arXiv subjects

T. E. Woods

Publications and source records attributed to T. E. Woods.

At least 19 recordsLinked to original sources

arXiv2026

Euclid: Early Release Observations -- The star-formation history of massive early-type galaxies in the Perseus cluster

The Euclid Early Release Observations (ERO) programme targeted the Perseus galaxy cluster in its central region over 0.7deg$^2$. We combined the exceptional image quality and depth of the ERO-Perseus with FUV and NUV observations from GALEX and AstroSat/UVIT, as well as $ugrizHα$ data from MegaCam at the CFHT, to deliver FUV-to-NIR magnitudes of the 87 brightest galaxies within the Perseus cluster. We reconstructed the star-formation history (SFH) of 59 early-type galaxies (ETGs) within the sample, through the spectral energy distribution (SED) fitting code CIGALE and state-of-the-art stellar population (SP) models to reproduce the galactic UV emission from hot, old, low-mass stars (i.e. the UV upturn). In addition, for the six most massive ETGs in Perseus [stellar masses $\log_{10}(M_{\ast}/M_{\odot}) \geq 10.3$], we analysed their spatially resolved SP through a radial SED fitting. In agreement with our previous work on Virgo ETGs, we found that (i) the majority of ETGs needs the presence of an UV upturn to explain their FUV emission, with temperatures $\langle T_{\rm UV}\rangle$~33800 K; (ii) ETGs have grown their stellar masses quickly, with SF timescales $τ\lesssim 1500$ Myr. We found that all ETGs in the sample have formed more than about 30% of their stellar masses at z~5, up to ~100%. At z~5, the stellar masses of the most massive nearby ETGs, which have present-day stellar masses $\log_{10}(M_{\ast}/M_{\odot})\gtrsim 10.8$, are then found to be comparable to those of the red quiescent galaxies observed by JWST at similar redshifts (z>4.6). This study can be extended to ETGs in the 14000 deg$^2$ extragalactic sky that will soon be observed by Euclid, in combination with those from other major upcoming surveys (e.g. Rubin/LSST), and UV observations, to ultimately assess whether the nearby massive ETGs represent the progeny of the massive high-z JWST red quiescent galaxies.

astro-ph.GA↗

arXiv2025

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) XVIII. Reconstructing the star formation history of early-type galaxies through the combination of their UV and H$α$ emission

We reconstruct the SFHs of 7 massive ($M_{\star}\gtrsim 10^{10} M_{\odot}$) early-type galaxies (ETGs) in the Virgo cluster by analysing their spatially resolved stellar population (SP), including their UV and H$α$ emission. As part of the VESTIGE survey, we used H$α$ images to select ETGs that show no signs of ongoing star formation. We combined VESTIGE with images from Astrosat/UVIT, GALEX and CFHT from the NGVS to analyse radial spectral energy distributions (SEDs) from the FUV to the NIR. The UV emission in these galaxies is likely due to old, low mass stars in post main sequence (PMS) phases, the UV upturn. We fit the radial SEDs with novel SP models that include an old, hot stellar component of PMS stars with various temperatures and energetics. This way, we explore the main stellar parameters responsible for UV upturn stars irregardless of their evolutionary path. Standard models are not able to reproduce the galaxies' central FUV emission (SMA/$R_{eff}\lesssim1$), while the new models well characterise it through PMS stars with temperatures T$\gtrsim$25000 K. All galaxies are old (mass-weighted ages $\gtrsim10$ Gyr) and the most massive M49 and M87 are supersolar within SMA/$R_{\rm eff}\lesssim0.2$. Overall, we found flat age gradients ($\nabla$Log(Age)$\sim -0.04 - 0$ dex) and shallow metallicity gradients ($\nabla$Log(Z)$<-0.2$ dex), except for M87 ($\nabla$Log($Z_{\rm M87}$)$\simeq-0.45$ dex). Our results show that these ETGs formed with timescales $τ\lesssim1500$ Myr, having assembled between $\sim40-90\%$ of their stellar mass at $z\sim5$. This is consistent with recent JWST observations of quiescent massive galaxies at high$-z$, which are likely the ancestors of the largest ETGs in the nearby Universe. The derived flat/shallow gradients indicate that major mergers might have contributed to the formation and evolution of these galaxies.

