Create a black body Transient

skysurvey contains a simple module (skysurvey.tools.blackbody) that contains basic functionality to create a black body transient, whose amplitude and temperature can evolve as a function of phase.

It thus can be used to set a time serie transient (skysurvey.TSTransient) as a generic transient model.

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Create a Black Body Transient source

A black body transient has three component:

• phase: array in days

• temperature: one per phase, could be constant

• amplitude: one per phase

Say we want to create a transient that will exponentially decay in flux, while getting cooler

import numpy as np
from skysurvey.tools import blackbody

phase = np.linspace(0, 100, 50) # phase definition range
time_scale=5.
amplitude = np.exp(-phase/time_scale) # fast decay
temperature = np.linspace(20_000, 5_000, len(phase)) # goes down from 20k to 5k Kelvin

let’s see how it looks from 1 000 to 10 000 Angstrom

lbda = np.linspace(800, 10_000, 1000)
fluxes = blackbody.get_blackbody_transient_flux(lbda, temperature=temperature, amplitude=amplitude)

import matplotlib.pyplot as plt

fig = plt.figure(figsize=[7,4])
ax = fig.add_subplot(111)

cmap = plt.get_cmap("coolwarm_r") # blue is hot
colors = cmap((temperature - temperature.min())/(temperature.max()-temperature.min()))
_ = [ax.plot(lbda, flux_, color=c) for flux_,c in zip(fluxes, colors)]
ax.set_yscale("log")

To get the sncosmo.TimeSeriesSources associated to that do, you can use:

bb_source = blackbody.get_blackbody_transient_source(phase=phase, 
                                                    amplitude=amplitude, 
                                                    temperature=temperature, 
                                                   lbda=lbda) # lbda has a default

Use that to create a skysurvey target

import skysurvey
bb_transient = skysurvey.TSTransient(bb_source)

and use it as usual

bb_transient.draw(1000, inplace=True, zmax=0.05, tstart="2018-06-10", tstop="2019-10-01")

	z	t0	magabs	magobs	amplitude	ra	dec	template
0	0.0475	58492.917969	-19.191141	17.501118	4.160976e-15	318.533478	-42.468357	bb_transient
1	0.0225	58498.386719	-17.713640	17.316551	4.931990e-15	330.921692	7.018897	bb_transient
2	0.0445	58533.238281	-17.538025	19.007900	1.038681e-15	113.697273	-10.048860	bb_transient
3	0.0315	58485.074219	-19.090195	16.685028	8.823302e-15	271.259521	-8.754927	bb_transient
4	0.0385	58597.300781	-18.577682	17.644352	3.646710e-15	307.160004	-25.681547	bb_transient
...	...	...	...	...	...	...	...	...
995	0.0475	58627.394531	-17.172358	19.519901	6.481595e-16	16.521893	18.062544	bb_transient
996	0.0465	58635.191406	-19.929432	16.715069	8.582515e-15	278.602570	81.465393	bb_transient
997	0.0285	58299.574219	-15.629739	19.923378	4.469827e-16	183.311356	42.363636	bb_transient
998	0.0225	58368.027344	-18.294930	16.735262	8.424378e-15	304.070068	13.531969	bb_transient
999	0.0455	58724.343750	-18.054243	18.541494	1.596042e-15	247.709259	-40.826050	bb_transient

1000 rows × 8 columns

or, more generically

flat_magabs_model = {"magabs":{"func": np.random.uniform, "kwargs":{"low":-18, "high":-15}}}

bb_transient = skysurvey.TSTransient.from_draw(size=1000, template=bb_source,
                                              tstart="2018-06-10", tstop="2019-10-01",
                                              model=flat_magabs_model)

bb_transient

{'redshift': {'kwargs': {'zmax': 0.05}, 'as': 'z'},
 't0': {'func': <built-in method uniform of numpy.random.mtrand.RandomState object at 0x1093f7640>,
        'kwargs': {'low': 56000, 'high': 56200}},
 'magabs': {'func': <built-in method uniform of numpy.random.mtrand.RandomState object at 0x1093f7640>,
            'kwargs': {'low': -18, 'high': -15}},
 'magobs': {'func': 'magabs_to_magobs',
            'kwargs': {'z': '@z', 'magabs': '@magabs'}},
 'amplitude': {'func': 'magobs_to_amplitude', 'kwargs': {'magobs': '@magobs'}},
 'radec': {'func': <function random_radec at 0x296b4cf70>, 'as': ['ra', 'dec']}}

bb_transient.data

	z	t0	magabs	magobs	amplitude	ra	dec	template
0	0.0445	58540.160156	-15.887897	20.658028	2.272121e-16	60.175255	47.641422	bb_transient
1	0.0355	58307.421875	-15.305688	20.735458	2.115722e-16	287.561584	-48.719982	bb_transient
2	0.0305	58434.007812	-16.296543	19.407036	7.191635e-16	245.787521	6.398428	bb_transient
3	0.0255	58397.296875	-17.101751	18.205046	2.175826e-15	150.021851	56.035976	bb_transient
4	0.0225	58390.644531	-16.538809	18.491381	1.671437e-15	155.195236	13.290114	bb_transient
...	...	...	...	...	...	...	...	...
995	0.0385	58717.601562	-15.918970	20.303066	3.150763e-16	55.223614	4.612903	bb_transient
996	0.0435	58638.941406	-16.580090	19.914923	4.504778e-16	111.257767	48.796371	bb_transient
997	0.0365	58408.253906	-17.737062	18.365986	1.876066e-15	122.067268	69.206398	bb_transient
998	0.0455	58588.230469	-16.179472	20.416267	2.838805e-16	145.690247	11.741833	bb_transient
999	0.0445	58603.808594	-15.793406	20.752520	2.082738e-16	209.389389	-24.976082	bb_transient

1000 rows × 8 columns