`castor_etc.transit`

Transit Calulations

The castor_etc.transit package provides methods and classes to simulate a transit event such as observations.

Module Contents

Classes

Observation

Observation class.

Functions

`addflux2pix`	Usage: pixels=addflux2pix(px,py,pixels,fmod)
`gen_unconv_image`

Data

_OPTIMAL_APER_FACTOR

API

castor_etc.transit._OPTIMAL_APER_FACTOR = 1.4

castor_etc.transit.addflux2pix(px, py, pixels, fmod)

Usage: pixels=addflux2pix(px,py,pixels,fmod)

Drizel Flux onto Pixels using a square PSF of pixel size unity px,py are the pixel position (integers) fmod is the flux calculated for (px,py) pixel and it has the same length as px and py pixels is the image.

castor_etc.transit.gen_unconv_image(pars, starmodel_flux, xcoo, ycoo)

class castor_etc.transit.Observation(TelescopeObj, SourceObj, BackgroundObj, stellar_model_dir)

Observation class.

Initialization

Initialize class for transit calculations.

Note that the Source object (i.e., the SourceObj parameter) should be a point source.

Parameters

TelescopeObj :: castor_etc.Telescope object The castor_etc.Telescope object containing the telescope parameters.

SourceObj :: castor_etc.Source object The castor_etc.Source object contaning the target source parameters.

BackgroundObj :: castor_etc.Background object The castor_etc.Background object containing the background parameters. Dictionary keys must match the TelescopeObj.passbands keys.

stellar_model_dir :: str Path to the stellar models directory.

Attributes

TelescopeObj :: castor_etc.Telescope object The castor_etc.Telescope object containing the telescope parameters.

SourceObj :: castor_etc.Source object The castor_etc.Source object contaning the target source parameters.

BackgroundObj :: castor_etc.Background object The castor_etc.Background object containing the background parameters.

Returns

Transit instance

calc_sky_background_erate()

Noise associated with the sky background. This calculation is copy and pasted from calc_snr_or_t function in the photometry class.

Attributes

sky_background_noise :: dict of float
    Sky background noise (electron/s/pixel) associated with each passband name

Returns

None

_photon_count(temp=5780.0, metallicity=0.0, logg=4.44, Gmag=7.0, Gmag_abs=4.635, radius=1.0)

Calculate photon count from model for chosen passband name.

Parameters

temp :: float
    Effective temperature of the stellar atmosphere model

metallicity :: float
    Metallicity of the stellar atmosphere model

logg :: float
    logg value of the stellar atmosphere model

Gmag :: float
    Gaia G magnitude of the stellar atmoshpere model

Gmag_abs :: float
    Absolute Gaia G magnitude of the stellar atmosphere model

radius :: float
    Radius of the star

dpc :: float
    Distance to the star. Included for testing *Not currently used*

Returns cnt_rate ::

gaia_flux ::

specify_bandpass(passband_name=None)

Set bandpass specific parameters

Parameters

passband_name :: str
    The bandpass id to determine bandpass specific parameters

Attributes

passband_name :: str
    The bandpass id to determine bandpass specific parameters

Return

None

id_guide_stars(gs_criteria=None, plot_SN=False)

Parameters

gs_criteria :: dict
    Criteria for guide star
        SN_pix :: int or float
            Minimum S/N per pixel associated with each guide star
        exptime :: int or float
            Assume 2 Hz for guide camera, i.e., 0.5 sec
        ccd_aperture :: int or float
            Radius [pxl] to evaluate max S/N associated with each source, ask Dr. Woods

plot_SN :: bool
    If True, then a Max. S/N per pixel vs. Gaia G [mag] graph is plotted.

Return

None

_remove_aper_mask_nan_row_col(center): Remove columns and rows of the aperture mask containing all NaNs. Modifies the following attributes: _aper_mask, source_weights, sky_background_weights, dark_current_weights, _aper_xs, _aper_ys. Also updates _aper_extent to reflect changed arrays.

Parameters

center :: 2-element 1D array of floats The (x, y) center of the aperture relative to the center of the source in arcsec. Positive values means the source is displaced to the bottom/left relative to the aperture center.

