Sine temporal model

This model parametrises a time model of sinusoidal modulation.

\[F(t) = 1 + amp \cdot \sin(\omega \cdot (t-t_{\rm{ref}}))\]

Example plot

Here is an example plot of the model:

import numpy as np
from astropy import units as u
from astropy.time import Time
import matplotlib.pyplot as plt
from gammapy.modeling.models import (
    Models,
    PowerLawSpectralModel,
    SineTemporalModel,
    SkyModel,
)

time_range = [Time.now(), Time.now() + 16 * u.d]
omega = np.pi / 4.0 * u.rad / u.day
sine_model = SineTemporalModel(
    amp=0.5, omega=omega, t_ref=(time_range[0].mjd - 0.1) * u.d
)
sine_model.plot(time_range)
plt.grid(which="both")

YAML representation

Here is an example YAML file using the model:

model = SkyModel(
    spectral_model=PowerLawSpectralModel(),
    temporal_model=sine_model,
    name="sine-model",
)
models = Models([model])

print(models.to_yaml())

/Users/terrier/Code/anaconda3/envs/gammapy-dev/lib/python3.8/site-packages/astropy/time/core.py:2410: TimeDeltaMissingUnitWarning: Numerical value without unit or explicit format passed to TimeDelta, assuming days
  warn('Numerical value without unit or explicit format passed to'
components:
-   name: sine-model
    type: SkyModel
    spectral:
        type: PowerLawSpectralModel
        parameters:
        -   name: index
            value: 2.0
        -   name: amplitude
            value: 1.0e-12
            unit: cm-2 s-1 TeV-1
        -   name: reference
            value: 1.0
            unit: TeV
    temporal:
        type: SineTemporalModel
        parameters:
        -   name: amp
            value: 0.5
        -   name: omega
            value: 0.7853981633974483
            unit: d-1 rad
        -   name: t_ref
            value: 59890.20113946895
            unit: d