We present the late-time optical light curve of the ejecta of SN 1987A measured from HST imaging observations spanning the past 17 years. We find that the flux from the ejecta declined up to around year 2001, powered by the radioactive decay of 44Ti.
Then the flux started to increase, more than doubling by the end of 2009. We show that the increase is the result of energy deposited by X-rays produced in the interaction with the circumstellar medium. We suggest that the change of the dominant energy input to the ejecta, from internal to external, marks the transition from supernova to supernova remnant. The details of the observations and the modelling are described in the accompanying supplementary information.
We study the two-dimensional distribution and kinematics of the stellar and gaseous components in the centre of the blue compact dwarf galaxy, He 2-10. The aim is to compare the kinematics of gas and stars in order to determine whether they are consi
stent with one another, or if stars and gas can be decoupled due to gravitational perturbations and feedback from star formation. We have used the integral field unit ARGUS, part of FLAMES on the European Southern Observatorys Very Large Telescope, to target the near-infrared Ca-triplet in the central 300 times 480 parsecs of He 2-10. The selected wavelength regime includes several prominent spectral features, including the Paschen series and an [SIII] emission-line, which we have used to derive the kinematics of the ionised interstellar medium. We find no systematic trend in the velocities of the stars over the observed field of view and conclude that the stellar kinematics is governed by random motions. This is in contrast to the motions the ionised interstellar medium, where we find spatial velocity variations up to 60 km/s. Our gas velocity field is consistent with previous studies of both the molecular gas and the feedback-driven outflow in He 2-10. We interpret the kinematic decoupling between the stars and the gas as He 2-10 being in the process of transformation to a dwarf elliptical galaxy.
