Abstract
Study of the double-detonation Type Ia supernova scenario, in which a helium-shell detonation triggers a carbon-core detonation in a sub-Chandrasekhar-mass white dwarf (WD), has experienced ...a resurgence in the past decade. New evolutionary scenarios and a better understanding of which nuclear reactions are essential have allowed for successful explosions in WDs with much thinner helium shells than in the original, decades-old incarnation of the double-detonation scenario. In this paper, we present the first suite of light curves and spectra from multidimensional radiative transfer calculations of thin-shell double-detonation models, exploring a range of WD and helium-shell masses. We find broad agreement with the observed light curves and spectra of nonpeculiar Type Ia supernovae, from subluminous to overluminous subtypes, providing evidence that double detonations of sub-Chandrasekhar-mass WDs produce the bulk of observed Type Ia supernovae. Some discrepancies in spectral velocities and colors persist, but these may be brought into agreement by future calculations that include more accurate initial conditions and radiation transport physics.
Abstract
Despite the importance of Type Ia supernovae (SNe Ia) throughout astronomy, the precise progenitor systems and explosion mechanisms that drive SNe Ia are still unknown. An explosion scenario ...that has gained traction recently is double detonation, in which an accreted shell of He detonates and triggers a secondary detonation in the underlying white dwarf. Our research presents a number of high-resolution, multidimensional, full-star simulations of thin-He-shell, sub-Chandrasekhar-mass white dwarf progenitors that undergo a double detonation. This suite of thin-shell progenitors incorporates He shells that are thinner than those in previous multidimensional studies. We confirm the viability of the double detonation across a range of He-shell parameter space, as well as present bulk yields and ejecta profiles for each progenitor. The yields obtained are generally consistent with previous works and indicate the likelihood of producing observables that resemble SNe Ia. The dimensionality of our simulations allow us to examine features of the double detonation more closely, including the details of the off-center secondary ignition and asymmetric ejecta. We find considerable differences in the high-velocity extent of postdetonation products across different lines of sight. The data from this work will be used to generate predicted observables and may further support the viability of the double detonation scenario as an SN Ia channel, as well as show how the properties of the progenitor or viewing angle may influence trends in observable characteristics.
Abstract
We present observations of SN 2022joj, a peculiar Type Ia supernova discovered by the Zwicky Transient Facility. SN 2022joj exhibits an unusually red
g
ZTF
−
r
ZTF
color at early times and a ...rapid blueward evolution afterward. Around maximum brightness, SN 2022joj shows a high luminosity (
M
g
ZTF
,
max
≃
−
19.7
mag), a blue broadband color (
g
ZTF
−
r
ZTF
≃ −0.2 mag), and shallow Si
ii
absorption lines, consistent with those of overluminous, SN 1991T-like events. The maximum-light spectrum also shows prominent absorption around 4200 Å, which resembles the Ti
ii
features in subluminous, SN 1991bg-like events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red ultraviolet minus optical colors at maximum luminosity (
u
−
v
≃ 0.6 mag and
uvw
1 −
v
≃ 2.5 mag), suggesting a suppression of flux at ∼2500–4000 Å. Strong C
ii
lines are also detected at peak. We show that these unusual spectroscopic properties are broadly consistent with the helium-shell double detonation of a sub-Chandrasekhar mass (
M
≃ 1
M
⊙
) carbon/oxygen white dwarf from a relatively massive helium shell (
M
s
≃ 0.04–0.1
M
⊙
), if observed along a line of sight roughly opposite to where the shell initially detonates. None of the existing models could quantitatively explain all the peculiarities observed in SN 2022joj. The low flux ratio of Ni
ii
λ
7378 to Fe
ii
λ
7155 emission in the late-time nebular spectra indicates a low yield of stable Ni isotopes, favoring a sub-Chandrasekhar mass progenitor. The significant blueshift measured in the Fe
ii
λ
7155 line is also consistent with an asymmetric chemical distribution in the ejecta, as is predicted in double-detonation models.
