Stellar parameters

Stellar parameters#

To compute certain quantities, nuance requires the physical parameters of a star, which can be manipulated using the Star object

from nuance import Star

star = Star(mass=0.159, radius=0.189)

\((\tau, \delta)\)#

Given a star with a certain variability period and amplitude, this object can be used to compute the relative \((\tau, \delta)\) parameters presented in the nuance paper:

# stellar variability paramters
star.period = 0.45  # days
star.amplitude = 0.05

tau, delta = star.period2tau(15), star.radius2delta(1.5)
print(f"tau = {tau:.2f}, delta = {delta:.2f}")

tau = 3.46, delta = 9.44

which helps indentify where nuance might be beneficial compared to more traditional techniques based on detrending.

Optimal grids#

Another case where the Star object might be useful is to compute optimal grids of search parameters. For example, the optimal grid of periods following Ofir (2014) can be obtained with

time_span = 2.0  # days

star.period_grid(time_span)

array([0.52420807, 0.5288679 , 0.53361132, 0.5384406 , 0.5433581 ,
       0.54836624, 0.55346755, 0.55866468, 0.56396033, 0.56935734,
       0.57485864, 0.58046729, 0.58618646, 0.59201946, 0.5979697 ,
       0.60404077, 0.61023638, 0.6165604 , 0.62301687, 0.62960999,
       0.63634414, 0.64322391, 0.65025407, 0.65743959, 0.6647857 ,
       0.67229783, 0.67998167, 0.68784319, 0.69588861, 0.70412446,
       0.7125576 , 0.72119518, 0.73004475, 0.73911419, 0.74841181,
       0.75794633, 0.76772691, 0.77776322, 0.7880654 , 0.79864417,
       0.80951082, 0.82067726, 0.83215607, 0.84396054, 0.85610473,
       0.86860353, 0.88147268, 0.89472891, 0.90838994, 0.9224746 ,
       0.9370029 , 0.95199615, 0.96747702, 0.98346971, 1.        ])

where the minimum orbital period is found using the Roche limit and its associated period (assuming a circular orbit)

star.roche_period()

np.float64(0.5242080656950339)
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