Publications (203)
Crustal Emission and the Quiescent Spectrum of the Neutron Star in KS 1731-260
Robert E. Rutledge, Lars Bildsten, Edward F. Brown +3
(Abridged). The type-I X-ray bursting low mass X-ray binary KS 1731-260 was recently detected for the first time in quiescence by Wijnands et al., following an approximately 13 yr…
Oceanography of Accreting Neutron Stars: Non-Radial Oscillations and Periodic X-Ray Variability
Lars Bildsten, Andrew Cumming, Greg Ushomirsky +1
Observations of quasi-periodic oscillations (QPOs) in the luminosity from many accreting neutron stars (NS) have led us to investigate a source of periodicity prevalent in other st…
Wakes from Companion Interactions in Type Ia Supernovae Nebular Emission Line Profiles
Kathlynn Simotas, Lars Bildsten, Logan J. Prust
Thermonuclear supernovae (SNe) are the result of the nuclear transformation of carbon/oxygen (C/O) white dwarfs (WDs) to the radioactive element and intermediate…
ZTF 18aaqeasu (SN 2018byg): A Massive Helium-shell Double Detonation on a Sub-Chandrasekhar Mass White Dwarf
Kishalay De, Mansi M. Kasliwal, Abigail Polin +24
The detonation of a helium shell on a white dwarf has been proposed as a possible explosion triggering mechanism for Type Ia supernovae. Here, we report ZTF 18aaqeasu (SN 2018byg/A…
The Long-Term Evolution of Double White Dwarf Mergers
Ken J. Shen, Lars Bildsten, Daniel Kasen +1
In this paper, we present a model for the long-term evolution of the merger of two unequal mass C/O white dwarfs (WDs). After the dynamical phase of the merger, magnetic stresses r…
A Spreading Layer Origin for Dwarf Nova Oscillations
Anthony L. Piro, Lars Bildsten
Dwarf nova outbursts often show coherent () sinusoidal oscillations with the largest pulsed fraction in the extreme ultraviolet. Called dwarf nova oscillations (DNO…
Identification of A Transient Neutron Star in Quiescence in the Globular Cluster NGC 5139
Robert E. Rutledge, Lars Bildsten, Edward F. Brown +2
Using the Chandra/ACIS-I detector, we have identified an X-ray source (CXOU 132619.7-472910.8) in the globular cluster NGC 5139 with a thermal spectrum identical to that observed f…
Spreading of Accreted Material on White Dwarfs
Anthony L. Piro, Lars Bildsten
When a white dwarf (WD) is weakly magnetized and its accretion disk is thin, accreted material first reaches the WD's surface at its equator. This matter slows its orbit as it come…
Exposing the Nuclear Burning Ashes of Radius Expansion Type I X-ray Bursts
Nevin N. Weinberg, Lars Bildsten, Hendrik Schatz
We solve for the evolution of the vertical extent of the convective region of a neutron star atmosphere during a Type I X-ray burst. The convective region is well-mixed with ashes…
White Dwarf Donors in Ultracompact Binaries: The Stellar Structure of Finite Entropy Objects
Christopher J. Deloye, Lars Bildsten
We discuss the mass-radius (M-R) relations for low-mass (M<0.1 Msun) white dwarfs (WDs) of arbitrary degeneracy and evolved (He, C, O) composition. We do so with both a simple anal…
The Angular Momentum of Accreting Neutron Stars
Lars Bildsten
I review the rotation measurements of accreting neutron stars. Many of the highly magnetic accreting X-ray pulsars have been continuously observed with the Burst and Transient Sour…
Sinking of Ne-22 in Liquid White Dwarf Interiors
Christopher J. Deloye, Lars Bildsten
We assess the impact of the trace element Ne-22 on the cooling and seismology of a liquid C/O white dwarf (WD). Due to this element's neutron excess, it sinks towards the interior…
Rapidly Decaying Supernova 2010X: A Candidate ".Ia" Explosion
Mansi M. Kasliwal, S. R. Kulkarni, Avishay Gal-Yam +33
We present the discovery, photometric and spectroscopic follow-up observations of SN 2010X (PTF 10bhp). This supernova decays exponentially with tau_d=5 days, and rivals the curren…