astro-ph.GA↗

arXiv2023

From Stellar Death to Cosmic Revelations: Zooming in on Compact Objects, Relativistic Outflows and Supernova Remnants with AXIS

Compact objects and supernova remnants provide nearby laboratories to probe the fate of stars after they die, and the way they impact, and are impacted by, their surrounding medium. The past five decades have significantly advanced our understanding of these objects, and showed that they are most relevant to our understanding of some of the most mysterious energetic events in the distant Universe, including Fast Radio Bursts and Gravitational Wave sources. However, many questions remain to be answered. These include: What powers the diversity of explosive phenomena across the electromagnetic spectrum? What are the mass and spin distributions of neutron stars and stellar mass black holes? How do interacting compact binaries with white dwarfs - the electromagnetic counterparts to gravitational wave LISA sources - form and behave? Which objects inhabit the faint end of the X-ray luminosity function? How do relativistic winds impact their surroundings? What do neutron star kicks reveal about fundamental physics and supernova explosions? How do supernova remnant shocks impact cosmic magnetism? This plethora of questions will be addressed with AXIS - the Advanced X-ray Imaging Satellite - a NASA Probe Mission Concept designed to be the premier high-angular resolution X-ray mission for the next decade. AXIS, thanks to its combined (a) unprecedented imaging resolution over its full field of view, (b) unprecedented sensitivity to faint objects due to its large effective area and low background, and (c) rapid response capability, will provide a giant leap in discovering and identifying populations of compact objects (isolated and binaries), particularly in crowded regions such as globular clusters and the Galactic Center, while addressing science questions and priorities of the US Decadal Survey for Astronomy and Astrophysics (Astro2020).

astro-ph.HE↗

arXiv2020

LIN 358: A symbiotic binary accreting above the steady hydrogen fusion limit

Symbiotic binaries are long period interacting binaries consisting of a white dwarf (WD) accreting material from a cool evolved giant star via stellar winds. In this paper we study the symbiotic binary LIN 358 located in the SMC. We have observed LIN 358 with the integral field spectrograph WiFeS and obtained its line emission spectrum. With the help of the plasma simulation and spectral synthesis code Cloudy, we have constructed a 2D photo-ionisation model of LIN 358. From comparison with the observations, we have determined the colour temperature of the WD in LIN 358 to be 19 eV, its bolometric luminosity $L = (1.02 \pm 0.15) \times 10^{38}$ erg s$^{-1}$, and the mass-loss rate from the donor star to be $ 1.2 \times 10^{-6}$ M$_{\odot}$ yr$^{-1}$. Assuming a solar H to He ratio in the wind material, a lower limit to the accreted mass fraction in LIN 358 is 0.31. The high mass-accretion efficiency of a wind Roche lobe overflow implies that the WD is accreting above the upper boundary of stable hydrogen fusion and thus growing in mass with the maximal rate of $\approx 4 \times 10^{-7}$ M$_{\odot}$ yr$^{-1}$. This causes the WD photosphere to expand, which explains its low colour temperature. Our calculations show that the circumstellar material in LIN 358 is nearly completely ionized except for a narrow cone around the donor star, and that the WD emission is freely escaping the system. However, due to its low colour temperature, this emission can be easily attenuated by even moderate amounts of neutral ISM. We speculate that other symbiotic systems may be operating in a similar regime, thus explaining the paucity of observed systems.

astro-ph.SR↗

arXiv2020

Discovery of a ~30-Year-Duration Post-Nova Pulsating Supersoft Source in the Large Magellanic Cloud

