  Monitor of All sky X-ray Image (MAXI) discovered a new outburst of an X-ray
transient source named MAXI J1421-613. Because of the detection of three X-ray
bursts from the source, it was identified as a neutron star low-mass X-ray
binary. The results of data analyses of the MAXI GSC and the Swift XRT
follow-up observations suggest that the spectral hardness remained unchanged
during the first two weeks of the outburst. All the XRT spectra in the 0.5-10
keV band can be well explained by thermal Comptonization of multi-color disk
blackbody emission. The photon index of the Comptonized component is $\approx$
2, which is typical of low-mass X-ray binaries in the low/hard state. Since
X-ray bursts have a maximum peak luminosity, it is possible to estimate the
(maximum) distance from its observed peak flux. The peak flux of the second
X-ray burst, which was observed by the GSC, is about 5 photons cm$^{-2}$
s$^{-1}$. By assuming a blackbody spectrum of 2.5 keV, the maximum distance to
the source is estimated as 7 kpc. The position of this source is contained by
the large error regions of two bright X-ray sources detected with Orbiting
Solar Observatory-7 (OSO-7) in 1970s. Besides this, no past activities at the
XRT position are reported in the literature. If MAXI J1421-613 is the same
source as (one of) them, the outburst observed with MAXI may have occurred
after the quiescence of 30-40 years.
