Archival BeppoSAX/MECS observation of MAXI J1409-619 and INTEGRAL upper limit

ATel #2965; V. Sguera, M. Orlandini, F. Frontera, (INAF/IASF Bologna), A. Bazzano (INAF/IASF Roma), A. J. Bird (Univ. Southampton)
on 22 Oct 2010; 12:40 UT
Credential Certification: Vito Sguera (sguera@astro.soton.ac.uk)

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Following the discovery of the galactic transient MAXI J1409-619 (ATel #2959) and the accurate localization by Swift/XRT (ATel #2962), we performed a search for this transient in the archival data from BeppoSAX and INTEGRAL.

We found that the Swift/XRT source position was within the field of view of the BeppoSAX/MECS instrument for 19 ks on 2000 January 29. Two sources are clearly detected in the MECS field of view, one is consistent with the Swift/XRT position: it is detected at ~8 sigma level (2-10 keV) and has coordinates RA(J2000) = 14h 08m 00.6s and Dec(J2000) = -61d 58m 19.9s (45 arcsec uncertainty). The 2-10 keV MECS spectrum of this source, rather hard, is well fit with an absorbed power law model having photon index 0.86 (+0.28/-0.28), absorption ~2.2 x 10²² cm^-2 (compatible with galactic absorption) and unabsorbed flux of 2.5 x 10^-12 erg cm^-2 s^-1 which is a factor of ~52 lower than that measured by Swift/XRT. The source MECS light curve shows variability over the entire observation with a count rate varying by a factor of ~2. We have carried out a Fourier analysis in the range from 1 to 1000 seconds and no significant coherent pulsations were found. In the 15-100 keV energy band, a marginal signal (3.6 sigma, 0.247(+0.069/-0.069) cts/s) is detected in the PDS data, consistent with the extrapolation of the MECS spectrum to higher energies. However, we cannot attribute for sure the PDS emission to the MECS source because of the lack of imaging capability of the PDS instrument which has a field of view of 1.3 degrees (FWHM), hexagonal in shape.

INTEGRAL/IBIS observed the region of the sky including MAXI J1409-619 for a total of ~2.3 Ms, no source was detected providing a 2 sigma upper limit of 0.2 mCrab (20-40 keV) and 0.4 mCrab (40-100 keV) for persistent emission. When assuming the source flux in outburst as measured by Swift/BAT, we can infer a dynamic range greater than 150 in the same energy band.

We point out that the inferred dynamical ranges of MAXI J1409-619 supports the proposed nature of candidate Supergiant Fast X-ray Transient (ATel #2962). Furthermore, we note that this X-ray transient is located inside the error circle (0.5 degrees radius) of a transient MeV source discovered by AGILE on 2008 February 21 during a flare lasting only ~1 day (ATel #1394).

We encourage further multiwavelength observations of this transient source.