113 research outputs found
Some stars fade quietly: Varied Supernova explosion outcomes and their effects on the multi-phase interstellar medium
We present results from galaxy evolution simulations with a mutiphase
Interstellar medium (ISM), a mass resolution of M and a spatial
resolution of 0.5 pc. These simulations include a stellar feedback model that
includes the resolved feedback from individual massive stars and accounts for
heating from the far UV-field, non-equilibrium cooling and chemistry and
photoionization. In the default setting, individual supernova (SN) remnants are
realized as thermal injections of erg; this is our reference
simulation WLM-fid. Among the remaining seven simulations, there are two runs
where we vary this number by fixing the energy at erg and
erg (WLM-1e50 and WLM-1e52, respectively). We carry out three variations with
variable SN-energy based on the data of Sukhbold et al. (2016) (WLM-variable,
WLM-variable-lin, and WLM-variable-stoch). We run two simulations where only 10
or 60 percent of stars explode as SNe with erg, while the remaining
stars do not explode (WLM-60prob and WLM-10prob). We find that the variation in
the SN-energy, based on the tables of Sukhbold et al. (2016), has only minor
effects: the star formation rate changes by roughly a factor of two compared to
the fiducial run, and the strength of the galactic outflows in mass and energy
only decreases by roughly 30 percent, with typical values of
and (measured at a height of 3 kpc after the hot wind is
fully decoupled from the galactic ISM). In contrast, the increase and decrease
in the canonical SN-energy has a clear impact on the phase structure, with
loading factors that are at least 10 times lower/higher and a clear change in
the phase structure. We conclude that these slight modulations are driven not
by the minor change in SN-energy but rather by the stochasticity of whether or
not an event occurs when variable SN-energies are applied.Comment: 21 Pages, 9 Figures, 2 Tables, comments welcome! Submitted to Ap
Shock Breakout in 3-Dimensional Red Supergiant Envelopes
Using Athena++, we perform 3D Radiation-Hydrodynamic calculations of the
radiative breakout of the shock wave in the outer envelope of a red supergiant
(RSG) which has suffered core collapse and will become a Type IIP supernova.
The intrinsically 3D structure of the fully convective RSG envelope yields key
differences in the brightness and duration of the shock breakout (SBO) from
that predicted in a 1D stellar model. First, the lower-density `halo' of
material outside of the traditional photosphere in 3D models leads to a shock
breakout at lower densities than 1D models. This would prolong the duration of
the shock breakout flash at any given location on the surface to 1-2
hours. However, we find that the even larger impact is the intrinsically 3D
effect associated with large-scale fluctuations in density that cause the shock
to break out at different radii at different times. This substantially prolongs
the SBO duration to 3-6 hours and implies a diversity of radiative
temperatures, as different patches across the stellar surface are at different
stages of their radiative breakout and cooling at any given time. These
predicted durations are in better agreement with existing observations of SBO.
The longer durations lower the predicted luminosities by a factor of 3-10
(), and we derive the new
scalings of brightness and duration with explosion energies and stellar
properties. These intrinsically 3D properties eliminate the possibility of
using observed rise times to measure the stellar radius via light-travel time
effects.Comment: 12 pages, 13 figures, Accepted by Ap
Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
We update the capabilities of the software instrument Modules for Experiments
in Stellar Astrophysics (MESA) and enhance its ease of use and availability.
Our new approach to locating convective boundaries is consistent with the
physics of convection, and yields reliable values of the convective core mass
during both hydrogen and helium burning phases. Stars with
become white dwarfs and cool to the point where the electrons are degenerate
and the ions are strongly coupled, a realm now available to study with MESA due
to improved treatments of element diffusion, latent heat release, and blending
of equations of state. Studies of the final fates of massive stars are extended
in MESA by our addition of an approximate Riemann solver that captures shocks
and conserves energy to high accuracy during dynamic epochs. We also introduce
a 1D capability for modeling the effects of Rayleigh-Taylor instabilities that,
in combination with the coupling to a public version of the STELLA radiation
transfer instrument, creates new avenues for exploring Type II supernovae
properties. These capabilities are exhibited with exploratory models of
pair-instability supernova, pulsational pair-instability supernova, and the
formation of stellar mass black holes. The applicability of MESA is now widened
by the capability of importing multi-dimensional hydrodynamic models into MESA.
