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INTEGRAL detection of a new outburst from the accreting pulsar GS 1843-02

ATel #7386; Ducci, L. (ISDC, Switzerland; IAAT, Germany), A. Bodaghee (GCSU, USA), E. Kuulkers (ESA/ESAC), E. Bozzo (ISDC, Switzerland)
on 13 Apr 2015; 19:39 UT
Distributed as an Instant Email Notice Transients
Credential Certification: E. Bozzo (enrico.bozzo@unige.ch)

Subjects: Transient

Referred to by ATel #: 8392, 9339

During the observations of the Scutum/Sagittarius arm performed from 2015 April 12 at 22:25 (UTC) to 2015 April 13 at 02:07 (UTC), the IBIS/ISGRI on board INTEGRAL detected renewed activity from the Be/X-ray binary system GS 1843-02 (aka 3A 1845-024).

The source is detected in the IBIS/ISGRI mosaic at a significance level of 12 (7) sigma and a flux of 19+/-1 mCrab (16+/-2 mCrab) in the 20-40 keV (40-80 keV) energy band. The source was not detected in the JEM-X mosaics. We estimated a 3 sigma upper limit of 5 mCrab in the 3-10 keV energy band (effective exposure time 6.4 ks).

The IBIS/ISGRI spectrum (effective exposure time 8.8 ks) can be reasonably well fit with a power-law model (chi^2_red/d.o.f. = 0.4/5). We estimated a power-law photon index of 2.2+/- 0.5. The 20-80 keV flux obtained from the spectral fit is (2.8+/-0.4)E-10 erg/cm2/s. Uncertainties are given at 90% c.l.

The previous outburst of GS 1843-02 was detected in 2012 August by Swift/BAT, when the source reached a 15-50 keV flux of about 40 mCrab (Atel #4350).

The outbursts detected by IBIS/ISGRI and Swift/BAT are spaced by about 959 days. Assuming the orbital period of 242.18 days reported by Finger et al. (1999), this interval corresponds to about four orbital revolutions.