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We report results from the spectro-timing analysis of the atoll source 4U1636$-$536 observed with NuSTAR and AstroSat during its hard spectral state. Inthree observations of 207 ks total exposure, we identify 31 thermonuclear X-raybursts including five doublets and a triplet. Recurrence time as short as 3.8minutes is seen in one of the doublets. To the best of our knowledge, this isthe shortest recurrence time known for this source. Our time-averagedspectroscopy during the bursts indicate the presence of an additional powerlawor a blackbody component in a few cases, perhaps due to varying temperaturesduring bursts or plausible deviation from ideal blackbody behavior, however, itis difficult to probe this using the time-resolved spectroscopy owing tolimited statistics. Time-resolved bursts are well fit using an absorbedblackbody model with temperatures varying between 1.7 and 2.2 keV. Burstoscillations around 581 Hz are detected with 3$\sigma$ confidence during thedecay phase in two of the X-ray bursts. One of the burst oscillations is seenat 582 Hz, a frequency observed during the 2001 superburst in this source.

NuSTAR and AstroSat observations of thermonuclear X-ray bursts with short-recurrence times in 4U 1636$-$536