Gautham Narayan
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View article: Testing Lens Models of PLCK G165.7+67.0 Using Lensed SN H0pe
Testing Lens Models of PLCK G165.7+67.0 Using Lensed SN H0pe Open
Supernova H0pe is a multiply-imaged Type Ia supernova (SN Ia) and the second lensed SN to yield a measurement of the Hubble constant by the time-delay cosmography method, finding $H_0 = 75.4^{+8.1}_{-5.5} \text{km s}^{-1} \text{Mpc}^{-1}$.…
View article: Neural Post-Einsteinian Test of General Relativity with the Third Gravitational-Wave Transient Catalog
Neural Post-Einsteinian Test of General Relativity with the Third Gravitational-Wave Transient Catalog Open
Gravitational waves (GWs) from compact binaries are excellent probes of gravity in the strong- and dynamical-field regime. We report a test of general relativity (GR) with the third GW Transient Catalog (GWTC-3) using the recently develope…
View article: SN 2019tsf: Evidence for Extended Hydrogen-poor CSM in the Three-peaked Light Curve of Stripped Envelope of a Type Ib Supernova
SN 2019tsf: Evidence for Extended Hydrogen-poor CSM in the Three-peaked Light Curve of Stripped Envelope of a Type Ib Supernova Open
We present multiband ATLAS and ZTF photometry for SN 2019tsf, a Type Ib stripped-envelope supernova (SESN). The slow spectral evolution could be associated with an uncommon explosion mechanism specific to this SN. Possible explanations inc…
View article: <tt>Mantis Shrimp</tt>: Exploring Photometric Band Utilization in Computer Vision Networks for Photometric Redshift Estimation
Mantis Shrimp: Exploring Photometric Band Utilization in Computer Vision Networks for Photometric Redshift Estimation Open
We present Mantis Shrimp , a multisurvey deep learning model for photometric redshift estimation that fuses ultraviolet (Galaxy Evolution Explorer), optical (PanSTARRS), and infrared (UnWISE) imagery. Machine learning is now an established…
View article: Characterizing the standardization properties of type ia supernovae in the <i>z</i> band with hierarchical Bayesian modelling
Characterizing the standardization properties of type ia supernovae in the <i>z</i> band with hierarchical Bayesian modelling Open
Type Ia supernovae (SNe Ia) are standardizable candles: their peak magnitudes can be corrected for correlations between light-curve properties and their luminosities to precisely estimate distances. Understanding SN Ia standardization acro…
View article: Characterising the Standardisation Properties of Type Ia Supernovae in the z band with Hierarchical Bayesian Modelling
Characterising the Standardisation Properties of Type Ia Supernovae in the z band with Hierarchical Bayesian Modelling Open
Type Ia supernovae (SNe Ia) are standardisable candles: their peak magnitudes can be corrected for correlations between light curve properties and their luminosities to precisely estimate distances. Understanding SN Ia standardisation acro…
View article: DAmodel: hierarchical Bayesian modelling of DA white dwarfs for spectrophotometric calibration
DAmodel: hierarchical Bayesian modelling of DA white dwarfs for spectrophotometric calibration Open
We use hierarchical Bayesian modelling to calibrate a network of 32 all-sky faint DA white dwarf (DA WD) spectrophotometric standards ($16.5 < V < 19.5$) alongside three CALSPEC standards, from 912 Å to 32 $\mu$m. The framework is th…
View article: The Fastest Path to Discovering the Second Electromagnetic Counterpart to a Gravitational Wave Event
The Fastest Path to Discovering the Second Electromagnetic Counterpart to a Gravitational Wave Event Open
The discovery of a second electromagnetic counterpart to a gravitational wave event represents a critical goal in the field of multi-messenger astronomy. In order to determine the optimal strategy for achieving this goal, we perform compre…
View article: Mantis Shrimp: Exploring Photometric Band Utilization in Computer Vision Networks for Photometric Redshift Estimation
Mantis Shrimp: Exploring Photometric Band Utilization in Computer Vision Networks for Photometric Redshift Estimation Open
We present Mantis Shrimp, a multi-survey deep learning model for photometric redshift estimation that fuses ultra-violet (GALEX), optical (PanSTARRS), and infrared (UnWISE) imagery. Machine learning is now an established approach for photo…
View article: ORACLE- A family of real-time, hierarchical classifiers for transient and variable phenomena in LSST alert streams.
