B. J. Shappee
A5034783890- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Nuclear Physics and Applications
- Superconducting Materials and Applications
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Particle Detector Development and Performance
- Particle accelerators and beam dynamics
- Advanced X-ray and CT Imaging
- Geological and Geophysical Studies
- Crystal Structures and Properties
- Radio Astronomy Observations and Technology
- Nuclear reactor physics and engineering
University of Hawaii System
2017-2024
University of Hawaiʻi at Mānoa
2019-2024
Norfolk State University
2023
University of Hawaii–West Oahu
2023
The Ohio State University
2012-2021
Carnegie Observatories
2015-2020
Carnegie Institution for Science
2015-2020
Las Cumbres Observatory Global Telescope Network
2017
Seikei University
2014
After the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered a significant brightening of inner region NGC 2617, we began ~70 day photometric and spectroscopic monitoring campaign from X-ray through near-infrared (NIR) wavelengths. We report that 2617 went dramatic outburst, during which its flux increased by over an order magnitude followed increase optical/ultraviolet (UV) continuum almost magnitude. classified as Seyfert 1.8 galaxy in 2003, is now 1 due to appearance broad...
The All-Sky Automated Survey for Supernovae (ASAS-SN) is working toward imaging the entire visible sky every night to a depth of mag. present data covers and spans ∼2–5 years with ∼100–400 epochs observation. should contain some ∼1 million variable sources, ultimate goal have database these observations publicly accessible. We describe here first step, simple but unprecedented web interface https://asas-sn.osu.edu/ that provides an up date aperture photometry light curve any user-selected...
On 2017 August 17, gravitational waves were detected from a binary neutron star merger, GW170817, along with coincident short gamma-ray burst, GRB170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, and infrared light curves SSS17a extending 10.9 hours to 18 days post-merger. constrain radioactively-powered resulting ejection neutron-rich material. The fast rise curves, subsequent...
On 2017 August 17, the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo interferometer detected gravitational waves emanating from a binary neutron star merger, GW170817. Nearly simultaneously, Fermi INTEGRAL telescopes gamma-ray transient, GRB 170817A. 10.9 hours after wave trigger, we discovered transient fading optical source, Swope Supernova Survey 2017a (SSS17a), coincident with SSS17a is located in NGC 4993, an S0 galaxy at distance of 40 megaparsecs. The precise...
The All-Sky Automated Survey for Supernovae (ASAS-SN) is the first optical survey to routinely monitor whole sky with a cadence of $\sim2-3$ days down V$\lesssim17$ mag. ASAS-SN has monitored since 2014, collecting $\sim100-500$ epochs observations per field. V-band light curves candidate variables identified during search supernovae are classified using random forest classifier and visually verified. We present catalog 66,179 bright, new variable stars discovered our supernovae, including...
On 2017 August 17, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of binary neutron star gravitational wave event GW170817. We report time-series spectroscopy SSS17a from 11.75 hours until 8.5 days after merger. Over first hour observations ejecta rapidly expanded and cooled. Applying blackbody fits to spectra, we measure photosphere cooling $11,000^{+3400}_{-900}$ K $9300^{+300}_{-300}$ K, determine a photospheric velocity roughly 30% speed light. The...
We present ground-based and Swift photometric spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at center PGC 043234 ($d\simeq90$ Mpc) by All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity $L\simeq10^{44}$ ergs s$^{-1}$ total integrated energy $E\simeq7\times10^{50}$ radiated over $\sim6$ months presented. UV/optical emission is well-fit blackbody with roughly constant temperature $T\sim35,000$ K, while...
ASASSN-14ae is a candidate tidal disruption event (TDE) found at the center of SDSS J110840.11+340552.2 ($d\simeq200$~Mpc) by All-Sky Automated Survey for Supernovae (ASAS-SN). We present ground-based and Swift follow-up photometric spectroscopic observations source, finding that transient had peak luminosity $L\simeq8\times10^{43}$~erg~s$^{-1}$ total integrated energy $E\simeq1.7\times10^{50}$ ergs radiated over $\sim5$ months presented. The blackbody temperature remains roughly constant...
Photons from a gravitational wave event Two neutron stars merging together generate signal and have also been predicted to emit electromagnetic radiation. When the GW170817 was detected, astronomers rushed search for source using conventional telescopes (see Introduction by Smith). Coulter et al. describe how One-Meter Two-Hemispheres (1M2H) collaboration first locate source. Drout present 1M2H measurements of its optical infrared brightness, Shappee report their spectroscopy event, which is...
We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as most luminous supernova yet found. At redshift z = 0.2326, reached an absolute magnitude M_{u,AB} -23.5+/-0.1 and bolometric luminosity L_bol (2.2+/-0.2)x 10^45 ergs s^-1, is more than twice any previously known supernova. It has several major features characteristic hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources progenitors are currently poorly understood. In contrast to SLSNe-I that reside in...
We present the ATLAS discovery and initial analysis of first 18 days unusual transient event, ATLAS18qqn/AT2018cow. It is characterized by a high peak luminosity ($\sim$1.7 $\times$ 10$^{44}$ erg s$^{-1}$), rapidly evolving light curves ($>$5 mag rise to in $\sim$3.5 days), hot blackbody spectra, peaking at $\sim$27000 K that are relatively featureless unchanging over two weeks. The bolometric curve cannot be powered radioactive decay under realistic assumptions. detection high-energy...
The variable stars in the VSX catalog are derived from a multitude of inhomogeneous data sources and classification tools. This inhomogeneity complicates our understanding star types, statistics, properties, it directly affects attempts to build training sets for current (and next) generation all-sky, time-domain surveys. We homogeneously analyze ASAS-SN V-band light curves ${\sim}412,000$ variables catalog. classified using an updated random forest classifier with $F_1$ score 99.4\%...
