Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2609.35956

Discovery of the Infrared Counterpart of the Rapid Burster with JWST

Malina M. Desai·Kevin B. Burdge·Cristina Pallanca·Saul Rappaport·Francesco R. Ferraro·Barbara Lanzoni·Mason Ng·Paul Draghis·Emma T. Chickles·Ilaria Caiazzo·Deepto Chakrabarty
View original source ↗Read source document ↗Export metadata ↓

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 $\sim$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 $\sim$ 2.5 magnitudes in JWST's F200W band (1.755$-$2.227 $μ$m) 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.

Explore related subjects

astro-ph.HE

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Malina M. Desai, Kevin B. Burdge, Cristina Pallanca, Saul Rappaport, Francesco R. Ferraro, Barbara Lanzoni, Mason Ng, Paul Draghis, Emma T. Chickles, Ilaria Caiazzo, Deepto Chakrabarty. 2026-09-28. Discovery of the Infrared Counterpart of the Rapid Burster with JWST. https://arxiv.org/abs/2609.35956

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

The Life and Death of Stars That Capture Primordial Black Holes

Primordial black holes (PBHs) in the asteroid mass window ($10^{17}-10^{23}\,{\rm g}$) remain viable dark matter candidates and can be captured by stars. We develop the first global framework for the evolution of stars that capture PBHs, combining analytic calculations, stellar evolution models, 3D general-relativistic magnetohydrodynamic simulations, and Monte Carlo population synthesis. We find that the fate of these systems bifurcates: PBHs that form an accretion disk before consuming the host drive explosive disruption, whereas PBHs captured too late or growing too slowly consume the star quietly. Capture is dominated by three-body interactions with planetary or stellar companions. For a solar-type host with a Jupiter analog, inspiral within a main-sequence lifetime requires $M_{\rm BH}^{\rm crit}\gtrsim 10^{22}\,{\rm g}$, while lighter PBHs generally require tighter companions. Once deposited at the center, the PBH grows through inefficient quasi-spherical Bondi accretion; if it reaches the angular-momentum threshold before consuming the host, the inflow circularizes into a disk. Our Monte Carlo calculations yield sizable quiet-consumption and explosive-disruption populations, with final PBH masses $M_{\rm BH}\sim0.01-1\,M_\odot$ and disk-forming PBH spins $a_\ast\approx0.8$. Disk formation is the point of no return: disk winds and relativistic jets of $\sim10^{45}-10^{50}\,{\rm erg\,s^{-1}}$ disrupt the star within minutes. The resulting transients may include a $\sim$day-long UV/blue signal, radio afterglow, and, if the jet escapes, an X-ray-flash/low-luminosity gamma-ray-burst (XRF/llGRB) signal. For an $O(1)$ PBH dark matter fraction and optimistic capture assumptions, the event rate can reach that of llGRBs. The low-mass, high-spin remnants offer a complementary PBH probe and possible source for subsolar BH mergers.

astro-ph.HE↗
arXiv2026

A New Scaling of Neutron Star Tidal Deformability for Directly Probing the Central Equation of State Parameter

The dimensionless tidal deformability, $Λ$, of neutron stars (NSs), inferred from gravitational-wave (GW) observations, has thus far been used primarily to constrain the pressure of dense matter near twice nuclear saturation density, leaving the core equation of state (EOS) largely inaccessible to inspiral-phase GW observations. We show that a fundamental central EOS parameter can be probed directly through $Λ$ using a perturbative analysis of the dimensionless stellar-structure and tidal-response equations formulated in terms of scaled intrinsic variables, without invoking any specific EOS model. We uncover a remarkable EOS-insensitive scaling relation between $Λ$ and the central EOS parameter $\rm{X}\equiv P_{\rm c}/\varepsilon_{\rm c}$, where $P_{\rm c}$ and $\varepsilon_{\rm c}$ denote the central pressure and energy density, respectively. The relation is validated against a broad ensemble of physically viable EOSs. Applying it to tidal deformabilities inferred from events such as GW170817 enables a direct determination of $\rm{X}$. By adopting the previously established effective upper bound $\rm{X}\lesssim0.381$, we infer a tight lower bound, $Λ_{\rm{TOV}}\gtrsim9.1^{+0.5}_{-0.5}$, for maximum-mass NSs along stable mass-radius sequences, quantitatively demonstrating that even the most compact stable NSs remain distinctly separated from black holes, for which $Λ_{\rm{BH}}=0$. These findings reveal a previously unrecognized connection between inspiral-phase tidal deformability and the central EOS parameter $\rm{X}$, establishing a direct link between GW observables and the microphysics of ultradense matter in the strong-gravity regime. The resulting scaling establishes inspiral-phase tidal deformability as a direct and largely model-insensitive probe of the central EOS parameter $\rm{X}$, and hence of key properties of NS cores.

astro-ph.HE↗
arXiv2026

Search for Diffuse Supernova Neutrino Background in the Full KamLAND Dataset with Neural-Network-Based Event Classification

We report a search for the diffuse supernova neutrino background (DSNB) with the KamLAND detector, targeting electron antineutrinos via inverse beta decay in the neutrino energy range of 8.3 to 30.8 MeV. Using liquid-scintillator exposures of 9.02 kton-year for 8.3 to 9.3 MeV and 9.42 kton-year for 9.3 to 30.8 MeV, we observe seven candidate events after applying a new deep-neural-network-based event classification technique. This result is consistent with the background-only expectation of 16.2 plus or minus 9.4 events, including systematic uncertainties associated with the neural-network selection. A spectral analysis of the energy and radial distributions finds no significant excess attributable to the DSNB. We therefore set 90 percent confidence-level upper limits on the DSNB flux of 38 to 43 per square centimeter per second, depending on the assumed DSNB model. We also derive model-independent 90 percent confidence-level upper limits on the electron-antineutrino flux, obtaining some of the most stringent constraints below 13.3 MeV. Beyond the DSNB search itself, this work demonstrates neural-network-based event classification as a promising approach for suppressing neutron-associated backgrounds in liquid-scintillator neutrino detectors.

astro-ph.HE↗