Discovery of burst oscillations in the newly discovered millisecond X-ray pulsar SRGA J144459.2$-$604207

Abstract

Burst oscillations during thermonuclear X-ray bursts are powered by thermonuclear energy on the neutron star (NS) surface and typically occur close to the spin frequency of the NS. We performed a comprehensive timing analysis of all thermonuclear bursts from the newly discovered millisecond X-ray pulsar SRGA J144459.2$-$604207, observed with NICER, XMM-Newton, and NuSTAR during the 2024 outburst. A total of 39 bursts were detected, allowing for a detailed search for burst oscillations, which had not been previously observed from this source. We report the discovery of burst oscillations at 447.7$-$448.0 Hz from SRGA J144459.2$-$604207 using XMM-Newton and NuSTAR data, consistent with the spin frequency of the NS. The strongest burst oscillation in the XMM-Newton data occurred with a single-trial significance of $5.1\sigma$ and maximum $Z^2$ power of $\sim 31$. In the NuSTAR data, the strongest oscillation signal has a significance of $5.2\sigma$ and maximum $Z^2$ power of $\sim 32$. The folded pulse profile corresponding to the strongest signal in the 0.5-10 keV band of the XMM-Newton data shows a sinusoidal shape with a fractional rms amplitude of $\sim 8.5\%$, while the measurements of the NuSTAR data (3-40 keV range) yield $\sim 21\%$. These results represent the first detection of burst oscillations in SRGA J144459.2$-$604207. Additionally, we report the detection of 447.6 Hz oscillations occurring just before a burst onset observed with XMM-Newton. This marks only the second instance in which burst oscillations have been observed before the burst onset.

arXiv commentAccepted for publication in ApJ

References in corpus (26)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• The SRG X-ray orbital observatory, its telescopes and first scientific results
• Cyclotron lines in highly magnetized neutron stars
• Thermonuclear burst oscillations
• Propagation of thermonuclear flames on rapidly rotating neutron stars: extreme weather during type I X-ray bursts
• Rotational Evolution During Type I X-Ray Bursts
• X-ray binaries
• The ART-XC telescope on board the SRG observatory
• Broad relativistic iron emission line observed in SAX J1808.4-3658
• Helium-rich thermonuclear bursts and the distance to the accretion-powered millisecond pulsar SAX J1808.4-3658
• The magnetic field strengths of accreting millisecond pulsars
• The Frequency Stability of Millisecond Oscillations in Thermonuclear X-Ray Bursts
• Accreting Millisecond X-Ray Pulsars
• Measurement of neutron star parameters: a review of methods for low-mass X-ray binaries
• Discovery of nearly coherent oscillations with a frequency of ~567 Hz during type-I X-ray bursts of the X-ray transient and eclipsing binary X 1658-298
• Accretion-powered millisecond pulsars
• A uniform search for thermonuclear burst oscillations in the RXTE legacy dataset
• A variable 0.58--2.44 Hz quasi-periodic oscillation in the eclipsing and dipping low-mass X-ray binary EXO 0748-676
• Discovery of Polarized X-Ray Emission from the Accreting Millisecond Pulsar SRGA J144459.2-604207
• Nuclear-powered X-ray millisecond pulsars
• Discovery of a 584.65 Hz Burst Oscillation in the Low Mass X-Ray Binary 4U 1730--22
• Three-dimensional instability of flame fronts in type I X-ray bursts
• NinjaSat monitoring of Type-I X-ray bursts from the clocked burster SRGA J144459.2$-$604207
• Disk reflection and energetics from the accreting millisecond pulsar SRGA J144459.2-604207