We present velocity-resolved reverberation results for five active galactic nuclei. recovered velocity-delay maps using the maximum-entropy method four objects: Mrk 335, 1501, 3C120, and PG2130+099. For fifth, 6, we were only able to measure mean time delays in different velocity bins of Hbeta emission line. The show unique dynamical signatures each object. Balmer lines kinematic consistent with both an inclined disk infalling gas, but HeII 4686 line is suggestive inflow. PG 2130+099 signs...
We present multi-wavelength observations that trace more than 40 years in the life of active galactic nucleus (AGN) Mrk 590, traditionally known as a classic Seyfert 1 galaxy. From spectra recently obtained from HST, Chandra, and Large Binocular Telescope, we find activity 590 has diminished so significantly continuum luminosity is factor 100 lower peak probed by our long baseline observations. Furthermore, broad emission lines, once prominent UV/optical spectrum, have all but disappeared....
We accurately determine a new Cepheid distance to M101 (NGC 5457) using archival Hubble Space Telescope (HST)/Advanced Camera for Surveys V and I time series photometry of two fields within the galaxy. make slight modification ISIS image subtraction package obtain optimal differential light curves from HST data. discovered 827 Cepheids with periods between 3 80 days, largest extragalactic sample observed by factor two. With this large sample, we find that relative Large Magellanic Cloud is...
We present the results from a detailed analysis of photometric and spectrophotometric data on five Seyfert 1 galaxies observed as part recent reverberation mapping program. The were collected at several observatories over 140 day span beginning in 2010 August ending 2011 January. obtained high sampling-rate light curves for Mrk 335, 1501, 3C 120, 6, PG 2130+099, which we have measured time lag between variations 5100 Å continuum Hβ broad emission line. then used these measurements to...
We present ground-based and Swift photometric spectroscopic observations of the tidal disruption event (TDE) ASASSN-15oi, discovered at centre 2MASX J20390918−3045201 (d ≃ 216 Mpc) by All-Sky Automated Survey for SuperNovae. The source peaked a bolometric luminosity L 1.3 × 1044 erg s−1 radiated total energy E 6.6 1050 over first ∼3.5 months observations. early optical/UV emission can be fit blackbody with temperature increasing from T ∼ 2 104 K to 4 while declines 2.3 1043 s−1, requiring...
Using a sample of high-redshift lensed quasars from the CASTLES project with observed-frame ultraviolet or optical and near-infrared spectra, we have searched for possible biases between supermassive black hole (BH) mass estimates based on C iv, Hα, Hβ broad emission lines. Our is upon that Greene, Peng, & Ludwig, expanded new near-IR spectroscopic observations, consistently analyzed high signal-to-noise ratio (S/N) consistent continuum luminosity at 5100 Å. We find BH full width...
We present observations of SN 2015bn (= PS15ae = CSS141223-113342+004332 MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift $z=0.1136$. As well as being one the closest SLSNe yet discovered, it is intrinsically brighter ($M_U\approx-23.1$) and in fainter galaxy ($M_B\approx-16.0$) than other $z\sim0.1$. used this opportunity to collect most extensive dataset for any SLSN date, including densely-sampled spectroscopy photometry, from UV NIR, spanning $-$50 +250 days...
Over a broad range of initial inclinations and eccentricities, an appreciable fraction hierarchical triple star systems with similar masses are essentially unaffected by the Kozai–Lidov mechanism (KM) until primary in central binary evolves into compact object. Once it does, may be much less massive than other components ternary, enabling "eccentric Kozai (EKM)": mutual inclination between inner outer binaries can flip signs driving to very high eccentricity, leading close or collision. We...
Kozai-Lidov (KL) oscillations can accelerate compact object mergers via gravitational wave (GW) radiation by driving the inner binaries of hierarchical triples to high eccentricities. We perform direct three-body integrations mass ratio triple systems using Fewbody including post-Newtonian terms. find that binary undergoes rapid eccentricity (REOs) on timescale outer orbital period which drive it higher eccentricities than secular theory would otherwise predict, resulting in substantially...
The All-Sky Automated Survey for Supernovae (ASAS-SN) provides long baseline (${\sim}4$ yrs) light curves sources brighter than V$\lesssim17$ mag across the whole sky. Transiting Exoplanet Satellite (TESS) has started to produce high-quality with a of at least 27 days, eventually most combination ASAS-SN and TESS probes both short term variability in great detail, especially towards continuous viewing zones (CVZ) ecliptic poles. We have produced ${\sim}1.3$ million V-band covering total...
Abstract The merging neutron star gravitational-wave event GW170817 has been observed throughout the entire electromagnetic spectrum from radio waves to γ -rays. resulting energetics, variability, and light curves are shown be consistent with originating merger of two stars, in all likelihood followed by prompt gravitational collapse massive remnant. available -ray, X-ray, data provide a clear probe for nature relativistic ejecta non-thermal processes occurring within, while ultraviolet,...
Abstract We present the discovery and validation of a three-planet system orbiting nearby (31.1 pc) M2 dwarf star TOI-700 (TIC 150428135). lies in TESS continuous viewing zone Southern Ecliptic Hemisphere; observations spanning 11 sectors reveal three planets with radii ranging from 1 R ⊕ to 2.6 orbital periods 9.98 37.43 days. Ground-based follow-up combined diagnostic vetting tests enables us rule out common astrophysical false-positive scenarios validate planets. The outermost planet, d,...