Attributes

_aper_mask :: (M x N) 2D array of floats The aperture mask, including fractional pixel weights. The aperture mask shows the fractional overlap between the aperture and the pixel, ranging from (0, 1]. A pixel that is wholly contained in the aperture has an aperture weight equal to 1. Similarly, a pixel that is partially contained in the aperture has a weight between 0 and 1 (exclusive) directly proportional to the area of the aperture that overlaps the pixel. A pixel that is wholly outside the aperture has a weight of NaN. Now without rows and columns containing only NaNs.

source_weights :: (M x N) 2D array of floats The pixel weights for the source. Now without rows and columns containing only NaNs (based on _aper_mask). Note that changing the source weights for a point source will not affect the final photometry calculation. Instead, set the encircled_energy parameter in the calc_snr_or_t() method.

sky_background_weights :: (M x N) 2D array of floats The pixel weights for the sky background. Now without rows and columns containing only NaNs (based on _aper_mask).

dark_current_weights :: (M x N) 2D array of floats The pixel weights for the dark current. Now without rows and columns containing only NaNs (based on _aper_mask).

_aper_xs :: (M x N) 2D array of floats The aperture array containing the x-coordinates (in arcsec) relative to the center of the aperture. Now without rows and columns containing only NaNs (based on _aper_mask).

_aper_ys :: (M x N) 2D array of floats The aperture array containing the y-coordinates (in arcsec) relative to the center of the aperture. Now without rows and columns containing only NaNs (based on _aper_mask).

_aper_extent :: 4-element 1D list of floats The [xmin, xmax, ymin, ymax] extent of the aperture in arcsec (for plotting the weight arrays). Updated to reflect the extent containing only rows and columns with at least 1 non-NaN value.

Returns

None

_calc_source_weights(center): Calculate the source weights for the given profile.

Parameters

center :: 2-element 1D array of floats The (x, y) center of the aperture relative to the center of the source in arcsec. Positive values means the source is displaced to the bottom/left relative to the aperture center.

Returns

source_weights :: (M x N) 2D array of floats The source weights for each pixel in the aperture. These represent the flux of the source at each pixel relative to the flux at the center of the source.

_create_aper_arrs(half_x, half_y, center, overwrite=False): Parameters

half_x, half_y :: floats The half-widths (in arcsec) of the aperture in the x- and y-directions, respectively. (e.g., semimajor/semiminor axes, half of a rectangle’s length/width, etc.)

center :: 2-element 1D array of floats The (x, y) center of the aperture relative to the center of the source in arcsec. Positive values means the source is displaced to the bottom/left relative to the aperture center.

overwrite :: bool If True, allow overwriting of any existing aperture arrays.

Attributes

_aper_xs :: (M x N) 2D array of floats The aperture array containing the x-coordinates (in arcsec) relative to the center of the aperture.

_aper_ys :: (M x N) 2D array of floats The aperture array containing the y-coordinates (in arcsec) relative to the center of the aperture.

_aper_extent :: 4-element 1D list of floats The [xmin, xmax, ymin, ymax] extent of the aperture in arcsec (for plotting the weight arrays).

sky_background_weights :: (M x N) 2D array of floats The pixel weights for the sky background (incl. Earthshine, zodiacal light, geocoronal emission). This is currently all ones (1) (i.e., uniform noise).

dark_current_weights :: (M x N) 2D array of floats The pixel weights for the dark current. This is currently all ones (1) (i.e., uniform noise).

Returns

center_px :: 2-element 1D list of floats The (x, y) center index of the aperture coordinates arrays (i.e., _aper_xs and _aper_ys). To be very explicit, this is not (0, 0) but rather the center of the 2D arrays.

_use_optimal_aperture(factor=_OPTIMAL_APER_FACTOR, overwrite=False): Parameters

factor :: int or float The factor by which to scale the telescope’s FWHM. The radius of the optimal aperture will be R = factor * (FWHM/2).

quiet :: bool If False, print a message if the point source’s diameter is larger than the telescope’s FWHM as well as print the encircled energy fraction.

overwrite :: bool If True, allow overwriting of any existing aperture associated with this Photometry object.

