SHAO Astrophysics Colloquia
Title: Models for Fast Radio Bursts and Future Astrophysical Tests
Speaker: Zigao Dai (Nanjing University)
Time: 3 PM, May 18th (Thursday)
Abstract:
Fast radio bursts (FRBs) are millisecond-duration flashes of coherent GHz radio emission of unknown physical origin. Most of them arise from high Galactic latitudes, but their inferred dispersion measures are much larger than expected for propagation through the cold plasma of our Galaxy and its halo, strongly suggesting that they are at cosmological distances. FRBs seem to fall into two classes: non-repeating and repeating. Only one repeating case discovered so far is FRB 121102. In my talk, I will review the recent progress of FRB studies and discuss some models for FRB's physical origin and future astrophysical tests in detail.
Seminar talk
Title: Electromagnetic Counterparts to Gravitational Wave Detections: Bridging the Gap between Theory and Observation
Speaker: Prof. Zachariah Etienne (West Virginia University)
Time: May 17 afternoon at 2 PM (Wednesday)
Location: Middle Conference Room (3rd floor)
Abstract:
LIGO has proven that gravitational waves (GWs) from black hole binary mergers are detectable, and we expect within years it will detect GWs from double neutron star and black hole--neutron star mergers as well. In the extreme violence of merger, intense tidal forces can become sufficient to rip the neutron star(s) apart, which can lead to significant electromagnetic (EM) emission. If detected, a coincident EM and GW observation could for the first time reveal the anatomy of a gamma-ray burst or kilonova and provide the deepest probe yet into the behavior and composition of degenerate nuclear matter. However, the scientific understanding gained from these observations will be limited by the accuracy of our theoretical modeling, which must fully account for the effects of general relativity. To this end, I will review the physics behind current numerical relativity (NR) simulations of these extreme merger events and preview the next generation of NR simulations, which will be capable of predicting not only gravitational wave timeseries with unprecedented accuracy, but also electromagnetic spectra.
Title: ESASky, ESA’s new science-driven portal for ESA space astronomy missions
Speaker: Bruno Merín (Astronomy Archives Science Lead at the European Space Astronomy Centre of ESA, near Madrid, in Spain)
Date: Wednesday, 17th May, 3pm
Location: 17th floor classroom
Abstract: ESASky is a new science-driven discovery portal for all ESA space astronomy missions (http://sky.esa.int). It also includes missions from international partners such as Suzaku, Chandra, and soon Spitzer. The first public release of ESASky features interfaces for sky exploration and for single and multiple target searches. Using the application requires no user registration, no prior-knowledge of any of the missions involved and gives users world-wide simplified access to high-level science-ready image data products and catalogues from INTEGRAL, XMM-Newton, Chandra, HST, Hipparcos, Gaia, ISO, Herschel and Planck. We will highlight the latest features developed, including one that allows the user to project onto the sky the footprints of the JWST instruments, at any chosen position and orientation to plan future observations and another that allows users to find solar system objects serendipitously observed by observatory missions. We will end by describing how the Chinese astronomical community can help shaping the future of this tool to maximize its usefulness for them.
Bio: Astronomer working as Astronomy Archives Science Lead at the ESAC Science Data Centre of ESA in Spain. Scientifically, he is interested in star and planet formation studies, mostly in transitional disks and large-scale statistics of disk evolution as compared with currently known statistics of exoplanet populations. For his functional work, he is interested in exploitation of the data from the Astronomy missions, scientific software, machine learning, astronomical archival research, usability of user interfaces and citizen science projects. (more info at his research site http://brunomerin.com)
Group meetings
Black hole Accretion and High-energy Astrophysics /Black Hole Feedback and Cosmic Ray Astrophysics Seminar
Location: 1608
Time: 14:00-16:00, Wednesday(May 17th)
Speaker: Quan Guo(郭铨)
In this talk, I willl discuss my previous works including: 1) The luminosity
functions, spatial distribution around isolated galaxies
measured from SDSS galaxy samples. 2) How these properties including angular
distribution of satellite galaxies depend on the large scale structure:
filaments 3)The lopsided distribution of satellites galaxy around galaxy pairs. 4)The
comparison of the general properties of model galaxies predicted by
Eagle (hydro simulation) and SA models (Galform, L-galaxies).
Galactic Dynamics Group Journal Club
Location:1608
Time: Thursday (May 18th)
Title: The Cannon and its application to the LAMOST and APOGEE surveys
Speaker: Iulia Simion
Abstract:
Recent years have seen the release of vast spectroscopic stellar surveys e.g., SEGUE, RAVE, LAMOST, APOGEE, Gaia-ESO, GALAH and soon Gaia. The Cannon (Ness et al. 2015) is a data driven approach that aims to bring qualitatively these surveys that use different instruments, operate at different wavelength regions at different resolutions and SNRs, onto a consistent stellar parameter and chemical abundance scale. The code learns from the `known' labels (e.g. Teff, log g, X/Fe) of reference stars how the spectra depend on these labels by fitting a model at each wavelength; then, The Cannon uses this model to derive labels for the remaining survey stars (or self-labeling, see Ness et al. 2015) or stars from a different survey (cross-calibration, see Ho et al. 2016, 2017). This process aims to make stellar parameter estimation and element abundance tagging more precise and consistent. In this talk I will present The Cannon's application to the APOGEE and LAMOST surveys.
References:
Ness et al. 2015 https://arxiv.org/pdf/1501.07604.pdf
Ho et al. 2016 https://arxiv.org/abs/1602.00303.pdf
Ho et al. 2017 https://arxiv.org/pdf/1609.03195.pdf
Visitors
Name: Prof. Paul Wiita
Affiliation: The College of New Jersey, USA
Dates: 19/04/2017-12/05/2017
Host: Prof. Minfeng Gu
Office: 1519