X-ray Bursts Research Articles

Hydrogen-triggered X-Ray Bursts from SAX J1808.4−3658? The Onset of Nuclear Burning

We present a study of weak, thermonuclear X-ray bursts from the accreting millisecond X-ray pulsar SAX J1808.4−3658. We focus on a burst observed with the Neutron Star Interior Composition Explorer on 2019 August 9, and describe a similar burst observed with the Rossi X-ray Timing Explorer in 2005 June. These bursts occurred soon after outburst onset, 2.9 and 1.1 days, after the first indications of fresh accretion. We measure peak burst bolometric fluxes of 6.98 ± 0.50 × 10−9 and 1.54 ± 0.10 × 10−8 erg cm−2 s−1, respectively, which are factors of ≈30 and 15 less than the peak flux of the brightest, helium-powered bursts observed from this source. From spectral modeling we estimate the accretion rates and accreted columns at the time of each burst. For the 2019 burst we estimate an accretion rate of M ⊙ yr−1, and a column in the range 3.9–5.1 × 107 g cm−2. For the 2005 event the accretion rate was similar, but the accreted column was half of that estimated for the 2019 burst. The low accretion rates, modest columns, and evidence for a cool neutron star in quiescence, suggest these bursts are triggered by thermally unstable CNO cycle hydrogen burning. The post-burst flux level in the 2019 event appears offset from the pre-burst level by an amount consistent with quasi-stable hydrogen burning due to the temperature-insensitive, hot-CNO cycle, further suggesting hydrogen burning as the primary fuel source. This provides strong observational evidence for hydrogen-triggered bursts. We discuss our results in the context of previous theoretical modeling.

Pulse profile modelling of thermonuclear burst oscillations − I. The effect of neglecting variability

ABSTRACT We study the effects of the time-variable properties of thermonuclear X-ray bursts on modelling their millisecond-period burst oscillations. We apply the pulse profile modelling technique that is being used in the analysis of rotation-powered millisecond pulsars by the Neutron Star Interior Composition Explorer to infer masses, radii, and geometric parameters of neutron stars. By simulating and analysing a large set of models, we show that overlooking burst time-scale variability in temperatures and sizes of the hot emitting regions can result in substantial bias in the inferred mass and radius. To adequately infer neutron star properties, it is essential to develop a model for the time-variable properties or invest a substantial amount of computational time in segmenting the data into non-varying pieces. We discuss prospects for constraints from proposed future X-ray telescopes.

Revealing the Spectral State Transition of the Clocked Burster, GS 1826-238, with NuSTAR StrayCats

We present the long-term analysis of GS 1826-238, a neutron star X-ray binary known as the Clocked Burster, using data from NuSTAR StrayCats. StrayCats, a catalog of NuSTAR stray light data, contains data from bright, off-axis X-ray sources that have not been focused by the NuSTAR optics. We obtained stray light observations of the source from 2014–2021, reduced and analyzed the data using nustar-gen-utils Python tools, demonstrating the transition of the source from the island atoll state to a banana branch. We also present the light-curve analysis of Type I X-ray bursts from the Clocked Burster and show that the bursts from the banana/soft state are systematically shorter in duration than those from the island/hard state and have a higher burst fluence. From our analysis, we note an increase in the mass accretion rate of the source, and a decrease in burst frequency with the transition.

Tidal Stripping of a White Dwarf by an Intermediate-mass Black Hole

During the inspiralling of a white dwarf (WD) into an intermediate-mass black hole (∼102−5 M ⊙), both gravitational waves (GWs) and electromagnetic (EM) radiation are emitted. Once the eccentric orbit’s pericenter radius approaches the tidal radius, the WD would be tidally stripped upon each pericenter passage. The accretion of this stripped mass would produce EM radiation. It is suspected that the recently discovered new types of transients, namely the quasiperiodic eruptions and the fast ultraluminous x-ray bursts, might originate from such systems. Modeling these flares requires a prediction of the amount of stripped mass from the WD and the details of the mass supply to the accretion disk. We run hydrodynamical simulations to study the orbital parameter dependence of the stripped mass. We find that our results match the analytical estimate that the stripped mass is proportional to z 5/2, where z is the excess depth by which the WD overfills its instantaneous Roche lobe at the pericenter. The corresponding fallback rate of the stripped mass is calculated, which may be useful in interpreting the individual flaring light curve in candidate EM sources. We further calculate the long-term mass-loss evolution of a WD during its inspiral and the detectability of the GW and EM signals. The EM signal from the mass-loss stage can be easily detected: the limiting distance is ∼320(M h/104 M ⊙) Mpc for the Einstein Probe. The GW signal, for space-borne detectors such as Laser Interferometer Space Antenna or TianQin, can be detected only within the Local Supercluster (∼33 Mpc).

