arXiv subjects

David R. Young

Publications and source records attributed to David R. Young.

At least 19 recordsLinked to original sources

arXiv2026

An analysis of the Type Ia SN 2024gy and a comparison of different host extinction estimation techniques

Type Ia supernovae (SNe Ia) are well-known standardisable candles, and are one of the main ways to measure the distance to their host galaxies. However, extinction due to interstellar dust causes objects to appear fainter and redder. Correcting for this requires estimating the amount of intervening material and how the extinction changes as a function of wavelength. We present and analyse optical and near-infrared data of the well-observed SN 2024gy and use these to compare different extinction estimation techniques, making use of photometric, spectroscopic, and polarimetric data. SN 2024gy is a normal SN Ia with high velocity (HV) components in Si II $\lambda6355$ (phase $<-10$ days) and a particularly strong HV feature in the Ca II near-infrared triplet (up to peak). Modelling SN 2024gy with TARDIS shows better matches with a double-detonation scenario compared to a delayed-detonation scenario due to a better match to the Ca II HV component. A measurement of the stable Ni/Fe ratio however favours a delayed-detonation scenario. Host extinction estimates range from $E(B-V)_{host}=0.12\pm0.02$ mag (narrow interstellar absorption lines) to $E(B-V)_{host}=0.24\pm0.06$ mag (Lira law) with a mean of $E(B-V)_{host}=0.22\pm0.04$ mag, assuming $R_V=3.1$. The spread between different methods highlights the challenge of accurately estimating the amount of extinction light suffers before being observed.

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arXiv2026

AT2024wpp: An Extremely Luminous Fast Ultraviolet Transient Powered by Accretion onto a Black Hole

We present the discovery of AT 2024wpp ("Whippet"), a fast and luminous 18cow-like transient. At a redshift of z=0.0868, revealed by Keck Cosmic Web Imager spectroscopy of its faint star-forming host, it is the fourth-nearest example of its class to date. Rapid identification of the source in the Zwicky Transient Facility data stream permitted ultraviolet-through-optical observations to be obtained prior to peak, allowing the first determination of the peak bolometric luminosity (2x10^45 erg/s), maximum photospheric radius (10^15 cm), and total radiated energy (10^51 erg) of an 18cow-like object. We present results from a comprehensive multiwavelength observing campaign, including a far-UV spectrum from the Cosmic Origins Spectrograph on the Hubble Space Telescope and deep imaging extending >100 days post-explosion from the Very Large Telescope, Hubble Space Telescope, Very Large Array, and Atacama Large Millimetre Array. We interpret the observations under a model in which a rapidly-accreting central engine blows a fast (~0.2c) wind into the surrounding medium and irradiates it with X-rays. The high Doppler velocities and intense ionization within this wind prevent identifiable spectroscopic features from appearing in the ejecta or in the surrounding circumstellar material. Weak H and He signatures do emerge in the spectra after 35 days in the form of double-peaked narrow lines. Each peak is individually narrow (full width ~3000 km/s) but the two components are separated by ~6600 km/s, indicating stable structures of denser material, possibly representing streams of tidal ejecta or an ablated companion star.

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arXiv2026

ATLAS100 -- I. A volume-limited sample of supernovae and related transients within 100 Mpc

We present ATLAS100 -- a sample of 1729 supernovae and other explosive optical transients within $\sim 100$ Mpc observed by the ATLAS survey over a span of 5.75 years from 2017 September 21 to 2023 June 21. The volume-limited sample includes transients associated with galaxies with a spectroscopic redshift of $z \leq 0.025$, and spectroscopically classified transients within this redshift threshold where a host redshift was not available in existing catalogues. Our host galaxy list is constructed from aggregating all available galaxy redshift and distance catalogues. We carefully select all transients within a projected radius of 50\,kpc of these hosts. The ATLAS100 transient sample has a host galaxy redshift completeness fraction of $83$ per cent, consistent with expectations for the redshift completeness of local galaxy catalogues. Within this volume, the spectroscopic classifications are 87 per cent complete and we reclassify many ambiguous transients with joint light curve and spectroscopic considerations. Here, we release the catalogue together with compiled, binned and cleaned ATLAS photometry for all transients. We fit the light curve data to derive peak luminosity and characteristic timescales. We explore the sample characteristics, demographics and discuss completeness and purity of the sample.

