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.
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.