracting the reference magnitude exhibited a rapid drop and recovery during Flare II, followed by a minor after-peak evolution in blue colors. We applied a canonical tidal disruption event (TDE) fitting on the light curves, which gives a decay index p of   for Flare II and   for Flare III. The blackbody fitting shows lower temperatures (∼103.8 K) with minor after-peak evolution. The blackbody radius (≳1016 cm) and luminosity (∼1045 erg s‑1) are larger than the typical TDE sample's. The time lag (in rest frame) between the ZTF g and r bands (  days) significantly exceeds the prediction from the standard accretion disk. Pre-burst spectra reveal prominent Bowen fluorescence lines, indicating a vigorous or potentially long-lasting process that enriches the local metallicity. Additionally, we derived black hole masses of   and   using Hβ and Hα emission lines. The variation and recurring features of AT 2021aeuk are not likely induced by the radio-beaming effect or Type II superluminous supernova; however, we cannot rule out the possibility of TDE or enhanced active galactic nuclei accretion process. The unusually high occurrence of three flares within 5 yr may also induced by the complex local environment.

Keywords: Accretion, Supermassive black holes, Tidal disruption, Active galactic nuclei
Slow Rotation for the Super-puff Planet Kepler-51d. Super-puffs are low-density planets of unknown origin and composition. If they form by accreting nebular gas through a circumplanetary disk, one might expect super-puffs to be spinning quickly. Here, we derive upper limits on the rotational oblateness of the super-puff Kepler-51d, based on precise transit observations with the NIRSpec instrument on board the James Webb Space Telescope. The absence of detectable oblateness-related anomalies in the light curve leads to an upper limit of about 0.15 on the planet's sky-projected oblateness. Assuming the sky-projected oblateness to be representative of the true oblateness, the rotation period of Kepler-51d is ≳40 hr, or equivalently, its rotation speed is ≲42% of the breakup speed. Alternatively, if the apparently low density of Kepler-51d is due to an opaque planetary ring, the ring must be oriented within 30∘ of face on and have an inner radius smaller than 1.2 times the planet's radius. Separately, the lack of anomalies exceeding 0.01% in the ingress and egress portions of the light curve places a constraint on the model of Wang &amp; Dai, in which the planet's apparently low density is due to a dusty outflowing atmosphere.

Keywords: Transit photometry, James Webb Space Telescope, Oblateness, Exoplanets
Black Hole Scaling Relations in the Dwarf-galaxy Regime with Gaia-Sausage/Enceladus and ωCentauri. The discovery of fast moving stars in Milky Way's most massive globular cluster, ωCentauri (ωCen), has provided strong evidence for an intermediate-mass black hole (IMBH). However, ωCen is known to be the stripped nuclear star cluster (NSC) of an ancient, now-destroyed, dwarf galaxy. The best candidate to be the original host progenitor of ωCen is the tidally disrupted dwarf Gaia-Sausage/Enceladus (GSE), a former Milky Way satellite as massive as the Large Magellanic Cloud. I compare ωCen/GSE with other central BH hosts and place it within the broader context of BH–galaxy (co)evolution. The IMBH of ωCen/GSE follows the scaling relation between central BH mass and host stellar mass (MBH–M⋆) extrapolated from local massive galaxies (M⋆ ≳ 1010 M⊙). Therefore, the IMBH of ωCen/GSE suggests that this relation extends to the dwarf-galaxy regime. I verify that ωCen (GSE), as well as other NSCs with candidate IMBHs and ultracompact galaxies also follow the MBH–σ⋆ relation with stellar velocity dispersion. Under the assumption of direct collapse BH, ωCen/GSE's IMBH would require a low initial mass (≲10,000 M⊙) and almost no accretion over ∼3 Gyr, which could be the extreme opposite of high-z galaxies with overmassive BHs such as GN-z11. If ωCen/GSE's IMBH formed from a Population III supernova remnant, then it could indicate that both light and heavy seeding mechanisms of central BH formation are at play. Other stripped NSCs and dwarf galaxies could help further populate the MBH–M⋆ and MBH–σ⋆ relations in the low-mass regime and constrain IMBH demographics and their formation channels.

