Fast-transient Searches in Real Time with ZTFReST: Identification of Three Optically-discovered Gamma-ray Burst Afterglows and New Constraints on the Kilonova Rate

Abstract

While optical surveys regularly discover slow transients like supernovae on their own, the most common way to discover extragalactic fast transients, fading away in a few nights, is via follow-up observations of gamma-ray burst and gravitational-wave triggers. However, wide-field surveys have the potential to also identify rapidly fading transients independently of such external triggers. The volumetric survey speed of the Zwicky Transient Facility (ZTF) makes it sensitive to faint and fast-fading objects as kilonovae, the optical counterparts to binary neutron stars and neutron star-black hole mergers, out to almost 200Mpc. We introduce an open-source software infrastructure, the ZTF REaltime Search and Triggering, ZTFReST, designed to identify kilonovae and fast optical transients in ZTF data. Using the ZTF alert stream combined with forced photometry, we have implemented automated candidate ranking based on their photometric evolution and fitting to kilonova models. Automated triggering of follow-up systems, such as Las Cumbres Observatory, has also been implemented. In 13 months of science validation, we found several extragalactic fast transients independent of any external trigger (though some counterparts were identified later), including at least one supernova with post-shock cooling emission, two known afterglows with an associated gamma-ray burst, two known afterglows without any known gamma-ray counterpart, and three new fast-declining sources (ZTF20abtxwfx, ZTF20acozryr, and ZTF21aagwbjr) that are likely associated with GRB200817A, GRB201103B, and GRB210204A. However, we have not found any objects which appear to be kilonovae; therefore, we constrain the rate of GW170817-like kilonovae to $R<900$Gpc${}^{-3}$yr${}^{-1}$. A framework such as ZTFReST could become a prime tool for kilonova and fast transient discovery with the Vera C. Rubin Observatory.

Submitted for publication

References in corpus (58)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Advanced Virgo: a 2nd generation interferometric gravitational wave detector
• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• Origin of the heavy elements in binary neutron-star mergers from a gravitational wave event
• Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. II. UV, Optical, and Near-IR Light Curves and Comparison to Kilonova Models
• Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger
• INTEGRAL Detection of the First Prompt Gamma-Ray Signal Coincident with the Gravitational Wave Event GW170817
• The X-ray counterpart to the gravitational wave event GW 170817
• A kilonova as the electromagnetic counterpart to a gravitational-wave source
• The Zwicky Transient Facility: Science Objectives
• Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis
• Illuminating Gravitational Waves: A Concordant Picture of Photons from a Neutron Star Merger
• Constraining the Maximum Mass of Neutron Stars From Multi-Messenger Observations of GW170817
• The Emergence of a Lanthanide-Rich Kilonova Following the Merger of Two Neutron Stars
• Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger
• Swift and NuSTAR observations of GW170817: detection of a blue kilonova
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South
• GW170817: Joint Constraint on the Neutron Star Equation of State from Multimessenger Observations
• Neutron-star radius constraints from GW170817 and future detections
• A Radio Counterpart to a Neutron Star Merger
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. III. Optical and UV Spectra of a Blue Kilonova From Fast Polar Ejecta
• Identification of strontium in the merger of two neutron stars
• The discovery of the electromagnetic counterpart of GW170817: kilonova AT 2017gfo/DLT17ck
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. V. Rising X-ray Emission from an Off-Axis Jet
• The Zwicky Transient Facility: Surveys and Scheduler
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. VI. Radio Constraints on a Relativistic Jet and Predictions for Late-Time Emission from the Kilonova Ejecta
• The Zwicky Transient Facility: Observing System
• Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger
• MASTER optical detection of the first LIGO/Virgo neutron stars merging GW170817
• Fully-Automated Reduction of Longslit Spectroscopy with the Low Resolution Imaging Spectrometer at Keck Observatory
• A Deep Chandra X-ray Study of Neutron Star Coalescence GW170817
• Time-Dependent Models of Accretion Disks Formed from Compact Object Mergers
• Follow up of GW170817 and its electromagnetic counterpart by Australian-led observing programs
• J-GEM observations of an electromagnetic counterpart to the neutron star merger GW170817
• Double neutron stars: merger rates revisited
• The GROWTH Marshal: A Dynamic Science Portal for Time-Domain Astronomy
• The Rapid Reddening and Featureless Optical Spectra of the optical counterpart of GW170817, AT 2017gfo, During the First Four Days
• The Zwicky Transient Facility Alert Distribution System
• Observations of the first electromagnetic counterpart to a gravitational wave source by the TOROS collaboration
• Gamma Ray Bursts
• Spitzer Mid-Infrared Detections of Neutron Star Merger GW170817 Suggests Synthesis of the Heaviest Elements
• GROWTH on S190814bv: Deep Synoptic Limits on the Optical/Near-Infrared Counterpart to a Neutron Star-Black Hole Merger
• ZTF Early Observations of Type Ia Supernovae I: Properties of the 2018 Sample
• Optical follow-up of the neutron star-black hole mergers S200105ae and S200115j
• Implications of the search for optical counterparts during the first six months of the Advanced LIGO's and Advanced Virgo's third observing run: possible limits on the ejecta mass and binary properties
• Palomar Gattini-IR: Survey overview, data processing system, on-sky performance and first results
• An analysis of the durations of Swift Gamma-Ray Bursts
• iPTF14yb: The First Discovery of a GRB Afterglow Independent of a High-Energy Trigger
• The Needle in the 100 deg2 Haystack: Uncovering Afterglows of Fermi GRBs with the Palomar Transient Factory
• Short gamma-ray bursts within 200 Mpc
• Observations of the GRB afterglow ATLAS17aeu and its possible association with GW170104
• Measuring the Hubble Constant with a sample of kilonovae
• A Search for Kilonovae in the Dark Energy Survey
• An empirical limit on the kilonova rate from the DLT40 one day cadence Supernova Survey
• 2900 square degree search for the optical counterpart of short gamma-ray burst GRB 180523B with the Zwicky Transient Facility

