English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

With a booming number of Type Ia supernovae (SNe Ia) discovered within a fewdays of their explosions, a fraction of SNe Ia that show luminosity excess inthe early phase (early-excess SNe Ia) have been confirmed. In this article, wereport early-phase observations of seven photometrically normal SNe Ia (sixearly detections and one deep non-detection limit) at the COSMOS field througha half-year transient survey as a part of the Hyper Suprime-Cam SubaruStrategic Program (HSC SSP). In particular, a blue light-curve excess wasdiscovered for HSC17bmhk, a normal SN Ia with rise time longer than 18.8 days,during the first four days after the discovery. The blue early excess inoptical wavelength can be explained not only by interactions with anon-degenerate companion or surrounding dense circumstellar matter but alsoradiation powered by radioactive decays of $^{56}$Ni at the surface of the SNejecta. Given the growing evidence of the early-excess discoveries in normalSNe Ia that have longer rise times than the average and a similarity in thenature of the blue excess to a luminous SN Ia subclass, we infer that earlyexcess discovered in HSC17bmhk and other normal SNe Ia are most likelyattributed to radioactive $^{56}$Ni decay at the surface of the SN ejecta. Inorder to successfully identify normal SNe Ia with early excess similar to thatof HSC17bmhk, early UV photometries or high-cadence blue-band surveys arenecessary.

The HSC-SSP Transient Survey: Implications from Early Photometry and Rise Time of Normal Type Ia Supernovae