41 research outputs found
Constraints on the Binary Companion to the SN Ic 1994I Progenitor
Core-collapse supernovae (SNe), which mark the deaths of massive stars, are among the most powerful explosions in the universe and are responsible, e.g., for a predominant synthesis of chemical elements in their host galaxies. The majority of massive stars are thought to be born in close binary systems. To date, putative binary companions to the progenitors of SNe may have been detected in only two cases, SNe 1993J and 2011dh. We report on the search for a companion of the progenitor of the Type Ic SN 1994I, long considered to have been the result of binary interaction. Twenty years after explosion, we used the Hubble Space Telescope to observe the SN site in the ultraviolet (F275W and F336W bands), resulting in deep upper limits on the expected companion: F275W > 26.1 mag and F336W > 24.7 mag. These allow us to exclude the presence of a main sequence companion with a mass ≳ 10 M_⊙. Through comparison with theoretical simulations of possible progenitor populations, we show that the upper limits to a companion detection exclude interacting binaries with semi-conservative (late Case A or early Case B) mass transfer. These limits tend to favor systems with non-conservative, late Case B mass transfer with intermediate initial orbital periods and mass ratios. The most likely mass range for a putative main sequence companion would be ~5–12 M_⊙, the upper end of which corresponds to the inferred upper detection limit
Recommended from our members
Effect of binary evolution on the inferred initial and final core masses of hydrogen-rich, Type II supernova progenitors
The majority of massive stars, which are the progenitors of core-collapse supernovae (SNe), are found in close binary systems. In a previous work, we modeled the fraction of hydrogen-rich, Type II SN progenitors whose evolution is affected by mass exchange with their companion, finding this to be between ≈1/3 and 1/2 for most assumptions. Here we study in more depth the impact of this binary history of Type II SN progenitors on their final pre-SN core mass distribution, using population synthesis simulations. We find that binary star progenitors of Type II SNe typically end their life with a larger core mass than they would have had if they had lived in isolation because they gained mass or merged with a companion before their explosion. The combination of the diverse binary evolutionary paths typically leads to a marginally shallower final core mass distribution. In discussing our results in the context of the red supergiant problem, that is, the reported lack of detected high luminosity progenitors, we conclude that binary evolution does not seem to significantly affect the issue. This conclusion is quite robust against our variations in the assumptions of binary physics. We also predict that inferring the initial masses of Type II SN progenitors by "age-dating"their surrounding environment systematically yields lower masses compared to methods that probe the pre-SN core mass or luminosity. A robust discrepancy between the inferred initial masses of a SN progenitor from those different techniques could indicate an evolutionary history of binary mass accretion or merging. © ESO 2020.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Rejuvenated accretors have less bound envelopes: Impact of Roche lobe overflow on subsequent common envelope events
Common envelope (CE) evolution is an outstanding open problem in stellar
evolution, critical to the formation of compact binaries including
gravitational-wave (GW) sources. In the "classical" isolated binary evolution
scenario for double compact objects, the CE is usually the second mass transfer
phase. Thus, the donor star of the CE is the product of a previous binary
interaction, often stable Roche-lobe overflow (RLOF). Because of the accretion
of mass during the first RLOF, the main-sequence core of the accretor star
grows and is "rejuvenated". This modifies the core-envelope boundary region and
decreases significantly the envelope binding energy for the remaining
evolution. Comparing accretor stars from self-consistent binary models to stars
evolved as single, we demonstrate that the rejuvenation can lower the energy
required to eject a CE by for both black hole and neutron star
progenitors, depending on the evolutionary stage and final orbital separation.
Therefore, GW progenitors experiencing a first stable mass transfer may more
easily survive subsequent possible CE events and result in possibly wider final
separations compared to current predictions. Despite their high mass, our
accretors also experience extended "blue loops", which may have observational
consequences for low-metallicity stellar populations and asteroseismology.Comment: updated to fix broken link
Predictions for the hydrogen-free ejecta of pulsational pair-instability supernovae
Present time-domain astronomy efforts will unveil a variety of rare
transients. We focus here on pulsational pair-instability evolution, which can
result in signatures observable with electromagnetic and gravitational waves.
