Lund Observatory

department of Astronomy and Theoretical Physics

Seminars at Lund Observatory

Astronomy seminars are given in English. They are open to all, but aimed at an audience with basic knowledge in astrophysics. Unless otherwise noted, seminars take place on Thursdays 14:15 in Lundmarksalen.

Spring 2018


PhD seminars

2018-01-25 Mirek Giersz
Black holes in stellar clusters
2018-02-01 Jayne Birkby
New frontiers in exoplanet characterisation
Exoplanet characterization is undergoing a rapid evolution, especially in the study of exoplanet atmospheres. I will discuss the very latest results from both space and ground-based observations and highlight how they are helping us to understand exoplanet origins and diversity. I will focus part of my talk on high-resolution spectroscopy, which is a robust and powerful tool in exoplanet characterization. It uses changes in the Doppler shift of a planet to disentangle its spectrum from the glare of its host star. The technique is sensitive to the depth, shape, and position of a planet’s spectral lines, and thus reveals information about the planet’s composition, atmospheric structure, mass, global wind patterns, and rotation. I will present MEASURE: the MMT Exoplanet Atmosphere SURvEy. This 40 night survey is the largest high-resolution study of exoplanet atmospheres to date. It contains spectra of exoplanets from hot Jupiters to warm Neptunes, both transiting and non-transiting, observing both their dayside and nightside thermal emission. I will describe the survey and present some of its exciting preliminary results. The survey not only enables a homogenous dataset to perform comparative exoplanetology, but provides complementary high-resolution spectra for exoplanets observed with HST and Spitzer. The combination of high- and low-resolution spectroscopy can provide stringent constraints on planet metallicity and C/O ratios, and signifies the next step in the detailed characterization of exoplanet atmospheres.

The Dynamical Universe for ALL

2018-02-08 Beibei Liu
Understanding the formation and evolution of super-Earth planets
Disk migration theory predicts that super-Earth planets would end up at resonance. However, the Kepler mission has found that the period ratios of these planets do not show strong pile-ups near mean motion resonances (MMRs). Here I explain a mechanism, magnetospheric rebound that can rearrange the orbits of the resonant planets during the disk dispersal phase. We conduct N-body simulations of two-planet systems and investigate under which conditions planets can escape resonances. Meanwhile, I will present a possible scenario for the formation of TRAPPIST-1. The system contains a 0.08 solar-mass star and 7 Earth planets within 0.1AU. In our scenario, planetesimal is formed at the snow line by streaming instabilities. Further mass growth is lead by efficient accretion of mm to cm-size pebbles that drifted from the outer disk. In this way, the disk solid mass is able to efficiently transferred into the planet masses.
2018-02-15 Ariel Goobar
Cosmic transparency and the dimming of standard candles
Accurate accounting for the dimming of light along the line of sight for distant sources is of great importance in astronomy. Furthermore, it is an essential step in the measurements of cosmological distances used to probe the cosmic composition. In spite of the great success in the last two decades in the use of Type Ia supernovae to measure the properties of the accelerating universe, understanding the wavelength dependence of the extinction in the supernova host galaxies has remained elusive. I will explain why this has been a puzzle and present a possible solution. A measurement of the transparency of the intergalactic medium will be discussed
2018-02-22 Marie Martig
Liverpool John Moores University
The structure of galactic thick disks
ATP talk
Wed. 15:15
Johanna Larsson
How does the culture of physics affect physics teacher education?

COMPUTE Winter meeting

2018-03-08 Fabio Antonini
University of Surrey
Nuclear clusters and (supermassive) black holes
ATP talk
Wed. 15:15
Johan Thoren
Colors in QCD
2018-03-15 Hiranya Peiris
Towards fundamental physics from cosmological surveys
Wed. 14:15
Gillian Nave
Spectra of Th/Ar and U/Ne hollow cathode lamps for spectrograph calibration
PhD defence, 09:00
Asli Pehlivan Rhodin
Experimental and computational atomic spectroscopy for astrophysics
COMPUTE seminar Mon. 14:15
Martin Turbet
Exploring the diversity of planetary atmospheres with Global Climate Models
More than 50 years ago, scientists created the first Global Climate Models (GCMs) to study the atmosphere of the Earth. Since then, the complexity and the level of realism of these models (that can now include the effect of oceans, clouds, aerosols, chemistry, vegetation, etc.) have considerably increased. The large success of these models have recently motivated the development of an entire family of GCMs designed to study extra-terrestrial environments in our solar system (Venus, Mars, Titan, Pluto) and even beyond (extrasolar planets).
I will first show various GCM applications on Venus, Mars, Titan and Pluto. Solar system GCMs successes and sometimes failures teach us useful lessons to investigate and possibly predict the possible climates on planets where no (or almost no) observations are available. I will then present several examples of studies recently performed using a 'generic' Global Climate Model developed at the Laboratoire de Météorologie Dynamique in Paris, designed to explore the possible atmospheres and the habitability of ancient planets or extrasolar planets.
Wed. 14:15
Ivan Minchev
AIP, Potsdam
Semi-empirical estimation of stellar birth radii and the time evolution of the Milky way ISM abundance gradients
Licenciate defence, Thursday 10:00
Iryna Kushniruk
Searching for kinematic structures in the Solar neighbourhood
ATP talk
Wed. 15:15
Holly Capelo
Fluid instability in the particle stream of a dilute-gas flow: experiments in connection with planetesimal formation
Abstract: For the past half century, the origin of planetary precursor bodies - planetesimals- has remained an open and challenging question. Breakthrough theoretical studies have established that particle-gas-drag induced fluid instabilities are an efficient way to concentrate solid particles in the process of planet formation. I will introduce an experimental facility that was designed to provide the first empirical tests of whether such fluid instabilities exist and if they are as robust as numerical simulations suggest that they should be. I will present experimental results demonstrating evidence for a fluid instability in a low-pressure dust-gas mixture.