Double detonations of sub-Chandrasekhar-mass white dwarfs (WDs) in unstably
mass-transferring double WD binaries have become a leading contender to explain
most, if not all, Type Ia supernovae. ...However, past theoretical studies of the
explosion process have assumed relatively ad hoc initial conditions for the
helium shells in which the double detonations begin. In this work, we construct
realistic C/O WDs to use as the starting points for multidimensional double
detonation simulations. We supplement these with simplified one-dimensional
detonation calculations to gain a physical understanding of the conditions
under which shell detonations can propagate successfully. We find that C/O WDs
<= 1.0 Msol, which make up the majority of C/O WDs, are born with structures
that can support double detonations. More massive C/O WDs require ~1e-3 Msol of
accretion before detonations can successfully propagate in their shells, but
such accretion may be common in the double WD binaries that host massive WDs.
Our findings strongly suggest that if the direct impact accretion stream
reaches high enough temperatures and densities during mass transfer from one WD
to another, the accreting WD will undergo a double detonation. Furthermore, if
the companion is also a C/O WD <= 1.0 Msol, it will undergo its own double
detonation when impacted by the ejecta from the first explosion. Exceptions to
this outcome may explain the newly discovered class of hypervelocity supernova
survivors.
The precise origin of Type Ia supernovae (SNe Ia) is unknown despite their
value to numerous areas in astronomy. While it is a long-standing consensus
that they arise from an explosion of a ...carbon/oxygen white dwarf, the exact
progenitor configurations and explosion mechanisms that lead to SNe Ia are
still debated. One popular theory is the double detonation in which a helium
layer, accreted from a binary companion, detonates on the surface of the
primary star, leading to a converging shock-induced detonation of the
underlying core. It has recently been seen in simulations that a helium-rich
degenerate companion may undergo its own explosion triggered by the impact from
the ejecta of the primary star. We show 2D simulations that approximate a white
dwarf undergoing a double detonation which triggers the explosion of the
degenerate companion, leading to either a triple or quadruple detonation. We
also present the first multi-dimensional radiative transfer results from the
triple and quadruple detonation scenario. We find that within a range of mass
configurations of the degenerate binary, the synthetic light curves and spectra
of these events match observations as well as theoretical models of isolated
double detonations do. Notably, double and quadruple detonations that are
spectrally similar and reach the same peak brightnesses have drastically
different ejection masses and produce different amounts of Si- and Fe-group
elements. Further understanding of this scenario is needed in order to
determine if at least some observed SNe Ia actually originate from two stars
exploding.
Study of the double detonation Type Ia supernova scenario, in which a helium shell detonation triggers a carbon core detonation in a sub-Chandrasekhar-mass white dwarf, has experienced a resurgence ...in the past decade. New evolutionary scenarios and a better understanding of which nuclear reactions are essential have allowed for successful explosions in white dwarfs with much thinner helium shells than in the original, decades-old incarnation of the double detonation scenario. In this paper, we present the first suite of light curves and spectra from multi-dimensional radiative transfer calculations of thin-shell double detonation models, exploring a range of white dwarf and helium shell masses. We find broad agreement with the observed light curves and spectra of non-peculiar Type Ia supernovae, from subluminous to overluminous subtypes, providing evidence that double detonations of sub-Chandrasekhar-mass white dwarfs produce the bulk of observed Type Ia supernovae. Some discrepancies in spectral velocities and colors persist, but these may be brought into agreement by future calculations that include more accurate initial conditions and radiation transport physics.
