arXiv subjects

Jason T. Hinkle

Publications and source records attributed to Jason T. Hinkle.

At least 19 recordsLinked to original sources

arXiv2026

The host galaxies of 2003fg-like type Ia supernovae

SN~2003fg-like events are a peculiar type Ia supernova (SN~Ia) subtype characterized by broader light curves, higher near-infrared luminosities, and stronger carbon absorptions at early times. Here we present observations of the largest compilation of 2003fg-like SN Ia host galaxies to date, obtained with Integral Field Spectroscopy (IFS). For 20 objects, we study both the global host-galaxy properties and, for the first time for a sizeable sample, the local environment at the SN position. Globally, 2003fg-like SNe~Ia occur in galaxies with lower stellar mass, lower oxygen abundance, and marginally higher specific star-formation rate (sSFR) than those of normal SNe~Ia, although their hosts are not as extreme in such properties as superluminous SNe, nor representative of metal-poor dwarf-galaxy samples. Locally, the SN positions show lower star-formation-rate, stellar-mass surface densities, and lower sSFR, than normal SN~Ia environments, consistent with a significant preference for the outskirts of their hosts, while their stellar age indicators are typical. The most distinctive local property is metallicity, with 2003fg-like SNe~Ia occupying the most metal-poor environments among SNe~Ia. We also find a tentative positive correlation between the light-curve width and the oxygen abundance for 2003fg-like events. Our results imply that 2003fg-like SNe~Ia arise from the merger of two white dwarfs (WDs) or the core-degenerate scenario, but disfavor the single, rapidly rotating super-M$_{ch}$ C-O WD progenitor, as this channel requires a young stellar population that we do not observe at the SN positions. The preference of 2003fg-like SNe~Ia for low-metallicity environments suggests that they may have been more common in the early Universe. (abridged)

astro-ph.CO↗

arXiv2026

The Delay Time Distribution of Quasi-Periodic Eruptions

Quasi-periodic eruptions (QPEs) are quasi-periodic X-ray bursts observed in the nucleus of a galaxy. Multiple pieces of observational evidence link QPEs to tidal disruption events (TDEs), which occur when stars are disrupted after approaching a supermassive black hole too closely. Post-starburst galaxies are overrepresented among the host galaxies of both TDEs and QPEs, though the mechanism causing this overrepresentation is unknown. While their physical origin is unclear, the delay time distribution (DTD) of QPEs, or rate of QPEs as a function of time since a burst of star formation, can constrain what mechanisms influence the QPE rate and possible QPE formation channels. We compile a catalog of 10 QPE host galaxies with optical spectra, model the stellar populations with Bagpipes, and retrieve the age of the most recent burst of star formation to construct the DTD of QPEs. We find that the QPE rate increases with post-burst age to reach a peak at ~1 Gyr relative to a control sample, similar to the observational TDE DTD, though we cannot rule out a flat distribution of burst ages relative to a control sample. However, the fraction of QPE host galaxies with high (>1%) burst mass fractions is larger than the fraction of galaxies with high burst mass fractions in either a sample of TDE host galaxies or a sample of control galaxies. If the preferred QPE formation channel requires extreme mass ratio inspirals (EMRIs), then such EMRIs may be more readily produced by large, ~1-Gyr-old bursts of star formation.

astro-ph.GA↗

arXiv2026

JWST Spectroscopy of Type Ia Supernova 2025rbs from Maximum Light to the Nebular Phase

We present JWST observations of the Type Ia supernova (SN Ia) 2025rbs ($D=$14.5 Mpc) at +1, +23, and +84 days after B-band maximum, spanning peak light through a wavelength-dependent transition toward the nebular phase. Combined with ground-based optical and near-infrared (NIR) data, our panchromatic spectra (0.4-14 $\mu$m) include the first maximum-light mid-infrared (MIR) spectrum and the earliest MIR spectroscopic sequence of an SN Ia to date. At peak light, the MIR spectrum exhibits a continuum with permitted and forbidden features, including Si II, Ni II, and early-emerging [Ni III-IV] and [Ar II-III]. By +23 days the MIR is dominated by forbidden lines with a weak continuum, and by +84 days it is fully nebular, whereas the optical/NIR spectra remain transitional. The nebular spectrum reveals strongly stratified ejecta, with stable Ni concentrated at the lowest velocities, radioactive Co at intermediate velocities but absent within ~2000 km s$^{-1}$, and Ar occupying an outer shell. We detect small-scale substructure in [Ca IV] 3.21 $\mu$m with fractional amplitudes of a few percent and a characteristic velocity scale of ~800 km s$^{-1}$, which may reflect compositional structure, ionization variations, or both. Radiative-transfer calculations substantially underpredict these MIR Mg II features despite approximately reproducing the NIR Mg II 1.0927 $\mu$m line, suggesting that the relative strengths of these transitions are sensitive to the treatment of Mg ionization and excitation. These observations demonstrate that MIR spectroscopy beginning near maximum light simultaneously probes the emerging inner ejecta and rapidly fading outer burning products, providing new constraints for explosion and radiative-transfer models.