Bayes Day meeting

Nik Piskunov
How to get a transmission spectrum of an exoplanet from observations?
Abstract: Extracting a transmission spectrum from observations is not easy. The projected area of a planetary atmosphere on its host star is small while the S/N of individual observations is limited by the planet motion. I will present possible methodology and a few numerical and real data tests supporting feasibility of such measurements with soon-available ground- and space-based instruments.
Lennart Lindegren
Gaia DR2
Wed. 10:30
Christine Borgman
The durability and fragility of knowledge infrastructures: lessons learned from astronomy
Abstract: Infrastructures are not inherently durable or fragile, yet all are fragile over the long term. Durability requires care and maintenance of individual components and the links between them. Astronomy is an ideal domain in which to study knowledge infrastructures, due to its long history, transparency, and accumulation of observational data over a period of centuries. This talk draws upon a long-term study of scientific data practices to ask questions about the durability and fragility of infrastructures for data in astronomy. Methods include interviews, ethnography, and document analysis. As astronomy has become a digital science, the community has invested in shared instruments, data standards, digital archives, metadata and discovery services, and other relatively durable infrastructure components. Several features of data practices in astronomy contribute to the fragility of that infrastructure. These include different archiving practices between ground- and space-based missions, between sky surveys and investigator-led projects, and between observational and simulated data. Infrastructure components are tightly coupled, based on international agreements. However, the durability of these infrastructures relies on much invisible work – cataloging, metadata, and other labor conducted by information professionals. Our research in astronomy seeks general lessons for science in the stewardship of data and the sustainability of knowledge infrastructures.
COMPUTE seminar Tue 10:30
Alice Quillen
Astro-viscoelastodynamics or Soft Astronomy: Tidal encounters, tidal evolution and spin dynamics
Abstract: Mass spring models, originally developed for graphics and gaming applications, can measure remarkably small deformations while conserving angular momentum. By combining a mass spring model with an N-body simulation, we simulate tidal spin down of a viscoelastic moon, directly tying simulated rheology to orbital drift and internal heat generation. I describe a series of applications of mass spring models in planetary science. Close tidal encounters among large planetesimals and moons were more common than impacts. Tidal encounters can induce sufficient stress on the surface to cause large scale brittle failure of an icy crust. Strong tidal encounters may be responsible for the formation of long chasmata in ancient terrain of icy moons such as Dione and Charon. The new Horizons mission discovered that Pluto and Charon’s minor satellites Styx, Nix, Kerberos, and Hydra, are rapidly spinning, but surprisingly they have spin axis tilted into the orbital plane (they have high obliquities). Simulations of the minor satellites in a drifting Pluto-Charon binary system exhibit rich resonant spin dynamics, including spin-orbit resonance capture, tumbling resonance and spin-binary resonances. We have found a type of spin-precession mean-motion resonance with Charon that can lift obliquities of the minor satellites in the Pluto/Charon system.
ATP talk
Wed. 15:15
Najmeh Abiri
"Nothing" better exists with deep learning

Kallen symposium: Exoplanets towards the future

Master seminar
Mon. 09:15
Erik Dahlof
Master seminar
Mon. 11:15
Linn Eriksson
Master seminar
Mon. 14:15
Maria Lomaeva
Master seminar
Tue. 13:15
Sofia Savvidou
Master seminar
Tue. 15:15
Eric Andersson
Dave Armstrong
Circumbinary planets: detection and populations
Jon Holtzman
New Mexico State University
Chemical Cartography of the Milky Way Disk with SDSS/APOGEE
Abstract: The SDSS Apache Point Observatory Galactic Evolution Experiment (APOGEE) has collected high resolution near-IR spectra of several hundred thousand stars across the Milky Way. I'll describe some observational results about the spatial variation of chemical abundances as a function of Galactocentric radius and distance from the midplane, discussing mean abundances, metallicity distribution function, and the variation of abundance ratios of multiple elements. Additional information related to stellar ages can be obtained from [C/N] for red giant stars. Several lines of evidence suggest that radial migration has had a significant impact on the Galactic disk.
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