A5063738049- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Pulsars and Gravitational Waves Research
- Isotope Analysis in Ecology
- COVID-19 diagnosis using AI
- Planetary Science and Exploration
- Smart Grid and Power Systems
- Astronomical Observations and Instrumentation
- Optical Systems and Laser Technology
- Neutrino Physics Research
- Solar and Space Plasma Dynamics
- Industrial Vision Systems and Defect Detection
- Space Exploration and Technology
- Particle Detector Development and Performance
- Statistical and numerical algorithms
- Foot and Ankle Surgery
- Advanced Power Generation Technologies
- Ionosphere and magnetosphere dynamics
- Advanced Vision and Imaging
University of Hawaii System
2019-2024
Space Telescope Science Institute
2023-2024
University of Hawaiʻi at Mānoa
2020-2023
The Royal Free Hospital
2020-2022
University College London
2020-2022
Pinderfields Hospital
2022
Mid Yorkshire Hospitals NHS Trust
2022
Wellesley College
2022
Barts Health NHS Trust
2020
Royal London Hospital
2020
We present the discovery that ASASSN-14ko is a periodically flaring AGN at center of galaxy ESO 253-G003. At time its by All-Sky Automated Survey for Supernovae (ASAS-SN), it was classified as supernova close to nucleus. The subsequent six years V- and g-band ASAS-SN observations reveal has nuclear flares occurring regular intervals. seventeen observed outbursts show evidence decreasing period over time, with mean $P_0 = 114.2 \pm 0.4$ days derivative $\dot{P} -0.0017\pm0.0003$. most recent...
ABSTRACT We present observations of ASASSN-19dj, a nearby tidal disruption event (TDE) discovered in the post-starburst galaxy KUG 0810+227 by All-Sky Automated Survey for Supernovae (ASAS-SN) at distance d ≃ 98 Mpc. observed ASASSN-19dj from −21 to 392 relative peak ultraviolet (UV)/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From ASAS-SN g-band data, we determine that TDE began brighten on 2019 February 6.8 first 16 rise was consistent with flux ∝t2...
Binaries containing a compact object orbiting supermassive black hole are thought to be precursors of gravitational wave events, but their identification has been extremely challenging. Here, we report quasi-periodic variability in x-ray absorption, which interpret as outflows (QPOuts) from previously low-luminosity active galactic nucleus after an outburst, likely caused by stellar tidal disruption. We rule out several models based on observed properties and instead show using general...
We present observations of ASASSN-20hx, a nearby ambiguous nuclear transient (ANT) discovered in NGC 6297 by the All-Sky Automated Survey for Supernovae (ASAS-SN). observed ASASSN-20hx from $-$30 to 275 days relative peak UV/optical emission using high-cadence, multi-wavelength spectroscopy and photometry. From Transiting Exoplanet Satellite (TESS) data, we determine that ANT began brighten on 2020 June 22.8 with linear rise flux at least first week. peaked 30 later July (MJD = 59052.8)...
We present an updated strong-lensing analysis of the massive cluster Abell 370 (A370), continuing work first presented in Lagattuta et al. (2017). In this new analysis, we take advantage deeper imaging data from Hubble Space Telescope (HST) Frontier Fields program, as well a large spectroscopic mosaic obtained with Multi-Unit Spectroscopic Explorer (MUSE). Thanks to extended coverage mosaic, probe full 3D distribution galaxies field, giving us unique picture structure and its surroundings....
The transformation of Jupiter's South Equatorial Belt (SEB) from its faded, whitened state in 2009-2010 to normal brown appearance is documented via comparisons thermal-infrared (5-20 $\mu$m) and visible-light imaging between November 2010 2011. SEB revival consisted convective eruptions triggered over $\sim100$ days, potentially powered by the latent heat released condensation water. plumes rise water cloud base ultimately diverge cool stably-stratified upper troposphere. Thermal-IR images...
ABSTRACT We present the discovery of ASASSN-18jd (AT 2018bcb), a luminous optical/ultraviolet(UV)/X-ray transient located in nucleus galaxy 2MASX J22434289–1659083 at z = 0.1192. Over year after discovery, Swift UltraViolet and Optical Telescope (UVOT) photometry shows UV spectral energy distribution to be well modelled by slowly shrinking blackbody with temperature $T \sim 2.5 \times 10^{4} \, {\rm K}$, maximum observed luminosity $L_{\rm max} 4.5^{+0.6}_{-0.3}\times 10^{44} erg \,s}^{-1}$,...
ASASSN-14ko is a recently discovered periodically flaring transient at the center of AGN ESO 253-G003 with slowly decreasing period. Here we show that flares originate from northern, brighter nucleus in this dual-AGN, post-merger system. The light curves for two occurred May 2020 and September are nearly identical over all wavelengths. For both events, Swift observations showed UV optical wavelengths brightened unison. effective temperature UV/optical emission rises falls increase subsequent...
Abstract ASASSN-14ko is a nuclear transient at the center of AGN ESO 253−G003 that undergoes periodic flares. Optical flares were first observed in 2014 by All-Sky Automated Survey for Supernovae (ASAS-SN) and their peak times are well-modeled with period <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>115.2</mml:mn> </mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.2</mml:mn> <mml:mo>+</mml:mo> <mml:mn>1.3</mml:mn> </mml:msubsup>...
We present the Spectroscopic Classification of Astronomical Transients (SCAT) survey, which is dedicated to spectrophotometric observations transient objects such as supernovae and tidal disruption events. SCAT uses SuperNova Integral-Field Spectrograph (SNIFS) on University Hawai'i 2.2-meter (UH2.2m) telescope. SNIFS was designed specifically for accurate spectrophotometry, including absolute flux calibration host-galaxy removal. describe data reduction pipeline spectral extraction,...