astro-ph.HE↗

arXiv2026

ATLAS22kjn (AT 2022fpx): A Coronal Line Emitter with an Early Light Curve Bump and Mid-Infrared Dust Echo

We present an analysis of ATLAS22kjn (AT 2022fpx), whose high-ionisation coronal lines (CLs) and pre-peak light curve bump provide distinctive opportunities to investigate the physical mechanisms powering tidal disruption events (TDEs). In addition to CLs, the optical spectra show common TDE features, including a strong, blue continuum and broad Balmer and He II lines. The CLs appear before UV/optical light curve peak, preceding the detection of X-rays by $\sim 300$ days and persisting after X-rays are no longer detected, suggesting the X-ray emission is obscured at both early and late times. Using the CL luminosities, we constrain the temperature evolution of the ionising source, finding a decrease of $\lesssim 10 \%$ over 500 days. In the UV/optical light curve, we observe a $9 \substack{+4 \\ -2}$ day bump that peaks $125 \substack{+5 \\ -3}$ rest-frame days before the peak of the main flare. Although we cannot definitively determine the origins of the bump, we find that its timescale and luminosity are most consistent with theoretical predictions for a precursor feature produced by a stream-stream collision or a wind-stream collision. ATLAS22kjn also shows a prominent dust echo in its mid-infrared (MIR) light curves, indicating a high dust covering fraction $f_c \simeq 0.40 \pm 0.03$, similar to the covering fractions of other CL-emitting TDEs. From the multi-wavelength observations of ATLAS22kjn, we estimate the size and relative radii of the emission regions in its nuclear environment and determine that the CL region lies between the broad line region and the MIR-emitting dust. ATLAS22kjn demonstrates the importance of multi-wavelength and early-time observations, and the utility of CLEs in characterising the otherwise unobservable EUV/ultrasoft X-ray emission of TDEs.

astro-ph.HE↗

arXiv2026

AT2021yky: A Fast-Rising Optical Transient with Evolving Broad Hydrogen Emission Consistent with an Ambiguous Nuclear Transient

Nuclear transients are powerful probes of supermassive black hole properties, offering insight into black hole mass, accretion physics, and the structure of galactic nuclei. Among these, a growing class of events cannot be classified as either tidal disruption events (TDEs) or active galactic nuclei (AGN) flares, and their physical origins remain poorly understood. We present a multi-wavelength photometric and spectroscopic analysis of AT2021yky (ZTF21abzciqh), an ambiguous nuclear transient (ANT) at a redshift of $z = 0.076$. AT2021yky reached a peak bolometric luminosity of $L_{\rm peak} = (4.1 \pm 1.1) \times 10^{43}~\mathrm{erg~s^{-1}}$, with a rise-time of $18.2 \pm 0.7$ days. The early-time UV/optical emission is well described by a blackbody with a temperature of $T \simeq 1.4 \times 10^{4}$ K, cooler than most optically selected TDEs. No X-ray emission from the transient is detected, with a $3\sigma$ limit of $L_X \lesssim 3.4 \times 10^{41}$ erg s$^{-1}$ near peak. Spectroscopic observations reveal a largely featureless blue continuum with broad (FWHM$\sim 11,000$ km s$^{-1}$) H$\alpha$ emission line that appears around 20$-$40 days post-peak. The host-galaxy emission-line ratios indicate the presence of an AGN, though the absence of optical or mid-IR variability and a non-AGN mid-IR color suggest it is weak. AT2021yky exhibits a rapid rise time comparable to that of luminous fast blue optical transients (LFBOTs), while its decay timescale and late-time broad H$\alpha$ emission resemble those observed in TDEs. However, its cooler blackbody temperature and the absence of He II and Balmer emission lines other than H$\alpha$ instead favour its classification as an ANT.

