EXOFAST Output Parameters and Products
Documentation
Using the Service:- Accessing EXOFAST
- Overview of the Inputs Tab
- Accepted Input File Formats:
- Editing and Plotting Input Files
- Input Parameters and Options
- Output Parameters and Products
- Accessing Previous Results
- Usage Tips and Troubleshooting
Recipe: Run a Simple Fit
Recipe: Run an Advanced Fit
Acknowledgments
This page describes possible EXOFAST outputs when using the NASA Exoplanet Archive interface. These parameters display in the Results tab after running EXOFAST.
Left Panel: PDF Viewer
This panel displays a quick view of any PDFs generated during the run. Available files can be selected using the Select Product drop-down menu. These may include:
| File Name | Run Type | Description |
|---|---|---|
| exofast.model.e.f.pdf | All Runs | Plots of the calculated best-fit models overlaid on the input RV and/or photometric transit data. |
| exofast.covar.e.f.pdf | MCMC | Covariance contour plots for all MCMC output parameters against one another. |
| exofast.median.e.f.pdf | MCMC | LaTeX-compiled table of MCMC output system parameters (median values and 68% confidence intervals). |
| Exofast.pdf.e.f.pdf | MCMC | Plots of MCMC posterior probability distributions for each output parameter. |
Center Panel: EXOFAST Run Log
Statistics From Best Fit
Best Peaks in RV Fit: A list of the parameters for the initial RV fits at the periods of each of the strongest peaks of the RV periodogram. Not shown for transit-only fits.
χ2/dof, scaling errors, RMS of residuals (dof=number of degrees of freedom): The uncertainties in the input data files are not assumed to be correct, but are scaled such that the chance of getting getting χ2 or smaller is 50%, or P(χ2) = 0.5 (roughly χ2/dof=1) once the best fit is found. This ensures the relative weights of RV and transit data are appropriate. Shown as available for each of initial RV fit, initial transit fit, and combined fit.
Stellar Parameters
| Parameter | Description |
|---|---|
| M⁎ | Stellar mass, in solar masses. In fits including transits, this is derived from the transit plus stellar logg and guided by the Torres relation (see equation 24 in Eastman et al., 2013). If only RV is fit, we use the Torres relation alone. |
| R⁎ | Stellar radius, in solar radii. In fits including transits, this is derived from the transit plus stellar logg and guided by the Torres relation (see equation 24 in Eastman et al., 2013). If only RV is fit, we use the Torres relation alone. |
| L⁎ | Stellar luminosity, in solar luminosity. |
| ρ⁎ | Stellar density, in g cm-3. This simultaneously includes the constraints from the mass/radius of the star and the transit. |
| logg⁎ | The stellar surface gravity. Constrained by the transit and/or its prior. |
| Teff | The stellar effective temperature in Kelvin. This is mostly constrained by the prior. |
| [Fe/H] | The stellar metallicity. This is mostly constrained by the prior. |
Planetary Parameters
| Parameter | Description |
|---|---|
| e | The eccentricity of the orbit. Not shown for circular fits. |
| ω⁎ | The argument of periastron of the star's orbit, in degrees. Not shown for circular fits. |
| P | The period of the orbit in days. |
| a | The semi-major axis of the orbit in au. |
| MP | The mass of the planet in Jupiter masses. Not shown for RV-only fits. |
| RP | The radius of the planet in Jupiter radii. Not shown for RV-only fits. |
| ρP | The density of the planet in g cm-3. Not shown for RV-only fits. | log(gP) | The log of the surface gravity of the planet in cm s-2. Not shown for RV-only fits. |
| Teq | The equilibrium temperature of the planet, assuming perfect redistribution and no albedo. |
| Θ | The Safronov number. Not shown for RV-only fits. |
| <F> | The time-averaged incident flux the planet receives, in units of 109 erg s-1 cm-2. |
RV Parameters
| Parameter | Description |
|---|---|
| e cos ω* | Eccentricity times the cosine of the argument of periastron. Not shown for circular fits. |
| e sin ω* | Eccentricity times the sine of the argument of periastron. Not shown for circular fits. |
| K | The RV semi-amplitude, in m/s. Not shown for transit-only fits. |
| MΡ sin i | The minimum mass, in Jupiter masses. Not shown for transit-only fits. |
| MΡ/M* | The mass ratio of the planet to the star. Not shown for transit-only fits. |
| γ | The systemic velocity (or instrumental velocity) in m/s. |
 |
The slope in RV, in m s-1 day -1. Only displayed if RV data are fit and Fit Slope to RV is checked. |
Primary Transit Parameters
| Parameter | Description |
|---|---|
| TΡ | The time of periastron in BJDTDB. |
| TC | The time of transit center (or time of Conjunction) in BJDTDB. |
| RP/R⁎ | Radius of the planet in stellar radii. Not shown for RV-only fits. |
| a/R⁎ | Semi-major axis in stellar radii. |
| u1 | The linear limb-darkening coefficient. |
| u2 | The quadratic limb-darkening coefficient. |
| i | The inclination of the orbit in degrees. Not shown for RV-only fits. |
| b | The impact parameter. Not shown for RV-only fits. |
| δ | (RP/R⁎)2, which is the transit depth for non-grazing transits with no limb darkening. |
| TFWHM | The duration of the Full Width at Half Maximum Transit (from mid-ingress to mid-egress), or the time it takes for the center of the planet to cross the entire star. For eccentric orbits, this uses the approximations of Winn 2010. If no transit is fit, we assume a point planet (RP=0) and a central crossing (b=0), and therefore TFWHM is not displayed because it equals T14. |
