NICER / ISS Science Nugget
for November 7, 2019

MAXI points NICER to a new brightening source

On November 3rd, NICER began observations of the new X-ray transient called MAXI J0637-430. Discovered earlier in the day by the ISS JAXA payload MAXI, MAXI J0637-430's position was determined with high accuracy by NASA's Swift observatory.

NICER observations have shown a clear brightening and spectral hardening (see figure) over the past 4 days. MAXI J0637-430 seems to be a new low mass X-ray binary (LMXB). A LMXB is a binary system that includes a low mass star as well as a compact object such as a black hole or neutron star.

NICER will continue observations to look for clues as to the nature of the compact object.

Light curve and hardness ratio for MAXI J0637-430

Figure: The measured X-ray flux of MAXI J0637-430 determined by NICER on November 3–7, 2019 is shown in the top panel. The bottom channel shows how the spectral shape has evolved in the source over the same time period. The spectral shape change is captured in a measure of the "hardness" of the source that relates count rates in high energy and a low energy bandpasses.

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