AstroSat and NuSTAR observations of XTE J1739−285 during the 2019–2020 outburst

ABSTRACT We report results from a study of XTE J1739−285, a transient neutron star low mass X-ray binary observed with AstroSat and NuSTAR during its 2019–2020 outburst. We detected accretion-powered X-ray pulsations at 386 Hz during very short intervals (0.5–1 s) of X-ray flares. These flares were observed during the 2019 observation of XTE J1739−285. During this observation, we also observed a correlation between intensity and hardness ratios, suggesting an increase in hardness with the increase in intensity. Moreover, a thermonuclear X-ray burst detected in our AstroSat observation during the 2020 outburst revealed the presence of coherent burst oscillations at 383 Hz during its decay phase. The frequency drift of 3 Hz during X-ray burst can be explained with r modes. Thus, making XTE J1739−285 belong to a subset of NS-LMXBs which exhibit both nuclear- and accretion-powered pulsations. The power density spectrum created using the AstroSat-laxpc observations in 2020 showed the presence of a quasi-periodic oscillation at ∼0.83 Hz. Our X-ray spectroscopy revealed significant changes in the spectra during the 2019 and 2020 outburst. We found a broad iron line emission feature in the X-ray spectrum during the 2020 observation, while this feature was relatively narrow and has a lower equivalent width in 2019, when the source was accreting at higher rates than 2020. Hard X-ray tail was observed during the 2019 observations, indicating the presence of non-thermal component in the X-ray spectra.

Multi-point study of the energy release and impulsive CME dynamics in an eruptive C7 flare

Context. The energy release in eruptive flares and the kinematics of the associated coronal mass ejections (CMEs) are interlinked and require favorable observing positions as both on-disk and off–limb signatures are necessary to characterize these events. Aims. We combine observations from different vantage points to perform a detailed study of a long duration eruptive C7 class flare that occurred on 17 April 2021 and was partially occulted from Earth view. The dynamics and thermal properties of the flare-related plasma flows, the flaring arcade, and the energy releases and particle acceleration are studied together with the kinematic evolution of the associated CME in order to place this long duration event in context of previous eruptive flare studies. Methods. We use data from the Spectrometer-Telescope for Imaging X-rays (STIX) onboard the Solar Orbiter to analyze the spectral characteristics, timing, and spatial distribution of the flare X-ray emission. Data from the Extreme Ultraviolet Imager (EUVI) onboard the Solar TErrestrial RElations Observatory-Ahead (STEREO-A) spacecraft are used for context images as well as to track the ejected plasma close to the Sun. With Atmospheric Imaging Assembly extreme ultraviolet (EUV) images from the Solar Dynamics Observatory, the flare is observed off–limb and differential emission measure maps are reconstructed. The coronagraphs onboard STEREO-A are used to track the CME out to around 8 R⊙. Results. The flare showed hard X-ray (HXR) bursts over the duration of an hour in two phases lasting from 16:04 UT to 17:05 UT. During the first phase, a strong increase in emission from hot plasma and impulsive acceleration of the CME was observed. The CME acceleration profile shows a three-part evolution of slow rise, acceleration, and propagation in line with the first STIX HXR burst phase, which is triggered by a rising hot (14 MK) plasmoid. During the CME acceleration phase, we find signatures of ongoing magnetic reconnection behind the erupting structure, in agreement with the standard eruptive flare scenario. The subsequent HXR bursts that occur about 30 min after the primary CME acceleration show a spectral hardening (from δ ≈ 7 to δ ≈ 4) but do not correspond to further CME acceleration and chromospheric evaporation. Therefore, the CME-flare feedback relationship may only be of significance within the first 25 min. of the event under study, as thereafter the flare and the CME eruption evolve independently of each other.