astro-ph.HE↗

arXiv2026

NAPTIME: A Neural-Process Framework for Rubin Alert Classification

The Vera C. Rubin Observatory Legacy Survey of Space and Time will produce a high-volume stream of irregularly sampled multiband alerts for which spectroscopic confirmation will be available only for a small minority of sources. Tidal disruption events are rare phenomena that provide a direct probe of dormant massive black holes, but their light curves can be confused with nuclear variability and other transient subclasses. We present NAPTIME (Neural Astrophysical Photometric Transient Identification and Modeling Engine), a neural-process framework for photometric transient classification under sparse and partial observational context. NAPTIME models irregular multiband light curves directly, combining probabilistic light-curve reconstruction with classification and optional host-galaxy context, as well as photometric-redshift information. We evaluate on two simulated benchmarks: ELAsTiCC2, our primary Rubin-like broad-classification benchmark, and MALLORN, a photometry-only TDE-focused benchmark. On the 15-family ELAsTiCC2 task, the metadata-aware model reaches macro $\mathrm{F1} = 0.903$ and macro $\mathrm{AUROC} = 0.991$, while a matched photometry-only variant reaches 0.874 and 0.986. Viewed as a TDE-versus-rest ranking model, the classifier yields TDE average precision 0.985 with metadata and 0.979 without. Metadata is most valuable in the low-context regime. Using only the earliest 10\% of detected observations, macro F1 is $\sim$0.42 with metadata and $\sim$0.34 without it. On MALLORN, NAPTIME reaches macro $\mathrm{F1} = 0.693$ and macro $\mathrm{AUROC} = 0.958$. These results show that neural processes provide a practical probabilistic framework for Rubin-like transient classification and remain effective for TDE-focused candidate recovery.

astro-ph.IM↗

arXiv2026

Comparison of X-ray Emission Properties of TDEs and Soft Flares from AGNs

X-ray flaring activity from active galactic nuclei (AGNs) may mimic the expected emission from tidal disruption events (TDEs), thus contaminating TDE searches. To compare X-ray emission properties between TDEs and AGNs, we cross-match publicly available XMM-Newton and Swift-XRT point source catalogs with the Million Quasars Catalog and optically selected TDEs. We find that AGNs tend to become softer with a similar hardness ratio (HR) value as TDEs during their flaring events. The soft HRs during flaring events in these AGNs are driven by the emergence of a blackbody-like component below $\sim$2 keV, likely associated with the soft X-ray excess, as well as the continuum emission becoming steeper with the increase of accretion rate. We find 2.5% in XMM-Newton (23 out of 920) and 4.4% in Swift-XRT (179 out of 4089) AGNs display flares with peak count rate $>$$2\sigma$ from the median count rate and peak HR$<$$-0.75$. The rate of such flares in XMM-Newton and Swift-XRT is (1.1-2.5)$\times10^{-3}\rm\ galaxy^{-1}\ yr^{-1}$ and (0.9-2.0)$\times10^{-3}\rm\ galaxy^{-1}\ yr^{-1}$, respectively. We also estimate the rate of flares with a maximum flux change (peak/min) of $>20\times$ over on a rest-frame time scale of two years or more with a HR$<$$-0.75$ at peak to be (4.7-11.0)$\times10^{-5}\rm\ galaxy^{-1}\ yr^{-1}$ and (3.1-7.1)$\times10^{-5}\rm\ galaxy^{-1}\ yr^{-1}$ in XMM-Newton and Swift-XRT, respectively. Finding an optical or infrared counterpart may help to identify these flaring AGNs. We confirm 61% and 79% of flaring sources from XMM-Newton and Swift-XRT, respectively, as AGNs through variability in ZTF light curves or a WISE $W1$$-$$W2$$>$0.8 mag color cut.

astro-ph.HE↗

arXiv2026

A Disappearing Act: Constraints From "Missing" Flares of Repeating Partial TDE Candidates

