New effective eccentric mchirp parameter

[rahuldhurkunde]

Added a new eccentric mchirp parameter as defined in arXiv:2107.14736.

Standard information about the request

This is a: new feature

This change affects: the offline search.

This change changes:result presentation / plotting

Motivation

A new effective mchirp-e parameter might be better for eccentric searches, i.e. may lead to better bank placement.

Contents

Added a new method in conversions.py

Testing performed

Reproduced the Figure 3. in the paper.

Additional notes

• The author of this pull request confirms they will adhere to the code of conduct

[ahnitz]

@rahuldhurkunde Nice. I might suggest two things.

(1) (minor) is there a better name than 'ecc mchirp'?
(2) Is it possible to write an inverse function? e.g. give back the mchirp from the 'ecc mchirp' + ecc.

[rahuldhurkunde]

@ahnitz The inverse function requires a root solver. So to avoid adding a scipy dependency, I had to include a new bisection root solver function: solve_root.

Simple testing seems to be working:

>>> conversions.ecc_mchirp_from_mchirp_ecc(20.0, 0.2)
20.668174895333745
>>> conversions._mchirp_from_ecc_mchirp_ecc(20.668174895333745, 0.2)
19.999999648528163

Sorry I can't think of any better name for the new parameter. Happy to change if you have any suggestions.

[rahuldhurkunde]

@ahnitz I've dropped the e^6 term, simplified the inversion to a quadratic one and renamed the new parameter to Emchirp.