Attributes

_aper_mask :: (M x N) 2D array of floats The aperture mask, including fractional pixel weights. The aperture mask shows the fractional overlap between the aperture and the pixel, ranging from (0, 1]. A pixel that is wholly contained in the aperture has an aperture weight equal to 1. Similarly, a pixel that is partially contained in the aperture has a weight between 0 and 1 (exclusive) directly proportional to the area of the aperture that overlaps the pixel. A pixel that is wholly outside the aperture has a weight of NaN.

source_weights :: (M x N) 2D array of floats The pixel weights for the source. Note that changing the source weights for a point source will not affect the final photometry calculation. Instead, set the encircled_energy parameter in the calc_snr_or_t() method.

sky_background_weights :: (M x N) 2D array of floats The pixel weights for the sky background.

dark_current_weights :: (M x N) 2D array of floats The pixel weights for the dark current.

Returns

None

_point_source_sim(target_flux_fraction, scene_phot_count)

Parameters

target_flux_fraction :: int or float Used to reduce target star flux when injecting transit signal

scene_phot_count :: int or float Photon count from the source

Returns

pixels_final.T :: array of floats
    point source simulation

pixels_err.T :: array of floats
    error associated with the point source simulation 

scene_sim(all_sources=True, return_scene=False, update_gaia=True, quiet=None, return_SN_only=False)

Generate simulated scene using sources listed in self.SourceObj.gaia

Parameter

all_sources :: Boolean
    True -> Include all Gaia sources in scene
    False -> Include only the target
return_scene :: Booleans
    True -> scene_flux = self.scene_sim()
quiet :: Boolean
    To print 'Generating scene...'
return_SN_only :: Boolean
    Return S/N without updating object (used for guide star identification)

Return

if return_SN_only:
    SN_pix,SN_ap
if return_scene:
    pixels_final.T,pixels_err.T

plot_fov(plot_guide_stars=True, vmin=None, vmax=None, add_scene_sim=True)

Ask James

Parameters

pa :: 
plot_guide_stars :: Boolean
vmin ::
vmax ::
plot_grid :: Boolean
add_scene_sim :: Boolean

Return

None

specify_pl_model(RpRs, P, t0, b, aRs)

Model planet for transit simulation

Parameters

RpRs :: int or float
    Planet-star radius ratio
P :: int or float
    Orbital period <Need to read pytransit for units>
t0 :: int of float
    Zero epoch <Need to read pytransit for units>
b :: int or float
    Impact parameter, which is the projected distance between the planet disk and the stellar disk at mid-transit
aRs :: int of float
   Ratio of the semi-major axis to the stellar radius

Attributes

pl_model :: dict of arrays of floats
    Planet model parameters

Return

None

specify_exposure_parameters(exptime=60 * u.second, nstack=10, tstart=0.0 * u.d, tend=6.0 / 24.0 * u.d)

Exposure parameters for planet transit simulation

Parameters

exptime :: int
    Exposure time
nstack :: int 
    Number of exposures to stack (t_tot = exptime*nstack)
tstart :: int of float
    Light curve start time [days]
tend :: int or float
    Light curve end time [days]

Attributes

exptime :: int
    Exposure time
nstack :: int 
    Number of exposures to stack (t_tot = exptime*nstack)
tstart :: int of float
    Light curve start time [days]
tend :: int or float
    Light curve end time [days]

Return

None

calc_pl_model(model='pytransit_QuadraticModel', t_grid=[], exp_time=-1)

Parameters

Planet model
t_grid :: array
exp_time :: 

Return

_pl_lc_tot ::

lc_sim(quiet=False, return_lc=False, cadence=-1, exp_time=-1)

Light curve simulation.

Parameters

quite :: Boolean
    For conditional rendering of some lines of code
return_lc :: Boolean
cadence ::
exp_time ::

Return if return_lc: return t_grid, fl

plot_lc(plot_model=True, exp_time=-1, t_from_mid=True, t_unit='d')

Rough plot. Need to update

Parameters

plot_model :: Boolean
exp_time
t_from_mid :: Boolean
t_unit :: str

castor_etc.transit

Transit Calulations

Module Contents

Classes

Functions

Data

API

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`castor_etc.transit`