Flashing with colours: Photometric indicators of an early interaction in type II supernovae
Abstract
We present early-time optical photometry and spectroscopy for a sample 27 previously unpublished type II supernovae (SNe II) observed by the Precision Observations of Infant Supernova Explosions (POISE) collaboration, combined with a literature sample of 59 events to form a total sample of 86 objects. The resulting light curves comprise near-daily cadence, percent-level precision uBgVri photometry. From spectra acquired within four days of the estimated explosion time, transient narrow emission lines of highly ionised elements, referred to as `flash features', can be identified. Based on the presence or absence of these lines, the SNe were categorised. We estimate key photometric properties, including rise times, peak absolute magnitude, and colour evolution. Our tests indicate that flash SNe are, on average, more luminous at the peak than their non-flash counterparts, which is consistent with previous studies. Interestingly, statistically significant differences were found in the rise times in the B band, with flash SNe exhibiting a tail towards longer rise times. Flash SNe are generally bluer than non-flash events, with distinct colour distributions at 20 days post explosion, likely reflecting intrinsic differences rather than host-galaxy extinction. Colour-curve breaks within 30 days of explosion provide a clear separation between flash and non-flash SNe. The change in slopes across the break, combined with the absolute peak magnitude, yield a strong diagnostic of the flash-spectroscopic properties. This indicates that photometric observations alone may be used to identify SNe experiencing an interaction with dense circumstellar material, even in the absence of early-time spectroscopy.
Related
- Neutron star-companion interaction in core-collapse supernovae. Population synthesis based on detailed binary evolution models
- The diversity of late-time interaction in Type II supernovae
- Neutron star-companion interaction in core collapse supernovae. Population synthesis based on detailed binary evolution models
- Circumbinary discs as the origin of circumstellar material around interacting H-poor supernovae and fast blue optical transients
- The impact of stellar binaries and star cluster dynamics on pair-instability supernovae
BibTeX
@misc{mendezllorca2026flashing,
title = {{Flashing with colours: Photometric indicators of an early interaction in type II supernovae}},
author = {A. Mendez-Llorca and G. Folatelli and C. P. Gutierrez and K. Ertini and C. R. Burns and N. Morrell and M. D. Stritzinger and M. Bersten and J. M. DerKacy and L. Ferrari and L. Galbany and J. T. Hinkle and W. B. Hoogendam and M. A. Tucker and C. Ashall and K. Auchettl and E. Y. Hsiao and K. Medler and C. Pfeffer and H. Xiao},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.23852},
eprint = {2610.23852},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.23852},
}
RIS
TY - UNPB
TI - Flashing with colours: Photometric indicators of an early interaction in type II supernovae
AU - A. Mendez-Llorca
AU - G. Folatelli
AU - C. P. Gutierrez
AU - K. Ertini
AU - C. R. Burns
AU - N. Morrell
AU - M. D. Stritzinger
AU - M. Bersten
AU - J. M. DerKacy
AU - L. Ferrari
AU - L. Galbany
AU - J. T. Hinkle
AU - W. B. Hoogendam
AU - M. A. Tucker
AU - C. Ashall
AU - K. Auchettl
AU - E. Y. Hsiao
AU - K. Medler
AU - C. Pfeffer
AU - H. Xiao
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2610.23852
UR - https://arxiv.org/abs/2610.23852
AB - We present early-time optical photometry and spectroscopy for a sample 27 previously unpublished type II supernovae (SNe II) observed by the Precision Observations of Infant Supernova Explosions (POISE) collaboration, combined with a literature sample of 59 events to form a total sample of 86 objects. The resulting light curves comprise near-daily cadence, percent-level precision uBgVri photometry. From spectra acquired within four days of the estimated explosion time, transient narrow emission lines of highly ionised elements, referred to as `flash features', can be identified. Based on the presence or absence of these lines, the SNe were categorised. We estimate key photometric properties, including rise times, peak absolute magnitude, and colour evolution. Our tests indicate that flash SNe are, on average, more luminous at the peak than their non-flash counterparts, which is consistent with previous studies. Interestingly, statistically significant differences were found in the rise times in the B band, with flash SNe exhibiting a tail towards longer rise times. Flash SNe are generally bluer than non-flash events, with distinct colour distributions at 20 days post explosion, likely reflecting intrinsic differences rather than host-galaxy extinction. Colour-curve breaks within 30 days of explosion provide a clear separation between flash and non-flash SNe. The change in slopes across the break, combined with the absolute peak magnitude, yield a strong diagnostic of the flash-spectroscopic properties. This indicates that photometric observations alone may be used to identify SNe experiencing an interaction with dense circumstellar material, even in the absence of early-time spectroscopy.
ER -