[Paper Review] From Out of the Blue: Swift Links 2002es-like, 2003fg-like, and Early-Time Bump Type Ia Supernovae

W. B. Hoogendam, B. J. Shappee+4 more|arXiv (Cornell University)|Sep 20, 2023

Gamma-ray bursts and supernovaePhysics and Astronomy3 citations

TL;DR

This study analyzes 42 Type Ia supernovae with Swift UV photometry and finds that 2002es-like and 2003fg-like SNe Ia exhibit distinct UV color evolution, with UVM2-UVW1 > 1.0 mag at t = -10 days, distinguishing them from normal SNe Ia. These peculiar SNe Ia also show early-time light curve bumps and two-component power-law rises, suggesting a possible progenitor continuum linking their unique UV colors, early bumps, and luminosity differences.

ABSTRACT

We collect a sample of 42 SNe Ia with Swift UV photometry and well-measured early-time light curve rises and find that 2002es-like and 2003fg-like SNe Ia have different pre-peak UV color evolutions compared to normal SNe Ia and other spectroscopic subtypes. Specifically, 2002es-like and 2003fg-like SNe Ia are cleanly separated from other SNe Ia subtypes by UVM2-UVW1>=1.0~mag at 10 days prior to B-band maximum. Furthermore, the SNe Ia that exhibit non-monotonic bumps in their rising light curves, to date, consist solely of 2002es-like and 2003fg-like SNe Ia. We also find that SNe Ia with two-component power-law rises are more luminous than SNe Ia with single-component power-law rises at pre-peak epochs. Given the similar UV colors, along with other observational similarities, we discuss a possible progenitor scenario that places 2002es-like and 2003fg-like SNe Ia along a continuum and may explain the unique UV colors, early-time bumps, and other observational similarities between these objects. Ultimately, further observations of both subtypes, especially in the near-infrared, are critical for constraining models of these peculiar thermonuclear explosions.

Motivation & Objective

• Investigate UV color evolution in early-time SNe Ia to identify subtypes with anomalous behavior.
• Determine whether 2002es-like and 2003fg-like SNe Ia share observational similarities beyond their spectroscopic classification.
• Explore the connection between early-time light curve bumps and UV color evolution in peculiar SNe Ia.
• Assess whether two-component power-law light curve fits correlate with increased luminosity in pre-peak phases.
• Propose a unified progenitor scenario that explains the co-occurrence of unique UV colors, early bumps, and luminosity in 2002es-like and 2003fg-like SNe Ia.

Proposed method

• Collected UV photometry from Swift for 42 SNe Ia with well-constrained early-time light curves.
• Calculated UV color evolution using the UVM2-UVW1 color index at t = -10 days relative to B-band maximum.
• Classified SNe Ia based on light curve morphology: single vs. two-component power-law rises and presence of early-time bumps.
• Compared UV color distributions across spectroscopic subtypes, focusing on 2002es-like and 2003fg-like SNe Ia.
• Used host-galaxy extinction estimates from Na i D line measurements and Milky Way extinction models.
• Evaluated TESS and other photometric data for early-time features, including bumps and non-monotonic rises.

Experimental results

Research questions

• RQ1 Do 2002es-like and 2003fg-like SNe Ia exhibit distinct UV color evolution compared to normal SNe Ia at pre-peak epochs?
• RQ2 Is there a correlation between early-time light curve bumps and the UV color evolution in peculiar SNe Ia?
• RQ3 Do SNe Ia with two-component power-law light curve rises show enhanced luminosity at pre-peak phases compared to single-component rises?
• RQ4 Can the observed UV colors and early-time light curve features be explained by a single progenitor scenario?
• RQ5 What role does host-galaxy extinction play in shaping the observed UV color distribution of SNe Ia?

Key findings

• 2002es-like and 2003fg-like SNe Ia are cleanly separated from other SNe Ia subtypes by UVM2-UVW1 ≥ 1.0 mag at t = -10 days relative to B-band maximum.
• All SNe Ia exhibiting non-monotonic early-time bumps in their light curves are classified as 2002es-like or 2003fg-like.
• SNe Ia with two-component power-law light curve rises are more luminous than those with single-component rises at pre-peak epochs.
• The observed UV color evolution, early-time bumps, and luminosity differences suggest a possible progenitor continuum linking 2002es-like and 2003fg-like SNe Ia.
• The similarity in UV colors and light curve morphology implies a shared physical origin, though further near-infrared observations are needed to constrain progenitor models.
• Despite some uncertainty in bump detection (e.g., SN 2021zny), the majority of early-time bump SNe Ia are consistently classified as 2002es-like or 2003fg-like.