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SOPHIE cross-correlation files

SOPHIE science exposures are subjected to an automatic cross-correlation process using the spectral type information given in the relevant catalog entry. If no spectral type is specified, or none corresponds, it is correlated with a G2 mask. The CCF is ca lculated over a ±30 km/s interval and a gaussian is fitted to the profile of the strongest dip detected.

Results from this automatic fitting procedure should be treated with caution in the case of early-type or peculiar stars, where spurious values can result, such as highly negative velocities with large FWHMs. Failure is represented by rv = 999 km/s and FW HM = 0. In all cases a look at the CCF plot should quickly dispel any doubts.

The following CCF information is presented :

  • seq : sequence number, a unique identifier for each SOPHIE exposure
  • objname : object identifier, chosen from a valid SIMBAD catalog
  • date : calendar date for the exposure
  • mask : spectral mask used for the CCF (F0,G2,K5,M4,M5)
  • rv : radial velocity, corrected to the barycenter of the Solar System (km/s)
    • dvrms : estimated 1-σ radial-velocity uncertainty, based on photon noise alone, good for S/N > 100
    • err : estimated 1-σ error on CCF radial velocity, derived from contrast and FWHM, better for S/N < 100
  • fwhm : full width at half maximum of the CCF dip (km/s)
  • span : bisector velocity span, a measure of line asymmetry (km/s)
  • maxcpp : maximum number of counts/pixel in CCF (electrons)
  • contrast : contrast of CCF, expressed as percent depth of dip (%)
  • lines : number of absorption lines used to compute the CCF
  • view_head : display information contained in header of CCF file
  • get_ccf : download a 40-line FITS image (either 61 or 121 pixes wide) with the CCF computed for each order. Line 40 contains the average CCF. An accompanying ASCII file (not yet available) contains the individual radial velocities derived for e ach order.
  • CCF shape : plot of the average CCF over the entire 60 km/s velocity interval.

Future development

Should become available : information about the velocity drift (for simultaneous Thorium exposures).

OHP data distribution policy

All data available from this Archive are the property of OHP (Observatoire de Haute-Provence). Access to SOPHIE observations is restricted to the original PI for a one-year period, but some large key programs are granted an extended (5-year) protection. Data benefiting from this extension are still released after a year, but in a modified form where the exact time of observation is truncated. All data will be available with time information unmasked after the 5-year period. This prescription also applies to CCF results.

Last updated : 3 March 2014