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arXiv2026

SN 2024abvb: a Type Ibn/Icn supernova with evidence of helium and an extreme offset from its host galaxy

We present spectroscopic and photometric observations and analysis of SN 2024abvb, a peculiar transitional Type Ibn/Icn supernova located at an unusually large projected distance from its host galaxy (21.5 kpc). SN 2024abvb displays an extended rise time in the $g$- and $o$-bands (10.1 and 10.6 days respectively), followed by a linear decline in all photometric bands. Comparisons with other supernova subclasses show that the photometric and spectroscopic evolution of SN 2024abvb are distinct from Type~Ibn and Type Icn events, with a higher peak $r$-band luminosity and lower blackbody temperatures. Spectra reveal an initial blue continuum and narrow P-Cygni profiles, with C {\sc ii} $λ$5890 dominating in emission, persisting at late phases, and showing a rapid decline in the expansion velocity. Weak He {\sc i} $λ$5876 features are tentatively detected at early times. Analysis of progenitor scenarios rules out thermonuclear origins based on incompatible light curve shapes and spectral signatures. A rare massive star progenitor appears unlikely given the low local star formation rate. The most plausible origin is an ultra-stripped supernova scenario involving a binary system; this best explains the observed separation from the host, the low circumstellar material mass, the fast photometric evolution and the low nickel production, although a discrepancy in model versus observed ejecta mass remains. These results reinforce the classification of SN 2024abvb as a distinctive Type Ibn/Icn event and highlight the diversity of progenitor channels for interacting supernovae.

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arXiv2025

MALLORN: Many Artificial LSST Lightcurves based on Observations of Real Nuclear transients

The Vera C. Rubin Observatory's 10-Year Legacy Survey of Space and Time (LSST) is expected to produce a hundredfold increase in the number of transients we observe. However, there are insufficient spectroscopic resources to follow up on all of the wealth of targets that LSST will provide. As such it is necessary to be able to prioritise objects for followup observations or inclusion in sample studies based purely on their LSST photometry. We are particularly keen to identify tidal disruption events (TDEs) with LSST. TDEs are immensely useful for determining black hole parameters and probing our understanding of accretion physics. To assist in these efforts, we present the Many Artificial LSST Lightcurves based on the Observations of Real Nuclear transients (MALLORN) data set and the corresponding classifier challenge for identifying TDEs. MALLORN comprises 10178 simulated LSST light curves, constructed from real Zwicky Transient Facility (ZTF) observations of 64 TDEs, 727 nuclear supernovae and 1407 AGN with spectroscopic labels using Gaussian process fitting, empirically-motivated spectral energy distributions from SNCosmo and the baseline from the Rubin Survey Simulator. Our novel approach can be easily adapted to simulate transients for any photometric survey using observations from another, requiring only the limiting magnitudes and an estimate of the cadence of observations. The MALLORN Astronomical Classification Challenge, launched on Kaggle on 15/10/2025, will allow competitors to test their photometric classifiers on simulated LSST data to find TDEs and improve upon their capabilities prior to the start of LSST.

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arXiv2025

Identifying Transient Hosts in LSST's Deep Drilling Fields with Galaxy Catalogues

The upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will enable astronomers to discover rare and distant astrophysical transients. Host-galaxy association is crucial for selecting the most scientifically interesting transients for follow-up. LSST Deep Drilling Field observations will detect distant transients occurring in galaxies below the detection limits of most all-sky catalogues. Here we investigate the use of pre-existing smaller-scale, field-specific catalogues for host identification in the Deep Drilling Fields (DDFs) and a ranking of their usefulness. We have compiled a database of 70 deep catalogues that overlap with the Rubin DDFs and constructed thin catalogues to be homogenised and combined for transient-host matching. A systematic ranking of their utility is discussed and applied based on the inclusion of information such as spectroscopic redshifts and morphological information. Utilising this data against a Dark Energy Survey (DES) sample of supernovae with pre-identified hosts in the XMM-LSS and ECDFS fields, we evaluate different methods for transient-host association in terms of both accuracy and processing speed. We also apply light data-cleaning techniques to identify and remove contaminants within our associations, such as diffraction spikes and blended galaxies where the correct host cannot be determined with confidence. We use a lightweight machine learning approach in the form of extreme gradient boosting to generate confidence scores in our contaminant selections and associated metrics. Finally, we discuss the computational expense of implementation within the LSST transient alert brokers, which will require efficient, fast-paced processing to handle the large stream of survey data.