Keywords: Intermediate-mass black holes, Dwarf galaxies, Star clusters
Quantitative Constraint on the Contribution of Resolved Gamma-Ray Sources to the Sub-PeV Galactic Diffuse Gamma-Ray Flux Measured by the Tibet ASγ Experiment. Motivated by the difference between the fluxes of sub-PeV Galactic diffuse gamma-ray emission (GDE) measured by the Tibet ASγ experiment and the LHAASO collaboration, our study constrains the contribution to the GDE flux measured by Tibet ASγ from the sub-PeV gamma-ray sources in the first LHAASO catalog plus the Cygnus Cocoon. After removing the gamma-ray emission of the sources masked in the observation by Tibet ASγ, the contribution of the sources to the Tibet diffuse flux is found to be subdominant; in the sky region of 25° &lt; l &lt; 100° and ∣b∣ &lt; 5°, it is less than 26.9% ± 9.9%, 34.8% ± 14.0%, and   at 121 TeV, 220 TeV, and 534 TeV, respectively. In the sky region of 50° &lt; l &lt; 200° and ∣b∣ &lt; 5°, the fraction is less than 24.1% ± 9.5%, 27.1% ± 11.1%, and  . After subtracting the source contribution, the hadronic diffusive nature of the Tibet diffuse flux is the most natural interpretation although some contributions from very faint unresolved hadronic gamma-ray sources cannot be ruled out. Different source-masking schemes adopted by Tibet ASγ and LHAASO for their diffuse analyses result in different effective Galactic latitudinal ranges of the sky regions observed by the two experiments. Our study concludes that the effect of the different source-masking schemes leads to the observed difference between the Tibet diffuse flux measured in 25° &lt; l &lt; 100° and ∣b∣ &lt; 5° and LHAASO diffuse flux in 15° &lt; l &lt; 125° and ∣b∣ &lt; 5°.

Keywords: Galactic cosmic rays, Gamma-ray astronomy, High-energy cosmic radiation
A Repeating Fast Radio Burst Source in a Low-luminosity Dwarf Galaxy. We present the localization and host galaxy of FRB 20190208A, a repeating source of fast radio bursts (FRBs) discovered using CHIME/FRB. As part of the Pinpointing REpeating ChIme Sources with EVN dishes repeater localization program on the European VLBI Network (EVN), we monitored FRB 20190208A for 65.6 hr at ∼1.4 GHz and detected a single burst, which led to its very long baseline interferometry localization with 260 mas uncertainty (2σ). Follow-up optical observations with the MMT Observatory (i ≳ 25.7 mag (AB)) found no visible host at the FRB position. Subsequent deeper observations with the Gran Telescopio Canarias, however, revealed an extremely faint galaxy (r = 27.32 ± 0.16 mag), very likely (99.95%) associated with FRB 20190208A. Given the dispersion measure of the FRB (∼580 pc cm‑3), even the most conservative redshift estimate ( ) implies that this is the lowest-luminosity FRB host to date (≲108 L ⊙), even less luminous than the dwarf host of FRB 20121102A. We investigate how localization precision and the depth of optical imaging affect host association and discuss the implications of such a low-luminosity dwarf galaxy. Unlike the other repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday rotation measure of a few tens of rad m‑2, and EVN plus Very Large Array observations reveal no associated compact persistent radio source. We also monitored FRB 20190208A for 40.4 hr over 2 yr as part of the Extragalactic Coherent Light from Astrophysical Transients repeating FRB monitoring campaign on the Nançay Radio Telescope and detected one burst. Our results demonstrate that, in some cases, the robust association of an FRB with a host galaxy will require both high localization precision and deep optical follow-up.

