and

## Transit False Positive Probabilities

`(isochrones)`
`(vespa)`

Timothy Morton

(Princeton/UFlorida/Flatiron)

I have X-, Y-, and Z-band photometry of a star.

What kind of star is it?

``````~\$ pip install isochrones
~\$ ipython
In [1]: from isochrones import StarModel, get_ichrone
In [2]: mist = get_ichrone('mist')
In [3]: model = StarModel(mist, X=(12, 0.05), Y=(11, 0.05), Z=(10, 0.05))
In [4]: model.fit()``````

from python terminal/script:

``````X = 12, 0.05
Y = 11, 0.05
Z = 10, 0.05``````

mystar/star.ini

``\$ starfit mystar``

From command line:

``````X = 12, 0.05
Y = 11, 0.05
Z = 10, 0.05

Teff = 5300, 80
feh = -0.1, 0.1
logg = 4.6, 0.15``````

mystar/star.ini

``\$ starfit mystar ``

Also:

``````X = 12, 0.05
Y = 11, 0.05
Z = 10, 0.05

Teff = 5300, 80
feh = -0.1, 0.1
logg = 4.6, 0.15``````

mystar/star.ini

``\$ starfit mystar --binary``

Or:

• In principle can use arbitrary stellar model grids
• 3-d linear interpolation in (M, log(age), [Fe/H])
• Any observable property can be called at any (in-bounds) values of (M, log(age), [Fe/H]); thus any property provided by stellar grids can be used as observed data for conditioning model
• Uses MultiNest to fit by default;  will use emcee if MultiNest not installed.

• Uses local [Fe/H] prior based on SDSS

## To do / in progress

• Include other built-in model grids (e.g., PARSEC)
• Interpolate in EEP rather than mass
• Improve treatment of extinction
• Clever tricks to speed up model fitting?
• Write/publish an overview paper!

I have a transit signal.

What is the probability it's an astrophysical false positive?

``~\$ pip install vespa``
``````name = myplanet
ra = 296.003693
dec = 44.277561
rprs = 0.012585031528
period = 384.845905
photfile = myphotometry.csv

[constraints]
secthresh = 0.000120176767205
``````
``````g = 13.8735234, 0.05
r = 13.3370844, 0.05
i = 13.1663488, 0.05
z = 13.1029807, 0.05
J = 12.263, 0.02
H = 11.919, 0.02
K = 11.852, 0.02
Kepler = 13.426
``````

myplanet/star.ini

myplanet/fpp.ini

``````~\$ starfit --all myplanet
~\$ calcfpp myplanet``````

## Group Projects (Tues/Wed)

1. How much do different follow-up observations contribute to FPP? (apply to GJ 9827)
2. Unvalidated Planets I (based on Cabrera+ 2017)
3. Unvalidated Planets II (based on Shporer+ 2017)

Goal: learn careful, thoughtful use of vespa!

N.B. Stay tuned for TESS-related updates!

By Tim Morton

# isochrones-and-vespa for sagan2018

A quick overview of my packages to fit stellar parameters and calculate the false positive probability of transiting planet candidates.

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