The Open University
10 files

Radial velocities and activity time-series measurements for the star "HD42936" ("DMPP-3")

posted on 2022-12-01, 13:11 authored by Adam StevensonAdam Stevenson, John Barnes

These data are the underlying measurements behind a search for exoplanets around the star with the name HD42936 (with the identifier DMPP-3 given by the Dispersed Matter Planet Project, DMPP, working at the Open University). The files consist of: radial velocities, the measurements of motion towards and away from earth-based observers we can use to determine if planets are pulling the star around as they orbit, taken with the HARPS spectrograph on the 3.6m telescope in La Silla; and measurements of the star's activity level (monitoring presence of features like starspots and stellar flares) at each observation time, extracted from different aspects of the spectra recorded with the spectrograph.

For information on the DMPP, see Haswell, C. A.,  et al., 2020, “Dispersed Matter Planet Project discoveries of ablating planets orbiting nearby bright stars”, Nature Astronomy, 4, 408.

HD42936_TERRA_RV.txt : contains the HARPS-TERRA reduced radial velocities for this system. The columns are:

Time (BJD-2450000); Radial Velocity (m/s); Error on RV (m/s); and Observational Dataset (dimensionless numbering). BJD is the Barycentric Julian Date, and a measure of time, in days, from a reference epoch.

TERRA uses a template matching process to extract radial velocities in a more accurate manner. For more information see Anglada-Escudé G., Butler R. P., 2012, ApJS, 200, 15

HD42936_DRS_BIS.txt, HD42936_DRS_FWHM.txt, HD42936_DRS_CCF_contrast.txt: these files contain the ancillary measurements from HARPS spectra, originating from the HARPS data reduction software (DRS). The full width half max (FWHM), bisector inverse slope (BIS) and contrast are measured from the cross-correlation function approach used in extracting radial velocities. They can all be used to investigate changes in the activity level of the star. These files have columns of: 

FWHM: Time (BJD); Value (km/s); error (km/s)

BIS: Time (BJD-2400000); Value (m/s); error (m/s)

Contrast: Time (BJD); Value (%, dimensionless); error (%, dimensionless)

HD42936_corrected_FWHM.txt: FWHM values after correction, where 4 outlying points have been removed in total, as well as removing a polynomial trend evident in HARPS pre fibre upgrade points, and a fibre upgrade related offset. For information on this trend, see Costes J. C., et al., 2021, MNRAS, 505, 830.

The columns of this file are: Time (BJD); Median Subtracted FWHM value (km/s); FWHM error (km/s)

HD42936_CaHK_JB.txt, HD42936_Halpha_JB.txt, HD42936_NaD1_JB.txt, HD42936_NaD2_JB.txt, HD42936_NaD1D2_JB.txt: Activity time series values, reduced from publicly available HARPS spectra (ESO archive). We have extracted line strengths for Calcium II H and K, Hydrogen alpha, Sodium D lines 1, 2, and 1&2 combined. These have been extracted using optimised, uniform (rectangular) line summing, with differing line core respective passband half widths. 0.3 [Angstroms] for Ca H, Na D1 & D2. 0.25 [Angstroms] for Hydrogen alpha. 0.2 [Angstroms] for Ca K. For further information on the reduction process used, see Barnes J. R., Haswell C. A., Staab D., Anglada-Escudé G., 2016, MNRAS,
462, 1012.

The columns of these files are in the format of: Time (BJD-2400000); line strength value (dimensionless); Error on value (dimensionless).


STFC studentship


Research Group

  • Astronomy

Usage metrics

    School of Physical Sciences