MACHO-96-BLG-5 is a microlensing event observed towards the bulge of the Galaxy with exceptionally long duration of $\sim 970$ days. The microlensing parallax fit parameters were used to estimate the lens mass $M=6^{ +10}_{ -3}$ M$_{ \odot}$ and its distance $d$ which results to be in the range 0.5 kpc - 2 kpc. The upper limit on the absolute brightness for main-sequence stars of the same mass is less than 1 $L_{ \odot}$ so that the lens is a good black hole candidate. If it is so, the black hole would accrete by interstellar medium thereby emitting in the $X$-ray band. Here, the analysis of an { \it XMM} deep observation towards MACHO-96-BLG-5 lens position is reported. Only an upper limit (at 99.8% confidence level) to the $X$-ray flux from the lens position of $9.10\times 10^{ -15}$-- $1.45\times 10^{ -14}$ erg cm$^{ -2}$ s$^{ -1}$ in the energy band $0.2-10$ keV has been obtained from that deep observation allowing to constrain the putative black hole accretion parameters.
Categories: astro-ph