ORACLE- A family of real-time, hierarchical classifiers for transient and variable phenomena in LSST alert streams. Open
ORACLE is the first hierarchical deep-learning model for real-time, context-aware classification of transient and variable astrophysical phenomena. It uses a recurrent neural network with Gated Recurrent Units (GRUs), and has been trained …
View article: Faint White Dwarf Flux Standards: Data and Models
Faint White Dwarf Flux Standards: Data and Models Open
Fainter standard stars are essential for the calibration of larger telescopes. This work adds to the calibration spectra (CALSPEC) database of 19 faint white dwarfs (WDs) with all-sky coverage and V magnitudes between 16.5 and 18.7. Includ…
View article: Double “acct”: A Distinct Double-peaked Supernova Matching Pulsational Pair Instability Models
Double “acct”: A Distinct Double-peaked Supernova Matching Pulsational Pair Instability Models Open
We present multiwavelength data of SN 2020acct, a double-peaked stripped-envelope supernova (SN) in NGC 2981 at ∼150 Mpc. The two peaks are temporally distinct, with maxima separated by 58 rest-frame days and a factor of 20 reduction in fl…
View article: DAmodel: Hierarchical Bayesian Modelling of DA White Dwarfs for Spectrophotometric Calibration
DAmodel: Hierarchical Bayesian Modelling of DA White Dwarfs for Spectrophotometric Calibration Open
We use hierarchical Bayesian modelling to calibrate a network of 32 all-sky faint DA white dwarf (DA WD) spectrophotometric standards ($16.5 < V < 19.5$) alongside three CALSPEC standards, from 912 Å to 32 $μ$m. The framework is the first …
View article: SN 2021foa: The “Flip-flop” Type IIn/Ibn Supernova
SN 2021foa: The “Flip-flop” Type IIn/Ibn Supernova Open
We present a comprehensive analysis of the photometric and spectroscopic evolution of SN 2021foa, unique among the class of transitional supernovae for repeatedly changing its spectroscopic appearance from hydrogen-to-helium-to-hydrogen do…
View article: The Fastest Path to Discovering the Second Electromagnetic Counterpart to a Gravitational Wave Event
The Fastest Path to Discovering the Second Electromagnetic Counterpart to a Gravitational Wave Event Open
The discovery of a second electromagnetic counterpart to a gravitational wave event represents a critical goal in the field of multi-messenger astronomy. In order to determine the optimal strategy for achieving this goal, we perform compre…
View article: Faint white dwarf flux standards: data and models
Faint white dwarf flux standards: data and models Open
Fainter standard stars are essential for the calibration of larger telescopes. This work adds to the CALSPEC (calibration spectra) database 19 faint white dwarfs (WDs) with all-sky coverage and V magnitudes between 16.5 and 18.7. Included …
View article: NEXUS Early Data Release: NIRCam Imaging and WFSS Spectroscopy from the First (Partial) Wide Epoch
NEXUS Early Data Release: NIRCam Imaging and WFSS Spectroscopy from the First (Partial) Wide Epoch Open
We present the Early Data Release of the Multi-Cycle JWST-NEXUS Treasury program (2024-2028), which includes NIRCam imaging and WFSS observations from the first (partial) NEXUS-Wide epoch covering the central 100 ${\rm arcmin^2}$ of the NE…
View article: Rubin ToO 2024: Envisioning the Vera C. Rubin Observatory LSST Target of Opportunity program
Rubin ToO 2024: Envisioning the Vera C. Rubin Observatory LSST Target of Opportunity program Open
The Legacy Survey of Space and Time (LSST) at Vera C. Rubin Observatory is planned to begin in the Fall of 2025. The LSST survey cadence has been designed via a community-driven process regulated by the Survey Cadence Optimization Committe…
View article: Anomaly Detection and Approximate Similarity Searches of Transients in Real-time Data Streams