| τ | The duration of ingress/egrees (1st to 2nd contact or 3rd to 4th contact). For eccentric orbits, this uses the approximations of Winn 2010. If no transit is fit, we assume a point planet (RP=0) and a central crossing (b=0) and therefore τ is not displayed because it is equal to 0. |
| T14 | The duration of transit (1st to 4th contact). For eccentric orbits, this uses the approximations of Winn 2010. If no transit is fit, we assume a point planet (RP=0) and a central crossing (b=0). |
| PT | The a priori non-grazing transit probability, assuming no knowledge of the inclination. If no transit is fit, we assume a point planet (RP=0); and therefore PT = PT,G. This is useful for transit searches of RV planets or to correct for geometric biases for transiting planets. |
| PT, G | The a priori grazing transit probability, assuming no knowledge of the inclination. |
| F0 | The average out-of-transit flux. Should be close to 1. |
Secondary Eclipse Parameters
| Parameter | Description |
|---|---|
| TS | The time of secondary eclipse center in BJDTDB. |
| bS | The impact parameter for the secondary eclipse. Only shown if eccentricity is free (otherwise it's identical to the primary). |
| TS,FWHM | The duration of the Full Width at Half Maximum of the eclipse (from mid ingress to mid egress), or the time it takes for the center of the planet to cross the entire star. Only shown if eccentricity is free (otherwise it's identical to the primary). We use the approximations of Winn 2010. If no transit is fit, we assume a point planet (RP=0) and a central crossing (b=0). |
| τS | The duration of ingress/egress (1st to 2nd contact or 3rd to 4th contact). Only shown if eccentricity is free (otherwise it's identical to the primary). We use the approximations of Winn 2010. If no transit is fit, we assume a point planet (RP=0) and a central crossing (b=0). |
| TS,14 | The duration of eclipse (1st to 4th contact). Only shown if eccentricity is free (otherwise it's identical to the primary). We use the approximations of Winn 2010. If no transit is fit, we assume a point planet (RP=0) and a central crossing (b=0). |
| PS | The a priori non-grazing eclipse probability, assuming no knowledge of the inclination. To determine posterior eclipse probability: bS < 1-p ⇒ eclipse. Only shown if eccentricity is free (otherwise it's identical to the primary). |
| PS,G | The a priori grazing eclipse probability, assuming no knowledge of the inclination. To determine posterior eclipse probability: bS < 1+p ⇒ eclipse. Only shown if eccentricity is free (otherwise it's identical to the primary). |
Note: The times are only in BJDTDB if the input times are in BJDTDB, as required by the input.
Right Panel: EXOFAST Products and Input Parameter Summary
This provides links to download any of the products available from the output of the current EXOFAST run. These may include:
| File Name or Type | Run Type | Description |
|---|---|---|
| All Products tar file | All | This is a single downloadable .tar file that bundles all the output files together. After downloading, the individual files can be extracted using the following command at the terminal: tar –xvf filename.tar, where filename.tar is the name of the tar file (usually exofast.tar). Your browser may also provide the capability to automatically extract the individual files on download. |
| Output Parameters | All | A plain text file (.txt) with all output parameters extracted from the EXOFAST Run Log, in IPAC table format. |
| EXOFAST Log File | All | This is the raw, plain text output log file produced by EXOFAST, and contains essentially the same information as presented in the EXOFAST Run Log center panel, with the exception that the latter is slightly reformatted for easier viewing. |
| MCMC IDL Save File | MCMC | This is an IDL save file (usually large!) that includes the array of steps populated by the Markov chain, including all derived quantities. To maintain a complete record of all steps, this array includes the burn-in. The save file also includes the corresponding χ2 at each step, the LaTeX-style names of all parameters, and the index of the first useful link in the chain (before which is considered the “burn-in”). Variables included in the file are:
|
| Posterior Distribution Function Plots | MCMC | Plots of all the posterior probability distribution functions calculated for each output parameter, in PostScript format. |
| Covariance Parameter Plots | MCMC | Covariance contour plots for all output parameters against one another, in PostScript format. |
| Median Values | MCMC | LaTeX source code to create a nicely formatted table containing the median output parameter values and 68% confidence intervals, in PostScript format. |
| Best-Fit Models and Residuals Plots | All | Plots of the calculated best-fit models overlaid on the input RV and/or photometric transit data, in PostScript format. |
| Transit Model (if input transit photometry is provided) | All | A plain text, space-separated data table containing the flux values for the best-fit photometric model, in the same units as the corresponding input file.
|
| Radial Velocity Model (if input RV data are provided) | All | As for Transit Model, a plain text space-separated data table containing radial velocity values for the best-fit radial velocity curve, in the same units as the corresponding input file.
|
Input Parameter Summary
This provides a simple quick-look summary of the input parameters provided by the user prior to the current EXOFAST run. These can be revisited and edited for a subsequent run by returning to the EXOFAST Inputs tab. More information on the available inputs is described on the EXOFAST Input Parameters page.
«Previous Input Parameters and Options Accessing Previous Results Next »
Last updated: 19 July 2017