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arXiv2025

SN 2021aaev: a Hydrogen-Rich Superluminous Supernova with Early Flash and Long-Lived Circumstellar Interaction in an Unusual Host Environment

We present photometric and spectroscopic observations of SN\,2021aaev, a hydrogen-rich, superluminous supernova with persistent (at least $\sim100$ days) narrow Balmer lines (SLSN-IIn) at redshift $z=0.1557$. We observed SN\,2021aaev to rise in $32.5 \pm 1.0$ days since first light and reach a peak absolute magnitude of $-21.46 \pm 0.01$ in the ATLAS $o$ band. The pre-peak spectra resemble those of typical SNe IIn with flash-ionization features arising from the interaction with a dense, confined circumstellar medium (CSM), albeit the flash timescale is longer than usual ($>20$ days). Post peak, the narrow emission lines evolve slowly, and the absence of ejecta features indicates strong deceleration by the CSM. The total radiated energy (about $1.41\times10^{51}$~ergs) is possible with a low-mass (1--$2\,M_{\odot}$) ejecta ploughing into a massive (9--$19\,M_{\odot}$), extended (outer radius $>1\times10^{16}$~cm) H-rich CSM, or alternatively, with magnetar-powered models. Interestingly, the host environment consists of a spiral galaxy with a red substructure in the south-eastern part, and the SN's exact location coincided with the quiescent red substructure (star-formation rate$=0.02^{+0.13}_{-0.02}\,M_{\odot}$~yr$^{-1}$). Given the atypical environment and the obscuring effect of the massive CSM, a thermonuclear (Type Ia-CSM) origin cannot be ruled out. Altogether, SN\,2021aaev is a compelling case to study the diversity of SLSN-IIn features and their host environment.

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arXiv2025

Dust production rates in Jupiter-family comets II: Trends and population insights from ATLAS photometry of 116 JFCs

Jupiter-family comets (JFCs) have orbital periods of less than 20 years and therefore undergo more frequent sublimation compared to other comet populations. The JFCs therefore represent the ideal dynamical population for investigating the dust production rates at high-cadence. We analyzed observations by the Asteroid Terrestrial-impact Last Alert System (ATLAS) of 74 JFCs that reached perihelion in 2022 and 2023. The work contained in this study builds upon our previous work (Gillan et al. 2024), for a total of 116 JFCs over a four-year period. Using the Afrho parameter, we measured the dust production rates of each JFC as a function of heliocentric distance. We found that there remained a clear preference for JFCs to reach their maximum A(0)frho post-perihelion, with 170P/Christensen, 254P/McNaught and P/2020 WJ5 (Lemmon) reaching a maximum A(0)frho between 200-400 days after perihelion. However, all JFCs reached their maximum dust production within 10% of their orbital period relative to perihelion. Fitting A(0)fp as a function of Rh^n, we measured statistically significant differences in the distribution of pre-perihelion and post-perihelion activity index n, with average activity indices of -5.2 +/- 4.5 and -3.2 +/- 2.7 respectively. We derived upper limits for the nuclear radii of comets 444P/WISE-PANSTARRS and 459P/Catalina as Rn \leq 1.5 +/- 0.2 km and Rn \leq 1.7 +/- 0.1 km respectively. We measured six outbursts in comets 97P/Metcalf-Brewington, 99P/Kowal 1, 118P/Shoemaker-Levy 4, 285P/LINEAR and 382P/Larson. From our four years of observing JFC outbursts in the ATLAS data, the average increase in magnitude was - 1.3 +/- 0.8.

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arXiv2025

The Type I Superluminous Supernova Catalogue II: Spectroscopic Evolution in the Photospheric Phase, Velocity Measurements, and Constraints on Diversity

