SN 2021zny: an early flux excess combined with late-time oxygen emission suggests a double white dwarf merger event

Dimitriadis, G.; Maguire, K.; Karambelkar, Viraj; Lebron, Ryan J; Liu, Chang; Kozyreva, Alexandra; Miller, A. A.; Ridden-Harper, Ryan; Anderson, J. P.; Chen, Ting-Wan; Coughlin, M. W.; Valle, M. Della; Drake, A. J.; Galbany, L.; Gromadzki, M.; Groom, Steven L.; Gutiérrez, C. P.; Ihanec, N.; Inserra, C.; Johansson, Joel; Müller-Bravo, T. E.; Nicholl, Matt; Polin, Abigail; Rusholme, B.; Schulze, S.; Sollerman, J.; Taggart, K.; Wang, Q.; Yang, Yi; Young, D. R.

doi:10.1093/mnras/stad536

Cited by 15 publications

(41 citation statements)

References 173 publications

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“…MUSSES16D4 (Jiang et al 2017) and SN 2018aoz (Ni et al 2022(Ni et al , 2023b, on the other hand, show early red excesses. Normal Type Ia SN 2018oh (Dimitriadis et al 2019a;Li et al 2019;Shappee et al 2019) and overluminous (03fg-like) Type Ia SN 2021zny (Dimitriadis et al 2023) also show early excesses in their high-cadence unfiltered light curves from Kepler 2 and the Transiting Exoplanet Survey Satellite (TESS), respectively, although the color of this excess is not known. An excess can be ruled out in three other SNe Ia with equivalent data from Kepler (Olling et al 2015).…”

Section: Introductionmentioning

confidence: 99%

The Early Light Curve of SN 2023bee: Constraining Type Ia Supernova Progenitors the Apian Way

Hosseinzadeh,

Sand,

Sarbadhicary

et al. 2023

ApJL

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We present very early photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2023bee, starting about 8 hr after the explosion, which reveal a strong excess in the optical and nearest UV (U and UVW1) bands during the first several days of explosion. This data set allows us to probe the nature of the binary companion of the exploding white dwarf and the conditions leading to its ignition. We find a good match to the Kasen model in which a main-sequence companion star stings the ejecta with a shock as they buzz past. Models of double detonations, shells of radioactive nickel near the surface, interaction with circumstellar material, and pulsational delayed detonations do not provide good matches to our light curves. We also observe signatures of unburned material, in the form of carbon absorption, in our earliest spectra. Our radio nondetections place a limit on the mass-loss rate from the putative companion that rules out a red giant but allows a main-sequence star. We discuss our results in the context of other similar SNe Ia in the literature.

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Section: Introductionmentioning

confidence: 99%

The Early Light Curve of SN 2023bee: Constraining Type Ia Supernova Progenitors the Apian Way

Hosseinzadeh,

Sand,

Sarbadhicary

et al. 2023

ApJL

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“…Recent attention has been focused on a handful of SNe Ia that display early excess flux or bumps in their UV/optical light curves relative to a power-law rise. These have been observed in normal SNe Ia (Marion et al 2016;Hosseinzadeh et al 2017;Miller et al 2018;Dimitriadis et al 2019;Wang et al 2023) and a high fraction of peculiar SNe Ia (Cao et al 2015;Jiang et al 2017Jiang et al , 2021De et al 2019;Miller et al 2020;Dimitriadis et al 2023;Srivastav et al 2023). Furthermore, the diversity of early excess flux features in their strength, duration, and color likely suggests that multiple mechanisms can lead to their formation (Jiang et al 2018).…”

Section: Introductionmentioning

confidence: 88%

“…Existing theoretical models have trouble describing all of the characteristic properties of the high-luminosity carbon-rich 03fg-like subclass of SNe Ia. No formal subclassification criteria exist for these events, but these SNe often exhibit broad light curves (Δm 15 (B) < 1.3 mag) and high peak luminosities (M B > −19.5 mag, Howell et al 2006;Yamanaka et al 2009;Scalzo et al 2010), strong carbon absorption and low absorption velocities at early times (Hicken et al 2007;Silverman et al 2011;Chakradhari et al 2014;Parrent et al 2016;Taubenberger et al 2019;Ashall et al 2021), lowionization nebular spectra (Taubenberger et al 2013a;Ashall et al 2021), forbidden calcium emission at late times (Taubenberger et al 2019;Dimitriadis et al 2022Dimitriadis et al , 2023, and early flux excesses (Jiang et al 2017(Jiang et al , 2021Chen et al 2019;Srivastav et al 2023). These SNe also tend to occur in either low-mass host galaxies or remote locations in more massive galaxies, potentially indicating a lower-metallicity progenitor than those of normal SNe Ia (Taubenberger et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…The early spectroscopic properties indicate a dense C/O-rich CSM, but the exact progenitor system is debated. Several studies invoke a DD progenitor whose CSM is produced during a dynamical disruption of one of the WDs (Taubenberger et al 2013a;Raskin & Kasen 2013;Dimitriadis et al 2022Dimitriadis et al , 2023Srivastav et al 2023), while others suggest instead that these SNe are produced from the ejecta interacting with the envelope of an asymptotic giant branch star (the "core-degenerate" scenario, Kashi & Soker 2011;Hsiao et al 2020;Ashall et al 2021). Each of these scenarios has drawbacks.…”

