Parameters and Conventions¤

Every waveform's params dict uses a name from this glossary. Consult a model's parameter_names for the ordered set a specific model expects — not every model uses every parameter below.

Compact-binary coalescences¤

Mass¤

Name	Meaning	Units
`M_c`	Chirp mass \(\mathcal{M} = (m_1 m_2)^{3/5} / (m_1+m_2)^{1/5}\)	solar masses
`eta`	Symmetric mass ratio \(\eta = m_1 m_2 / (m_1+m_2)^2 \in (0, 0.25]\)	dimensionless

ripple parameterises by \((\mathcal{M}, \eta)\) rather than component masses \((m_1, m_2)\) — use ripplegw.conversions to convert between them:

import jax.numpy as jnp
from ripplegw.conversions import Mc_eta_to_ms, ms_to_Mc_eta

m1, m2 = Mc_eta_to_ms(jnp.array([Mc, eta]))    # -> component masses, m1 >= m2
Mc, eta = ms_to_Mc_eta(jnp.array([m1, m2]))    # -> chirp mass, symmetric mass ratio

Packed arrays, not separate scalars

Every ripplegw.conversions function takes a single packed array — Mc_eta_to_ms(jnp.array([Mc, eta])), not Mc_eta_to_ms(Mc, eta).

ripplegw.conversions and ripplegw.constants are not re-exported at the top level; import them explicitly.

Spin¤

Aligned-spin models use only the spin components along the orbital angular momentum:

Name	Meaning	Range
`s1_z`, `s2_z`	Dimensionless aligned spin of the primary/secondary	\([-1, 1]\)

Precessing models (IMRPhenomPv2, IMRPhenomXP, IMRPhenomXPHM) additionally take the in-plane components:

Name	Meaning	Range
`s1_x`, `s1_y`, `s2_x`, `s2_y`	In-plane dimensionless spin components	\([-1, 1]\)

Tidal deformability¤

Tidal models (TaylorF2, IMRPhenomD_NRTidalv2, IMRPhenomXAS_NRTidalv3) take the dimensionless tidal deformability of each body, in one of two parameterisations selected by the model's use_lambda_tildes constructor argument:

`use_lambda_tildes`	Parameters	Meaning
`False` (default)	`lambda_1`, `lambda_2`	Dimensionless tidal deformability of the primary/secondary
`True`	`lambda_tilde`, `delta_lambda_tilde`	The mass-weighted combinations of arXiv:1402.5156 Eq. 5–6

Convert between them with ripplegw.conversions.lambdas_to_lambda_tildes / lambda_tildes_to_lambdas (also packed-array signatures, (lambda_1, lambda_2, mass_1, mass_2)).

Extrinsic parameters¤

Name	Meaning	Units
`d_L`	Luminosity distance	Mpc
`phase_c`	Coalescence phase	radians
`iota`	Inclination angle between the orbital angular momentum and the line of sight	radians

d_L is what at_unit_distance sets to 1.0. There is no t_c (time of coalescence) parameter — see the FAQ for why.

Bursts¤

`SineGaussian`¤

Name	Meaning	Units
`Q`	Quality factor of the sine-Gaussian envelope	dimensionless
`f_0`	Central frequency	Hz
`hrss`	Root-sum-squared strain amplitude	dimensionless (strain)
`phase`	Phase	radians
`e`	Eccentricity — controls the relative \(h_+\)/\(h_\times\) amplitude	\([0, 1]\)

SineGaussian's axis is a time grid centred at zero, not a frequency grid: t = jnp.arange(-duration/2, duration/2, 1/fs).

Continuous waves¤

The pulsar models use a time axis and share the following source parameters. The ephemerides, observation start time, and number of spin-down terms are set when constructing the waveform, rather than in params. The observing site's location, however, is a params entry (see Site location below) -- it needs to vary per call so a single model instance can be jax.vmaped over multiple sites.

Sky position and polarization¤

Name	Meaning	Units
`alpha`	Right ascension (α)	radians
`delta`	Declination (δ)	radians
`aplus`	Plus-polarization amplitude \(A_+\)	dimensionless (strain)
`across`	Cross-polarization amplitude \(A_\times\)	dimensionless (strain)

Phase evolution¤

Name	Meaning	Units
`f0`	Gravitational-wave frequency at the reference epoch	Hz
`phi0`	Phase at the reference epoch	radians
`f1`, `f2`, ..., `fN`	First through \(N\)th frequency derivatives	Hz/s, Hz/s\(^2\), ..., Hz/s\(^N\)

The waveform includes f1 through fN when it is constructed with n_spindowns=N. With the default n_spindowns=0, only f0 is used.

Site location¤

Name	Meaning	Units
`site_x`, `site_y`, `site_z`	Observing site's geocentric Cartesian location	metres

This is fixed instrument/site metadata (e.g. a LALDetectors.h vertex for H1/L1/V1) -- not a physical source parameter -- and should never be treated as a quantity to sample or place a prior on. It lives in params rather than in the constructor purely so a single model instance can be jax.vmaped over multiple observing sites in one call, sharing the expensive site-independent part of the barycentering (Earth ephemeris, rotation, precession/nutation, Einstein delay) across sites instead of recomputing it once per site.

Binary-pulsar orbit (`BinaryPulsarSignal`)¤

BinaryPulsarSignal uses all the parameters above and adds the orbital elements below.

Name	Meaning	Units
`asini`	Projected semi-major axis, \(a\sin i\)	light-seconds
`ecc`	Orbital eccentricity	dimensionless
`period`	Orbital period	seconds
`argp`	Argument of periapsis	radians
`tp_ssb`	Time of periapsis at the Solar System barycentre	GPS seconds

Physical constants¤

ripplegw.constants exposes the constants used internally (MSUN, MRSUN, MTSUN, G, C, PI, TWO_PI, MPC, EULERGAMMA) as plain Python floats, for anyone building parameter conversions of their own.