LTE¶
- class sbpy.activity.LTE[source]¶
Bases:
object
LTE Methods for calculating production_rate
Methods Summary
cdensity_Bockelee
(integrated_flux, mol_data)Basic equation relating column density with observed integrated flux without the need for an initial column density to be given.
from_Drahus
(integrated_flux, mol_data, ephemobj)Returns production rate based on Drahus 2012 model referenced.
Methods Documentation
- cdensity_Bockelee(integrated_flux, mol_data)[source]¶
Basic equation relating column density with observed integrated flux without the need for an initial column density to be given. This is found in equation 10 in https://ui.adsabs.harvard.edu/abs/2004come.book..391B and is derived from data from JPLSpec, feel free to use your own column density to calculate production rate or use this function with your own molecular data as long as you are aware of the needed data.
- Parameters:
- integrated_flux
Quantity
Integrated flux of emission line.
- mol_data
sbpy.data.phys
sbpy.data.phys
object that contains AT LEAST the following data:- Transition frequency in MHzEinstein Coefficient (1/s)
This function will calculate the column density from Bockelee-Morvan et al. 2004 and append it to the phys object as ‘Column Density’ or any of its alternative field names. The values above can either be given by the user or obtained from the functions
einstein_coeff
andbeta_factor
Keywords that can be used for these values are found underfieldnames
documentation. We recommend the use of the JPL Molecular Spectral Catalog and the use offrom_jplspec
to obtain these values in order to maintain consistency. Yet, if you wish to use your own molecular data, it is possible. Make sure to inform yourself on the values needed for each function, their units, and their interchangeable keywords as part of the Phys data class.
- integrated_flux
- Returns:
- Column Density
astropy.units.Quantity
Column density from Bockelee-Morvan et al. 2004 as astropy Quantity (1/m^2)
- Column Density
- from_Drahus(integrated_flux, mol_data, ephemobj, vgas=<Quantity 1. km / s>, aper=<Quantity 25. m>, b=1.2)[source]¶
Returns production rate based on Drahus 2012 model referenced. Does not include photodissociation, good for first guesses for more computationally intensive methods or for the Haser model under
sbpy.activity.gas.productionrate.from_Haser
- Parameters:
- integrated_flux
Quantity
Line integral derived from spectral data in Kelvins * km/s
- mol_data
sbpy.data.phys
sbpy.data.phys
object that contains the following data:- Transition frequency in MHzTemperature in KelvinsPartition function at designated temperature (unitless)Upper state degeneracy (unitless)Upper level energy in JoulesDegrees of freedom (unitless)Einstein Coefficient (1/s)
These fields can be given by the user directly or calculated using
from_jplspec
,einstein_coeff
, Keywords that can be used for these values are found underfieldnames
documentation. We recommend the use of the JPL Molecular Spectral Catalog and the use offrom_jplspec
to obtain these values in order to maintain consistency. Yet, if you wish to use your own molecular data, it is possible. Make sure to inform yourself on the values needed for each function, their units, and their interchangeable keywords as part of the Phys data class.- ephemobj
sbpy.data.ephem
sbpy.data.ephem
object holding ephemeride information including distance from comet to Sun [‘r’] and from comet to observer [‘delta’]- vgas
Quantity
Gas velocity approximation in km / s. Default is 1 km / s
- aper
Quantity
Telescope aperture in meters. Default is 25 m
- bint
Dimensionless factor intrinsic to every antenna. Typical value, and the default for this model, is 1.22. See references for more information on this parameter.
- integrated_flux
- Returns:
- q
Quantity
Production rate, not including photodissociation
- q
References
Drahus et al. September 2012. The Sources of HCN and CH3OH and the Rotational Temperature in Comet 103P/Hartley 2 from Time-resolved Millimeter Spectroscopy. The Astrophysical Journal, Volume 756, Issue 1.
Examples
>>> import astropy.units as u >>> from astropy.time import Time >>> from sbpy.data import Ephem, Phys >>> from sbpy.activity import LTE, einstein_coeff, intensity_conversion
>>> temp_estimate = 47. * u.K >>> target = '103P' >>> vgas = 0.8 * u.km / u.s >>> aper = 30 * u.m >>> b = 1.13 >>> mol_tag = 27001 >>> transition_freq = (265.886434 * u.GHz).to('MHz') >>> integrated_flux = 1.22 * u.K * u.km / u.s
>>> time = Time('2010-11-3 00:48:06', format='iso') >>> ephemobj = Ephem.from_horizons( ... target, epochs=time, closest_apparition=True, ... id_type='designation')
>>> mol_data = Phys.from_jplspec(temp_estimate, transition_freq, ... mol_tag)
>>> intl = intensity_conversion(mol_data) >>> mol_data.apply([intl.value] * intl.unit, ... name='intl')
>>> au = einstein_coeff(mol_data) >>> mol_data.apply([au.value] * au.unit, ... name='eincoeff')
>>> lte = LTE() >>> q = lte.from_Drahus(integrated_flux, mol_data, ... ephemobj, vgas, aper, b=b)
>>> q <MaskedQuantity 1.09899965e+25 1 / s>