Keywords: Radio bursts, Dwarf galaxies, Very long baseline interferometry, Radio transient sources
Three Quenched, Faint Dwarf Galaxies in the Direction of NGC 300: New Probes of Reionization and Internal Feedback. We report the discovery of three faint and ultrafaint dwarf galaxies—Sculptor A, Sculptor B, and Sculptor C—in the direction of NGC 300 (D = 2.0 Mpc), a Large Magellanic Cloud─mass galaxy. Deep ground-based imaging with Gemini/GMOS resolves all three dwarf galaxies into stars, each displaying a red giant branch indicative of an old, metal-poor stellar population. No young stars or H I gas are apparent, and the lack of a GALEX UV detection suggests that all three systems are quenched. Sculptor C (D = 2.04  Mpc; MV = −9.1 ± 0.1 mag or LV = (3.7 ) × 105L⊙) is consistent with being a satellite of NGC 300. Sculptor A (D = 1.35  Mpc; MV = −6.9 ± 0.3 mag or LV = (5 ) × 104L⊙) is likely in the foreground of NGC 300 and at the extreme edge of the Local Group, analogous to the recently discovered ultrafaint Tucana B in terms of its physical properties and environment. Sculptor B (D = 2.48  Mpc; MV = −8.1 ± 0.3 mag or LV = (1.5 ) × 105L⊙) is likely in the background, but future distance measurements are necessary to solidify this statement. It is also of interest due to its quiescent state and low stellar mass. Both Sculptor A and B are ≳2─4 rvir from NGC 300 itself. The discovery of three dwarf galaxies in isolated or low-density environments offers an opportunity to study the varying effects of ram-pressure stripping, reionization, and internal feedback in influencing the star formation history of the faintest stellar systems.

Keywords: Galaxy quenching, Dwarf galaxies, Quenched galaxies
The Impact of Shear on Disk Galaxy Star Formation Rates. Determining the physical processes that control galactic-scale star formation rates is essential for an improved understanding of galaxy evolution. The role of orbital shear is currently unclear, with some models expecting reduced star formation rates and efficiencies with increasing shear, e.g., if shear stabilizes gas against gravitational collapse, while others predicting enhanced rates, e.g., if shear-driven collisions between giant molecular clouds trigger star formation. Expanding on the analysis of 16 galaxies by C. Suwannajak et al., we assess the shear dependence of star formation efficiency (SFE) per orbital time (ϵorb) in 49 galaxies selected from the PHANGS-ALMA survey. In particular, we test a prediction of the shear-driven giant molecular cloud (GMC) collision model that ϵorb ∝ (1─0.7β), where  , i.e., SFE per orbital time declines with decreasing shear. We fit the function ϵorb = ϵorb,0(1 − αCCβ) finding αCC ≃ 0.76 ± 0.16; an alternative fit with ϵorb normalized by the median value in each galaxy yields  . These results are in good agreement with the prediction of the shear-driven GMC collision theory. We also examine the impact of a galactic bar on ϵorb finding a modest decrease in SFE in the presence of a bar, which can be attributed to lower rates of shear in these regions. We discuss the implications of our results for the GMC life cycle and environmental dependence of star formation activity.

Keywords: Interstellar medium, Galaxy dynamics, Star formation, Disk galaxies
Reliable Transmission Spectrum Extraction with a Three-parameter Limb-darkening Law. Stellar limb darkening must be properly accounted for to accurately determine the radii of exoplanets at various wavelengths. The standard approach to address limb darkening involves either using laws with coefficients from modeled stellar spectra or determining the coefficients empirically during light-curve fitting of the data. Here, we test how accurately three common laws—quadratic, power, and a three-parameter law—can reproduce stellar limb darkening at different wavelengths and across a broad range of stars. We show that using a quadratic limb-darkening law, which is most frequently employed by the community, leads to wavelength-dependent offsets in retrieved transmission spectra. For planets with high impact parameters (b larger than about 0.5), the amplitude of these offsets can reach 1% of the transit depth, which in some cases is comparable to and can even exceed the expected signals from the planetary atmosphere. Furthermore, the quadratic law causes an offset in the value of the impact parameter when it is determined by fitting the broadband transit light curves. In contrast, using the Kipping–Sing three-parameter law leads to robust retrievals. We advocate the use of this law in retrievals, especially for transits with large impact parameters.