Discovery of the linear energy dependence of the spectral lag of X-ray bursts from SGR J1935+2154

ABSTRACTSpectral lag of the low-energy photons with respect to the high-energy ones is a common astrophysical phenomenon (such as gamma-ray bursts and the Crab Pulsar) and may serve as a key probe to the underlying radiation mechanism. However, spectral lag in keV range of the magnetar bursts has not been systematically studied yet. In this work, we perform a detailed spectral lag analysis with the Li et al.’s Cross-Correlation Function (Li-CCF) method for SGR J1935+2154 bursts observed by Insight-Hard X-ray Modulation Telescope (HXMT), Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor (GECAM), and Fermi/Gamma-ray Burst Monitor (GBM) from 2014 July to 2022 January. We discover that the spectral lags of about 61 per cent (non-zero significance >1σ) bursts from SGR J1935+2154 are linearly dependent on the photon energy (E) with tlag(E) = α(E/keV) + C, which may be explained by a linear change of the temperature of the blackbody-emitting plasma with time. The distribution of the slope (α) approximately follows a Gaussian function with mean and standard deviation of 0.02 ms keV−1 (i.e. high-energy photons arrive earlier) and 0.02 ms keV−1, respectively. We also find that the distribution can be well fitted with three Gaussians with mean values of ∼−10.009, 0.013, and 0.039 ms keV−1, which may correspond to different origins of the bursts. These spectral lag features may have important implications on the magnetar bursts.

K-shell radiation and bright spot characteristics of high-energy-density Fe-Cr-Ni plasmas influenced by X-pinch load geometry

K-shell radiation is diagnostically advantageous for the study of high-energy-density plasmas. The current work investigates the influence of load geometry on K-shell x-rays in Z-pinch plasmas produced on the 1-MA Zebra generator. Stainless steel (Fe: 69%, Cr: 20%, Ni: 9%) X-pinch wire loads are fielded with an interwire angle of 31° (small-angle) or 62.5° (large-angle), respectively and studied using various x-ray diode, imaging, and spectroscopic diagnostics. The large-angle geometry produced large, individual x-ray-emitting bright spots (> 3 keV) at the wire cross-point averaging areas ≥ 1 mm2, with noteworthy soft x-ray (> 0.75 keV) bursts and radiation yields ≤ 14.6 kJ. The small-angle geometry produced multiple x-ray-emitting bright spots extending the pinch axis with smaller average sizes (≤ 0.5 mm2), consistent with stronger current, increased radiation yield (≥ 15.5 kJ), and notable hard x-ray (> 9 keV) bursts, which peak with largest cumulative bright spot size. Spectroscopic analysis is performed with non-LTE collisional-radiative modeling, indicating a cold, nonthermal plasma region radiating from neutral to Ne-like ions, a hot, thermal region radiating from Fe and Cr He- and Li-like ions, and an intermediate region radiating Kα satellites from Li-like to O-like ions. Modeling of the nonthermal and satellite features imply a fractional hot electron abundance ∼0.1% and ∼0.5% for large- and small-angle geometries, respectively. Relative intensity analysis is performed on Heα and Kα lines, revealing intensity ratios that deviate from the original wire composition. Optical depth estimates allude to optically thick, thermal K-shell plasmas with densities consistent with non-LTE modeling.

Estimation of plasma parameters of X-pinch with time-resolved x-ray spectroscopy

We estimate the parameters of a Cu plasma generated by an X-pinch by comparing experimentally measured x-rays with synthetic data. A filtered absolute extreme ultraviolet diode array is used to measure time-resolved x-ray spectra with a spectral resolution of ∼1 keV in the energy range of 1–10 keV. The synthetic spectra of Cu plasmas with different electron temperatures, electron densities, and fast electron fractions are calculated using the FLYCHK code. For quantitative comparison with the measured spectrum, two x-ray power ratios with three different spectral ranges are calculated. We observe three x-ray bursts in X-pinch experiments with two Cu wires conducted on the SNU X-pinch at a current rise rate of ∼0.2 kA/ns. Analysis of the spectra reveals that the first burst comprises x-rays emitted by hot spots and electron beams, with characteristics similar to those observed in other X-pinches. The second and third bursts are both generated by long-lived electron beams formed after the neck structure has been completely depleted. In the second burst, the formation of the electron beam is accompanied by an increase in the electron density of the background plasma. Therefore, the long-lived electron beams generate the additional strong x-ray bursts while maintaining a plasma channel in the central region of the X-pinch. Moreover, they emit many hard x-rays (HXRs), enabling the SNU X-pinch to be used as an HXR source. This study confirms that the generation of long-lived electron beams is crucial to the dynamics of X-pinches and the generation of strong HXRs.

