Scientific workflow in astrophysics
White dwarfs in open clusters
Ernst Paunzen
&
Michal Prisegen
2019
● Over 99% of stars will eventually end up as white dwarfs
(WDs)
● Many interesting properties: mainly from degenerate
matter, cool in a very predictable way
Credit:
Kalirai (2000)
C/O core WD atmosphere (H or He, 10-14
Msun
)
R scales with M-1/3
Mass: less than 1.44 Msun
(majority around 0.6 Msun
)
Radius: about 104
km
g: 106
m/s2
Escape speed: 0.02 c
Althaus+ (2010)
Credit: ESA/Gaia/DPAC
No. of Wds known:
Y 1999: ~2000 objects
Y 2017: > 30 000 (just before Gaia DR2)
Y 2019: ~ 260 000 (Gaia DR2)
Future: 13*106
(LSST)
Possible science
● Refinement of Teff and log(g) values for the catalog
WDs when matched to a cluster (more precise
distance and reddening for clusters than in the field)
● Are WDs retained in the clusters? Are they hidden
in binaries?
● Statistics: No. of WDs as a function of cluster
parameters (age, mass...)
● Mass determination via gravitational redshift
(Hyades; Pasquini+ 2019)
Supernovae
Heger+ (2003)
● How massive are stars still forming WDs?
● Tlif = Tcluster – Tcooling →stellar progentior mass
● Detection of neutron star binaries and single massive WDs in
clusters with a turn-off mass of about 10 Msun would provide a
direct evidence for multiple supernova channels
Richer+ (2019)
Where does the
boundary between the
neutron stars and
Wds lie? Potentially
massive effects
affecting large area of
astrophysics!
Salaris & Bedin (2019)
Preliminary workflow
● Use the catalog of open clusters and white dwarfs, match
them together based on positional, astrometric and distance
criteria.
● Validate the white dwarfs against the open clusters
● Compute the white dwarfs and cluster parameters (e.g. mass
of the progenitor, cooling age, etc.)
● Address other science cases using the catalog (if possible…)
● Write the paper. Everyone should contribute to a section of
the paper based on one’s expertise.
● Submit the paper, respond to the referee’s comments
Preliminary plan for the semester
● We are flexible!
● Weekly pitch, lectures or hands-on sessions
about selected aspects of the science case or
analysis
● Begin to write the paper draft in ~early
November, submitting it before the end of the
semester