Supersoft X-ray sources (SSS) have been identified as white dwarfs accreting from binary companions and undergoing nuclear-burning of the accreted material on their surface. Although expected to be a relatively numerous population from both binary evolution models and their identification as Type Ia supernova progenitor candidates, given the very soft spectrum of SSSs relatively few are known. Here we report on the X-ray and optical properties of 1RXS J050526.3-684628, a previously unidentified accreting nuclear-burning white dwarf located in the Large Magellanic Cloud (LMC). XMM-Newton observations enabled us to study its X-ray spectrum and measure for the first time short period oscillations of ~170 s. By analysing newly obtained X-ray data by eROSITA, together with Swift observations and archival ROSAT data, we have followed its long-term evolution over the last 3 decades. We identify 1RXS J050526.3-684628 as a slowly-evolving post-nova SSS undergoing residual surface nuclear-burning, which finally reached its peak in 2013 and is now declining. Though long expected on theoretical grounds, such long-lived residual-burning objects had not yet been found. By comparison with existing models, we find that the effective temperature and luminosity evolution are consistent with a ~0.7 $M_{\odot}$ carbon-oxygen white dwarf accreting ~10$^{-9}~\rm{M}_{\odot}$/yr. Our results suggest there may be many more undiscovered SSSs and "missed" novae awaiting dedicated deep X-ray searches in the LMC and elsewhere.

astro-ph.HE↗

arXiv2020

The binary evolution of SAX J1808.4-3658: Implications of an evolved donor star

Observations of the accretion powered millisecond pulsar SAX J1808.4-3658 have revealed an interesting binary evolution, with the orbit of the system expanding at an accelerated rate. We use the recent finding that the accreted fuel in SAX J1808.4-3658 is hydrogen depleted to greatly refine models of the progenitor and prior evolution of the binary system. We constrain the initial mass of the companion star to 1.0-1.2 M$_{\mathrm{\odot}}$, more massive than previous evolutionary studies of this system have assumed. We also infer the system must have undergone strongly non-conservative mass transfer in order to explain the observed orbital period changes. Following Jia & Li (2015), we include mass loss due to the pulsar radiation pressure on the donor star, inducing an evaporative wind which is ejected at the inner Lagrangian point of the binary system. The resulting additional loss of angular momentum resolves the discrepancy between conservative mass transfer models and the observed orbital period derivative of this system. We also include a treatment of donor irradiation due to the accretion luminosity, and find this has a non-negligible effect on the evolution of the system.

astro-ph.HE↗

arXiv2019

Maximally accreting supermassive stars: a fundamental limit imposed by hydrostatic equilibrium

Major mergers of gas-rich galaxies provide promising conditions for the formation of supermassive black holes (SMBHs; $\gtrsim10^5$ M$_\odot$) by direct collapse because they can trigger mass inflows as high as $10^4-10^5$ M$_\odot$ yr$^{-1}$ on sub-parsec scales. However, the channel of SMBH formation in this case, either dark collapse (direct collapse without prior stellar phase) or supermassive star (SMS; $\gtrsim10^4$ M$_\odot$), remains unknown. Here, we investigate the limit in accretion rate up to which stars can maintain hydrostatic equilibrium. We compute hydrostatic models of SMSs accreting at $1-1000$ M$_\odot$ yr$^{-1}$, and estimate the departures from equilibrium a posteriori by taking into account the finite speed of sound. We find that stars accreting above the atomic cooling limit ($\gtrsim10$ M$_\odot$ yr$^{-1}$) can only maintain hydrostatic equilibrium once they are supermassive. In this case, they evolve adiabatically with a hylotropic structure, that is, entropy is locally conserved and scales with the square root of the mass coordinate. Our results imply that stars can only become supermassive by accretion at the rates of atomically cooled haloes ($\sim0.1-10$ M$_\odot$ yr$^{-1}$). Once they are supermassive, larger rates are possible.