We close by introducing software modules for handling floating point exceptions
and stellar model optimization, and four new software tools -- MESAWeb,
MESA-Docker, pyMESA, and mesastar.org -- to enhance MESA's education and
research impact.Comment: 64 pages, 61 figures; Accepted to AAS Journal
From Discovery to the First Month of the Type II Supernova 2023ixf: High and Variable Mass Loss in the Final Year Before Explosion
We present the discovery of Type II supernova (SN) 2023ixf in M101, among the
closest core-collapse SNe in the last several decades, and follow-up
photometric and spectroscopic observations in the first month of its evolution.
The light curve is characterized by a rapid rise ( days) to a
luminous peak ( mag) and plateau ( mag)
extending to days with a smooth decline rate of mag
day. During the rising phase, color shows blueward evolution,
followed by redward evolution in the plateau phase. Prominent flash features of
hydrogen, helium, carbon, and nitrogen dominate the spectra up to
days after first light, with a transition to a higher ionization state in the
first days. Both the color and flash ionization states suggest
a rise in the temperature, indicative of a delayed shock-breakout inside dense
circumstellar material (CSM). From the timescales of CSM interaction, we
estimate its compact radial extent of cm. We then
construct numerical light-curve models based on both continuous and eruptive
mass-loss scenarios shortly before explosion. For the continuous mass-loss
scenario, we infer a range of mass-loss history with in the final years before explosion, with a potentially
decreasing mass loss of in
years towards the explosion. For the eruptive mass-loss scenario, we favor
eruptions releasing of the envelope at about a year before
explosion, which result in CSM with mass and extent similar to the continuous
scenario. We discuss the implications of the available multi-wavelength
constraints obtained thus far on the progenitor candidate and SN 2023ixf to our
variable CSM models.Comment: 15 pages, 5 figures, submitted to ApJ
Luminous Type II Short-Plateau Supernovae 2006Y, 2006ai, and 2016egz: A Transitional Class from Stripped Massive Red Supergiants
The diversity of Type II supernovae (SNe II) is thought to be driven mainly
by differences in their progenitor's hydrogen-rich (H-rich) envelope mass, with
SNe IIP having long plateaus ( days) and the most massive H-rich
envelopes. However, it is an ongoing mystery why SNe II with short plateaus
(tens of days) are rarely seen. Here we present optical/near-infrared
photometric and spectroscopic observations of luminous Type II short-plateau
SNe 2006Y, 2006ai, and 2016egz. Their plateaus of about -- days and
luminous optical peaks ( mag) indicate significant pre-explosion
mass loss resulting in partially-stripped H-rich envelopes and early
circumstellar material (CSM) interaction. We compute a large grid of
MESA+STELLA single-star progenitor and light-curve models with various
progenitor zero-age main-sequence (ZAMS) masses, mass-loss efficiencies,
explosion energies, Ni masses, and CSM densities. Our model grid shows a
continuous population of SNe IIP--IIL--IIb-like light-curve morphology in
descending order of H-rich envelope mass. With large Ni masses
(), short-plateau SNe II lie in a confined parameter
space as a transitional class between SNe IIL and IIb. For SNe 2006Y, 2006ai,
and 2016egz, our findings suggest high-mass red supergiant (RSG) progenitors
(--) with small H-rich envelope masses
() that experience enhanced mass
loss () for the last few
decades before the explosion. If high-mass RSGs result in rare short-plateau
SNe II, then these events might ease some of the apparent under-representation
of higher-luminosity RSGs in observed SN II progenitor samples.Comment: 26 pages, 16 figures, submitted to Ap
Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
peer reviewedWe update the capabilities of the open-knowledge software instrument Modules for Experiments in Stellar Astrophysics (MESA). RSP is a new functionality in MESAstar that models the non-linear radial stellar pulsations that characterize RR Lyrae, Cepheids, and other classes of variable stars. We significantly enhance numerical energy conservation capabilities, including during mass changes. For example, this enables calculations through the He flash that conserve energy to better than 0.001 %. To improve the modeling of rotating stars in MESA, we introduce a new approach to modifying the pressure and temperature equations of stellar structure, and a formulation of the projection effects of gravity darkening. A new scheme for tracking convective boundaries yields reliable values of the convective-core mass, and allows the natural emergence of adiabatic semiconvection regions during both core hydrogen- and helium-burning phases. We quantify the parallel performance of MESA on current generation multicore architectures and demonstrate improvements in the computational efficiency of radiative levitation. We report updates to the equation of state and nuclear reaction physics modules. We briefly discuss the current treatment of fallback in core-collapse supernova models and the thermodynamic evolution of supernova explosions. We close by discussing the new MESA Testhub software infrastructure to enhance source-code development
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