Hydrogen-poor superluminous supernovae (SLSNe) are among the most energetic explosions in the universe, reaching luminosities up to 100 times greater than those of normal supernovae. Detailed spectral analysis hold the potential to reveal their progenitors and underlying energy sources. This paper presents the largest compilation of SLSN photospheric spectra to date, encompassing data from ePESSTO+, the FLEET search and all published spectra up to December 2022. The dataset includes a total of 974 spectra of 234 SLSNe. By constructing average phase binned spectra, we find SLSNe initially exhibit high temperatures (10000 to 11000 K), with blue continua and weak lines. A rapid transformation follows, as temperatures drop to 5000 to 6000 K by 40 days post peak, leading to stronger P-Cygni features. These averages also suggest a fraction of SLSNe may contain some He at explosion. Variance within the dataset is slightly reduced when defining the phase of spectra relative to explosion, rather than peak, and normalising to the population's median e-folding time. Principal Component Analysis (PCA) supports this, requiring fewer components to explain the same level of variation when binning data by scaled days from explosion, suggesting a more homogeneous grouping. Using PCA and K-Means clustering, we identify outlying objects with unusual spectroscopic evolution and evidence for energy input from interaction, but find not support for groupings of two or more statistically significant subpopulations. We find Fe II λ5169 lines velocities closely track the radius implied from blackbody fits, indicating formation near the photosphere. We also confirm a correlation between velocity and velocity gradient, which can be explained if all SLSNe are in homologous expansion but with different scale velocities. This behaviour aligns with expectations for an internal powering mechanism.

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arXiv2024

Main-belt and Trojan Asteroid Phase Curves from the ATLAS Survey

Sparse and serendipitous asteroid photometry obtained by wide field surveys such as the Asteroid Terrestrial-impact Last Alert System (\ATLAS) is a valuable resource for studying the properties of large numbers of small Solar System bodies. We have gathered a large database of \ATLAS photometry in wideband optical cyan and orange filters, consisting of 9.6\e{7} observations of 4.5\e{5} main belt asteroids and Jupiter Trojans. We conduct a phase curve analysis of these asteroids considering each apparition separately, allowing us to accurately reject outlying observations and to remove apparitions and asteroids not suitable for phase curve determination. We obtain a dataset of absolute magnitudes and phase parameters for over 100,000 selected asteroids observed by \ATLAS, $\sim66,000$ of which had sufficient measurements to derive colours in the \ATLAS filters. To demonstrate the power of our dataset we consider the properties of the Nysa-Polana complex, for which the \ATLAS colours and phase parameters trace the S-like and C-like compositions amongst family members. We also compare the properties of the leading and trailing groups of Jupiter Trojans, finding no significant differences in their phase parameters or colours as measured by \ATLAS, supporting the consensus that these groups were captured from a common source population during planetary migration. Furthermore, we identify $\sim9000$ asteroids that exhibit large shifts in derived absolute magnitude between apparitions, indicating that these objects have both elongated shapes and spin axes with obliquity $\sim 90$ degrees.

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arXiv2024

Discovery and Extensive Follow-Up of SN 2024ggi, a nearby type IIP supernova in NGC 3621

We present the discovery and early observations of the nearby Type II supernova (SN) 2024ggi in NGC 3621 at 6.64 +/- 0.3 Mpc. The SN was caught 5.8 (+1.9 -2.9) hours after its explosion by the ATLAS survey. Early-phase, high-cadence, and multi-band photometric follow-up was performed by the Kinder (Kilonova Finder) project, collecting over 1000 photometric data points within a week. The combined o- and r-band light curves show a rapid rise of 3.3 magnitudes in 13.7 hours, much faster than SN 2023ixf (another recent, nearby, and well-observed SN II). Between 13.8 and 18.8 hours after explosion SN 2024ggi became bluer, with u-g colour dropping from 0.53 to 0.15 mag. The rapid blueward evolution indicates a wind shock breakout (SBO) scenario. No hour-long brightening expected for the SBO from a bare stellar surface was detected during our observations. The classification spectrum, taken 17 hours after the SN explosion, shows flash features of high-ionization species such as Balmer lines, He I, C III, and N III. Detailed light curve modeling reveals critical insights into the properties of the circumstellar material (CSM). Our favoured model has an explosion energy of 2 x 10^51 erg, a mass-loss rate of 10^-3 solar_mass/yr (with an assumed 10 km/s wind), and a confined CSM radius of 6 x 10^14 cm. The corresponding CSM mass is 0.4 solar_mass. Comparisons with SN 2023ixf highlight that SN 2024ggi has a smaller CSM density, resulting in a faster rise and fainter UV flux. The extensive dataset and the involvement of citizen astronomers underscore that a collaborative network is essential for SBO searches, leading to more precise and comprehensive SN characterizations.