Keywords: Limb darkening, Exoplanet atmospheres, Transmission spectroscopy
FAST H I 21 cm Study of Blueberry Galaxies. Green Peas (GPs) and blueberry galaxies (BBs) are thought to be local analogs (z &lt; 0.1) of high redshift Lyα emitters. H I study of these can help us understand the star formation in the primordial Universe. In this Letter, we present the results of H I 21 cm study of 28 high specific star formation rate (sSFR ≳ 10‑8yr ‑1) BBs at z ≲ 0.05 with the Five-hundred-meter Aperture Spherical radio Telescope. We report significant H I detection towards two BBs, namely J1026+0426 and J1132+0809, and discuss possible H I contribution from neighboring galaxies. The median 3σ upper limit of ∼2.0 × 108 M ⊙ was obtained on H I mass for galaxies with nondetections. We find BBs tend to have lower H I-to-stellar-mass ratio or gas fraction (f H I ) than expected from f H I –sSFR and f H I –M * relations for main-sequence galaxies. The BBs also have a median 3σ upper limit on H I gas depletion timescale (τ H I ) ∼ 0.5 Gyr, about 1 order of magnitude lower than τ H I  for local main-sequence galaxies. We find a significantly low H I detection rate of 2/28 (7.1 %) towards these galaxies, which is similar to previous H I studies of low redshift GPs of high ionization parameter indicator, O32 ≡ O[III]λ5007/O[II]λ3727 ratios ≳10.

Keywords: Radio spectroscopy, Starburst galaxies, Blue compact dwarf galaxies, H I line emission, Galaxies
ALMA Detection of [O III] 88 μm at z = 12.33: Exploring the Nature and Evolution of GHZ2 as a Massive Compact Stellar System. We present Atacama Large Millimeter/submillimeter Array observations on the high-redshift galaxy GHZ2 and report a successful detection of the rest-frame 88 μm atomic transition from doubly ionized oxygen at z = 12.3327 ± 0.0035. Based on these observations, combined with additional constraints on the [O III] 52 μm line luminosity and previous JWST data, we argue that GHZ2 is likely powered by compact and young star formation and show that it follows well-established relationships found for giant H II regions and metal-poor star-forming dwarf galaxies that are known to host bright super star clusters. Additionally, these observations provide new constraints on the oxygen electron density (100 ≲ n  e  [cm‑3] ≲ 4,000) and dynamical mass (M dyn ≈ 3–8 × 108 M ⊙). The existence of these massive starburst systems 13.3 Gyr ago might explain the origin of today's globular clusters, a long-standing question in astronomy. To test this, we present observational probes to investigate whether sources like GHZ2 are linked to the formation of today's globular clusters or other more massive compact stellar systems.