We simulate grids of bare helium stars to characterize the resulting black hole
(BH) masses and ejecta composition, velocity, and thermal state. The stars do
not react "elastically" to the thermonuclear explosion: there is not a
one-to-one correspondence between pair-instability driven ignition and mass
ejections, causing ambiguity in what is an observable pulse. In agreement with
previous studies, we find that for carbon-oxygen core masses 28Msun<
M_CO<30.5Msun the explosions are not strong enough to affect the surface. With
increasing mass, they first cause large radial expansion
(30.5Msun<M_CO<31.4Msun), and finally, also mass ejection episodes
(M_CO>31.4Msun). The lowest mass to be fully disrupted in a pair-instability
supernova is M_CO=57Msun. Models with M_CO>121Msun reach the
photodisintegration regime, resulting in BHs with M_BH>125Msun. If the
pulsating models produce BHs via (weak) explosions, the previously-ejected
material might be hit by the blast wave. We characterize the H-free
circumstellar material from the pulsational pair-instability of helium cores
assuming simply that the ejecta maintain a constant velocity after ejection.
Our models produce He-rich ejecta with mass 10^{-3}Msun<M_CSM<40Msun. These
ejecta are typically launched at a few thousand \kms and reach distances of
~10^{12}-10^{15} cm before core-collapse. The delays between mass ejection
events and the final collapse span a wide and mass-dependent range (from
sub-hour to 10^4 years), and the shells ejected can also collide with each
other. The range of properties we find suggests a possible connection with
(some) type Ibn supernovae.Comment: accepted versio
Properties of luminous red supergiant stars in the Magellanic Clouds
There is evidence that some red supergiants (RSGs) experience short lived
phases of extreme mass loss, producing copious amounts of dust. These episodic
outburst phases help to strip the hydrogen envelope of evolved massive stars,
drastically affecting their evolution. However, to date, the observational data
of episodic mass loss is limited. This paper aims to derive surface properties
of a spectroscopic sample of fourteen dusty sources in the Magellanic Clouds
using the Baade telescope. These properties may be used for future spectral
energy distribution fitting studies to measure the mass loss rates from present
circumstellar dust expelled from the star through outbursts. We apply MARCS
models to obtain the effective temperature () and extinction
() from the optical TiO bands. We use a routine to determine the
best fit model to the obtained spectra. We compute the using
empirical photometric relations and compare this to our modelled .
We have identified a new yellow supergiant and spectroscopically confirmed
eight new RSGs and one bright giant in the Magellanic Clouds. Additionally, we
observed a supergiant B[e] star and found that the spectral type has changed
compared to previous classifications, confirming that the spectral type is
variable over decades. For the RSGs, we obtained the surface and global
properties, as well as the extinction . Our method has picked up eight
new, luminous RSGs. Despite selecting dusty RSGs, we find values for that
are not as high as expected given the circumstellar extinction of these evolved
stars. The most remarkable object from the sample, LMC3, is an extremely
massive and luminous evolved massive star and may be grouped amongst the
largest and most luminous RSGs known in the Large Magellanic Cloud
(log(L/L5.5 and ).Comment: Accepted for publication in A&A. 17 pages, 14 figures, 4 table
The contribution from stars stripped in binaries to cosmic reionization of hydrogen and helium
Massive stars are often found in binary systems and it has been argued that
binary products boost the ionizing radiation of stellar populations. Accurate
predictions for binary products are needed to understand and quantify their
contribution to Cosmic Reionization.
We investigate the contribution of stars stripped in binaries since (1) they
are, arguably, the best-understood products of binary evolution, (2) we
recently produced the first non-LTE radiative transfer calculations for the
atmospheres of these stripped stars that predict their ionizing spectra, and
(3) they are very promising sources since they boost the ionizing emission of
stellar populations at late times. This allows stellar feedback to clear the
surroundings such that a higher fraction of their photons can escape and ionize
the intergalactic medium.
Combining our detailed predictions for the ionizing spectra with a simple
cosmic reionization model, we estimate that stripped stars contributed tens of
percent of the photons that caused cosmic reionization of hydrogen, depending
on the assumed escape fractions. More importantly, stripped stars harden the
ionizing emission. We estimate that the spectral index for the ionizing part of
the spectrum can increase to -1 compared to <-2 for single stars. At high
redshift, stripped stars and massive single stars combined dominate the
HeII-ionizing emission, but we expect active galactic nuclei drive cosmic
helium reionization.
Further observational consequences we expect are (1) high ionization states
for the intergalactic gas surrounding stellar systems, such as CIV and SiIV and
(2) additional heating of the intergalactic medium of up to a few thousand
Kelvin. Quantifying these warrants the inclusion of accurate models for
stripped stars and other binary products in full cosmological simulations.Comment: Under review in A&A, suggestions welcom