Recurrent tidal disruption events (rTDEs) are sources that exhibit multiple TDE-like flares; many are likely powered by the recurring partial disruption of a bound star, in a repeating partial TDE (rpTDE). Two such sources, TDE 2022dbl (ASASSN-22ci) and TDE 2020vdq (ZTF20acaazkt), each exhibited two UV/optical flares and, under the assumption of periodicity, both were expected to exhibit a third flare in early 2026. Neither exhibited such a flare, to limits of $L_{\textrm{UV/optical}} \lesssim 10^{42}$ erg s$^{-1}$, $\sim$30$\times$ fainter than the previous flares. Here, we examine several possible explanations. Observing two independent TDEs from the same galaxy within $\sim$2 yr has a probability of $\lesssim$0.5% for measured average TDE rates and currently expected rate enhancements, unless there is extreme intrinsic dispersion in the rates. Theoretical predictions for a double TDE of both stars in a binary are inconsistent with the observed flares. We therefore conclude that TDE 2022dbl and TDE 2020vdq are rpTDEs. To produce only two observable flares with similar energetics, our semi-analytical modeling strongly favors a main-sequence star promptly placed on a bound orbit with a deep initial tidal encounter at pericenter. These results suggest that the majority of rTDEs with multiple flares over a few-year baseline are likely to be rpTDEs, and that a significant fraction of systems may produce only two observable flares. This has important implications for the use of r(p)TDEs as probes of TDE physics and dynamical processes in the nuclei of other galaxies, in addition to the expected yield from upcoming surveys.

astro-ph.HE↗

arXiv2026

SCAT Data Release 1: 1812 optical spectra of 1331 transients

We present the first data release (DR1) of the Spectroscopic Classification of Astronomical Transients (SCAT) survey, covering the first $\approx 5$ years of observations (March 2018 - January 2023). DR1 includes 1812 spectra of 1331 transients, which we sort into broad spectroscopic classes including supernovae (SNe), transients originating in galactic nuclei, and stellar variability. We collect multi-filter light curves from imaging surveys and fit them with phenomenological models to estimate peak brightnesses and the time of explosion/first-light. Extragalactic transients are matched to candidate host galaxies, and we compare host-galaxy luminosities and projected offsets by SN type. SNe appear to be a reliable way to augment the redshift coverage of nearby ($z\lesssim 0.1$) galaxies in tandem with dedicated redshift surveys. We present new redshifts for roughly half of the SN host galaxies, most of which are low-luminosity dwarfs similar to the Magellanic Clouds ($M_r \gtrsim -18$ mag). This set of transient spectra, light curves, luminosities, redshifts, and host galaxies offers an excellent testbed for real-time photometric/light curve classification pipelines in the modern era of deep and large-area surveys. We conclude with a brief discussion of the provided data products and status of the SCAT survey.

astro-ph.HE↗

arXiv2026

Identifying Changing-Look AGN Transitions in Light Curve Data with the Zwicky Transient Facility

Changing-Look AGN (CL-AGN) are AGN which transition between Seyfert types, challenging AGN unification models. Most CL-AGN have been identified via repeat spectroscopy, making it difficult to determine the duration and magnitude of the CL-AGN transition. As such, the physical mechanisms behind this transition are still unknown. We use synthetic photometry in combination with ZTF light curve data to develop a new criterion to identify photometric CL-AGN transitions based on changes in g-band magnitude and g-r color. We find that a CL-AGN criterion of $| \Delta g| > 0.4$ mag and $| \Delta (g-r)| > 0.2$ mag recovers a photometric transition in $9.6^{+4.9}_{-3.4}\%$ of CL-AGN hosts over the six-year ZTF survey, including a candidate repeating changing-look event in SDSS J084957.78+274728.9. Using simulated AGN light curves, we estimate the false positive rate among the simulated Seyferts to be $1.6^{+0.19}_{-0.17}\%$. We find that the rate of similar flares among Type 1 Seyferts is $1.2^{+0.87}_{-0.50}\%$ , and among Type 2 Seyferts is $\leq 0.39\%$ over six years. Photometric CL-AGN transitions last between 21 and 560 days, with a median duration of 360 days, consistent with the thermal or orbital timescales for AGN disks. We do not detect a correlation between black hole mass and transition duration, likely due to the small sample of detected photometric transitions. This method can be applied to the upcoming Legacy Survey of Space and Time to identify CL-AGN candidates and test theories of their origins

astro-ph.GA↗

arXiv2026

A Natural $\gtrsim 100\times$ Telescope: Discovery of the Strongly Lensed Type II SN 2025mkn at $z=1.37$

