Journal Article

Two peculiar fast transients in a strongly lensed host galaxy

Richard, J., Broadhurst, T., Rodney, S. A., Weiner, B. J., Chirivì, G., Jauzac, M., Jha, S. W., Brammer, G., Foley, R. J., Riess, A. G., Suyu, S. H., Rosati, P., Molino, A., Treu, T., Williams, L. L. R., Bradac, M., McCully, C., Grillo, C., Hoag, A., Mobasher, B., Kelly, P. L., Selsing, J., Kawamata, R., Hemmati, S., Zitrin, A., Schmidt, K. B., Diego, J. M., Hjorth, J., Graur, O., Strolger, L.-G., Balestra, I., Oguri, M., Filippenko, A. V., Sharon, K., Caminha, G. B.

2018

Overview

A massive galaxy cluster can serve as a magnifying glass for distant stellar populations, as strong gravitational lensing magnifies background galaxies and exposes details that are otherwise undetectable. In time-domain astronomy, imaging programmes with a short cadence are able to detect rapidly evolving transients, previously unseen by surveys designed for slowly evolving supernovae. Here, we describe two unusual transient events discovered in a Hubble Space Telescope programme that combined these techniques with high-cadence imaging on a field with a strong-lensing galaxy cluster. These transients were faster and fainter than any supernovae, but substantially more luminous than a classical nova. We find that they can be explained as separate eruptions of a luminous blue variable star or a recurrent nova, or as an unrelated pair of stellar microlensing events. To distinguish between these hypotheses will require clarification of the cluster lens models, along with more high-cadence imaging of the field that could detect related transient episodes. This discovery suggests that the intersection of strong lensing with high-cadence transient surveys may be a fruitful path for future astrophysical transient studies. Two unusual transient events, discovered by Hubble behind a strong-lensing galaxy cluster, can be explained as separate eruptions of a luminous blue variable star or a recurrent nova, or as an unrelated pair of stellar microlensing events.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/33/34 / 639/33/34/863 / 639/33/34/867 / Astronomy / Astrophysics and Cosmology / Physics / Physics and Astronomy / Polls & surveys / Sciences of the Universe / Space telescopes