The broad-lined type Ic supernova 2020lao experienced an energetic explosion with no central-engine signatures
Journal article, 2026
We present infant-phase observations of the broad-line Type Ic supernova (SN Ic-BL) 2020lao, including optical spectroscopy beginning within about 48 hours of the inferred explosion epoch and extending to nearly 100 days. The explosion time was constrained by power-law fits to the rising TESS and ZTF light curves, with the first ZTF detection occurring only similar to 27 hours after explosion. The optical light curves show a rapid rise that lasted for approximate to 8.8 days and a peak luminosity typical of SNe Ic-BL (i.e., M-r similar or equal to -18.5 mag). Unlike some engine-driven SN Ic-BL events, the early light curve of SN 2020lao shows no evidence of an optical afterglow or excess emission, and the absence of any detectable shock-cooling component in the TESS and ZTF data constrains the progenitor to a compact Wolf-Rayet-like star whose R-star is less than or equal to a few times the R-circle dot, ruling out any extended envelope. The spectra resemble those of the X-ray-flash-associated SN 2006aj but with systematically higher expansion velocities. From Arnett-type fits to the bolometric light curve and measured Fe II lambda 5169 line velocities, we infer a Ni-56 mass of 0.23 +/- 0.03 M-circle dot, an ejecta mass (M-ej) of 3.2 +/- 0.8 M-circle dot, and a kinetic energy (E-K) of similar to(23.1 +/- 12.4)& times;10(51) erg, corresponding to a specific kinetic energy (E-K/M-ej) of approximate to(7.2 +/- 3.5)& times;10(51) erg M-circle dot(-1). Spectral synthesis modeling broadly reproduces the photospheric-phase spectra of SN 2020lao and suggests E-K/M-ej approximate to 4.9 & times; 10(51) erg M-circle dot(-1). SN 2020lao and SN 2006aj synthesized comparable amounts of Ni-56, yet SN 2020lao exhibits E-K/M-ej values on the order of 5-10 times larger. Published VLA and Swift/XRT non-detections reveal no afterglow emission, allowing us to place stringent limits on relativistic ejecta and dense circumstellar material. Given that SN 2020lao reaches a specific kinetic energy typical of engine-driven SNe Ic-BL, the lack of an early optical excess together with the non-detections in the radio and X-ray bands suggests that if a relativistic jet was launched, the explosion must have been viewed far off axis or the jet was choked before breakout. If there was no relativistic jet, SN 2020lao would therefore be an extreme nonrelativistic SN Ic-BL. This underscores the importance of continued infant-phase, multiwavelength monitoring of these explosions.
radiative transfer
gamma-ray burst: general
supernovae: general
supernovae: individual: SN 2020lao
Author
M. D. Stritzinger
Aarhus University
T. J. Moriya
National Institutes of Natural Sciences
The Graduate University for Advanced Studies (SOKENDAI)
Monash University
S. Bose
Aarhus University
P. A. Mazzali
Max Planck Society
Liverpool John Moores University
P. Lundqvist
Stockholm University
E. Karamehmetoglu
Aarhus University
L. S. Arndt
Aarhus University
C. Ashall
University of Hawaii
L. Galbany
Spanish National Research Council (CSIC)
Inst Estudis Espacials Catalunya IEEC
W. B. Hoogendam
University of Hawaii
E. Baron
Planetary Science Institute
J. M. DerKacy
Space Telescope Science Institute (STScI)
N. Elias-Rosa
Istituto nazionale di astrofisica (INAF)
Spanish National Research Council (CSIC)
E. Y. Hsiao
Florida State University
P. Hoflich
Florida State University
E. Pian
Istituto nazionale di astrofisica (INAF)
Erik Asbjörn Mikkelsen Jensen
Chalmers, Physics, Subatomic, High Energy and Plasma Physics
S. Moran
University Of Leicester
A. Pastorello
Istituto nazionale di astrofisica (INAF)
M. Shahbandeh
Space Telescope Science Institute (STScI)
G. Valerin
Istituto nazionale di astrofisica (INAF)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 708 A305Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202558378