We present the discovery of SN 2025mkn, a gravitationally lensed Type II supernova. First detected as a blue transient in ZTF, 0.83$^{\prime\prime}$ from a $z=0.42$ elliptical galaxy, follow-up SNIFS/UH2.2m and LRIS/Keck spectra revealed absorption lines at $z=1.371$. Later JWST NIRCam imaging shows that the bright transient is a close pair of point sources separated by $\sim 0.07^{\prime\prime}$, and a 30 times fainter counterimage opposite the lens, for which NIRSpec reveals strong H$\alpha$ emission also at $z=1.371$. The light curves and spectra are consistent with the Type II supernova source being magnified $\gtrsim 100$ times, with $\sim 250$ required to reconcile its luminosity with that of nearby events such as SN 2023ixf. Lens models are consistent with such high magnifications, and always show that the faint image arrived first (undetected in earlier ZTF imaging), consistent with the later spectral phase of this fainter image. A fourth image is also predicted and possibly detected in the NIRSpec data. Light-curve-based time-delay measurements are not possible due to the first image being the faintest; however, the resolved NIRSpec spectra offer a future opportunity for time-delay cosmography through supernova phase measurements.

astro-ph.CO↗

arXiv2026

Contemporaneous Optical and Near-Infrared Observations of the Interstellar Comet 3I/ATLAS Pre- and Post-Perihelion

Interstellar objects provide a unique view into the formation of other star systems. Here we present spectroscopic observations of the recently discovered interstellar object 3I/ATLAS between a heliocentric distance of $3.7$ to $1.8$~au on either side of its travels through perihelion. We obtained several observations with the Keck-I/LRIS, Keck-II/NIRES, Gemini/GMOS, and UH88/SNIFS spectrographs, covering a wavelength range of $0.3 - 2.5~\mathrm{\mu m}$. We report the continued emission of both Ni and CN, along with post-perihelion detections of Fe and a weak detection of $\mathrm{C_3}$. We determine the spectral slope across optical and NIR wavelengths and find a positive spectral slope in the optical, with values ranging from $\sim 21 - 27\%$ in the blue regions ($0.4 - 0.55~\mathrm{\mu m}$) to $\sim 6 - 10\%$ in the red ($0.65 - 0.9~\mathrm{\mu m}$) regions. In contrast, the NIR showed a negative spectral slope of $\sim -0.9 \%$ between $0.9 - 1.5~\mathrm{\mu m}$ and $\sim -2.3\%$ between $1.9 - 2.5~\mathrm{\mu m}$. 3I/ATLAS shows a clear turnover in its spectral shape at $\sim 1.1~\mathrm{\mu m}$, corresponding to scattered light from the dusty coma. Finally, in the NIR, we do not find an increase in the depth of the water features identified in an earlier NIR observation of 3I/ATLAS. Our observations of 3I/ATLAS in the NIR show a similar shape to the NIR spectrum of 2I/Borisov as it approached perihelion.

astro-ph.EP↗

arXiv2026

Post-Perihelion Integral Field Spectroscopy of the Interstellar Comet 3I/ATLAS

The environs of other stellar systems may be directly probed by analyzing the cometary activity of interstellar objects. The recently discovered interstellar object 3I/ATLAS was the subject of an intensive worldwide follow-up campaign in its pre-perihelion approach. Now, 3I/ATLAS has begun its post-perihelion departure from the Solar System. In this letter, we report the first post-perihelion blue-sensitive integral-field unit spectroscopy of 3I/ATLAS using the Keck Cosmic Web Imager on November 16, 2025. We confirm previously reported CN, Fe, and Ni outgassing along with detections of carbon chain molecules $\mathrm{C}_2$ and $\mathrm{C}_3$. We calculate production rates for each species. We find Fe and Ni production rates of $\mathrm{Q_{Fe}} = (9.55\pm3.96)\times10^{25}$ atoms s$^{-1}$, and $\mathrm{Q_{Ni}} = (6.61\pm2.74)\times10^{25}$ atoms s$^{-1}$, resulting in a ratio of $\log(\mathrm{Q_{Ni}} / \mathrm{Q_{Fe}}) = -0.16\pm0.03$, which matches Solar System comets well and continues the pre-perihelion trend of declining $\log(\mathrm{Q_{Ni}} / \mathrm{Q_{Fe}})$ with $r_h$. We investigate the radial distributions of these elemental species and find characteristic $e$-folding radii of 3880$\pm$39 km for Ni, 6053$\pm$68 km for CN, 4194$\pm$45 km for $\mathrm{C}_2$, and 3833$\pm$45 km for $\mathrm{C}_3$. Compared to pre-perihelion measurements, these radii have increased by a factor of $\sim$6.5--7. Our post-perihelion observations reveal that 3I/ATLAS continues to exhibit cometary behavior broadly consistent with Solar System comets.

