Discovery of the Infrared Counterpart of the Rapid Burster with JWST
Abstract
The Rapid Burster (MXB 1730−335) is the only known neutron star to produce both Type I and Type II X-ray bursts, making it a key system for understanding accretion physics onto neutron stars. It resides in Liller 1, a dense, metal-rich stellar system whose crowded core and ∼11 magnitudes of visual extinction have concealed the Rapid Burster's optical/infrared (OIR) counterpart for nearly five decades. Here, we present infrared observations of Liller 1 obtained with JWST/NIRCam that, for the first time, reveal the unambiguous OIR counterpart to the Rapid Burster. Caught in an X-ray active state, the counterpart exhibits dramatic infrared variability, fading by ∼ 2.5 magnitudes in JWST's F200W band (1.755−2.227 μm) with strong fluctuations on minute timescales. These observations provide an infrared anchor for the Rapid Burster and open the way for future spectroscopy and simultaneous IR and X-ray monitoring to constrain the donor's spectral type and the system's accretion physics.
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BibTeX
@misc{desai2026discovery,
title = {{Discovery of the Infrared Counterpart of the Rapid Burster with JWST}},
author = {Malina M. Desai and Kevin B. Burdge and Cristina Pallanca and Saul Rappaport and Francesco R. Ferraro and Barbara Lanzoni and Mason Ng and Paul Draghis and Emma T. Chickles and Ilaria Caiazzo and Deepto Chakrabarty},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.35956},
eprint = {2609.35956},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.35956},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Discovery of the Infrared Counterpart of the Rapid Burster with JWST
AU - Malina M. Desai
AU - Kevin B. Burdge
AU - Cristina Pallanca
AU - Saul Rappaport
AU - Francesco R. Ferraro
AU - Barbara Lanzoni
AU - Mason Ng
AU - Paul Draghis
AU - Emma T. Chickles
AU - Ilaria Caiazzo
AU - Deepto Chakrabarty
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.35956
UR - https://arxiv.org/abs/2609.35956
AB - The Rapid Burster (MXB 1730−335) is the only known neutron star to produce both Type I and Type II X-ray bursts, making it a key system for understanding accretion physics onto neutron stars. It resides in Liller 1, a dense, metal-rich stellar system whose crowded core and ∼11 magnitudes of visual extinction have concealed the Rapid Burster's optical/infrared (OIR) counterpart for nearly five decades. Here, we present infrared observations of Liller 1 obtained with JWST/NIRCam that, for the first time, reveal the unambiguous OIR counterpart to the Rapid Burster. Caught in an X-ray active state, the counterpart exhibits dramatic infrared variability, fading by ∼ 2.5 magnitudes in JWST's F200W band (1.755−2.227 μm) with strong fluctuations on minute timescales. These observations provide an infrared anchor for the Rapid Burster and open the way for future spectroscopy and simultaneous IR and X-ray monitoring to constrain the donor's spectral type and the system's accretion physics.
ER -