Detection of unresolved strongly lensed supernovae with the 7-Dimensional Telescope

¹ Astronomy Research Center, Research Institute of Basic Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea
² Korea Astronomy and Space Science Institute (KASI), 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Korea
³ KASI Campus, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
⁴ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
⁵ Department of Physics, University of California Merced, 5200 North Lake Road, Merced, CA 95343, USA
⁶ Department of Physics & Astronomy, University of California, Los Angeles 430 Portola Plaza, Los Angeles, CA 90095, USA
⁷ Astronomy Program, Department of Physics and Astronomy, SNU, Seoul, Republic of Korea
⁸ Department of Physics & Astronomy, University of San Francisco 2130 Fulton Street, San Francisco, CA 94117-1080, USA
⁹ Physics Division, Lawrence Berkeley National Laboratory 1 Cyclotron Road, Berkeley, CA 94720, USA

^⋆ Corresponding authors: e.khalouei1991@gmail.com, shafieloo@kasi.re.kr

Received: 24 January 2025
Accepted: 24 April 2025

Abstract

Gravitationally lensed supernovae (glSNe) are a powerful tool for exploring the realms of astronomy and cosmology. Time-delay measurements and the lens modeling of glSNe can provide a robust and independent method for constraining the expansion rate of the Universe. The study of the light curves of unresolved glSNe presents a unique opportunity for using small telescopes to investigate these systems. We investigate diverse observational strategies for the initial detection of glSNe using the 7-Dimensional Telescope (7DT). This multitelescope system is composed of twenty 50 cm telescopes. We implement different observing strategies on a subset of 5807 strong-lensing systems and candidates identified within the Dark Energy Camera Legacy Survey (DECaLS), as reported in various publications. Our simulations under ideal observing conditions indicate the maximum expected annual detection rates for various glSN types (type Ia and core-collapse (CC)) using the 7DT target-observing mode in the r band at a depth of 22.04 mag as follows: 7.46 events for type Ia, 2.49 for type Ic, 0.8 for type IIb, 0.52 for type IIL, 0.78 for type IIn, 3.75 for type IIP, and 1.15 for type Ib. Furthermore, in the case of medium-band filter observations (m6000) at a depth of 20.61 in the Wide-field Time-domain Survey (WTS) program, the predicted detection rate for glSNe Ia is 2.53 yr⁻¹. These initially detected systems will be followed-up with observations with more powerful telescopes, and we therefore applied a model-independent approach to forecast the ability of measuring H₀ using a Gaussian process from type Ia supernovae (SNe Ia) data and time-delay distance information derived from glSN systems, which include both Ia and CC types. We forecast that the expected detection rate of glSN systems can achieve a precision of 2.7% in estimating the H₀.