Afrho¶

class sbpy.activity.Afrho(value, unit=None, dtype=None, copy=True)[source]¶

Bases: DustComaQuantity

Coma dust quantity for scattered light.

Afrho objects behave like Quantity objects with units of length.

Parameters:

valuenumber, Quantity: The value(s).
unitstring, Unit, optional: The unit of the input value. Strings must be parseable by units package.
dtypedtype, optional: See Quantity.
copybool, optional: See Quantity.

Notes

Afρ is the product of dust albedo, dust filling factor, and circular aperture radius. It is nominally a constant for a steady-state coma in free expansion. See A’Hearn et al. (1984) for details.

References

A’Hearn et al. 1984, AJ 89, 579-591.

Examples

>>> from sbpy.activity import Afrho
>>> print(Afrho(1000.0, 'cm'))
1000.0 cm

Methods Summary

`from_fluxd`(wfb, fluxd, aper, eph, **kwargs)	Initialize from spectral flux density.
`to_fluxd`(wfb, aper, eph[, unit, phasecor, Phi])	Express as spectral flux density in an observation.
`to_phase`(to_phase, from_phase[, Phi])	Scale to another phase angle.

Methods Documentation

classmethod from_fluxd(wfb, fluxd, aper, eph, **kwargs)[source]¶

Initialize from spectral flux density.

Parameters:

wfbQuantity, SpectralElement, list: Wavelengths, frequencies, bandpass, or list of bandpasses of the observation. Bandpasses require synphot.
fluxdQuantity: Flux density per unit wavelength or frequency.
aperQuantity or Aperture: Aperture of the observation as a circular radius (length or angular units), or as an Aperture.
eph: dictionary-like, `~sbpy.data.Ephem`: Ephemerides of the comet. Required fields: ‘rh’, ‘delta’. Optional: ‘phase’.
**kwargs: Keyword arguments for to_fluxd.

to_fluxd(wfb, aper, eph, unit=None, phasecor=False, Phi=None)[source]¶

Express as spectral flux density in an observation.

Assumes the small angle approximation.

Parameters:

wfbQuantity, SpectralElement, list: Wavelengths, frequencies, bandpass, or list of bandpasses of the observation. Bandpasses require synphot. Ignored if S is provided.
aper: `~astropy.units.Quantity`, `~sbpy.activity.Aperture`: Aperture of the observation as a circular radius (length or angular units), or as an sbpy Aperture.
eph: dictionary-like, `~sbpy.data.Ephem`: Ephemerides of the comet. Required fields: ‘rh’, ‘delta’. Optional: ‘phase’.
unitUnit, string, optional: The flux density unit for the output.
phasecor: bool, optional: Scale the result by the phase function Phi, assuming Afrho is quoted for 0° phase. Requires phase angle in eph.
Phicallable, optional: Phase function, see to_phase().
**kwargs: Keyword arguments for observe.

Returns:

fluxdQuantity: Spectral flux density.

Examples

>>> from sbpy.activity import Afrho
>>> import astropy.units as u
>>> afrho = Afrho(1000 * u.cm)
>>> wave = 0.55 * u.um
>>> aper = 1 * u.arcsec
>>> eph = dict(rh=1.5 * u.au, delta=1.0 * u.au)
>>> fluxd = afrho.to_fluxd(wave, aper, eph)
>>> print(fluxd)    
6.730018324465526e-14 W / (um m2)

With a phase correction: >>> eph[‘phase’] = 30 * u.deg >>> fluxd = afrho.to_fluxd(wave, aper, eph, phasecor=True) >>> print(fluxd) # doctest: +FLOAT_CMP 2.8017202649540757e-14 W / (um m2)

In magnitudes through the Johnson V filter: >>> import sbpy.units as sbu >>> from sbpy.photometry import bandpass >>> bp = bandpass(‘Johnson V’) >>> fluxd = afrho.to_fluxd(bp, aper, eph, unit=sbu.JMmag, … phasecor=True) >>> print(fluxd) # doctest: +FLOAT_CMP 15.321242371548918 mag(JM)

to_phase(to_phase, from_phase, Phi=None)[source]¶

Scale to another phase angle.

Parameters:

to_phaseQuantity: New target phase angle.
from_phaseQuantity: Current target phase angle.
Phicallable, optional: Phase function, a callable object that takes a single parameter, phase angle as a Quantity, and returns a scale factor. Default is phase_HalleyMarcus.

Returns:

afrhoAfrho: The scaled Afρ quantity.

Examples

>>> from sbpy.activity import Afrho
>>> afrho = Afrho(10 * u.cm).to_phase(15 * u.deg, 0 * u.deg)
>>> print(afrho)                       
5.87201 cm

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Afrho¶