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arXiv2024

Enabling Science from the Rubin Alert Stream with Lasair

Lasair is the UK Community Broker for transient alerts from the Legacy Survey of Space and Time (LSST) from the Vera C. Rubin Observatory. We explain the system's capabilities, how users can achieve their scientific goals, and how Lasair is implemented. Lasair offers users a kit of parts that they can use to build filters to concentrate their desired alerts. The kit has novel lightcurve features, sky context, watchlists of special sky objects and regions of the sky, dynamic crossmatching with catalogues of known astronomical sources, and classifications and annotations from other users and partner projects. These resources can be shared with other users, copied, and modified. Lasair offers real-time machine-to-machine notifications of filtered transient alerts. Even though the Rubin Observatory is not yet complete, Lasair is a mature system: it has been processing and serving data from the similarly formatted stream of the Zwicky Transient Facility (ZTF) alerts.

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arXiv2024

Long-term follow-up observations of extreme coronal line emitting galaxies

We present new spectroscopic and photometric follow-up observations of the known sample of extreme coronal line emitting galaxies (ECLEs) identified in the Sloan Digital Sky Survey (SDSS). With these new data, observations of the ECLE sample now span a period of two decades following their initial SDSS detections. We confirm the nonrecurrence of the iron coronal line signatures in five of the seven objects, further supporting their identification as the transient light echoes of tidal disruption events (TDEs). Photometric observations of these objects in optical bands show little overall evolution. In contrast, mid-infrared (MIR) observations show ongoing long-term declines. The remaining two objects had been classified as active galactic nuclei (AGN) with unusually strong coronal lines rather than being TDE related, given the persistence of the coronal lines in earlier follow-up spectra. We confirm this classification, with our spectra continuing to show the presence of strong, unchanged coronal-line features and AGN-like MIR colours and behaviour. We have constructed spectral templates of both subtypes of ECLE to aid in distinguishing the likely origin of newly discovered ECLEs. We highlight the need for higher cadence, and more rapid, follow-up observations of such objects to better constrain their properties and evolution. We also discuss the relationships between ECLEs, TDEs, and other identified transients having significant MIR variability.

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arXiv2024

SN 2020pvb: a Type IIn-P supernova with a precursor outburst

We present photometric and spectroscopic data sets for SN 2020pvb, a Type IIn-P supernova (SN) similar to SNe 1994W, 2005cl, 2009kn and 2011ht, with a precursor outburst detected (PS1 w-band ~ -13.8 mag) around four months before the B-band maximum light. SN 2020pvb presents a relatively bright light curve peaking at M_B = -17.95 +- 0.30 mag and a plateau lasting at least 40 days before it went in solar conjunction. After this, the object is no longer visible at phases > 150 days above -12.5 mag in the B-band, suggesting that the SN 2020pvb ejecta interacts with a dense spatially confined circumstellar envelope. SN 2020pvb shows in its spectra strong Balmer lines and a forest of FeII lines with narrow P Cygni profiles. Using archival images from the Hubble Space Telescope, we constrain the progenitor of SN 2020pvb to have a luminosity of log(L/L_sun) <= 5.4, ruling out any single star progenitor over 50 M_sun. All in all, SN 2020pvb is a Type IIn-P whose progenitor star had an outburst ~ 0.5 yr before the final explosion, the material lost during this outburst is probably playing a role in shaping the physical properties of the supernova.

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arXiv2024

The metamorphosis of the Type Ib SN 2019yvr: late-time interaction

We present observational evidence of late-time interaction between the ejecta of the hydrogen-poor Type Ib supernova (SN) 2019yvr and hydrogen-rich circumstellar material (CSM), similar to the Type Ib SN 2014C. A narrow Hα emission line appears simultaneously with a break in the light-curve decline rate at around 80-100 d after explosion. From the interaction delay and the ejecta velocity, under the assumption that the CSM is detached from the progenitor, we estimate the CSM inner radius to be located at ~6.5-9.1 {\times} 10^{15} cm. The Hα emission line persists throughout the nebular phase at least up to +420 d post-explosion, with a full width at half maximum of ~2000 km/s. Assuming a steady mass-loss, the estimated mass-loss rate from the luminosity of the Hα line is ~3-7 {\times} 10^{-5} M_\odot yr^{-1}. From hydrodynamical modelling and analysis of the nebular spectra, we find a progenitor He-core mass of 3-4 M{_\odot}, which would imply an initial mass of 13-15 M{_\odot}. Our result supports the case of a relatively low-mass progenitor possibly in a binary system as opposed to a higher mass single star undergoing a luminous blue variable phase.

