stellaR (version 0.3-4)

keypoints: Extract relevant evolutionary points from stellar tracks or isochrones

Description

Extract some relevant evolutionary points from stellar tracks or stellar isochrones.

Usage

# S3 method for trk
keypoints(x, …)
# S3 method for trkset
keypoints(x, …)
# S3 method for iso
keypoints(x, …)
# S3 method for isoset
keypoints(x, …)

Arguments

x

an object of classes trk, trkset, iso, or isoset.

…

further arguments, not implemented.

Value

A data frame containing the observations relative to the selected evolutionary phases. The columns relative to mass (or age for isochrones), metallicity, initial He value, mixing-length, alpha-enhancement, and phase identifier are inserted in the data frame.

Details

keypoints.trk extracts from the object x$data the rows relative to the following evolutionary stages:

1. ZAMS: Zero-Age Main-Sequence, defined as the point for which the central H abundance drops below 99% of its initial value.

2. TO: Turn-Off, defined as the point for which the effective temperature reaches its maximum value. If multiple lines satisfy the constraint, the values of all the rows are averaged.

3. BTO: Brighter Turn-Off, defined as the point for which the effective temperature drops below the one of the TO minus 100 K. The points could not exist for low masses. See Chaboyer et al. (1996) for an analysis of the advantages of this evolutionary point with respect to TO.

4. exHc: Central H exhaustion, defined as the point for which the central H abundance is zero. For low masses the point could coincide with TO. This is the last point of the tracks with mass lower or equal to 0.50 Msun.

5. Heflash: Helium flash, the last point of the track for masses higher than 0.50 Msun.

keypoints.trkset performs the selection described above for all the set of objects.

The returned object contains the variable id, which labels the evolutionary phases with the following coding: 1 = ZAMS, 2 = TO, 3 = BTO, 4 = exHc, 5 = Heflash.

keypoints.iso extracts from the object x$data the rows relative to the following evolutionary stages:

1. TO: Turn-Off, defined as the point for which the effective temperature reaches its maximum value. If multiple lines satisfy the constraint, the values of all the rows are averaged.

2. BTO: Brighter Turn-Off, defined as the point for which the effective temperature drops below the one of the TO minus 100 K.

keypoints.isoset performs the selection described above for all the set of objects.

The returned object contains the variable id, which labels the evolutionary phases with the following coding: 1 = TO, 2 = BTO.

References

B. Chaboyer, P. Demarque, P.J. Kernan, L.M. Krauss, and A. Sarajedini (1996). An accurate relative age estimator for globular clusters. MNRAS, 283, 683-689.

Examples

# NOT RUN {
  
# }
# NOT RUN {
  trk <- getTrk(0.9, 0.002, 0.25, 1.7, 0)
  ### check return value from CDS
  if(!is.na(trk)[1]) keypoints(trk)

  is <- getIso(11, 0.002, 0.25, 1.7, 0)
  ### check return value from CDS
  if(!is.na(is)[1]) keypoints(is)
# }