Gaia DR1 + Pan-STARRS DR1
Magnier
City of London
Award-winning creative studio Play Nice spearheaded the project in partnership with London-based property developer Dominvs Group to platform the ideas of
The white dwarf mass-radius relation with Gaia Hubble and FUSE
Strong gravitational field causes broadening of the hydrogen lines. The value of log g is found by fitting a spectral model to the data. Nice 2017 Simon Joyce
Astrometry and Astrophysics in the Gaia Sky
Nice France. International Astronomical Union. ISSN 1743-9213 ngs of the ational ical Union. U osium. 330 ril 2017 ance rometry and trophysics he Gaia Sky.
Gaia Photometric Data: DR1 results and DR2 expectations
Apr 28 2017 IAUS 330 @ Nice
Gaia Garden is located in a quiet side road in Lambi area a few
gardens nicely decorated with a traditional Greek style. Gaia Village is a three star hotel ... a nice designed lobby and several two storey buildings.
Year Name Title Institute(s) Country Supervisor(s) Bibcode 2019
Gaia era. Department of. Astronomy. University of. Geneva. Switzerland. Laurent Eyer
How to make sure Gaia is not a God of Totality? with special
It's pretty standard to use the adjective “Alive” right? So Gaia-Alive does not say what it means to be alive
The white dwarf mass-radius relation
with Gaia, Hubble and FUSE https://filmentropy.wordpress.com/Simon Joyce 3rd year PhDSupervisors
Martin Barstow
Sarah Casewell
Jay Holberg (University of
Arizona)
Howard Bond (Pennsylvania
State University)srgj1@le.ac.uk
Why are white dwarfs interesting?
Natural laboratory for physics in
a high gravity environmentPotential to study the elemental composition of exoplanet systems.Cosmochronology : Using the temperature of a white dwarf to find its age, and the ages of associated stars.The initial-final mass relation and
chemical evolution of the galaxy. IFMR Material returned to ISMMass of starMass of white dwarfNice 2017 Simon Joyce White Dwarf Cosmochronology : Using the temperature of a white dwarf to find its age, and the ages of associated stars. Fontaine, Brassard, & Bergeron (2001, PASP, 113, 409)Nice 2017 Simon JoyceThe white dwarf mass-radius relation
Hamada & Salpeter 1961, ApJ, 134,683Nice 2017 Simon Joyce Refinements to the white dwarf mass-radius relationFontaine, Brassard, Bergeron, 2001, PASP, 113, 409Solid line = thick hydrogen layer, dashed line = thin hydrogen layerNice 2017 Simon Joyce
How to measure the mass of a white dwarf
The spectroscopic method
Figure from Bergeron et al 1992 ApJ, 394, 228Hubble spectrum of Balmer lines of Sirius BStrong gravitational field
causes broadening of the hydrogen lines.The value of log g is found by
fitting a spectral model to the data.Nice 2017 Simon JoyceWhy is the distance measurement so important?
Gaia parallax - distance
From spectral model
fitting:Normalisation
Log gNice 2017 Simon Joyce
How good are the pre-Gaia distance
measurements?Nice 2017 Simon JoyceThe advantages of Sirius-like binaries
How can Sirius-like binaries help?
: The initial Gaia data release (DR1) only contains parallaxes for a few WD's. : For Sirius-like binaries we can take the distance of the main sequence companion star to be the same as the distance for the WD. Many more of theseMS stars are included in DR1.
Barstow et al 2001, MNRAS, 322, 891WD in a multiple system resolved with HSTNice 2017 Simon JoyceThe benefits of Lyman lines
UV excess caused by
the white dwarf.Emission from the F6V main sequence stars. Burleigh, Barstow and Holberg 1998, MNRAS, 300, 511At the wavelength range of theLyman lines there is minimal
contamination from the main sequence companion.Balmer lines can only be used
if the WD can be resolved and an uncontaminated spectrum obtained.Nice 2017 Simon JoyceExample of Lyman and Balmer spectra for HZ43
FUSE Lyman line spectrum
HST Balmer line spectrumNice 2017 Simon Joyce
The Mass-Radius relation using Hipparcos parallaxesNice 2017 Simon Joyce The Mass-Radius relation using Gaia parallaxesNice 2017 Simon JoyceHow accurately can we expect to measure
distances in the future? For this sample, the average parallax error in DR1 is 0.39 mili arc sec.The final data release is expected to have parallax error of ~6.7 micro arc sec.Nice 2017 Simon Joyce
Conclusions and future plans
The distances from Gaia have removed much of the scatter in the observedmass-radius data and show that the overall form of the MRR is correct. The improved accuracy of the white dwarf distances in later data releases will
allows us to begin to truly test the theoretical mass-radius relation at an accuracy level where temperature and H layer thickness in the models can bedistinguished. The limiting factors contributing to uncertainty in the M-R mesurements are the
reliability of the spectral fitting and log g determination. A comparison of results from Lyman and Balmer lines shows that there may be
an unexplained systematic offset. It will be important to quantify the remaining sources of error and develop the
gravitaional redshift method to the required level of accuracy to take full advantage of the Gaia data. Nice 2017 Simon Joycequotesdbs_dbs1.pdfusesText_1[PDF] gain algébrique
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