astro-ph.SR↗

arXiv2019

Revealing the Origin and Cosmic Evolution of Supermassive Black Holes

The next generation of electromagnetic and gravitational wave observatories will open unprecedented windows to the birth of the first supermassive black holes. This has the potential to reveal their origin and growth in the first billion years, as well as the signatures of their formation history in the local Universe. With this in mind, we outline three key focus areas which will shape research in the next decade and beyond: (1) What were the "seeds" of the first quasars; how did some reach a billion solar masses before z$\sim7$? (2) How does black hole growth change over cosmic time, and how did the early growth of black holes shape their host galaxies? What can we learn from intermediate mass black holes (IMBHs) and dwarf galaxies today? (3) Can we unravel the physics of black hole accretion, understanding both inflows and outflows (jets and winds) in the context of the theory of general relativity? Is it valid to use these insights to scale between stellar and supermassive BHs, i.e., is black hole accretion really scale invariant? In the following, we identify opportunities for the Canadian astronomical community to play a leading role in addressing these issues, in particular by leveraging our strong involvement in the Event Horizon Telescope, the {\it James Webb Space Telescope} (JWST), Euclid, the Maunakea Spectroscopic Explorer (MSE), the Thirty Meter Telescope (TMT), the Square Kilometer Array (SKA), the Cosmological Advanced Survey Telescope for Optical and ultraviolet Research (CASTOR), and more. We also discuss synergies with future space-based gravitational wave (LISA) and X-ray (e.g., Athena, Lynx) observatories, as well as the necessity for collaboration with the stellar and galactic evolution communities to build a complete picture of the birth of supermassive black holes, and their growth and their influence over the history of the Universe.

astro-ph.GA↗

arXiv2019

Comprehensive models of novae at metallicity $Z = 0.02$ and $Z = 10^{-4}$

Novae are the observational manifestations of thermonuclear runaways on the surface of accreting white dwarfs (WDs). Although novae are an ubiquitous phenomenon, their properties at low metallicity are not well understood. Using the publicly-available stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA), we model the evolution of accreting carbon-oxygen WDs and consider models which accrete matter with metallicity Z=0.02 or $10^{-4}$. We consider both models without mixing and with matter enriched by CO-elements assuming that mixing occurs in the process of accretion (with mixing fraction 0.25). We present and contrast ignition mass, ejected mass, recurrence period and maximum luminosity of novae for different WD masses and accretion rates for these metallicities and mixing cases. We find that models with Z = 0.02 have ignition masses and recurrence periods smaller than models with low Z, while the ejected mass and maximum luminosity are larger. Retention efficiency during novae outbursts decreases with increasing metallicity. In our implementation, inclusion of mixing at the H/He interface reduces accreted mass, ejected mass and recurrence period as compared to the no-mixing case, while the maximum luminosity becomes larger. Retention efficiency is significantly reduced, becoming negative in most of our models. For ease of use, we provide a tabular summary of our results.

astro-ph.SR↗

arXiv2018

Excluding super-soft X-ray sources as progenitors for four Type Ia supernovae in the Large Magellanic Cloud

Type Ia supernovae are vital to our understanding of the Universe due to their use in measuring cosmological distances and their significance in enriching the interstellar medium with heavy elements. They are understood to be the thermonuclear explosions of white dwarfs, but the exact mechanism(s) leading to these explosions remains unclear. The two competing models are the single degenerate scenario, wherein a white dwarf accretes material from a companion star and explodes when it reaches the Chandrasekhar limit, and the double degenerate scenario, wherein the explosion results from a merger of two white dwarfs. Here we report results which rule out hot, luminous progenitors consistent with the single degenerate scenario for four young Type Ia supernova remnants in the Large Magellanic Cloud. Using the integral field spectrograph WiFeS, we have searched these remnants for relic nebulae ionized by the progenitor, which would persist for up to $\sim 10^5$ years after the explosion. We detected no such nebula around any of the remnants. By comparing our upper limits with photoionization simulations performed using Cloudy, we have placed stringent upper limits on the luminosities of the progenitors of these supernova remnants. Our results add to the growing evidence disfavouring the single degenerate scenario.

