WHITE DWARF COOLING SEQUENCES

readme file

last modification: 22 Jun 2010

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We provide cooling tracks for WD masses equal to 0.51, 0.55, 0.61, 0.68, 0.77, 0.87 and 1.0 Mo, with He+H envelopes (DA) and He envelopes only (DB), respectively. The mass thickness of the envelopes is M(He)=10^-2 M(WD) and M(H)=10^-4 M(WD) for the DA models, and M(He)=10^-3.5 M(WD) for the DB models. For each choice of the WD mass and envelope composition (DA or DB) we provide cooling tracks that include phase separation upon crystallization, and tracks that neglect this process. The WD cooling tracks have been transposed to several photometric systems, i.e., Johnson-Kron-Cousins UBVRI, the 2MASS JHKs ACS-HST and SDSS.

The coding of the file names containing the cooling tracks is as follows:

COOL(mass)BaSTIfinale(envelope type)(sep or no sep).(phot system)

As an example:
COOL100BaSTIfinaleDBnosep.Jhn
contains the cooling track in the Johnson-Kron-Cousins plus the 2MASS system, of a 1.0 Mo WD with pure-He envelopes (DB) and no phase separation.

As another example
COOL055BaSTIfinaleDAsep.acs
contains the cooling track in the HST-ACS system of a 0.55 Mo WD with He+H envelopes (DA) and phase separation included.

Each cooling track file displays the logarithm of the age (in years), the value of the WD mass (in solar units), logarithm of the effective temperature (in K), logarithm of the bolometric luminosity (in solar units), and absolute magnitudes in several photometric filters, as labeled in the header.

For the Johnson-Kron-Cousins plus the 2MASS system we list:
U, B, V, R, I, J, H, Ks

For the ACS-HST system (VEGAMAG) we list:
F435W, F475W, F502N, F550M, F555W, F606W, F625W, F658N, F660N, F775W, F814W, F850LP, F892N

For the SDSS system we list:
u, g, r, i, z

Upon request we can provide cooling tracks with a finer sampling, that include also the evolution of the model radius, central pressure, temperature and density.

The oxygen stratification (after Rayleigh-Taylor re-homogeneization, and before crystallization) of the CO cores of our models is also provided. For each mass we list the mass layer (in units of the core mass) and the corresponding oxygen mass fraction

For each of the 11 chemical compositions (for both scaled-solar and alpha-enhanced mixtures) in the BaSTI database we provide WD isochrones computed employing our cooling tracks (both DA and DB, with and without phase separation) and the semi-empirical Initial Final Mass Relation (IFMR) by Salaris et al. (2009 - their linear fit) extrapolated down to a value of the progenitor mass equal to 0.88Mo (M(WD)=0.54Mo). For lower progenitor masses we kept the final WD mass constant, and equal to M(WD)=0.54Mo. The upper limit of the IFMR is set by the value of the progenitor mass that produces a WD with M(WD)=1.00Mo.

The WD progenitor lifetimes (until central He exhaustion) have been taken from our BaSTI models.

It is important to notice that our aim is just to provide a baseline set of WD isochrones with standardized inputs. It is not possible to provide a universal set of WD isochrones applicable to any situation, whitout modifying the adopted IFMR.
The IMFR determined in the Galactic disk (like the one by Salaris et al. 2009) may not be appropriate. when comparing theoretical and observed WD populations in other environments due to chemical composition and/or dynamical effects (most relevant in star clusters).
Also, using the same IFMR at all metallicities, sometimes provide progenitor masses (for the most massive WD models) that according to our progenitor calculations, ignite carbon instead of undergoing thermal pulses.
Users are encouraged to compute isochrones, starting from our cooling tracks, using the IFMR they deem most appropriate to the problem at hand.

We provide isochrones for ages from 200 Myr up to 14 Gyr (for the lowest metallicities, in some case the upper age limit is lower, because of the age coverage of the cooling tracks). Also, for old ages, the more massive DB models do not appear along the isochrones, because their luminosities would be much lower than the minimum luminosity attained by our models - that is constrained by the input physics).

Each file displays the mass of the WD progenitor (in solar units), the mass of the evolving WD (in solar units), logarithm of the effective temperature (in K), logarithm of the bolometric luminosity (in solar units), and absolute magnitudes in several photometric filters, as labeled in the header. The coding of the file names containing the isochrones is as follows:

WDz(metallicity)y(He abundance)ot(age in Myr).(envelope type)(sep or no sep).(phot system)

As an example:
WDz803y256ot9500.DBsep.sdss
contains a 9.5 Gyr isochrone in the SDSS photometric system, for Z=0.008, Y=0.256, pure-He envelope (DB) and phase separation included

As for the case of cooling tracks, for the Johnson-Kron-Cousins plus the 2MASS system we list:
U, B, V, R, I, J, H, Ks

For the ACS-HST system (VEGAMAG) we list:
F435W, F475W, F502N, F550M, F555W, F606W, F625W, F658N, F660N, F775W, F814W, F850LP, F892N

For the SDSS system we list:
u, g, r, i, z

Our best regards!!!