---
title: Reloaded Rossiter-McLaughlin (RRM) Technique
url: https://www.emergentmind.com/topics/reloaded-rossiter-mclaughlin-rrm
type: topic
---

# Reloaded Rossiter-McLaughlin (RRM) Technique

The Reloaded Rossiter-McLaughlin (RRM) technique is a Rossiter-McLaughlin (RM) modelling method in which the spatially resolved stellar spectrum behind a transiting planet is measured directly by scaling the continuum flux of the spectra by the transit light curve and subtracting the in-transit spectra from the out-of-transit spectra to isolate the starlight behind the planet [1602.00322]. In contrast to traditional velocimetric RM analyses, which fit the radial-velocity anomaly of disk-integrated line profiles and generally assume rigid rotation and homogeneous local line shapes, RRM directly extracts local stellar cross-correlation functions (CCFs), permits the analysis of their shape, and can incorporate differential stellar rotation and centre-to-limb variations in the convective blueshift [1602.00322]. Applications to HD 189733 and WASP-8 established RRM as a method for probing the 3D spin-orbit geometry, differential stellar rotation, and spatially resolved stellar spectra, while also demonstrating that traditional RM analyses can be significantly biased when local CCF contrast or FWHM vary along the transit chord [1602.00322; 1611.07985].

## 1. Conceptual basis

The classical RM effect is the apparent radial-velocity anomaly produced when a transiting planet occults different parts of a rotating stellar surface. Since the line-of-sight velocities depend on stellar rotation, the RM waveform is sensitive to the star-planet alignment and has been widely used to estimate the sky-projected spin-orbit angle, $\

Source: https://www.emergentmind.com/topics/reloaded-rossiter-mclaughlin-rrm