Polluted White Dwarfs: Mixing Regions and Diffusion Timescales
Evan B. Bauer, Lars Bildsten
Many isolated white dwarfs (WDs) show spectral evidence of atmospheric metal pollution. Since heavy element sedimentation timescales are short, this most likely indicates ongoing a…
Orbital Evolution of Compact White Dwarf Binaries
David L. Kaplan, Lars Bildsten, Justin D. R. Steinfadt
The new-found prevalence of extremely low mass (ELM, Mhe<0.2 Msun) helium white dwarfs (WDs) in tight binaries with more massive WDs has raised our interest in understanding the na…
Neutronization During Type Ia Supernova Simmering
Anthony L. Piro, Lars Bildsten
Prior to the incineration of a white dwarf (WD) that makes a Type Ia supernova (SN Ia), the star "simmers" for ~1000 years in a convecting, carbon burning region. We have found tha…
Turbulence Supported Massive Star Envelopes
William Schultz, Lars Bildsten, Yan-Fei Jiang
The outer envelopes of massive () stars exhibit large increases in opacities from forests of lines and ionization transitions (particularly from iron and hel…
X-ray binaries in Sculptor
Thomas J. Maccarone, Arunav Kundu, Stephen E. Zepf +2
We report the results of a deep Chandra survey of the Sculptor dwarf spheroidal galaxy. We find five X-ray sources with L_X of at least 6*10^33 ergs/sec with optical counterparts e…
Year 1 of the ZTF high-cadence Galactic Plane Survey: Strategy, goals, and early results on new single-mode hot subdwarf B-star pulsators
Thomas Kupfer, Thomas A. Prince, Jan van Roestel +18
We present the goals, strategy and first results of the high-cadence Galactic plane survey using the Zwicky Transient Facility (ZTF). The goal of the survey is to unveil the Galact…
The Ignition of Carbon Detonations via Converging Shock Waves in White Dwarfs
Ken J. Shen, Lars Bildsten
The progenitor channel responsible for the majority of Type Ia supernovae is still uncertain. One emergent scenario involves the detonation of a He-rich layer surrounding a C/O whi…
X-ray diagnostics of chemical composition of the accretion disk and donor star in UCXBs II: XMM-Newton observations
Filippos Koliopanos, Marat Gilfanov, Lars Bildsten +1
We search for the Fe K line in spectra of Ultra Compact X-ray Binaries (UCXBs). For this purpose we have analyzed XMM-Newton observations of five confirmed UCXBs. We find that…
A Method for Distinguishing Between Transiently Accreting Neutron Stars and Black Holes, in Quiescence
Robert E. Rutledge, Lars Bildsten, Edward F. Brown +2
We fit hydrogen atmosphere models to the X-ray data for four neutron stars (three from a previous paper, plus 4U 2129+47) and six black hole candidates (A0620-00, GS 2000+25, GS 11…
Clearing the Gas from Globular Clusters & Dwarf Spheroidals with Classical Novae
Kevin Moore, Lars Bildsten
Observations of the intra-cluster medium (ICM) in galactic globular clusters (GCs) show a systematic deficiency in ICM mass as compared to that expected from accumulation of stella…
The rp Process Ashes from Stable Nuclear Burning on an Accreting Neutron Star
Hendrik Schatz, Lars Bildsten, Andrew Cumming +1
We calculate the nucleosynthesis during stable nuclear burning on an accreting neutron star. This is appropriate for weakly magnetic neutron stars accreting at near-Eddington rates…
Calcium-rich gap transients in the remote outskirts of galaxies
Mansi M. Kasliwal, S. R. Kulkarni, Avishay Gal-Yam +25
From the first two seasons of the Palomar Transient Factory, we identify three peculiar transients (PTF09dav, PTF10iuv, PTF11bij) with five distinguishing characteristics: peak lum…
Measuring White Dwarf Accretion Rates via their Effective Temperatures
Dean M. Townsley, Lars Bildsten
Our previous theoretical study of the impact of an accreting envelope on the thermal state of an underlying white dwarf (WD) has yielded equilibrium core temperatures, classical no…