Blazars are active galactic nuclei with their relativistic jets pointing toward the observer, two major sub-classes, flat spectrum radio quasars and BL Lac objects. We present multi-wavelength photometric spectroscopic monitoring observations of blazar, B2 1420+32, focusing on its outbursts in 2018-2020. Multi-epoch spectra show that blazar exhibited large scale spectral variability both continuum line emission, accompanied by dramatic gamma-ray optical factors up to 40 15, respectively,...
ABSTRACT We used Transiting Exoplanet Survey Satellite (TESS) data to identify 29 candidate active galactic nuclei (AGNs) through their optical variability. The high-cadence, high-precision TESS light curves present an opportunity for the identification of AGNs, including those not selected other methods. Of candidates, we found that 18 have either previously been identified as AGNs in literature or could based on emission-line diagnostics, mid-IR colours, X-ray luminosity. low-mass galaxies...
We investigate the relationship between AGN optical variability timescales, amplitudes, and supermassive black hole (SMBH) masses using homogeneous light curves from All-Sky Automated Survey for SuperNovae (ASAS-SN). fit a damped random walk (DRW) model to high-cadence, long-baseline ASAS-SN estimate characteristic timescale ($\tau_\text{DRW}$) amplitude ($\sigma$) 57 with precise SMBH mass measurements reverberation mapping dynamical methods. confirm significant correlation...
We analyze high-cadence data from the Transiting Exoplanet Survey Satellite (TESS) of ambiguous nuclear transient (ANT) ASASSN-18el. The optical changing-look phenomenon in ASASSN-18el has been argued to be due either a drastic change accretion rate existing active galactic nucleus (AGN) or result tidal disruption event (TDE). Throughout TESS observations, short-timescale stochastic variability is seen, consistent with an AGN. are able fit light curve damped-random-walk (DRW) model and...
Abstract We report photometry and spectroscopy of the outburst young stellar object Gaia19bey. have established light curve with archival Gaia “ G ,” ATLAS “Orange,” Zwicky Transient Facility r -band, Pan-STARRS rizy ”-filter photometry, showing an ~4 yr duration, longer than typical EX Lupi objects but shorter FU Orionis objects. Its pre-outburst spectral energy distribution shows a flat far-infrared spectrum, confirming early evolutionary state Gaia19bey its similarity to other deeply...
We present Multi-Unit Spectroscopic Explorer (MUSE) integral-field spectroscopy of ESO 253$-$G003, which hosts a known Active Galactic Nucleus (AGN) and the periodic nuclear transient ASASSN-14ko, observed as part All-weather MUse Supernova Integral-field Nearby Galaxies (AMUSING) survey. The MUSE observations reveal that inner region two AGN separated by $1.4\pm0.1~\rm{kpc}$ ($\approx 1.\!\!^{\prime\prime}7$). brighter nucleus has asymmetric broad, permitted emission-line profiles is...
ABSTRACT NGC 5273 is a known optical and X-ray variable AGN. We analyse new archival IR, optical, UV, data in order to characterize its long-term variability from 2000–2022. At least one changing-look event occurred between 2011 2014 when the AGN changed Type 1.8/1.9 Seyfert 1. It then faded considerably at all wavelengths, followed by dramatic but slow increase UV/optical brightness 2021 2022. Near-IR (NIR) spectra 2022 show prominent broad Paschen lines that are absent an spectrum 2010,...
We present individual dynamical masses for the nearby M9.5+T5.5 binary WISE J072003.20$-$084651.2AB, a.k.a. Scholz's star. Combining high-precision CFHT/WIRCam photocenter astrometry and Keck adaptive optics resolved imaging, we measure first high-quality parallactic distance ($6.80_{-0.06}^{+0.05}$ pc) orbit ($8.06_{-0.25}^{+0.24}$ yr period) this system composed of a low-mass star brown dwarf. find moderately eccentric ($e = 0.240_{-0.010}^{+0.009}$), incompatible with previous work based...
We present the discovery that ATLAS18mlw was a tidal disruption event (TDE) in galaxy WISEA J073544.83+663717.3, at luminosity distance of 334 Mpc. Initially discovered by Asteroid Terrestrial Impact Last Alert System (ATLAS) on 2018 March 17.3, TDE nature transient uncovered only recently with re-reduction SuperNova Integral Field Spectrograph (SNIFS) spectrum. This spectrum, taken Spectral Classification Astronomical Transients (SCAT) survey, shows strong blue continuum and broad H$\alpha$...
ABSTRACT We present extensive ultraviolet (UV) and optical photometric spectroscopic follow-up of supernova (SN) 2021gno by the ‘Precision Observations Infant Supernova Explosions’ (POISE) project, starting less than 2 d after explosion. Given its intermediate luminosity, fast evolution, quick transition to nebular phase with spectra dominated [Ca ii] lines, SN belongs small family Calcium-rich transients. Moreover, it shows double-peaked light curves, a phenomenon shared only four other...
We introduce the Hawai'i Supernova Flows project and present summary statistics of first 1,217 astronomical transients observed, 668 which are spectroscopically classified Type Ia Supernovae (SNe Ia). Our is designed to obtain systematics-limited distances SNe while consuming minimal dedicated observational resources. To date, we have performed almost 5,000 near-infrared (NIR) observations obtained spectra for over 200 host galaxies lacking published spectroscopic redshifts. In this survey...