Cited by in corpus (44)

• Rates of Compact Object Coalescences
• A very luminous jet from the disruption of a star by a massive black hole
• A data science platform to enable time-domain astronomy
• An updated nuclear-physics and multi-messenger astrophysics framework for binary neutron star mergers
• Kilonova Detectability with Wide-Field Instruments
• Updated observing scenarios and multi-messenger implications for the International Gravitational-wave Network's O4 and O5
• Target of Opportunity Observations of Gravitational Wave Events with Vera C. Rubin Observatory
• Linking the rates of neutron star binaries and short gamma-ray bursts
• Cosmological Fast Optical Transients with the Zwicky Transient Facility: A Search for Dirty Fireballs
• r-Process Radioisotopes from Near-Earth Supernovae and Kilonovae
• Optimizing Cadences with Realistic Light Curve Filtering for Serendipitous Kilonova Discovery with Vera Rubin Observatory
• Pulsar revival in neutron star mergers: multi-messenger prospects for the discovery of pre-merger coherent radio emission
• Eighteen Years of Kilonova Discoveries with Swift
• A Systematic Exploration of Kilonova Candidates from Neutron Star Mergers During the Third Gravitational Wave Observing Run
• Constraining the long-lived supramassive neutron stars by magnetar boosted kilonovae
• Kilonova and Optical Afterglow from Binary Neutron Star Mergers. II. Optimal Search Strategy for Serendipitous Observations and Target-of-opportunity Observations of Gravitational-wave Triggers
• GRANDMA Observations of ZTF/Fink Transients during Summer 2021
• The long-active afterglow of GRB 210204A: Detection of the most delayed flares in a Gamma-Ray Burst
• Give Me a Few Hours: Exploring Short Timescales in Rubin Observatory Cadence Simulations
• Neutrinos from explosive transients at the dawn of multi-messenger astronomy
• Enabling the discovery of fast transients: A kilonova science module for the Fink broker
• Possible origin of AT2021any: a failed GRB from a structured jet
• The luminosity functions of kilonovae from binary neutron star mergers under different equation of states
• Multi-messenger prospects for black hole - neutron star mergers in the O4 and O5 runs
• Evolution of A Peculiar Type Ibn Supernova SN 2019wep
• Searching For Fermi GRB Optical Counterparts With The Prototype Gravitational-Wave Optical Transient Observer (GOTO)
• In search of short gamma-ray burst optical counterpart with the Zwicky Transient Facility
• Inferring kilonova population properties with a hierarchical Bayesian framework I : Non-detection methodology and single-event analyses
• Results from the Pan-STARRS Search for Kilonovae: Contamination by Massive Stellar Outbursts
• SN 2023zaw: an ultra-stripped, nickel-poor supernova from a low-mass progenitor
• AT2019wxt: An ultra-stripped supernova candidate discovered in electromagnetic follow-up of a gravitational wave trigger
• IIb or not IIb: A Catalog of ZTF Kilonova Imposters
• Searching for Gravitational-Wave Counterparts using the Transiting Exoplanet Survey Satellite
• Kilonova-Targeting Lightcurve Classification for Wide Field Survey Telescope
• The automation of optical transient discovery and classification in Rubin-era time-domain astronomy
• The Gravitational-wave Optical Transient Observer (GOTO): prototype performance and prospects for transient science
• What to expect: kilonova light curve predictions via equation of state marginalization
• Detecting the early optical flashes of gamma-ray bursts with small telescope arrays
• Gravitational Waves and Electromagnetic Transients
• Machine-directed gravitational-wave counterpart discovery
• Afterglow Linear Polarization Signatures from Steep GRB Jets: Implications for Orphan Afterglows
• Kilonova Light Curve Parameter Estimation Using Likelihood-Free Inference
• Implications of low neutron star merger rates for gamma-ray bursts, r-process production and Galactic double neutron stars
• GRB 160410A: the first Chemical Study of the Interstellar Medium of a Short GRB