astro-ph.HE↗

arXiv2018

Balmer-Dominated Shocks Exclude Hot Progenitors for Many Type Ia Supernovae

The evolutionary mechanism underlying Type Ia supernova explosions remains unknown. Recent efforts to constrain progenitor models based on the influence that their high energy emission would have on the interstellar medium (ISM) of galaxies have proven successful. For individual remnants, Balmer-dominated shocks reveal the ionization state of hydrogen in the immediately surrounding gas. Here we report deep upper limits on the temperature and luminosity of the progenitors of four Type Ia remnants with associated Balmer filaments: SN 1006, 0509-67.5, 0519-69.0, and DEM L71. For SN 1006, existing observations of helium line emission in the diffuse emission ahead of the shock provide an additional constraint on the helium ionization state in the vicinity of the remnant. Using the photoionization code Cloudy, we show that these constraints exclude any hot, luminous progenitor for SN 1006, including stably hydrogen or helium nuclear-burning white dwarfs, as well as any Chandrasekhar-mass white dwarf accreting matter at $\gtrsim 9.5\times10^{-8}M_{\odot}/$yr via a disk. For 0509-67.5, the Balmer emission alone rules out any such white dwarf accreting $\gtrsim 1.4\times10^{-8}M_{\odot}/$yr. For 0519-69.0 and DEM L71, the inferred ambient ionization state of hydrogen is only weakly in tension with a recently hot, luminous progenitor, and cannot be distinguished from e.g., a relatively higher local Lyman continuum background, without additional line measurements. Future deep spectroscopic observations will resolve this ambiguity, and can either detect the influence of any luminous progenitor or rule out the same for all resolved SN Ia remnants.

astro-ph.HE↗

arXiv2017

No hot and luminous progenitor for Tycho's supernova

Type Ia supernovae have proven vital to our understanding of cosmology, both as standard candles and for their role in galactic chemical evolution; however, their origin remains uncertain. The canonical accretion model implies a hot and luminous progenitor which would ionize the surrounding gas out to a radius of $\sim$10--100 parsecs for $\sim$100,000 years after the explosion. Here we report stringent upper limits on the temperature and luminosity of the progenitor of Tycho's supernova (SN 1572), determined using the remnant itself as a probe of its environment. Hot, luminous progenitors that would have produced a greater hydrogen ionization fraction than that measured at the radius of the present remnant ($\sim$3 parsecs) can thus be excluded. This conclusively rules out steadily nuclear-burning white dwarfs (supersoft X-ray sources), as well as disk emission from a Chandrasekhar-mass white dwarf accreting $\gtrsim 10^{-8}M_{\odot}$yr$^{-1}$ (recurrent novae). The lack of a surrounding Strömgren sphere is consistent with the merger of a double white dwarf binary, although other more exotic scenarios may be possible.

astro-ph.SR↗

arXiv2017

On the Maximum Mass of Accreting Primordial Supermassive Stars

Supermassive primordial stars are suspected to be the progenitors of the most massive quasars at z~6. Previous studies of such stars were either unable to resolve hydrodynamical timescales or considered stars in isolation, not in the extreme accretion flows in which they actually form. Therefore, they could not self-consistently predict their final masses at collapse, or those of the resulting supermassive black hole seeds, but rather invoked comparison to simple polytropic models. Here, we systematically examine the birth, evolution and collapse of accreting non-rotating supermassive stars under accretion rates of 0.01-10 solar masses per year, using the stellar evolution code KEPLER. Our approach includes post-Newtonian corrections to the stellar structure and an adaptive nuclear network, and can transition to following the hydrodynamic evolution of supermassive stars after they encounter the general relativistic instability. We find that this instability triggers the collapse of the star at masses of 150,000-330,000 solar masses for accretion rates of 0.1-10 solar masses per year, and that the final mass of the star scales roughly logarithmically with the rate. The structure of the star, and thus its stability against collapse, is sensitive to the treatment of convection, and the heat content of the outer accreted envelope. Comparison with other codes suggests differences here may lead to small deviations in the evolutionary state of the star as a function of time, that worsen with accretion rate. Since the general relativistic instability leads to the immediate death of these stars, our models place an upper limit on the masses of the first quasars at birth.