Keywords: Globular star clusters, Early universe, Starburst galaxies, Compact galaxies, Young massive clusters, Emission line galaxies, Far infrared astronomy, Galaxy evolution, Ultracompact dwarf galaxies, Submillimeter astronomy, High-redshift galaxies, Galaxies
Evaluation of Several Explanations of the Strong X-Ray Polarization of the Black Hole X-Ray Binary 4U 1630-47. The Imaging X-ray Polarimetry Explorer observations of the X-ray binary 4U 1630–47 in the high soft state revealed high linear polarization degrees (PDs) rising from 6% at 2 keV to 10% at 8 keV. We discuss in this Letter three different mechanisms that impact the polarization of the observed X-rays: the reflection of gravitationally lensed emission by the accretion disk, reprocessing of the emission in outflowing plasma, and electron and ion anisotropies in the accretion disk atmosphere. We conducted detailed ray-tracing studies to evaluate the impact of the reflection of strongly gravitationally lensed emission on the PDs. Although the reflected emission can produce high PDs in the high-energy tail of the thermal emission component, we do not find models that describe the PDs and are consistent with independent estimates of the source distance. We discuss the energetics of another proposed mechanism: the emission or scattering of the X-rays in mildly relativistically moving plasma outflows. We argue that these models are disfavored as they require large mechanical luminosities on the order of, or even exceeding, the Eddington luminosity. We investigated the impact of electron and ion anisotropies but find that their impact on the observed PDs are likely negligible. We conclude with a discussion of all three effects and avenues for future research.

Keywords: Black hole physics, Black holes, High energy astrophysics, Plasma astrophysics, Stellar mass black holes, General relativity
Two Novel Hot Jupiter Formation Pathways: How White Dwarf Kicks Shape the Hot Jupiter Population. The origin of Hot Jupiters (HJs) is disputed between a variety of in situ and ex situ formation scenarios. One of the early proposed ex situ scenarios was the Eccentric Kozai─Lidov (EKL) mechanism combined with tidal circularization, which can produce HJs with the aid of a stellar or planetary companion. However, observations have revealed a lack of stellar companions to HJs, which challenges the importance of the binary star-driven-EKL-plus-tides scenario. In this work, we explore so far unaccounted-for stellar evolution effects on HJ formation, in particular the effect of white dwarf (WD) formation. Gaia observations have revealed that WDs often undergo a kick during formation, which can alter a binary's orbital configuration or even unbind it. Based on this WD kick, in this Letter, we propose and explore two novel HJ formation pathways: (1) HJs that are presently orbiting single stars but were initially formed in a binary that was later unbound by a WD kick; (2) binaries that survive the WD kick can trigger enhanced EKL oscillations and lead to second-generation HJ formation. We demonstrate that the majority of seemingly single HJs could have formed in binary star systems. As such, HJ formation in binaries via the EKL mechanism could be one of the dominant HJ formation pathways, and our results highlight that unaccounted-for stellar evolution effects, like WD formation, can obscure the actual origin of observed exoplanet populations.

Keywords: Exoplanet dynamics, Binary stars, Hot Jupiters, Exoplanets, White dwarf stars, Stellar evolution
Dominance of 2 Minute Oscillations near the Alfvén Surface. Alfvén waves, considered one of the primary candidates for heating and accelerating the fast solar wind, are ubiquitous in spacecraft observations, yet their origin remains elusive. In this study, we analyze data from the first 19 encounters of the Parker Solar Probe and report the dominance of 2 minute oscillations near the Alfvén surface. The frequency-rectified trace magnetic power spectral density (PSD) of these oscillations indicates that the fluctuation energy is concentrated around 2 minutes for the "youngest" solar wind. Further analysis using wavelet spectrograms reveals that these oscillations primarily consist of outward-propagating, spherically polarized Alfvén wave bursts. Through Doppler analysis, we show that the wave frequency observed in the spacecraft frame can be mapped directly to the launch frequency at the base of the corona, where previous studies have identified a distinct peak around 2 minutes (~8 mHz) in the spectrum of swaying motions of coronal structures observed by the Solar Dynamics Observatory Atmospheric Imaging Assembly. These findings strongly suggest that the Alfvén waves originate from the solar atmosphere. Furthermore, statistical analysis of the PSD deformation beyond the Alfvén surface supports the idea of dynamic formation of the otherwise absent 1/f range in the solar wind turbulence spectrum.

Keywords: Fast solar wind, Interplanetary turbulence, Solar wind, Solar coronal heating, Alfven waves, Solar corona, Solar coronal holes