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 ≲ 5.3 × 10 37 and ≲ 5.4 × 10 37 erg s −1 (0.3–10 keV), respectively, at ∼16–18 days after the explosion. With these limits, we constrain the pre-explosion mass-loss rate of the progenitor system to be M ̇ < 7.2 × 10 −9 and < 9.7 × 10 −9 M ⊙ yr −1 for each (at a wind velocity v w = 100 km s −1 and a radius of R ≈ 10 16 cm), assuming any X-ray emission would originate from inverse Compton emission from optical photons upscattered by the supernova shock. If the supernova environment was a constant-density medium, we would 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 α < 2.7 × 10 37 erg s −1 ) and helium ( L He, λ 6678 < 2.7 × 10 37 erg s −1 ) from a nondegenerate companion, corresponding to M H ≲ 0.7–2 × 10 −3 M ⊙ and M He ≲ 4 × 10 −3 M ⊙ . 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 subtypes of these explosions, and set statistical constraints on their circumbinary environments.
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Chandra fails to detect X-ray emission from Type Ia SN 2018fhw/ASASSN-18tb
We report on Chandra X-ray observations of ASASSN-18tb/SN 2018fhw, a low luminosity Type Ia supernova (SN) that showed a H line in its optical spectrum. No X-ray emission was detected at the location of the SN. Upper limits to the luminosity of up to 3 × 1039 erg s−1 are calculated, depending on the assumed spectral model, temperature, and column density. These are compared to Type Ia-CSM SNe, SN 2005gj, and SN 2002ic that have been observed with Chandra in the past. The upper limits are lower than the X-ray luminosity found for the Type Ia-CSM SN 2012ca, the only Type Ia SN to have been detected in X-rays. Consideration of various scenarios for the Hα line suggests that the density of the surrounding medium at the time of Hα line detection could have been as high as 108 cm−3, but must have decreased below 5 $\times \, 10^6$ cm−3 at the time of X-ray observation. Continual X-ray observations of SNe which show a H line in their spectrum are necessary in order to establish Type Ia SNe as an X-ray emitting class.
more » « less- Award ID(s):
- 1911061
- NSF-PAR ID:
- 10395816
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 520
- Issue:
- 1
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 1362-1370
- Size(s):
- ["p. 1362-1370"]
- Sponsoring Org:
- National Science Foundation
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