astro-ph.SR↗

arXiv2016

Modelling nova populations in galaxies

Theoretical modelling of the evolution of classical and recurrent novae plays an important role in studies of binary evolution, nucleosynthesis and accretion physics. However, from a theoretical perspective the observed statistical properties of novae remain poorly understood. In this paper, we have produced model populations of novae using a hybrid binary population synthesis approach for differing star formation histories (SFHs): a starburst case (elliptical-like galaxies), a constant star formation rate case (spiral-like galaxies) and a composite case (in line with the inferred SFH for M31). We found that the nova rate at 10\;Gyr in an elliptical-like galaxy is $\sim 10-20$ times smaller than a spiral-like galaxy with the same mass. The majority of novae in elliptical-like galaxies at the present epoch are characterized by low mass white dwarfs (WDs), long decay times, relatively faint absolute magnitudes and long recurrence periods. In contrast, the majority of novae in spiral-like galaxies at 10\;Gyr have massive WDs, short decay times, are relatively bright and have short recurrence periods. The mass loss time distribution for novae in our M31-like galaxy is in agreement with observational data for Andromeda. However, it is possible that we underestimate the number of bright novae in our model. This may arise in part due to the present uncertainties in the appropriate bolometric correction for novae.

astro-ph.SR↗

arXiv2015

Where are all of the nebulae ionized by supersoft X-ray sources?

Accreting, steadily nuclear-burning white dwarfs are associated with so-called close-binary supersoft X-ray sources (SSSs), observed to have temperatures of a few$\times 10^{5}$K and luminosities on the order of $10^{38}$erg/s. These and other types of SSSs are expected to be capable of ionizing their surrounding circumstellar medium, however, to date only one such nebula was detected in the Large Magellanic Cloud (of its 6 known close-binary SSSs), surrounding the accreting, nuclear-burning WD CAL 83. This has led to the conclusion that most SSSs cannot have been both luminous ($\gtrsim 10^{37}$erg/s) and hot ($\gtrsim$ few $\times 10^{4}$K) for the majority of their past accretion history, unless the density of the ISM surrounding most sources is much less than that inferred for the CAL 83 nebula (4--10$\rm{cm}^{-3}$). Here we demonstrate that most SSSs must lie in much lower density media than CAL 83. Past efforts to detect such nebulae have not accounted for the structure of the ISM in star-forming galaxies and, in particular, for the fact that most of the volume is occupied by low density warm \& hot ISM. CAL 83 appears to lie in a region of ISM which is at least $\sim 40$-fold overdense. We compute the probability of such an event to be $\approx 18\%$, in good agreement with observed statistics. We provide a revised model for the "typical" SSS nebula, and outline the requirements of a survey of the Magellanic clouds which could detect the majority of such objects. We then briefly discuss some of the possible implications, should there prove to be a large population of previously undiscovered ionizing sources.