astro-ph.EP↗

arXiv2025

FEADME: Fast Elliptical Accretion Disk Modeling Engine

We present FEADME (Fast Elliptical Accretion Disk Modeling Engine), a GPU-accelerated Python framework for modeling broad Balmer-line emission using a relativistic elliptical accretion-disk formalism. Leveraging JAX and NumPyro for differentiable forward modeling and efficient Bayesian inference, FEADME enables large-sample, reproducible analyses of disk-dominated emission-line profiles. We apply the framework to 237 double-peaked emitters (DPEs) from the literature and to five tidal disruption events (TDEs) with disk-like H$\alpha$ emission, fitting three physically motivated model families per spectrum and selecting the preferred model using the widely applicable information criterion (WAIC). After posterior-quality filtering, the disk-bearing active galactic nuclei (AGN) analysis sample contains 165 sources and the TDE sample contains 27 usable epochs. We find that AGN occupy a broad, continuous distribution of disk geometries and kinematics that is usefully summarized by five phenomenological Gaussian-mixture morphology bins. The TDE disk parameters overlap substantially with the AGN population in radial scale, local broadening, and emissivity slope, but TDEs are systematically less eccentric and show broader non-disk Gaussian components. The majority of both AGN and TDEs favor models that include both a disk and an additional broad-line component, suggesting that disk emission commonly coexists with more isotropic or wind-driven gas. These results indicate that once a line-emitting disk forms, its spectroscopic appearance is governed by similar physical processes in both persistent AGN and transient TDE accretion flows, and they demonstrate the utility of FEADME for population-level studies of disk structure in galactic nuclei.

astro-ph.HE↗

arXiv2025

Multiple outflows and delayed ejections revealed by early imaging of novae

Novae are thermonuclear eruptions on accreting white dwarfs in interacting binaries. Although most of the accreted envelope is expelled, the mechanism -- impulsive ejection, multiple outflows or prolonged winds, or a common-envelope interaction -- remains uncertain. GeV $\gamma$-ray detections from $>20$ Galactic novae establish these eruptions as nearby laboratories for shock physics and particle acceleration, underscoring the need to determine how novae eject their envelopes. Here we report on near-infrared interferometry, supported with multiwavelength observations, of two $\gamma$-ray detected novae. The images of the very fast 2021 nova V1674~Her, taken just 2--3 days after discovery, reveal the presence of two perpendicular outflows. The interaction between these outflows likely drives the observed $\gamma$-ray emission. Conversely, the images of the very slow 2021 nova V1405~Cas suggest a delay in the ejection of the bulk of the accreted envelope of more than 50 days after the start of eruption, as the nova slowly rises to visible peak and during which the envelope engulfed the system in a common envelope phase. These unprecedented images offer direct observational evidence that the mechanisms driving mass ejection from the surfaces of accreting white dwarfs are not as simple as previously thought, revealing multiple outflows and delayed ejections.

astro-ph.HE↗

arXiv2025

JCMT Constraints on the Early-Time HCN and CO Emission and HCN Temporal Evolution of 3I/ATLAS

Interstellar objects (ISOs), particularly those with cometary activity, provide unique insight into the primordial physical and chemical conditions present during the formation of the planetary system in which they originated. Observations in the sub-mm regime allow for direct measurements of several parent molecules released from the comet nucleus into the coma. Here we present observations of the third ISO, 3I/ATLAS, with the `\=U`\=u heterodyne receiver on the James Clerk Maxwell Telescope (JCMT), which targeted emission from HCN($J = 3 - 2$) and CO($J = 2 - 1$). Our observations, taken between 16 July 2025 and 21 July 2025 (UT), when 3I/ATLAS was at a heliocentric distance between 4.01 and 3.84 au, provide the earliest sub-mm constraints on its activity. We do not detect HCN or CO in these epochs, with 3$\sigma$ upper-limits on the production rates of $Q(HCN) < 1.7 \times 10^{24}$ s$^{-1}$ at $r_h = 4.01 - 3.97$ au and $Q(CO) < 1.1 \times 10^{27}$ s$^{-1}$ at $r_h = 3.94 - 3.84$ au, respectively. We combine this HCN limit with later JCMT observations of HCN to constrain its temporal evolution. Fitting the HCN detections with a $Q(HCN) \propto r_h^{-n}$ model and accounting for the upper-limits yields $n = 12.7^{+6.9}_{-2.5}$. This slope is steeper than those of typical Solar System comets, but consistent with the production rate slopes measured for other species in the coma of 3I/ATLAS.