The Outbursts and Orbit of the Accreting Pulsar GS 1843-02 = 2S 1845-024
Mark H. Finger, Lars Bildsten, Deepto Chakrabarty +5
We present observations of a series of 10 outbursts of pulsed hard X-ray flux from the transient 10.6 mHz accreting pulsar GS 1843-02, using the Burst and Transient Source Experime…
Dynamical He Flashes in Double White Dwarf Binaries
Tin Long Sunny Wong, Lars Bildsten
The detonation of an overlying helium layer on a carbon-oxygen (CO) white dwarf (WD) can detonate the CO WD and create a thermonuclear supernova (SN).…
Arbitrarily Degenerate Helium White Dwarfs as Donors in AM CVn Binaries
Christopher J. Deloye, Lars Bildsten, Gijs Nelemans
We apply the Deloye & Bildsten (2003) isentropic models for donors in ultracompact low-mass X-ray binaries to the AM CVn population of ultracompact, interacting binaries. The mass-…
Unstable Helium Shell Burning on Accreting White Dwarfs
Ken J. Shen, Lars Bildsten
AM Canum Venaticorum (AM CVn) binaries consist of a degenerate helium donor and a helium, C/O, or O/Ne WD accretor, with accretion rates of Mdot = 1e-13 - 1e-5 Msol/yr. For accreti…
Quiescent Thermal Emission from the Neutron Star in Aql X-1
Robert E. Rutledge, Lars Bildsten, Edward F. Brown +2
We report on the quiescent spectrum measured with Chandra/ACIS-S of the transient, type-I X-ray bursting neutron star Aql X-1, immediately following an accretion outburst. The neut…
Classical Nucleation Theory of the One-Component Plasma
Randall L. Cooper, Lars Bildsten
We investigate the crystallization rate of a one-component plasma (OCP) in the context of classical nucleation theory. From our derivation of the free energy of an arbitrary distri…
Unstable Nonradial Oscillations on Helium Burning Neutron Stars
Anthony L. Piro, Lars Bildsten
Material accreted onto a neutron star can stably burn in steady state only when the accretion rate is high (typically super-Eddington) or if a large flux from the neutron star crus…
A Search for Pulsations in Helium White Dwarfs
Justin D. R. Steinfadt, Lars Bildsten, David L. Kaplan +5
The recent plethora of sky surveys, especially the Sloan Digital Sky Survey, have discovered many low-mass (M < 0.45 Msun) white dwarfs that should have cores made of nearly pure h…
Nearly Coherent Oscillations in Type I X-Ray Bursts from KS 1731-260
Michael P. Muno, Derek W. Fox, Edward H. Morgan +1
We present an analysis of the nine type I X-ray bursts that were observed from KS 1731-260 with RXTE. We find that the bursts divide naturally into two populations: ``fast bursts''…
The Turbulent Story of X-ray Bursts: Effects of Shear Mixing on Accreting Neutron Stars
Anthony L. Piro, Lars Bildsten
During accretion, a neutron star (NS) is spun up as angular momentum is transported through its liquid surface layers. We study the resulting differentially rotating profile, focus…
Hydrostatic Expansion and Spin Changes During Type I X-Ray Bursts
Andrew Cumming, Sharon M. Morsink, Lars Bildsten +2
We present calculations of the spin-down of a neutron star atmosphere due to hydrostatic expansion during a Type I X-ray burst. We show that (i) Cumming and Bildsten overestimated…
Inferring Explosion Properties from Type II-Plateau Supernova Light Curves
Jared A. Goldberg, Lars Bildsten, Bill Paxton
We present advances in modeling Type IIP supernovae using MESA for evolution to shock breakout coupled with STELLA for generating light and radial velocity curves. Explosion models…
The effect of the adiabatic assumption on asteroseismic scaling relations for luminous red giants
Joel C. Zinn, Marc H. Pinsonneault, Lars Bildsten +1
Although stellar radii from asteroseismic scaling relations agree at the percent level with independent estimates for main sequence and most first-ascent red giant branch stars, th…
The Value of Progenitor Radius Measurements for Explosion Modeling of Type II-Plateau Supernovae
