Barycentric Correction Algorithm

class modules.barycentric_correction.src.alg_barycentric_corr.BarycentricCorrectionAlg(obs_config, config=None, logger=None, logger_name=None)

Barycentric velocity correction.

This module defines class ‘BarycentricCorrectionAlg’ and methods to calculate barycentric velocity correction and redshift for one single time point or a period of days.

Parameters:

• obs_config (dict|configparser.ConfigParser|None) – A dict instance or config context containing the key-value pairs related to the observation configuration for barycentric correction calculation.

• logger (logging.Logger) – Instance of logging.Logger passed from external application.

• logger_name (str, optional) – Selection of logger by the specified logger name. Defaults to None. Either the defined logger_name or the class name determines the logging.Logger instance for organizing the loggers.

zb_range

An array containing minimum and maximum redshift value over a period of days.

Type:

numpy.ndarray

zb_list

Array of redshift values over a period of days.

Type:

numpy.ndarray

obs_config

A dict instance storing key-value pairs related to observation configuration. The key list includes the name as the constants defined in class, i.e. RA, DEC, PMRA, PMDEC, PX, RV, LAT, LON, ALT and SPEC.

Type:

dict

Note

The following constants define the properties included in the dict instance used for barycentric velocity correction or redshift calculation, i.e. get_zb_long() and get_zb_from_bc_corr()

ALT = 'obsalt'

altitude of the observatory (meter)

DEC = 'dec'

DEC J2000 of the target (degrees)

EPOCH = 'epoch'

epoch in julian date

LAT = 'obslat'

latitude of the observatory, North (+ve) and South (-ve) (degree)

LON = 'obslon'

longitude of the observatory, East (+ve) and West (-ve) (degree)

PMDEC = 'pmdec'

proper motion in DEC (mas/yr)

PMRA = 'pmra'

proper motion in RA (mas/yr)

PX = 'parallax'

parallax of the target (mas)

RA = 'ra'

RA J2000 of the target (hours)

RV = 'star_rv'

star radial velocity estimation (km/s)

SPEC = 'instrument'

Observation instrument

STARNAME = 'starname'

star name

static find_existing_zb_file(ins, start_jd, days_period, target, data_path)

Compose the file path storing the redshift values from barycentric correction over a period of days.

Parameters:

• ins (str) – Observation instrument.

• start_jd (float) – Start day in Julian Date format.

• days_period (int) – Total days.

• target (str) – star name.

• data_path (str) – Path of the data file. Defaults to None, meaning a default path based on the setting of start_jd, days_period and instrument under KPF data test directory is applied.

Returns:

Data path. The default path is like ‘./+default_bc_file’ bc_corr_<start_jd>_<days_period>_<instrument>.csv*

Return type:

str

static get_bc_corr(obs_config, jd)

Compute Barycentric correction on single time point.

Parameters:

• obs_config (dict) – A dict instance containing observation configuration.

• jd (float) – Day in Julian Date format.

Returns:

Barycentric velocity [m/s] correction from barycorrpy.get_BC_vel.

Return type:

float

static get_bc_corr_period(obs_config, start_jd, days_period=None)

Compute redshift values from barycentric velocity correction over a period of days.

Parameters:

• obs_config (dict) – A dict instance containing observation configuration.

• start_jd (float) – Starting time point in Julian Date format.

• days_period – Period of days for BC correction calculation. Defaults to None for one day.

Returns:

redshift from barycentric velocity correction for a period of days.

Return type:

numpy.ndarray

static get_zb_from_bc_corr(obs_config, start_jd, days_period=None, data_path=None, save_to_path=None)

Find the BC values for a period of days or a single day by calling Barycentric velocity correction function

or from an existing file and store the result to the specified file if there is.

Parameters:

• obs_config (dict) – A dict instance containing observation configuration.

• start_jd (float) – Starting time point in Julian Date format.

• days_period (int, optional) – Period of days for Barycentric correction calculation. Defaults to None. If the value is None or 1, it means the redshift of a single time point is computed, or a list of redshift values over a time period is either computed or accessed from a file as specified by data_path.

• data_path (str, optional) – Path of the data file. Defaults to None for a default path per settings of jd, period, instrument and KPF data test directory.

• save_to_path (str, optional) – Path of the output file. Defaults to None for no output.

Returns:

An array of BC values (m/sec) over the specified period or a single time point.

Return type:

numpy.ndarray

get_zb_list(jd, period, data_path=None, save_to_path=None)

Get redshift values over the period.

Parameters:

• jd (float) – Starting day in Julian Date format.

• period (int) – Period of days.

• data_path (str, optional) – The path of the file containing predefined redshift values. Defaults to None for a default path.

• save_to_path (str, optional) – The path of the output file. Default to None for no output.

Returns:

redshift values over the period.

Return type:

list

get_zb_long(jd, period, data_path=None, save_to_path=None)

Get minimum and maximum redshift over a period of time.

Parameters:

• jd (float) – Starting day in Julian Date format.

• period (int) – Period of days.

• data_path (str, optional) – The path of the file containing predefined redshift values over a period of days. It could be a path to a file or a directory. Defaults to None for a default path based on the setting of jd, period, instrument name and KPF data test directory.

• save_to_path ((str, optional) – The path of the output file for the result. Defaults to None, meaning no output file created. It could be a path to a file or a directory.

Returns:

Minimum and maximum redshift values during the period starting from jd. The first element in the array is the minimum and the second one is the maximum.

Return type:

numpy.ndarray