MAXI J1621–501 is the first Swift /XRT Deep Galactic Plane Survey transient that was followed up with a multitude of space missions ( NuSTAR , Swift , Chandra , NICER , INTEGRAL , and MAXI ) and ground-based observatories ( Gemini , IRSF , and ATCA ) .
The source was discovered with MAXI on 2017 October 19 as a new , unidentified transient .
Further observations with NuSTAR revealed 2 Type I X-ray bursts , identifying MAXI J1621-501 as a Low Mass X-ray Binary ( LMXB ) with a neutron star primary .
Overall , 24 Type I bursts were detected from the source during a 15 month period .
At energies below 10 keV , the source spectrum was best fit with three components : an absorbed blackbody with kT = 2.3 keV , a cutoff power law with index \Gamma = 0.7 , and an emission line centered on 6.3 keV .
Timing analysis of the X-ray persistent emission and burst data has not revealed coherent pulsations from the source or an orbital period .
We identified , however , a super-orbital period \sim 78 days in the source X-ray light curve .
This period agrees very well with the theoretically predicted radiative precession period of \sim 82 days .
Thus , MAXI J1621-501 joins a small group of sources characterized with super-orbital periods .