Abstract
We report the MAXI/GSC detection of a possible long-duration burst from the ultra-compact X-ray binary 4U 1850-087 and the results of NICER follow-up observations that started just 3.1 minutes after the MAXI detection via the Orbiting High-energy Monitor Alert Network (OHMAN) on the International Space Station (ISS).
The MAXI/GSC ground-based nova alert system was triggered by an X-ray burst at 2024-04-24 12:40 UT. The X-ray flux at this time was approximately 250 mCrab (5.4 x 10-10 erg/sec/cm2) in the 2-10 keV band. If MAXI had observed the peak of the burst, the X-ray flux would likely have exceeded 1 Crab (cf. ATel #7500), so the new alert apparently originated during an observation of a burst already in its decay phase.
This event was also detected by the OHMAN software running on the ISS, and a follow-up observation by NICER was successfully initiated 3.1 minutes after the MAXI trigger.
The first 350 seconds of the NICER light curve data showed strong flux variations around an overall decay trend (decreasing from approximately 1000 to 500 cps in the 0.3–10 keV band), with a prominent broadband dip to approximately 350 cps lasting about 50 seconds. Similar variability in the tail of a burst from this source has been reported in the past (ATel #5972). No such strong variability was observed in subsequent intermittent NICER observations until 11,000 sec later, with the rate decreasing to about 90 cps and remaining constant. Assuming the flux was exponentially decaying, the estimated e-folding time is roughly 40 min.
Further NICER observations of this source are underway.
NICER is a 0.2–12 keV X-ray telescope operating on the ISS. The NICER mission and portions of the NICER science team activities are funded by NASA.
The MAXI/GSC ground-based nova alert system was triggered by an X-ray burst at 2024-04-24 12:40 UT. The X-ray flux at this time was approximately 250 mCrab (5.4 x 10-10 erg/sec/cm2) in the 2-10 keV band. If MAXI had observed the peak of the burst, the X-ray flux would likely have exceeded 1 Crab (cf. ATel #7500), so the new alert apparently originated during an observation of a burst already in its decay phase.
This event was also detected by the OHMAN software running on the ISS, and a follow-up observation by NICER was successfully initiated 3.1 minutes after the MAXI trigger.
The first 350 seconds of the NICER light curve data showed strong flux variations around an overall decay trend (decreasing from approximately 1000 to 500 cps in the 0.3–10 keV band), with a prominent broadband dip to approximately 350 cps lasting about 50 seconds. Similar variability in the tail of a burst from this source has been reported in the past (ATel #5972). No such strong variability was observed in subsequent intermittent NICER observations until 11,000 sec later, with the rate decreasing to about 90 cps and remaining constant. Assuming the flux was exponentially decaying, the estimated e-folding time is roughly 40 min.
Further NICER observations of this source are underway.
NICER is a 0.2–12 keV X-ray telescope operating on the ISS. The NICER mission and portions of the NICER science team activities are funded by NASA.
| Original language | English |
|---|---|
| Publication date | 25 Apr 2024 |
| Publication status | Published - 25 Apr 2024 |
| Series | The Astronomer's telegram |
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| Number | ATel #16600 |
Keywords
- X-ray
- Binary
- Neutron Star