Mass-energy equation and the theory of photon emission derived from Bohr's theory

The Einstein's relativistic mass-energy equation ε = mc2 is also obtained from Bohr's theory. The Schrödinger equation (SE) is modified using this equation. In the hydrogenlike atom, the modified SE is solved for consistency with the eigenvalues of electron's energy derived from the Dirac equation. Based on the consistency of their eigenvalues, the theory of photon emission is expressed. From this theory, an emission process different from bremsstrahlung is expressed. X-ray and gamma-ray bursts associated with thunderclouds and lightning are discussed by this process.

An Intermediate-field Fast Radio Burst Model and the Quasi-periodic Oscillation

Quasi-periodic oscillation (QPO) signals are discovered in some fast radio bursts (FRBs) such as FRB 20191221A, as well as in the X-ray burst associated with the galactic FRB from SGR 1935+2154. We revisit the intermediate-field FRB model where the radio waves are generated as fast-magnetosonic waves through magnetic reconnection near the light cylinder. The current sheet in the magnetar wind is compressed by a low frequency pulse emitted from the inner magnetosphere to trigger magnetic reconnection. By incorporating the wave dynamics of the magnetosphere, we demonstrate how the FRB frequency, the single pulse width, and luminosity are determined by the period, magnetic field, QPO frequency and quake energetics of the magnetar. We find that this model can naturally and self-consistently interpret the X-ray/radio event from SGR 1935+2154 and the QPO in FRB 20191221A. It can also explain the observed wide energy range of repeating FRBs in a narrow bandwidth.

Spectro-temporal and type I X-ray burst analysis of GX 3+1 using AstroSat observations

ABSTRACT GX 3+1, an atoll type neutron star low-mass X-ray binary, was observed four times by Soft X-ray Telescope and The Large Area X-ray Proportional Counter on-board AstroSat between 2017 October 5 and 2018 August 9. The hardness-intensity-diagram of the source showed it to be in the soft spectral state during all the four observations. The spectra of the source could be adequately fit with a model consisting of blackbody ($\tt {bbody}$) and power--law ($\tt {powerlaw}$) components. This yielded the blackbody radius and mass accretion rate to be ∼8 km and ∼2 × 10−9 M⊙ y−1, respectively. In one of the observations, a type I X-ray burst having a rise and e-folding time of 0.6 and 5.6 s, respectively, was detected. Time-resolved spectral analysis of the burst showed that the source underwent a photospheric radius expansion. The radius of the emitting blackbody in GX 3+1 and its distance were estimated to be 9.19 $\substack{+0.97\\ -0.82}$ km and 10.17 $\substack{+0.07\\ -0.18}$ kpc, respectively. Temporal analysis of the burst yielded upper limits of the fractional root mean square amplitude of 7${{\ \rm per\ cent}}$, 5${{\ \rm per\ cent}}$, and 6${{\ \rm per\ cent}}$ during burst start, burst maximum, and right after the radius expansion phase, respectively.

Experiments probing clustering effects in explosive nucleosynthesis

Nuclear clustering affects the nucleosynthesis occurring in a number of astrophysical environments. Highly-clusterized nuclear states typically occur near particle thresholds and therefore can produce dramatic impacts on the nuclear reaction rates. This is especially true for astrophysical explosions that are driven by the consumption of helium as fuel. Such burning can occur in X-ray bursts, supernovae type Ia, and core-collapse supernovae for instance. This article will focus on the explosive astrophysical events in which nuclear clustering is most important, will discuss the types of information and tools necessary to estimate the astrophysical reaction rates, and will discuss example experiments at Notre Dame and other facilities that have or will be performed to measure the critical nuclear data needed for such estimates.

A catalogue of unusually long thermonuclear bursts on neutron stars

ABSTRACT Rare, energetic (long) thermonuclear (Type I) X-ray bursts are classified either as intermediate-duration or ‘supern’ bursts, based on their duration. Intermediate-duration bursts lasting a few to tens of minutes are thought to arise from the thermonuclear runaway of a relatively thick (≈1010 g cm−2) helium layer, while superbursts lasting hours are attributed to the detonation of an underlying carbon layer. We present a catalogue of 84 long thermonuclear bursts from 40 low-mass X-ray binaries, and defined from a new set of criteria distinguishing them from the more frequent short bursts. The three criteria are: (1) a total energy release longer than 1040 erg, (2) a photospheric radius expansion phase longer than 10 s, and (3) a burst time-scale longer than 70 s. This work is based on a comprehensive systematic analysis of 70 bursts found with INTEGRAL, RXTE, Swift, BeppoSAX, MAXI, and NICER, as well as 14 long bursts from the literature that were detected with earlier generations of X-ray instruments. For each burst, we measure its peak flux and fluence, which eventually allows us to confirm the distinction between intermediate-duration bursts and superbursts. Additionally, we list 18 bursts that only partially meet the above inclusion criteria, possibly bridging the gap between normal and intermediate-duration bursts. With this catalogue, we significantly increase the number of long-duration bursts included in the MINBAR and thereby provide a substantial sample of these rare X-ray bursts for further study.

