INTEGRAL detection of hard X-ray emission from MAXI J1828-249

ATel #5476; E. Filippova (ISDC, Switzerland), E. Kuulkers, C. Sanchez-Fernandez (ESAC, Spain), J. Wilms, V. Grinberg (ECAP, Germany), M. Cadolle-Bel (TUM, Germany), J. Chenevez (DTU, Denmark), R. Wijnands (UVA, Netherlands), M. Del Santo, A. Tarana, F. Capitanio (INAF/IAPS, Italy), E. Bozzo, C. Ferrigno (ISDC, Switzerland), J. Rodriguez (CEA, France), A. Paizis (INAF/IASF, Italy), V. Beckmann (APC, France), K. Pottschmidt (CRESST-UMBC/NASA-GSFC, USA), K. Watanabe (FGCU, USA)
on 16 Oct 2013; 16:27 UT
Distributed as an Instant Email Notice Transients
Credential Certification: E. Bozzo (enrico.bozzo@unige.ch)

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The new transient source MAXI J1828-249 (Atel #5474) was detected by the IBIS/ISGRI on-board INTEGRAL during the observations performed in the direction of the Galactic Center (from 2013 October 15 at 18:03 to 2013 October 16 at 09:10 UTC).

The improved source position determined by ISGRI is at: RA= 277.23 deg, Dec=-25.03 deg (J2000) with a 90% confinement radius of 1.3 arcmin.

In the ISGRI mosaic the source is detected at a significance level of 22.4 sigma in the 20-40 keV energy band and 18.4 sigma in the 40-80 keV energy band (effective exposure time 33.6 ks). The corresponding fluxes were of 45+/-2 mCrab and 48+/-2 mCrab.

The preliminary analysis of the ISGRI data revealed that the source spectrum is well described by a power-law model with photon index of ~1.7. From the spectral fit we estimated a flux of 3.3E-10 (4.0E-10) ergs/cm^2/s in the 20-40 keV (40-80 keV) energy band. The spectrum measured by ISGRI does not favour the hypothesis of MAXI J1828-249 being a black-hole candidate in the soft state as reported in Atel #5474.

The source was outside the JEM-X field of view during the entire observation.

Further observations with INTEGRAL in the direction of MAXI J1828-249 are already planned for the next days.