astro-ph.HE↗

arXiv2015

Population synthesis of accreting white dwarfs: II. X-ray and UV emission

Accreting white dwarfs (WDs) with non-degenerate companions are expected to emit in soft X-rays and the UV, if accreted H-rich material burns stably. They are an important component of the unresolved emission of elliptical galaxies, and their combined ionizing luminosity may significantly influence the optical line emission from warm ISM. In an earlier paper we modeled populations of accreting WDs, first generating WD with main-sequence, Hertzsprung gap and red giant companions with the population synthesis code \textsc{BSE}, and then following their evolution with a grid of evolutionary tracks computed with \textsc{MESA}. Now we use these results to estimate the soft X-ray (0.3-0.7keV), H- and He II-ionizing luminosities of nuclear burning WDs and the number of super-soft X-ray sources for galaxies with different star formation histories. For the starburst case, these quantities peak at $\sim 1$ Gyr and decline by $\sim 1-3$ orders of magnitude by the age of 10 Gyr. For stellar ages of $\sim$~10 Gyr, predictions of our model are consistent with soft X-ray luminosities observed by Chandra in nearby elliptical galaxies and He II 4686$Å/\rm{H}β$ line ratio measured in stacked SDSS spectra of retired galaxies, the latter characterising the strength and hardness of the UV radiation field. However, the soft X-ray luminosity and He~II~4686$Å/\rm{H}β$ ratio are significantly overpredicted for stellar ages of $\lesssim 4-8$ Gyr. We discuss various possibilities to resolve this discrepancy and tentatively conclude that it may be resolved by a modification of the typically used criteria of dynamically unstable mass loss for giant stars.

astro-ph.SR↗

arXiv2014

Next generation population synthesis of accreting white dwarfs: I. Hybrid calculations using BSE + MESA

Accreting, nuclear-burning white dwarfs have been deemed to be candidate progenitors of type Ia supernovae, and to account for supersoft X-ray sources, novae, etc. depending on their accretion rates. We have carried out a binary population synthesis study of their populations using two algorithms. In the first, we use the binary population synthesis code \textsf{BSE} as a baseline for the "rapid" approach commonly used in such studies. In the second, we employ a "hybrid" approach, in which we use \textsf{BSE} to generate a population of white dwarfs (WD) with non-degenerate companions on the verge of filling their Roche lobes. We then follow their mass transfer phase using the detailed stellar evolution code \textsf{MESA}. We investigate the evolution of the number of rapidly accreting white dwarfs (RAWDs) and stably nuclear-burning white dwarfs (SNBWDs), and estimate the type Ia supernovae (SNe Ia) rate produced by "single-degenerate" systems (SD). We find significant differences between the two algorithms in the predicted numbers of SNBWDs at early times, and also in the delay time distribution (DTD) of SD SNe Ia. Such differences in the treatment of mass transfer may partially account for differences in the SNe Ia rate and DTD found by different groups. Adopting 100\% efficiency for helium burning, the rate of SNe Ia produced by the SD-channel in a Milky-way-like galaxy in our calculations is $2.0\times10^{-4}\rm{yr}^{-1}$, more than an order of magnitude below the observationally inferred value. In agreement with previous studies, our calculated SD DTD is inconsistent with observations.

astro-ph.SR↗

arXiv2014

Upper limits on the luminosity of the progenitor of type Ia supernova SN2014J

We analysed archival data of Chandra pre-explosion observations of the position of SN2014J in M82. No X-ray source at this position was detected in the data, and we calculated upper limits on the luminosities of the progenitor. These upper limits allow us to firmly rule out an unobscured supersoft X-ray source progenitor with a photospheric radius comparable to the radius of white dwarf near the Chandrasekhar mass (~1.38 M_sun) and mass accretion rate in the interval where stable nuclear burning can occur. However, due to a relatively large hydrogen column density implied by optical observations of the supernova, we cannot exclude a supersoft source with lower temperatures, kT < 80 eV. We find that the supernova is located in the centre of a large structure of soft diffuse emission, about 200 pc across. The mass, ~3x10^4 M_sun and short cooling time of the gas, tau_cool ~ 8 Myrs, suggest that it is a supernova-inflated super-bubble, associated with the region of recent star formation. If SN2014J is indeed located inside the bubble, it likely belongs to the prompt population of type Ia supernovae, with a delay time as short as ~ 50 Myrs. Finally, we analysed the one existing post-supernova Chandra observation and placed upper limit of ~ (1-2) 10^37 erg/s on the X-ray luminosity of the supernova itself.

astro-ph.HE↗