Type I X-ray bursts’ spectra and fuel composition from the atoll and transient source 4U 1730–22

NICER observed two outbursts from the neutron star low-mass X-ray binary 4U 1730–22 in 2021 and 2022, which showed a similar spectral evolution in the hardness-intensity diagram. Seventeen type I X-ray bursts were identified in both outbursts. The X-ray burst spectra showed clear deviations from the blackbody model, firstly ∼10 s after onset. Adding the enhanced persistent emission due to the Poynting-Robertson drag or the reflection from the accretion disk both significantly improved the fitting results. We found that 12 out of 17 X-ray bursts showed the photospheric radius expansion (PRE) characteristic. Considering the nine PRE bursts out of ten X-ray bursts observed by Insight-HXMT, 78% of bursts from 4U 1730–22 exhibited PRE. According to the burst rise time, the duration, the local accretion rate, and the burst fuel composition estimated from recurrence time, we propose that these PRE bursts were powered by pure helium. From the touchdown flux of PRE bursts, we estimate the source distance of d = 7.54 ± 0.46(X = 0) kpc for a canonical neutron star with MNS = 1.4 M⊙ and RNS = 10 km.

Centrifugal barriers in magnetospheric accretion

ABSTRACT We reconsider the dynamics of accretion flows onto magnetized central star. For dipolar magnetically aligned case, the centrifugal barrier is at Rcb = (2/3)1/3Rc = 0.87Rc, where Rc = (GM/Ω2)1/3 is the corotation radius. For oblique dipole direct accretion from the corotation radius Rc is possible only for magnetic obliquity satisfying $\tan \theta _\mu \ge 1/(2 \sqrt{3})$ (θμ ≥ 16.1°). The accretion proceeds in a form of funnel flows – along two streams centred on the μ–Ω plane, with azimuthal opening angle $\cos (\Delta \phi) = { \cot ^ 2 {\theta _\mu } }/{12}$. For the magnetosphere distorted by the diamagnetic disc, the centrifugal barrier can be at as small radius as Rcb = 0.719Rc for the fully confined dipole, extending out to Rcb ∼ Rc for the magnetically balanced case. Type-II X-ray bursts in accreting neutron stars may be mediated by the centrifugal barrier; this requires nearly aligned configuration. Centrifugally barriered material trapped in the magnetosphere may lead to periodic obscuration (‘dips’) in the light curve of the host star, e.g. as observed in accreting young stellar objects and X-ray binaries.

Laser-guided lightning

Lightning discharges between charged clouds and the Earth’s surface are responsible for considerable damages and casualties. It is therefore important to develop better protection methods in addition to the traditional Franklin rod. Here we present the first demonstration that laser-induced filaments—formed in the sky by short and intense laser pulses—can guide lightning discharges over considerable distances. We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics. An experimental campaign was conducted on the Säntis mountain in north-eastern Switzerland during the summer of 2021 with a high-repetition-rate terawatt laser. The guiding of an upward negative lightning leader over a distance of 50 m was recorded by two separate high-speed cameras. The guiding of negative lightning leaders by laser filaments was corroborated in three other instances by very-high-frequency interferometric measurements, and the number of X-ray bursts detected during guided lightning events greatly increased. Although this research field has been very active for more than 20 years, this is the first field-result that experimentally demonstrates lightning guided by lasers. This work paves the way for new atmospheric applications of ultrashort lasers and represents an important step forward in the development of a laser based lightning protection for airports, launchpads or large infrastructures.

