A. Mahabal
A5007384804- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Time Series Analysis and Forecasting
- Radio Astronomy Observations and Technology
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Spectroscopy and Chemometric Analyses
- Remote Sensing in Agriculture
- Scientific Computing and Data Management
- Astrophysics and Star Formation Studies
- Particle Accelerators and Free-Electron Lasers
- Neutrino Physics Research
- Semiconductor Lasers and Optical Devices
- Distributed and Parallel Computing Systems
- History and Developments in Astronomy
- Anomaly Detection Techniques and Applications
- GNSS positioning and interference
California Institute of Technology
2016-2025
Infrared Processing and Analysis Center
2020-2024
Inter-University Centre for Astronomy and Astrophysics
1996-2021
Jet Propulsion Laboratory
2008-2021
Astrogeology Science Center
2021
University of Minnesota
2021
Space Telescope Science Institute
2009
Palomar College
2000-2006
Research Institute for Advanced Computer Science
2006
TMT Observatory
2003-2005
The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides 47 deg2 field of view and 8 s readout time, yielding more than an order magnitude improvement in speed relative to its predecessor survey, Factory. We describe design implementation observing system. ZTF data system at Infrared Processing Analysis Center near-real-time reduction identify moving varying objects. outline analysis...
We report on the results from first six months of Catalina Real-Time Transient Survey (CRTS). In order to search for optical transients (OTs) with timescales minutes years, CRTS analyses data Sky which repeatedly covers 26,000 square degrees sky. The provides a public stream that are bright enough be followed up using small telescopes. Since beginning survey, all have been made available astronomers around world in real time HTML tables,RSS feeds, and VOEvents. As part our outreach program,...
The Zwicky Transient Facility (ZTF), a public-private enterprise, is new time domain survey employing dedicated camera on the Palomar 48-inch Schmidt telescope with 47 deg$^2$ field of view and 8 second readout time. It well positioned in development astronomy, offering operations at 10% scale style Large Synoptic Survey Telescope (LSST) single 1-m class telescope. public surveys will cover observable northern sky every three nights g r filters visible Galactic plane night r. Alerts...
We present ∼47,000 periodic variables found during the analysis of 5.4 million variable star candidates within a 20,000 deg2 region covered by Catalina Surveys Data Release-1 (CSDR1). Combining these with type ab RR Lyrae from our previous work, we produce an online catalog containing periods, amplitudes, and classifications for ∼61,000 variables. By cross-matching those prior surveys, find that >90% ∼8000 known in survey are recovered. For sources, excellent agreement between values...
Effective data visualization is a key part of the discovery process in era big data. It bridge between quantitative content and human intuition, thus an essential component scientific path from into knowledge understanding. Visualization also mining process, directing choice applicable algorithms, helping to identify remove bad analysis. However, high complexity or dimensionality modern sets represents critical obstacle. How do we visualize interesting structures patterns that may exist...
We report the first plausible optical electromagnetic counterpart to a (candidate) binary black hole merger. Detected by Zwicky Transient Facility, flare is consistent with expectations for kicked merger in accretion disk of an active galactic nucleus [B. McKernan, K. E. S. Ford, I. Bartos et al., Astrophys. J. Lett. 884, L50 (2019)AJLEEY2041-821310.3847/2041-8213/ab4886] and unlikely [<O(0.01%))] due intrinsic variability this source. The lack color evolution implies that it not supernova...
Hierarchical assembly models predict a population of supermassive black hole (SMBH) binaries. These are not resolvable by direct imaging but may be detectable via periodic variability (or nanohertz frequency gravitational waves). Following our detection 5.2-year signal in the quasar PG 1302−102, we present novel analysis optical 243 500 known spectroscopically confirmed quasars using data from Catalina Real-time Transient Survey (CRTS) to look for close (<0.1 pc) SMBH systems. Looking strong...
We present analysis of 12,227 type-ab RR Lyraes (RRLs) found among the 200 million public light curves in Catalina Surveys Data Release 1. These stars span largest volume Milky Way ever surveyed with RRLs, covering ∼20,000 deg2 sky (0° < α 360°, −22° δ 65°) to heliocentric distances up 60 kpc. Each RRLs is observed between and 419 times over a six-year period. Using period finding Fourier fitting techniques we determine periods apparent magnitudes for each source. find that are generally...
The Zwicky Transient Facility (ZTF) is a new robotic time-domain survey currently in progress using the Palomar 48-inch Schmidt Telescope. ZTF uses 47 square degree field with 600 megapixel camera to scan entire northern visible sky at rates of ~3760 degrees/hour median depths g ~ 20.8 and r 20.6 mag (AB, 5sigma 30 sec). We describe Science Data System that housed IPAC, Caltech. This comprises data-processing pipelines, alert production system, data archive, user interfaces for accessing...
Wide-field optical surveys have begun to uncover large samples of fast (trise ≲ 5 d), luminous (Mpeak < −18), blue transients. While commonly attributed the breakout a supernova shock into dense wind, great distances transients this class found so far hampered detailed investigation their properties. We present photometry and spectroscopy from comprehensive worldwide campaign observe AT 2018cow (ATLAS 18qqn), first fast-luminous transient be in real time at low redshift. Our spectra (<2 days...
