Seminar talk
Title: Fast Radio Bursts, GPUs, and the largest telescope in the Southern Hemisphere
Speaker: Dr. Chris Flynn(Swinburne University of Technology Hawthorn, Australia)
Time: TBD
Title: The Status of Las Campanas Observatory of Carnegie Institution and the Astronomy in Chile
Time: 3 PM, June 18 (Tuesday)
Speaker: Prof. Leopoldo Infante (Pontifical Catholic University of Chile & Las Campanas observatory of Carnegie Institution)
Location: Middle conference room, 3rd floor
Abstract: Prof. Infante would like to give an informal talk about the status of Las Campanas observatory of Carnegie Institution and the astronomy in Chile. He would also like to discuss the possible future collaborations between China (SHAO) and Chile (PUC and LCO).
Title: The purest brown dwarf & properties of low-mass celestial populations
Time: 10:30-11:30, July. 19
Place: middle conference room
Speaker: 张曾华 (ZengHua Zhang; Observatoire de Paris, PSL fellow)
Abstract:
The formation of sub-stars (often referred to as brown dwarfs) which are not massive enough to support steady nuclear reaction in their hearts were predicted in 1962. A few thousands of brown dwarfs have been discovered in the Galactic disk since 1995. However, very few halo brown dwarf candidates were reported.
I will present the discovery of an L type ultra subdwarf, SDSS J0104+15. Our analysis shows SDSS J0104+15 to be the most metal-poor and highest mass substellar object known to-date. SDSS J0104+15 is joined by another five L type extreme and ultra subdwarfs in a `halo brown dwarf transition zone’ in the Teff–[Fe/H] plane, which represents a narrow mass range in which unsteady nuclear fusion occurs. This halo brown dwarf transition zone forms a `substellar subdwarf gap’ for mid L to early T types.
In this talk, I will also try to clarify the difference between the following celestial populations: cool stars, brown dwarfs, and planets; red dwarfs, and ultracool dwarfs; low-mass stars, very low-mass stars, and substellar objects; dwarfs, subdwarfs, extreme subdwarfs, and ultra subdwarfs.
Paper: http://adsabs.harvard.edu/abs/2017MNRAS.468..261Z
RAS press:
http://www.ras.org.uk/news-and-press/2967-astronomers-identify-purest-most-massive-brown-dwarf
Group meetings and additional talks
Galactic Dynamics Group Journal Club
Title : Revisiting the Tale of Hercules: How Stars Orbiting the Lagrange Points Visit the Sun
Speaker: Yingying Zhou
Time:9:45 am, July 20th(Thursday)
reference: http://adsabs.harvard.edu/abs/2000AJ....119..800D
http://adsabs.harvard.edu/abs/2015MNRAS.450.4050W
http://adsabs.harvard.edu/abs/2017MNRAS.465.1621P
http://adsabs.harvard.edu/abs/2017ApJ...840L...2P
Abstract
The Hercules stream is an excess of stars with negative U velocities ( away from the Galactic center, GC) that also move
slower than the Sun's rotation velocity by V ∼ − 50 km s−1. Dehnen (2000) suggested that these stars reach the solar neighborhood (SNd) on orbits due to the Outer Lindblad resonance (OLR) of a short and fast Galactic bar. However, recent measurements show that the Galactic bar extends to 5.0 ± 0.2 kpc from the Galactic center (Wegg et al. 2015). Motivated by this, Pérez-Villegas et al. (2017) propose a novel explanation for the Hercules stream. Their model matches the 3D density of the red clump giant stars (RCGs) in the bulge and bar as well as stellar kinematics in the inner Galaxy. They find that the model naturally predicts a bimodality in the U–V-velocity distribution for nearby stars which is in good agreement with the Gaia DR1 TGAS, RAVE and LAMOST. In the model, the Hercules stream is made of stars orbiting the Lagrange points of the bar which move outward from the bar’s corotation radius to visit the SNd.
Visitors
Name: Prof. Leopoldo Infante
Affiliation: Pontifical Catholic University of Chile & Las Campanas Observatory of Carnegie Institution for Science
Dates: 17th-20th July
Host: Zhenya Zheng
Office: 1618
