Abstract:

Our dynamic universe helps us investigate its nature by continuously
providing explosive/eruptive transients that span an enormous range of
timescales, luminosities, and physical origins. From fast X-ray
transients, whose X-ray emission lasts from a few tens to several
thousand seconds, to supernovae that evolve over months, these
phenomena offer crucial insights into compact objects, massive stars,
and the final stages of stellar evolution. In the colloquium, I will
present two complementary studies of time-domain transients. First, I
will discuss our rigorous effort to search for optical counterparts to
fast X-ray transients discovered by the Einstein Probe mission within
the first year of its operation. Using rapid follow-up observations
with Lulin Observatory, we attempt to constrain the nature of these
enigmatic transient events. In the second part, I will turn to the
nearby Type IIP supernova SN 2024ggi in NGC 3621. I will summarize its
discovery and our early extensive follow-up campaign, and then present
constraints on its progenitor and explosion properties derived from
pre-explosion imaging and hydrodynamic modeling. Together, these
studies illustrate how coordinated multi-wavelength observations from
high-energy satellites to ground-based optical facilities, and
hydrodynamic simulations allow us to probe explosive/eruptive
astrophysical phenomena across vastly different timescales.