INTEGRAL's swan song: monitoring the flux evolution of the hard x-ray outburst from the AMXP IGR J17511-3057

ATel #17061; V. Sguera (INAF-OAS Bologna, Italy)
on 2 Mar 2025; 17:38 UT
Credential Certification: Vito Sguera (vito.sguera@inaf.it)

Tweet

On 10 February 2025, INTEGRAL detected the onset of a new hard X-ray outburst from the accreting millisecond X-ray pulsar (AMXP) IGR J17511-3057 (ATel #17029) after a ten-year-long quiescence phase. A prompt NICER follow-up detected 245 Hz pulsations and measured a 0.5-10 keV unabsorbed flux of about 4.3x10^-10 erg cm^-2 s^-1 (ATel #17032).

Since 10 February, INTEGRAL has performed further and regular observations of the source sky region. In the table below, we report the summary results of the INTEGRAL monitoring of the source flux evolution during the outburst in the two energy bands 28-60 keV and 60-100 keV. It is also listed the temporal range of the observation time, the effective exposure time on-source and the source significance detection.

After 2886 orbits, on 1 March 2025 17:31 UTC ESA's gamma-ray observatory INTEGRAL ended its science observations and stopped collecting scientific data.

TIME (UTC)	EXPO	FLUX 28-60 keV	DET	FLUX 60-100 keV	DET
07 Feb 15:04 - 08 Feb 11:21	13 ks	<5 mCrab	3σ U.L.	<13 mCrab	3σ U.L.
10 Feb 06:49 - 11 Feb 03:17	19 ks	16.8+-1.2 mCrab	14.5σ	21.2+-3.1 mCrab	7.0σ
11 Feb 12:50 - 12 Feb 10:11	19 ks	19.6+-1.0 mCrab	19.6σ	38.0+-3.0 mCrab	12.5σ
14 Feb 04:53 - 16 Feb 10:33	24 ks	19.8+-1.0 mCrab	20.0σ	21.2+-2.7 mCrab	8.0σ
17 Feb 19:48 - 18 Feb 13:07	14 ks	15.2+-1.3 mCrab	12.0σ	20.0+-3.5 mCrab	5.7σ
20 Feb 12:06 - 21 Feb 15:20	18 ks	18.7+-1.2 mCrab	15.5σ	20.0+-3.3 mCrab	6.0σ
22 Feb 04:27 - 24 Feb 09:04	50 ks	13.0+-0.7 mCrab	19.0σ	18.7+-1.8 mCrab	10.5σ
27 Feb 12:00 - 28 Feb 18:31	23 ks	7.4+-1.0 mCrab	7.4σ	12.0+-2.7 mCrab	4.4σ
01 Mar 01:56 - 01 Mar 17:31	10 ks	<5 mCrab	3σ U.L	<14 mCrab	3σ U.L