Amy Lien
NASA Goddard Space Flight Center
University of Maryland, Baltimore County
Code 661, Swift/BAT team
Office: Building 34, S225
Email: amy.y.lien at nasa.gov
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Gamma-ray bursts
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The Swift/BAT GRB Catalog
The Neil Gehrels Swift Observatory was launched in Nov. 20, 2004. The Burst Alert Telescope (BAT) onboard Swift has detected more than 1200 Gamma-ray Bursts (GRBs), of which about 1/3 of GRBs have redshift measurements, ranging from z = 0.03 to z = 9.38. We present the analyses of the BAT-detected GRBs for the past ~11 years up through GRB 151027B in the third Swift/BAT GRB catalog. The result summaries and data products are available at the public website: The Swift/BAT GRB Catalog, which is continued to be updated with recent bursts.
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The Swift/BAT Trigger Simulator
In order to maximize the number of GRB detections, the Swift Burst Alert Telescope (BAT) adopts a complex trigger algorithm. Swift has over 500 trigger criteria based on photon count rate and an additional image threshold for localization. To investigate possible systematic biases and explore the intrinsic GRB properties, we develop a script that is capable of simulating all the rate trigger criteria and mimicking the image threshold. We have used this "trigger simulator" to estimate the long GRB rate at high redshift and explore their connection with the cosmic star-formation history. We also use the trigger simulator to examine the detectability of other transients, such as short GRBs, high redshift GRBs, ultra-long GRBs, Fast Radio Bursts (FRBs), and the gravitational wave event GW170817.
- The trigger simulator code is available
here
- The paper about this trigger simulator is available here
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Forecasts of Core-Collapse Supernova detections for Future Surveys
My graduate study with Prof. Brian Fields focuses on detailed forecasting of core-collapse supernova detections for major future surveys in both optical and radio wavelengths (e.g. LSST, DES, SKA). In addition, we explore science potentials of these potential detections, such as precision measurement of the cosmic supernova rate and the diffuse supernova neutrino background, and probing failed supernovae via multi-messenger observations.
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The Diffuse Gamma-Ray Background from Type Ia Supernovae
The origin of the diffuse extragalactic gamma-ray background (EGB) has been intensively studied but remains unsettled. Current popular source candidates include unresolved star-forming galaxies, starburst galaxies, and blazars. We calculate the EGB contribution from the interactions of cosmic rays accelerated by Type Ia supernovae (SNe), extending earlier work that only included core-collapse SNe. Our updated EGB estimate continues to show that star-forming galaxies can represent a substantial portion of the signal measured by Fermi. In the case of quiescent galaxies, conversely, we find a wide range of possibilities for the EGB contribution.