  Low-mass ultrafast rotators show the typical signatures of magnetic activity
and are known to produce flares, probably as a result of magnetic reconnection.
As a consequence, the coronae of these stars exhibit very large X-ray
luminosities and high plasma temperatures, as well as a pronounced inverse FIP
effect. To probe the relationship between the coronal properties with a
spectral type of ultra-fast rotators with rotation period P < 1d, we analyse
the K3 rapid-rotator LO Peg observed with XMM-Newton and compare it with other
low-mass rapid rotators of spectral types G9-M1. We investigate the temporal
evolution of coronal properties like the temperatures, emission measures,
abundances, densities and the morphology of the involved coronal structures. We
find two distinguishable levels of activity in the XMM-Newton observation of
LO~Peg, which shows significant X-ray variability both in phase and amplitude,
implying the presence of an evolving active region on the surface. The X-ray
flux varies by 28%, possibly due to rotational modulation. During our
observation, a large X-ray flare with a peak X-ray luminosity of 2E30 erg/s and
an energy of 7.3E33 erg was observed. At the flare onset we obtain clear
signatures for the occurrence of the Neupert effect. The flare plasma also
shows an enhancement of iron by a factor of 2 during the rise and peak phase of
the flare. Our modeling analysis suggests that the scale size of the flaring
X-ray plasma is smaller than 0.5 R_star. Further, the flare loop length appears
to be smaller than the pressure scale height of the flaring plasma. Our studies
show that the X-ray properties of the LO~Peg are very similar to those of other
low-mass ultrafast rotators, i.e., the X-ray luminosity is very close to
saturation, its coronal abundances follow a trend of increasing abundance with
increasing first ionisation potential, the so-called inverse FIP effect.
