Time domain astronomy was revolutionized with the discovery of the first kilonova, AT2017gfo, in August 2017, which was associated with the gravitational wave signal GW170817. Since this event, numerous wide-field surveys have been optimizing search strategies to maximize their efficiency of detecting these fast and faint transients. With the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), we have been conducting a volume-limited survey for intrinsically faint and fast-fading events to a distance of D ≃ 200 Mpc. Two promising candidates have been identified from this archival search, with sparse data - PS15cey and PS17cke. Here, we present more detailed analysis and discussion of their nature. We observe that PS15cey was a luminous, fast-declining transient at 320 Mpc. Models of BH-NS mergers with a very stiff equation of state could possibly reproduce the luminosity and decline but the physical parameters are extreme. A more likely scenario is that this was an AT2018kzr-like merger event. PS17cke was a faint and fast-declining event at 15 Mpc. We explore several explosion scenarios of this transient including models of it as a NS-NS and BH-NS merger, the outburst of a massive luminous star, and compare it against other known fast-fading transients. Although there is uncertainty in the explosion scenario due to difficulty in measuring the explosion epoch, we find PS17cke to be a plausible kilonova candidate from the model comparisons.
Bibliographical noteFunding Information:
This work has made use of the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. ATLAS is primarily funded to search for near-earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogues from the survey area. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen’s University Belfast, and the Space Telescope Science Institute.
The discoveries from this program are a byproduct of the Pan-STARRS NEO survey observations. Operation of the Pan-STARRS1 and Pan-STARRS2 telescopes is primarily supported by the National Aeronautics and Space Administration (NASA) under grant no. NNX12AR65G and grant no. NNX14AM74G issued through the SSO Near Earth Object Observations Program.
SJS, KWS, and DRY acknowledge funding from the Science and Technology Facilities Council (STFC) grant ref: ST/P000312/1 and ST/S006109/1. CB acknowledges support from the Instituto Nazionale di Fisica Nucleare (INFN), under the Virgo-Prometeo initiative. MG is supported by the Polish NCN MAESTRO grant 2014/14/A/ST9/00121. MF is supported by a Royal Society – Science Foundation Ireland University Research Fellowship. MN is supported by a Royal Astronomical Society Research Fellowship. KM acknowledges support from the European Research Council (ERC) Starting grant no. 758638. TWC acknowledges the EU Funding under Marie Skłodowska-Curie grant agreement no. 842471. TW is funded by ERC grant 320360 and by European Commission grant 730980. TMB was funded by the CONICYT PFCHA/DOCTORADOBECAS CHILE/2017-72180113. FOE acknowledges support from the FONDECYT grant no. 1201223.
The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg, and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under grant no. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation grant no. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. ePESSTO observations were obtained under the European Southern Observatory (ESO) program ID 1103.D-0328 and 199.D-0143 (PI: Smartt). ePESSTO + observations were obtained under ESO program ID 1103.D-0328 (PI: Inserra). SALT:RSS observations were obtained under program ID 2016-1-MLT-007 (PI: Jha).
© 2020 The Author(s).
Copyright 2020 Elsevier B.V., All rights reserved.
- Black hole - neutron star mergers
- Supernovae: General
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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Supervisor: Smartt, S. (Supervisor) & Maguire, K. (Supervisor)
Student thesis: Doctoral Thesis › Doctor of PhilosophyFile