Section: Introductionmentioning

confidence: 99%

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An Asymmetric Double-degenerate Type Ia Supernova Explosion with a Surviving Companion Star

Siebert,

Foley,

Zenati

et al. 2023

ApJ

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We present nebular spectroscopy of SN 2020hvf, a Type Ia supernova (SN Ia) with an early bump in its light curve. SN 2020hvf shares many spectroscopic and photometric similarities to the carbon-rich high-luminosity “03fg-like” SNe Ia. At >240 days after peak brightness, we detect unambiguous emission from [Ca ii] λ λ7291, 7324, which is rarely observed in normal SNe Ia and only seen in peculiar subclasses. SN 2020hvf displays “sawtooth” emission profiles near 7300 Å that cannot be explained with single symmetric velocity components of [Fe ii], [Ni ii], and [Ca ii], indicating an asymmetric explosion. The broad [Ca ii] emission is best modeled by two velocity components offset by 1220 km s−1, which could be caused by ejecta associated with each star in the progenitor system, separated by their orbital velocity. For the first time in an SN Ia, we identify narrow (FWHM = 180 ± 40 km s−1) [Ca ii] emission, which we associate with a wind from a surviving, puffed-up companion star. Few published spectra have sufficient resolution and the signal-to-noise ratio necessary to detect similar narrow [Ca ii] emission; however, we have detected similar line profiles in other 03fg-like SNe Ia. The extremely narrow velocity width of [Ca ii] has only otherwise been observed in SNe Iax at late times. Since this event likely had a double-degenerate “super-Chandrasekhar” mass progenitor system, we suggest that a single white dwarf (WD) was fully disrupted and a wind from a surviving companion WD is producing the observed narrow emission. It is unclear whether this unique progenitor and explosion scenario can explain the diversity of 03fg-like SNe Ia, potentially indicating that multiple progenitor channels contribute to this subclass.

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“…Of particular interest are the origins of excess emission and high-velocity (HV) silicon and calcium lines seen in the early phases, and their relation to the Type Ia SN explosion mechanisms and progenitor systems. Excess emission has been identified within ∼5 days post-explosion in a few normal events (Marion et al 2016;Hosseinzadeh et al 2017;Jiang et al 2018Jiang et al , 2021Dimitriadis et al 2019Dimitriadis et al , 2023Deckers et al 2022;Sai et al 2022), and HV Si II and Ca II features, which are faster than the normal photospheric velocities (PVs) by 7000 km s −1 (Wang et al 2003;Gerardy et al 2004;Quimby et al 2006;Marion et al 2013;Silverman et al 2015), have been observed in a number of normal events before B-band maximum. In the case of the earliest Type Ia SN detected to date, SN 2018aoz, infant-phase excess emission during 1-12 hr since first light showed suppressed B-band flux attributed to line-blanket absorption by surface iron-peak elements (Ni et al 2022(Ni et al , 2023.…”

Section: Introductionmentioning

confidence: 97%

Origin of High-velocity Ejecta, Excess Emission, and Redward Color Evolution in the Infant Type Ia Supernova 2021aefx

Ni,

Moon,

Drout

et al. 2023

ApJ

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SN 2021aefx is a normal Type Ia supernova (SN) showing excess emission and redward color evolution over the first ∼ 2 days. We present analyses of this SN using our high-cadence KMTNet multiband photometry, spectroscopy, and publicly available data, including first measurements of its explosion epoch (MJD 59529.32 ± 0.16) and onset of power-law rise (t PL = MJD 59529.85 ± 0.55; often called first light) associated with the main ejecta 56Ni distribution. The first KMTNet detection of SN 2021aefx precedes t PL by ∼ 0.5 hr, indicating presence of additional power sources. Our peak-spectrum confirms its intermediate Type Ia subclassification between core-normal and broad-Line, and we estimate an ejecta mass of ∼ 1.34 M ⊙. The spectral evolution identifies material reaching >40,000 km s−1 (fastest ever observed in Type Ia SNe) and at least two split-velocity ejecta components expanding homologously: (1) a normal-velocity (∼ 12,400 km s−1) component consistent with typical photospheric evolution of near-Chandrasekhar-mass ejecta; and (2) a high-velocity (∼ 23,500 km s−1) secondary component visible during the first ∼ 3.6 days post-explosion, which locates the component within the outer <16% of the ejecta mass. Asymmetric subsonic explosion processes producing a nonspherical secondary photosphere provide an explanation for the simultaneous appearance of the two components, and may also explain the excess emission via a slight 56Ni enrichment in the outer ∼ 0.5% of the ejecta mass. Our 300 days post-peak nebular-phase spectrum advances constraints against nondegenerate companions and further supports a near-Chandrasekhar-mass explosion origin. Off-center ignited delayed-detonations are likely responsible for the observed features of SN 2021aefx in some normal Type Ia SNe.

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SN 2021zny: an early flux excess combined with late-time oxygen emission suggests a double white dwarf merger event

Cited by 15 publications

References 173 publications

The Early Light Curve of SN 2023bee: Constraining Type Ia Supernova Progenitors the Apian Way

The Early Light Curve of SN 2023bee: Constraining Type Ia Supernova Progenitors the Apian Way

An Asymmetric Double-degenerate Type Ia Supernova Explosion with a Surviving Companion Star

Origin of High-velocity Ejecta, Excess Emission, and Redward Color Evolution in the Infant Type Ia Supernova 2021aefx

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