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arXiv2024

A Precursor Plateau and Pre-Maximum [O II] Emission in the Superluminous SN2019szu: A Pulsational Pair-Instability Candidate

We present a detailed study on SN2019szu, a Type I superluminous supernova at $z=0.213$, that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry shows a pre-explosion plateau lasting $\sim$ 40 days. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from $\sim$15000 K to $\sim$20000 K over the first 70 days, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line even during the rising phase of the light curve, inconsistent with an apparently compact photosphere. We show that this early feature is [O II] $λλ$7320,7330. We also see evidence for [O III] $λλ$4959, 5007, and [O III] $λ$4363 further strengthening this line identification. Comparing with models for nebular emission, we find that the oxygen line fluxes and ratios can be reproduced with $\sim$0.25 M$_{\odot}$ of oxygen rich material with a density of $\sim10^{-15} \rm{g cm}^{-3}$. The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of $\sim$5500 Å. We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.

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arXiv2023

Dust production rates in Jupiter-family Comets: A two-year study with ATLAS photometry

Jupiter-family Comets (JFCs) exhibit a wide range of activity levels and mass-loss over their orbits. We analyzed high-cadence observations of 42 active JFCs with the wide-field Asteroid Terrestrial-impact Last Alert System (ATLAS) survey in 2020-2021. We measured dust production rates of the JFCs using the Afρparameter and its variation as a function of heliocentric distance. There is a tendency for our JFC sample to exhibit a maximum Afρafter perihelion, with 254P/McNaught and P/2020 WJ5 (Lemmon) having their maximum Afρover a year after perihelion. On average, the rate of change of activity post-perihelion was shallower than that pre-perihelion. We also estimated the mass maximum loss rate for 17 of the JFCs in our sample, finding 4P/Faye to be the most active. We present a subset of comets whose measured Afρhave been interpolated and extrapolated to a common distance of 2 au pre-perihelion and post-perihelion. From these measurements we found no correlation of intrinsic activity with current perihelion distance. For three of the JFCs in our sample, 6P/d'Arrest, 156P/Russell-LINEAR and 254P/McNaught, there was no visible coma but a constant absolute magnitude which we attributed to a probable detection of the nucleus. We derived upper limits for the nuclear radii of \leq 2.1 +/- 0.3 km, \leq 2.0 +/- 0.2 km and \leq 4.0 +/- 0.8 km respectively. Finally, we found that 4P/Faye, 108P/Ciffreo, 132P/Helin-Roman-Alu 2, 141P/Machholz 2, and 398P/Boattini experienced outbursts between 2020 and 2022.

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arXiv2023

NEural Engine for Discovering Luminous Events (NEEDLE): identifying rare transient candidates in real time from host galaxy images

Known for their efficiency in analyzing large data sets, machine learning classifiers are widely used in wide-field sky surveys. The upcoming Vera C. Rubin Observatory Legacy of Time and Space Survey (LSST) will generate millions of alerts every night, enabling the discovery of large samples of rare events. Identifying such objects soon after explosion will be essential to study their evolution. This requires a machine learning framework that makes use of all available transient and contextual information. Using $\sim5400$ transients from the ZTF Bright Transient Survey as input data, we develop NEEDLE, a novel hybrid classifier to select for two rare classes with strong environmental preferences: superluminous supernovae (SLSNe) preferring dwarf galaxies, and tidal disruption events (TDEs) occurring in the centres of nucleated galaxies. The input data includes detection and reference images, photometric information from the alert packets, and host galaxy magnitudes from Pan-STARRS. Despite having only a few tens of examples of the rare classes, our average (best) completeness on an unseen test set reaches 77% (93%) for SLSNe and 72% (87%) for TDEs. This may still result in a large fraction of false positives for the rare transients, given the large class imbalance in real surveys. However, the goal of NEEDLE is to find good candidates for spectroscopic classification, rather than to select pure photometric samples. Our network is designed with LSST in mind and we expect performance to improve further with the higher resolution images and more accurate transient and host photometry that will be available from Rubin. Our system will be deployed as an annotator on the UK alert broker, Lasair, to provide predictions to the community in real time.

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