Menu:

HKU Researcher Page: http://hub.hku.hk/cris/rp/rp01803

Research Projects

My most recent project involves working on gamma-ray pulsars, using Fermi-LAT data. In particular, I work on blind searches of LAT gamma-ray data. Prior to our work, no pulsar had ever been discovered in gamma rays, and only 6 pulsars were known to have GeV emission. In the first few months of our project, we discovered 16 new pulsars with the LAT and found that an additional 30 radio pulsars also emit gamma rays, including 8 milli-second pulsars. Our work was featured in the 14 August 2009 cover issue of Science. You can download our article on the discovery of the first 16 pulsars in blind searches of LAT data here. We have now passed the milestone of 100 gamma-ray pulsars! NASA celebrated this with a media teleconference. To learn about each and every one of these gamma-ray pulsars, you can click on this neat interactive page. I also work on using machine learning techniques to classify gamma-ray sources according to their likelihood of being pulsars. This is useful to find the best targets for our searches in all wavelengths (gamma, X-ray, and radio). Recently I completed a study on the LAT 3FGL catalog. You can have a look at the main scripts and results here.
Science Cover
As part of the Milagro collaboration, I also work on the Very High Energy (> 100 GeV) part of the spectrum. We recently analyzed 8 years of Milagro data looking for VHE emission from the brightest Fermi sources (mainly pulsars). Here is our most recent paper on this topic. Milagro map
I have also been heavily involved in the search for Very High Energy (> 100 GeV) emission from GRBs, using Milagro. One of the strengths of an all-sky instrument such as Milagro is that it has a very large field of view and duty cycle (much like Fermi), which allows for continuous observations of the northern hemisphere sky. Unfortunately, there have been no conclusive detections of emission in the Milagro energy range (100 GeV - 100 TeV), but in this paper, for instance, we placed the strongest constraints on the prompt VHE emission from short gamma-ray bursts (those lasting only a few seconds).
HAWC
The successor to Milagro is called HAWC and is nearing completion near the "Pico de Orizaba", Mexico. When fully operational, HAWC will be approximately 30 times more sensitive than Milagro. One of the projects I am currently pursuing with HAWC involves using pulsars to search for evidence of quantum gravity. You can read more about this project in this poster I presented at the HAWC inauguration, in March 2015 [click here for the Spanish version].