| Name: Shashikant Gupta |
| Affiliation: GD Goenka University, Gurugram |
| Conference ID: ASI2026_498 |
| Title: On the Relation between the Near-Infrared Secondary Maximum and the B-band Decline Rate of Type Ia Supernovae |
| Abstract Type: Poster |
| Abstract Category: Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Author(s) and Co-Author(s) with Affiliation: Jagriti Gaba(GD Goenka University, Gurugram-122103, India), Rahul Kumar Thakur(IILM University, Gurugram-122003, India), Dinkar Verma(GD Goenka University, Gurugram-122103, India), Naresh Sharma(GD Goenka University, Gurugram-122103, India), Shashikant Gupta(GD Goenka University, Gurugram-122103, India) |
| Abstract: Type Ia supernovae (SNe Ia) are among the most important cosmological probes at present. Their light curves in the optical and near-infrared (NIR) bands provide crucial information and were instrumental in the discovery of the accelerated expansion of the Universe. The Phillips relation, which links the peak luminosity to the B-band decline rate, has played a key role in calibrating SNe Ia as secondary distance indicators. Subsequent light-curve fitters, such as SALT2 and SNooPy, further improved this calibration by incorporating multi-band photometric observations. Recent studies suggest that NIR light curves can yield more precise distance estimates, as they are less affected by dust extinction. In particular, the J-band light curves of SNe Ia exhibit a prominent secondary maximum, which is believed to arise from changes in the ionization state of the ejecta. The timing of this NIR secondary maximum, denoted as $t_2$, is expected to correlate with the B-band decline rate parameter $\Delta m_{15}$.
In the present study, we investigate this relationship using a sample of 54 SNe Ia with well-defined secondary maxima, drawn from the Carnegie Supernova Project. Our analysis confirms the previously reported anti-correlation between $\Delta m_{15}$ and $t_2$. We further employ machine-learning–based regression techniques to capture possible nonlinear behavior in this relation. Our results indicate that the ($\Delta m_{15}$–$t_2 $) anti-correlation is not uniform, but instead shows a clear luminosity dependence. A break point at ($ \Delta m_{15} \sim 1.2 $) is identified, separating the SNe into two distinct groups associated with different host galaxy morphologies. These findings have important implications for improving the calibration of SNe Ia for precision distance measurements. |