Despite the importance of Type Ia supernovae (SNe Ia) throughout astronomy, the precise progenitor systems and explosion mechanisms that drive SNe Ia are still unknown. An explosion scenario that has ...gained traction recently is the double detonation in which an accreted shell of He detonates and triggers a secondary detonation in the underlying white dwarf. Our research presents a number of high resolution, multi-dimensional, full star simulations of thin-He-shell, sub-Chandrasekhar-mass white dwarf progenitors that undergo a double detonation. This suite of thin-shell progenitors incorporates He shells that are thinner than those in previous multi-dimensional studies. We confirm the viability of the double detonation across a range of He shell parameter space as well as present bulk yields and ejecta profiles for each progenitor. The yields obtained are generally consistent with previous works and indicate the likelihood of producing observables that resemble SNe Ia. The dimensionality of our simulations allow us to examine features of the double detonation more closely, including the details of the off-center secondary ignition and asymmetric ejecta. We find considerable differences in the high-velocity extent of post-detonation products across different lines of sight. The data from this work will be used to generate predicted observables and may further support the viability of the double detonation scenario as a SNe Ia channel as well as show how properties of the progenitor or viewing angle may influence trends in observable characteristics.
We present observations of SN 2022joj, a peculiar Type Ia supernova (SN Ia) discovered by the Zwicky Transient Facility (ZTF). SN 2022joj exhibits an unusually red \(g_\mathrm{ZTF}-r_\mathrm{ZTF}\) ...color at early times and a rapid blueward evolution afterward. Around maximum brightness, SN 2022joj shows a high luminosity (\(M_{g_\mathrm{ZTF},\mathrm{max}}\simeq-19.7\) mag), a blue broadband color (\(g_\mathrm{ZTF}-r_\mathrm{ZTF}\simeq-0.2\) mag), and shallow Si II absorption lines, consistent with those of overluminous, SN 1991T-like events. The maximum-light spectrum also shows prominent absorption around 4200 Å, which resembles the Ti II features in subluminous, SN 1991bg-like events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red ultraviolet minus optical colors at maximum luminosity (\(u-v\simeq0.6\) mag and \(uvw1 - v\simeq2.5\) mag), suggesting a suppression of flux at \(\sim\)2500--4000 Å. Strong C II lines are also detected at peak. We show that these unusual spectroscopic properties are broadly consistent with the helium-shell double detonation of a sub-Chandrasekhar mass (\(M\simeq1 \mathrm{M_\odot}\)) carbon/oxygen (C/O) white dwarf (WD) from a relatively massive helium shell (\(M_s\simeq0.04\)--\(0.1 \mathrm{M_\odot}\)), if observed along a line of sight roughly opposite to where the shell initially detonates. None of the existing models could quantitatively explain all the peculiarities observed in SN 2022joj. The low flux ratio of Ni II \(\lambda\)7378 to Fe II \(\lambda\)7155 emission in the late-time nebular spectra indicates a low yield of stable Ni isotopes, favoring a sub-Chandrasekhar mass progenitor. The significant blueshift measured in the Fe II \(\lambda\)7155 line is also consistent with an asymmetric chemical distribution in the ejecta, as is predicted in double-detonation models.
Abstract
Type Ia supernovae (SNe Ia) span a range of luminosities and timescales, from rapidly evolving subluminous to slowly evolving overluminous subtypes. Previous theoretical work has, for the ...most part, been unable to match the entire breadth of observed SNe Ia with one progenitor scenario. Here, for the first time, we apply non-local thermodynamic equilibrium radiative transfer calculations to a range of accurate explosion models of sub-Chandrasekhar-mass white dwarf detonations. The resulting photometry and spectra are in excellent agreement with the range of observed nonpeculiar SNe Ia through 15 days after the time of
B
-band maximum, yielding one of the first examples of a quantitative match to the entire Phillips relation. The intermediate-mass element velocities inferred from theoretical spectra at maximum light for the more massive white dwarf explosions are higher than those of bright observed SNe Ia, but these and other discrepancies likely stem from the one-dimensional nature of our explosion models and will be improved upon by future non-local thermodynamic equilibrium radiation transport calculations of multidimensional sub-Chandrasekhar-mass white dwarf detonations.
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