astro-ph.EP↗

arXiv2025

Expanding the parameter space of 2002es-like type Ia supernovae: on the underluminous ASASSN-20jq / SN 2020qxp

We present optical photometric and spectroscopic observations of the peculiar Type Ia supernova ASASSN-20jq/SN 2020qxp. It is a low-luminosity object with a peak absolute magnitude of $M_B=-17.1\pm0.5$ mag. Despite its low luminosity, its post-peak light-curve decline rate ($\Delta m_{15}(B)=1.35\pm0.09$ mag) and color-stretch parameter (sBV>0.82) are similar to normal SNe Ia, making it an outlier in the luminosity-width and luminosity-color-stretch relations. Early light curves suggest a "bump" during the first 1.4 days of explosion. ASASSN-20jq synthesized a low radioactive $^{56}$Ni mass of $0.09\pm0.01M_\odot$. Near-maximum light spectra reveal strong Si II absorption lines, indicating a cooler photosphere than normal SNe Ia, but lack Ti II absorption lines. Unusually strong O I $\lambda$7773 and Ca II near-infrared triplet absorption features are present. Nebular spectra show a strong, narrow forbidden [Ca II] $\lambda\lambda$7291,7324 doublet emission, rarely seen in SNe Ia except in some Type Iax events. Marginal detection of [O I] $\lambda\lambda$6300,6364 doublet emission, which is extremely rare, is observed. Both [Ca II] and [O I] lines are redshifted by $\sim2000$ km/s. A strong [Fe II] $\lambda$7155 emission line with a tilted-top profile, identical to the [Fe II] $\lambda$16433 profile, is also observed. These asymmetric [Fe II] profiles and redshifted [Ca II] and [O I] emissions suggest a high central density white dwarf progenitor undergoing an off-center delayed-detonation explosion mechanism, producing roughly equal amounts of $^{56}$Ni in deflagration and detonation phases. This distinguishes ASASSN-20jq from normal and subluminous SNe Ia. ASASSN-20jq's light curve and spectra do not align with any single SNe Ia subclass but show similarities to 2002es-like objects. Thus, we add it as an extreme candidate within the heterogeneous parameter space of 2002es-like SNe Ia.

astro-ph.HE↗

arXiv2024

On the Double: Two Luminous Flares from the Nearby Tidal Disruption Event ASASSN-22ci (AT2022dbl) and Connections to Repeating TDE Candidates

We present observations of ASASSN-22ci (AT2022dbl), a nearby tidal disruption event (TDE) discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d$_L \simeq 125$ Mpc. Roughly two years after the initial ASAS-SN discovery, a second flare was detected coincident with ASASSN-22ci. UV/optical photometry and optical spectroscopy indicate that both flares are likely powered by TDEs. The striking similarity in flare properties suggests that these flares result from subsequent disruptions of the same star. Each flare rises on a timescale of $\sim$30 days, has a temperature of $\approx$30,000 K, a peak bolometric luminosity of $L_{UV/Opt} = 10^{43.6 - 43.9} \textrm{ erg} \textrm{ s}^{-1}$, and exhibits a blue optical spectrum with broad H, He, and N lines. No X-ray emission is detected during either flare, but X-ray emission with an unabsorbed luminosity of $L_{X} = 3\times10^{41} \textrm{ erg} \textrm{ s}^{-1}$ and $kT = 0.042$ eV is observed between the flares. Pre-discovery survey observations rule out the existence of earlier flares within the past $\approx$6000 days, indicating that the discovery of ASASSN-22ci likely coincides with the first flare. If the observed flare separation of $720 \pm 4.7$ days is the orbital period, the next flare of ASASSN-22ci should occur near MJD 61075 (2026 February 04). Finally, we find that the existing sample of repeating TDE candidates is consistent with Hills capture of a star initially in a binary with a total mass between $\sim$$1 - 4$ M$_{\odot}$ and a separation of $\sim$$0.01 - 0.1$ AU.

astro-ph.HE↗