Detection of Oscillations in a Type I X-Ray Burst of 4U 0614+091 with SVOM/ECLAIRs

On 2025 January 10, a thermonuclear (Type I) X-ray burst from the neutron star low-mass X-ray binary $\mathit{\text{4U}}\mathit{\text{0614+091}}$ was detected with the ECLAIRs instrument on board the $\mathit{\text{SVOM}}$ mission. We present here a time-resolved spectroscopic analysis of the burst, along with the detection of burst oscillations within a 51-second interval during the decay phase. The oscillation frequency is measured to be $\nu =413.674\pm 0.002\mathrm{H}\mathrm{z}$, consistent with previous reports. However, we detect a significant downward frequency drift over the burst duration, characterized by $\dot{\nu }=(-4.7\pm 0.3)\times {10}^{-3}\mathrm{H}\mathrm{z}{\mathrm{s}}^{-1}$. This frequency evolution is atypical compared to those observed in similar burst oscillation sources. We tentatively attribute the observed drift to a Doppler shift induced by orbital motion. Under this interpretation, the inferred orbital period must be shorter than 20 minutes, placing $\mathit{\text{4U}}\mathit{\text{0614+091}}$ among the most compact known low-mass X-ray binaries.