Abstract We present a public catalog of transients from the Zwicky Transient Facility (ZTF) Bright Survey, magnitude-limited ( m < 19 mag in either g or r filter) survey for extragalactic ZTF stream. introduce cuts on coverage, sky visibility around peak light, and other properties unconnected to nature transient, show that resulting statistical sample is spectroscopically 97% complete at <18 mag, 93% <18.5 75% <19 mag. summarize fundamental this population, identifying distinct...
Abstract We conduct a systematic tidal disruption event (TDE) demographics analysis using the largest sample of optically selected TDEs. A flux-limited, spectroscopically complete 33 TDEs is constructed Zwicky Transient Facility over 3 yr (from 2018 October to 2021 September). infer black hole (BH) mass ( M BH ) with host galaxy scaling relations, showing that ranges from 10 5.1 ⊙ 8.2 . developed survey efficiency corrected maximum volume method rates. The rest-frame g -band luminosity...
Abstract We present a search for extragalactic fast blue optical transients (FBOTs) during Phase I of the Zwicky Transient Facility (ZTF). identify 38 candidates with durations above half-maximum light 1 day < t 1/2 12 days, which 28 have ( g − r ≲ −0.2 mag) colors at peak light. Of (28 FBOTs), 19 (13) can be spectroscopically classified as core-collapse supernovae (SNe): 11 (8) H- or He-rich (Type II/IIb/Ib) SNe, 6 (4) interacting IIn/Ibn) and 2 (1) H&He-poor Ic/Ic-BL) SNe. Two FBOTs...
The accretion disks of active galactic nuclei (AGN) are promising locations for the merger compact objects detected by gravitational wave (GW) observatories. Embedded within a baryon-rich, high density environment, mergers AGN only GW channel where an electromagnetic (EM) counterpart must occur (whether detectable or not). Considering with unusual flaring activity observed Zwicky Transient Facility (ZTF), we describe search candidate EM counterparts to binary black hole (BBH) LIGO/Virgo in...
Discovery of the cosmic reionization epoch would represent a significant milestone in cosmology. We present Keck spectroscopy quasar SDSS 1044-0125, at z = 5.73. The spectrum shows dramatic increase optical depth observed wavelengths λ ≳ 7550 Å, corresponding to zabs 5.2. Only few small, narrow transmission regions are beyond that point and out redshifts where signal begins. interpret this result as signature trailing edge epoch, which we estimate occur around ⟨z⟩ ~ 6 (as indeed confirmed by...
We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4 GHz in the FIRST survey with near-infrared 2MASS catalog and color-selecting red sources. Optical and/or spectroscopy provide broad wavelength sampling their spectral energy distributions that we use to determine reddening, characterized E(B-V). demonstrate reddening these is best-described SMC-like dust. This spans wide range redshift (0.1 < z 3, 0.1 E(B-V) 1.5), which investigate possible...
We report results from the Supernova Photometric Classification Challenge (SNPCC), a publicly released mix of simulated supernovae (SNe), with types (Ia, Ibc, and II) selected in proportion to their expected rate. The simulation was realized griz filters Dark Energy Survey (DES) realistic observing conditions (sky noise, point-spread function atmospheric transparency) based on years recorded at DES site. Simulations non-Ia type SNe are spectroscopically confirmed light curves that include...
Here, we present the results from our analysis of 6 yr optical photometry taken by Siding Spring Survey (SSS). This completes a search for periodic variable stars within 30 000 deg2 sky covered Catalina Surveys. The current covers 81 million sources with declinations between −20° and −75° median magnitudes in range 11 < V 19.5. We find approximately 34 new addition to ∼9000 RR Lyrae that previously discovered SSS data. brings total number variables identified data ∼110 000. mainly consist...
Abstract The Zwicky Transient Facility (ZTF) is performing a three-day cadence survey of the visible northern sky (∼3 π ) with newly found transient candidates announced via public alerts. ZTF Bright Survey (BTS) large spectroscopic campaign to complement photometric survey. BTS endeavors spectroscopically classify all extragalactic transients m peak ≤ 18.5 mag in either g or r filters, and publicly announce said classifications. discoveries are predominantly supernovae (SNe), making this...
ABSTRACT Efficient automated detection of flux-transient, re-occurring flux-variable, and moving objects is increasingly important for large-scale astronomical surveys. We present braai, a convolutional-neural-network, deep-learning real/bogus classifier designed to separate genuine astrophysical events from false positive, or bogus, detections in the data Zwicky Transient Facility (ZTF), new robotic time-domain survey currently operation at Palomar Observatory California, USA. Braai...
We present first results on polarization swings in optical emission of blazars obtained by RoboPol, a monitoring program an unbiased sample gamma-ray bright specially designed for effective detection such events. A possible connection swing events with periods high activity gamma rays is investigated using the dataset during season operation. It was found that brightest flares tend to be located closer time rotation events, which may indication two separate mechanisms responsible rotations....