Magnetar spin-down glitch clearing the way for FRB-like bursts and a pulsed radio episode

Magnetars are a special subset of the isolated neutron star family, with X-ray and radio emission mainly powered by the decay of their immense magnetic fields. Many attributes of magnetars remain poorly understood: spin-down glitches or the sudden reductions in the star’s angular momentum, radio bursts reminiscent of extragalactic fast radio bursts (FRBs) and transient pulsed radio emission lasting months to years. Here we unveil the detection of a large spin-down glitch event (fractional change in spin frequency $$| {{\Delta }}\nu /\nu | =5.{8}_{-1.6}^{+2.6}\times 1{0}^{-6}$$ ) from the magnetar SGR 1935+2154 on 5 October 2020 (±1 day). We find no change to the source-persistent surface thermal or magnetospheric X-ray behaviour, nor is there evidence of strong X-ray bursting activity. Yet, in the subsequent days, the magnetar emitted three FRB-like radio bursts followed by a month-long episode of pulsed radio emission. Given the rarity of spin-down glitches and radio signals from magnetars, their approximate synchronicity suggests an association, providing pivotal clues to their origin and triggering mechanisms with ramifications to the broader magnetar and FRB populations. We postulate that impulsive crustal plasma shedding close to the magnetic pole generates a wind that combs out magnetic field lines, rapidly reducing the star’s angular momentum while temporarily altering the magnetospheric field geometry to permit the pair creation needed to precipitate radio emission. An abrupt slow-down in a magnetar’s rotation rate (a ‘glitch’) may be related to the subsequent emission of three radio bursts (resembling fast radio bursts) and a month-long episode of pulsed radio emission.

Beta decay along the N=Z line and its relevance in rp-process and X-Ray bursts

Nucleosynthesis in Type I X-ray bursts (XRB) proceeds eventually through the rp-process near the proton drip-line. Several N=Z nuclei act as waiting points in the reaction network chain. Astrophysical calculations of XRB light curves depend upon the theoretical modelling of the beta decays of interest, with the N=Z waiting points 64Ge, 68Se, 72Kr, 76Sr, and their second-neighbours N=Z+2 being key nuclei in this context. We have carried out different experimental campaigns at ISOLDE (CERN) to determine the B(GT) distributions, in the decay of several N=Z, N=Z+2 and their daughters, of particular relevance in rp-process calculations. To this aim the Total Absorption Spectroscopy technique is applied. Here we present results on the beta decay of 64Ga and the status of the analysis of 64Ge. Our results provide benchmarks for testing and constraining models under terrestrial conditions that can be used later for predictions in stellar environments.

ERASSt J040515.6 − 745202, an X-ray burster in the Magellanic Bridge

Context. During the third all-sky survey (eRASS3), eROSITA, the soft X-ray instrument aboard Spectrum-Roentgen-Gamma, detected a new hard X-ray transient, eRASSt J040515.6 − 745202, in the direction of the Magellanic Bridge. Aims. We arranged follow-up observations and searched for archival data to reveal the nature of the transient. Methods. Using X-ray observations with XMM-Newton, NICER, and Swift, we investigated the temporal and spectral behaviour of the source for over about 10 days. Results. The X-ray light curve obtained from the XMM-Newton observation with an ∼28 ks exposure revealed a type-I X-ray burst with a peak bolometric luminosity of at least 1.4 × 1037 erg s−1. The burst energetics are consistent with a location of the burster at the distance of the Magellanic Bridge. The relatively long exponential decay time of the burst of ∼70 s indicates that it ignited in a H-rich environment. The non-detection of the source during the other eROSITA surveys, twelve and six months before and six months after eRASS3, suggests that the burst was discovered during a moderate outburst which reached 2.6 × 1036 erg s−1 in persistent emission. During the NICER observations, the source showed alternating flux states with the high level at a similar brightness as during the XMM-Newton observation. This behaviour is likely caused by dips as also seen during the last hour of the XMM-Newton observation. Evidence for a recurrence of the dips with a period of ∼21.8 h suggests eRASSt J040515.6 − 745202 is a low-mass X-ray binary (LMXB) system with an accretion disk seen nearly edge on. We identify a multi-wavelength counterpart to the X-ray source in UVW1 and g, r, i, and z images obtained by the optical/UV monitor on XMM-Newton and the Dark Energy Camera at the Cerro Tololo Inter-American Observatory. The spectral energy distribution is consistent with radiation from an accretion disk which dominates the UV and from a cool late-type star detected in the optical to infrared wavelengths. Conclusions. After the discovery of X-ray bursts in M 31, the Magellanic Bridge is only the second location outside of the Milky Way where an X-ray burster was found. The burst uniquely identifies eRASSt J040515.6 − 745202 as an LMXB system with a neutron star. Its location in the Magellanic Bridge confirms the existence of an older stellar population which is expected if the bridge was formed by tidal interactions between the Magellanic Clouds, which stripped gas and stars from the clouds.