Anomaly Detection and Approximate Similarity Searches of Transients in Real-time Data Streams Open
We present Lightcurve Anomaly Identification and Similarity Search ( LAISS ), an automated pipeline to detect anomalous astrophysical transients in real-time data streams. We deploy our anomaly detection model on the nightly Zwicky Transie…
View article: Double "acct": a distinct double-peaked supernova matching pulsational pair-instability models
Double "acct": a distinct double-peaked supernova matching pulsational pair-instability models Open
We present multi-wavelength data of SN2020acct, a double-peaked stripped-envelope supernova (SN) in NGC2981 at ~150 Mpc. The two peaks are temporally distinct, with maxima separated by 58 rest-frame days, and a factor of 20 reduction in fl…
View article: NEXUS: the North ecliptic pole EXtragalactic Unified Survey
NEXUS: the North ecliptic pole EXtragalactic Unified Survey Open
NEXUS is a JWST Multi-Cycle (Cycles 3-5; 368 primary hrs) GO Treasury imaging and spectroscopic survey around the North Ecliptic Pole. It contains two overlapping tiers. The Wide tier ($\sim 400~{\rm arcmin}^2$) performs NIRCam/WFSS 2.4-5 …
View article: Measuring the ejecta velocities of type Ia supernovae from the pan-STARRS1 medium deep survey
Measuring the ejecta velocities of type Ia supernovae from the pan-STARRS1 medium deep survey Open
There is growing evidence that Type Ia supernovae (SNe Ia) may originate from multiple explosion channels. Previous studies have indicated that the ejecta velocity of SNe Ia is one powerful tool to discriminate between different channels. …
View article: LAISS: Lightcurve Anomaly Identification and Similarity Search
LAISS: Lightcurve Anomaly Identification and Similarity Search Open
This is the official Zenodo version of the code LAISS (Lightcurve Anomaly Identification and Similarity Search), associated with the paper, "Anomaly Detection and Approximate Similarity Searches of Transients in Real-time Data Streams" by …
View article: Testing the LSST Difference Image Analysis Pipeline Using Synthetic Source Injection Analysis
Testing the LSST Difference Image Analysis Pipeline Using Synthetic Source Injection Analysis Open
We evaluate the performance of the Legacy Survey of Space and Time Science Pipelines Difference Image Analysis (DIA) on simulated images. By adding synthetic sources to galaxies on images, we trace the recovery of injected synthetic source…
View article: Neural post-Einsteinian framework for efficient theory-agnostic tests of general relativity with gravitational waves
Neural post-Einsteinian framework for efficient theory-agnostic tests of general relativity with gravitational waves Open
The parametrized post-Einsteinian (ppE) framework and its variants are widely used to probe gravity through gravitational-wave tests that apply to a large class of theories beyond general relativity. However, the ppE framework is not truly…
View article: Preliminary Report on Mantis Shrimp: a Multi-Survey Computer Vision Photometric Redshift Model
Preliminary Report on Mantis Shrimp: a Multi-Survey Computer Vision Photometric Redshift Model Open
The availability of large, public, multi-modal astronomical datasets presents an opportunity to execute novel research that straddles the line between science of AI and science of astronomy. Photometric redshift estimation is a well-establ…
View article: Windows on the Universe: Establishing the Infrastructure for a Collaborative Multi-messenger Ecosystem
Windows on the Universe: Establishing the Infrastructure for a Collaborative Multi-messenger Ecosystem Open
In this White Paper, we present recommendations for the scientific community and funding agencies to foster the infrastructure for a collaborative multi-messenger and time-domain astronomy (MMA/TDA) ecosystem. MMA/TDA is poised for breakth…