INTEGRAL observations of the SRGA J144459.2-60420, a new clocked burster?

ATel #16485; C. Sanchez-Fernandez (ESAC/ESA, Spain), E. Kuulkers (ESTEC/ESA, The Netherlands), C. Ferrigno (ISDC, Switzerland), J. Chenevez (DTU, Denmark)
on 26 Feb 2024; 18:03 UT
Credential Certification: Celia Sanchez-Fernandez (celia.sanchez@sciops.esa.int)

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We report here the results of INTEGRAL follow-up observations of the newly discovered transient source SRGA J144459.2-60420.

SRGA J144459.2-60420 was discovered on 2024-02-21 by the Mikhail Pavlinsky ART-XC telescope onboard the SRG observatory (Atel #16464; confirmed by MAXI, ATel #16469). The nature of the source was established as an accreting milisecond X-ray pulsar by NICER, which detected X-ray pulsations at a frequency of about 447.8 Hz (Atel #16474, #16480) and an X-ray burst in the source light curves. An independent detection on an X-ray burst was also provided by Swift/XRT (ATel #16475). The source has also been monitored at other wavelengths, and a near infra-red counterpart has been proposed (ATel #16470), while no firm optical counterpart has been established so far (ATel #16476).

INTEGRAL observed SRGA J144459.2-60420 between 2024-02-24 09:31:21 and 2024-02-25 02:51:28 (total exposure 60 ks). During these observations, the target was detected by the JEM-X detector with a significance of 230 sigma in the 3-25 keV band (effective exposure 35 ks) and by the IBIS/ISGRI detector with a significance of 33 sigma in the 28-40 keVband (effective exposure 56 ks).

10 X-ray bursts were detected by JEM-X during these observations in the 3-25 keV energy range. These bursts display typical durations of about 20 seconds, peak fluxes of about 1 Crab and e-folding decay times of about 9 seconds. The bursts also showed remarkably quasi-periodic recurrence times of 1.69 hours.

Further INTEGRAL TOO observations of the source will be executed between 2024-02-26 16:12:01 2024-02-26 16:12:01. High level INTEGRAL products will be provided at the following url: https://www.astro.unige.ch/mmoda/gallery/data-products-gallery/obs_rev_num_data_products Follow-up multi-wavelength observations are encouraged.

We thank the INTEGRAL Mission Operations and Science Operations teams for the prompt implementation of these observations.