Afrho

class sbpy.activity.Afrho[source]

Bases: sbpy.activity.dust.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, '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 / (m2 um)

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 / (m2 um)

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