[Paper Review] Circumstellar Medium Constraints on the Environment of Two Nearby Type Ia Supernovae: SN 2017cbv and SN 2020nlb

David J. Sand, Sumit K. Sarbadhicary+24 more|arXiv (Cornell University)|Aug 25, 2021

Gamma-ray bursts and supernovae192 references24 citations

TL;DR

This study presents deep Chandra X-ray observations of two nearby Type Ia supernovae, SN 2017cbv and SN 2020nlb, finding no X-ray emission down to luminosities of ≲5.4×10³⁷ erg s⁻¹ at ~16–18 days post-explosion. These limits constrain the circumstellar medium (CSM) to low mass-loss rates (Ṁ < 7.2×10⁻⁹ M⊙ yr⁻¹) and low number densities (nCSM < 36 cm⁻³), ruling out most single-degenerate progenitor scenarios involving symbiotic stars or significant wind mass loss.

ABSTRACT

We present deep Chandra X-ray observations of two nearby Type Ia supernovae, SN 2017cbv and SN 2020nlb, which reveal no X-ray emission down to a luminosity $L_X$$\lesssim$5.3$ imes$10$^{37}$ and $\lesssim$5.4$ imes$10$^{37}$ erg s$^{-1}$ (0.3--10 keV), respectively, at $\sim$16--18 days after the explosion. With these limits, we constrain the pre-explosion mass-loss rate of the progenitor system to be $\dot{M}$$<$7.2$ imes$10$^{-9}$ and $<$9.7$ imes$10$^{-9}$ M$_{\odot}$ yr$^{-1}$ for each (at a wind velocity $v_w$=100 km s$^{-1}$ and a radius of $R$$\approx$10$^{16}$ cm), assuming any X-ray emission would originate from inverse Compton emission from optical photons up-scattered by the supernova shock. If the supernova environment was a constant density medium, we find a number density limit of n$_{CSM}$$<$36 and $<$65 cm$^{-3}$, respectively. These X-ray limits rule out all plausible symbiotic progenitor systems, as well as large swathes of parameter space associated with the single degenerate scenario, such as mass loss at the outer Lagrange point and accretion winds. We also present late-time optical spectroscopy of SN 2020nlb, and set strong limits on any swept up hydrogen ($L_{H\alpha}$$<$2.7$ imes$10$^{37}$ ergs s$^{-1}$) and helium ($L_{He, \lambda 6678}$$<$2.7$ imes$10$^{37}$ ergs s$^{-1}$) from a nondegenerate companion, corresponding to $M_{H}$$\lesssim$0.7--2$ imes$10$^{-3}$ M$_{\odot}$ and $M_{He}$$\lesssim$4$ imes$10$^{-3}$ M$_{\odot}$. Radio observations of SN 2020nlb at 14.6 days after explosion also yield a non-detection, ruling out most plausible symbiotic progenitor systems. While we have doubled the sample of normal type Ia supernovae with deep X-ray limits, more observations are needed to sample the full range of luminosities and sub-types of these explosions, and set statistical constraints on their circumbinary environments.

Motivation & Objective

• . The paper aims to constrain the circumstellar environment of two nearby Type Ia supernovae using deep X-ray observations.
• It seeks to test the viability of single-degenerate (SD) progenitor scenarios, particularly those involving mass loss from a non-degenerate companion.
• The study investigates whether X-ray emission from inverse Compton scattering of optical photons by SN shock-heated electrons can be detected.
• It combines X-ray data with late-time optical and radio observations to provide multi-wavelength constraints on the progenitor system.
• The objective is to improve statistical understanding of SN Ia progenitor diversity by expanding the sample of deep X-ray-observed SNe Ia.

Proposed method

• . Deep Chandra X-ray observations were conducted at ~16–18 days after explosion for SN 2017cbv and SN 2020nlb.
• X-ray luminosity limits were derived using the inverse Compton emission model from Margutti et al. (2012), assuming upscattering of optical photons by relativistic electrons in the SN shock.
• The circumstellar medium (CSM) was modeled as either a constant-density ISM-like medium or a wind-like medium with ρCSM = Ṁ/(4πR²vw).
• Limits on mass-loss rate (Ṁ) and number density (nCSM) were derived by comparing observed X-ray upper limits to theoretical emission models.
• Late-time optical spectroscopy of SN 2020nlb was used to search for narrow Hα and He λ6678 emission lines from swept-up hydrogen and helium.
• Radio observations with the VLA at ~14.6 days post-explosion were used to further constrain the presence of dense CSM.

Experimental results

Research questions

• RQ1 . What is the upper limit on X-ray luminosity from the circumstellar medium of SN 2017cbv and SN 2020nlb at ~16–18 days after explosion?
• RQ2 What constraints do these X-ray limits place on the pre-explosion mass-loss rate and circumstellar number density of the progenitor systems?
• RQ3 Can the presence of a non-degenerate companion in the single-degenerate scenario be ruled out based on X-ray, optical, and radio data?
• RQ4 To what extent do the X-ray and multi-wavelength constraints rule out symbiotic progenitor systems for these SNe Ia?
• RQ5 How do the results from these two SNe Ia compare with previous X-ray limits from SN 2011fe and SN 2014J in constraining the SN Ia progenitor population?

Key findings

• . No X-ray emission was detected from SN 2017cbv or SN 2020nlb, with 0.3–10 keV luminosity limits of LX ≲ 5.3×10³⁷ erg s⁻¹ and ≲5.4×10³⁷ erg s⁻¹, respectively.
• . The circumstellar medium (CSM) number density is constrained to nCSM < 36 cm⁻³ and < 65 cm⁻³ for SN 2017cbv and SN 2020nlb, assuming a constant-density ISM-like medium.
• . The pre-explosion mass-loss rate is constrained to Ṁ < 7.2×10⁻⁹ M⊙ yr⁻¹ and < 9.7×10⁻⁹ M⊙ yr⁻¹ (at vw = 100 km s⁻¹), assuming a wind-like CSM.
• . These X-ray limits rule out all plausible symbiotic progenitor systems and large portions of parameter space for the single-degenerate scenario involving mass loss at the outer Lagrange point or accretion winds.
• . Late-time optical spectroscopy of SN 2020nlb sets strong limits on swept-up hydrogen (LHα < 2.7×10³⁷ erg s⁻¹) and helium (LHe,λ6678 < 2.7×10³⁷ erg s⁻¹), corresponding to MH ≲ 0.7–2×10⁻³ M⊙ and MHe ≲ 4×10⁻³ M⊙.
• . Radio observations at 14.6 days post-explosion also yielded a non-detection, further ruling out most plausible symbiotic progenitor systems, consistent with the X-ray results.