ORCID Profile
0000-0001-9171-5236
Current Organisation
San Diego State University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Astronomical Society
Date: 02-2021
Abstract: Some supernovae, such as pair-instability supernovae, are predicted to have a duration of more than a year in the observer frame. To constrain the rates of supernovae lasting for more than a year, we conducted a long-term deep transient survey using Hyper Suprime-Cam (HSC) on the 8.2 m Subaru telescope. HSC is a wide-field (a 1.75 deg 2 field-of-view) camera and it can efficiently conduct transient surveys. We observed the same 1.75 deg 2 field repeatedly using the g- , r- , i- , and z- band filters with the typical depth of 26 mag for four seasons (from late 2016 to early 2020). Using these data, we searched for transients lasting for more than a year. Two supernovae were detected in two continuous seasons, one supernova was detected in three continuous seasons, but no transients lasted for all four seasons searched. The discovery rate of supernovae lasting for more than a year with the typical limiting magnitudes of 26 mag is constrained to be . All the long-lasting supernovae we found are likely Type IIn supernovae and our results indicate that about 40% of Type IIn supernovae have long-lasting light curves. No plausible pair-instability supernova candidates lasting for more than a year are discovered. By comparing the survey results and survey simulations, we constrain the luminous pair-instability supernova rate up to z ≃ 3 is of the order of 100 Gpc −3 yr −1 at most, which is 0.01–0.1% of the core-collapse supernova rate.
Publisher: American Astronomical Society
Date: 04-2021
Abstract: We observed the episodically active asteroid (6478) Gault in 2020 with multiple telescopes in Asia and North America and found that it is no longer active after its recent outbursts at the end of 2018 and the start of 2019. The inactivity during this apparition allowed us to measure the absolute magnitude of Gault of H r = 14.63 ± 0.02, G r = 0.21 ± 0.02 from our secular phase-curve observations. In addition, we were able to constrain Gault’s rotation period using time-series photometric lightcurves taken over 17 hr on multiple days in 2020 August, September, and October. The photometric lightcurves have a repeating ≲0.05 mag feature suggesting that (6478) Gault has a rotation period of ∼2.5 hr and may have a semispherical or top-like shape, much like the near-Earth asteroids Ryugu and Bennu. The rotation period of ∼2.5 hr is near the expected critical rotation period for an asteroid with the physical properties of (6478) Gault, suggesting that its activity observed over multiple epochs is due to surface mass shedding from its fast rotation spin-up by the Yarkovsky–O’Keefe–Radzievskii–Paddack effect.
Publisher: American Astronomical Society
Date: 08-2021
Publisher: American Astronomical Society
Date: 15-09-2020
Publisher: American Astronomical Society
Date: 18-03-2019
Publisher: American Astronomical Society
Date: 04-09-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-12-2017
Abstract: The gravitational wave event GW170817 was caused by the merger of two neutron stars (see the Introduction by Smith). In three papers, teams associated with the GROWTH (Global Relay of Observatories Watching Transients Happen) project present their observations of the event at wavelengths from x-rays to radio waves. Evans et al. used space telescopes to detect GW170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. Hallinan et al. describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. Kasliwal et al. present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths. Science , this issue p. 1565 , p. 1579 , p. 1559 see also p. 1554
Publisher: American Astronomical Society
Date: 18-03-2019
Publisher: American Astronomical Society
Date: 17-06-2020
Publisher: American Astronomical Society
Date: 02-2022
Abstract: Massive stars play critical roles for the reionization of the universe. In idual massive stars at the reionization epoch ( z 6) are too faint to observe and quantify their contributions to reionization. Some massive stars, however, explode as superluminous supernovae (SLSNe) or pair-instability supernovae (PISNe) that are luminous enough to observe even at z 6 and allow for the direct characterization of massive star properties at the reionization epoch. In addition, hypothetical long-sought-after PISNe are expected to be present preferentially at high redshifts, and their discovery will have a tremendous impact on our understanding of massive star evolution and the formation of stellar mass black holes. The near-infrared Wide Field Instrument on the Nancy Grace Roman Space Telescope will excel at discovering such rare high-redshift supernovae. In this work, we investigate the best survey strategy to discover and identify SLSNe and PISNe at z 6 with Roman. We show that the combination of the F158 and F213 filters can clearly separate both SLSNe and PISNe at z 6 from nearby supernovae through their colors and magnitudes. The limiting magnitudes are required to be 27.0 mag and 26.5 mag in the F158 and F213 filters, respectively, to identify supernovae at z 6. If we conduct a 10 deg 2 transient survey with these limiting magnitudes for five years with a cadence of one year, we expect to discover 22.5 ± 2.8 PISNe and 3.1 ± 0.3 SLSNe at z 6, depending on the cosmic star formation history. The same survey is estimated to discover 76.1 ± 8.2 PISNe and 9.1 ± 0.9 SLSNe at 5 z 6. Such a supernova survey requires the total observational time of approximately 525 hr in five years. The legacy data acquired with the survey will also be beneficial for many different science cases including the study of high-redshift galaxies.
Publisher: American Astronomical Society
Date: 11-02-2021
Publisher: American Astronomical Society
Date: 12-12-2014
No related grants have been discovered for Robert Quimby.