Jared A. Goldberg, Lars Bildsten
Using Modules for Experiments in Stellar Astrophysics (MESA)+STELLA, we show that very different physical models can adequately reproduce a specific observed Type II-Plateau Supern…
Seismology of Accreting White Dwarfs
Phil Arras, Dean Townsley, Lars Bildsten
Pulsation modes have recently been observed in a handful of white dwarf (WD) primaries of cataclysmic variables, allowing an interesting new probe into the structure of accreting W…
New Views of Thermonuclear Bursts
Tod Strohmayer, Lars Bildsten
Since the advent of powerful new X-ray observatories, NASA's Rossi X-ray Timing Explorer (RXTE), the Italian - Dutch BeppoSAX mission, XMM-Newton and Chandra, a number of entirely…
The first ultracompact Roche lobe-filling hot subdwarf binary
Thomas Kupfer, Evan B. Bauer, Thomas R. Marsh +29
We report the discovery of the first short period binary in which a hot subdwarf star (sdOB) fills its Roche lobe and started mass transfer to its companion. The object was discove…
Four New Delta Scuti Pulsators from a Variability Survey of 131 Stars
J. L. Sokoloski, Lars Bildsten, R. Chornock +1
In a photometric variability survey of 131 stars with B < 14 mag, we have found four new Delta Scuti stars. We were sensitive to oscillation amplitudes as low as a few mmag. The de…
Turbulent Chemical Diffusion in Convectively Bounded Carbon Flames
Daniel Lecoanet, Josiah Schwab, Eliot Quataert +6
It has been proposed that mixing induced by convective overshoot can disrupt the inward propagation of carbon deflagrations in super-asymptotic giant branch stars. To test this the…
A Brown Dwarf Companion for the Accreting Millisecond Pulsar SAX J1808.4-3658
Lars Bildsten, Deepto Chakrabarty
BeppoSAX has revealed a population of faint neutron star X-ray transients in the Galactic bulge. King conjectured that these neutron stars are accreting from brown dwarfs (BD) with…
Hydrodynamic Thermonuclear Runaways in Superbursts
Nevin N. Weinberg, Lars Bildsten, Edward F. Brown
We calculate the thermal and dynamical evolution of the surface layers of an accreting neutron star during the rise of a superburst. For the first few hours following unstable 12C…
Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
Bill Paxton, Matteo Cantiello, Phil Arras +8
We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution modul…
Supernova 2011fe from an Exploding Carbon-Oxygen White Dwarf Star
Peter E. Nugent, Mark Sullivan, S. Bradley Cenko +36
Type Ia supernovae (SNe Ia) have been used empirically as standardized candles to reveal the accelerating universe even though fundamental details, such as the nature of the progen…
Constraints on the Progenitor System of the Type Ia Supernova SN 2011fe/PTF11kly
Weidong Li, Joshua S. Bloom, Philipp Podsiadlowski +25
Type Ia supernovae (SNe) serve as a fundamental pillar of modern cosmology, owing to their large luminosity and a well-defined relationship between light-curve shape and peak brigh…
Gravitational Settling of 22Ne in Liquid White Dwarf Interiors
Lars Bildsten, David M. Hall
The nuclear reactions that occur in the stellar progenitors of white dwarfs (WDs) lead to an internal composition of 12C, 16O, and a ``contaminant'' nucleus, 22Ne. The 22Ne is prod…
Thermally Stable Nuclear Burning on Accreting White Dwarfs
Ken J. Shen, Lars Bildsten
One of the challenges to increasing the mass of a white dwarf through accretion is the tendency for the accumulating hydrogen to ignite unstably and potentially trigger mass loss.…
Hot White Dwarf Donors in Ultracompact X-Ray Binaries
Lars Bildsten
The discovery of two accreting millisecond X-ray pulsars in binaries with 43 minute orbital periods allows for a new probe of the donor's structure. For XTE J1751-305, only a hot w…
Variability of massive stars in M31 from the Palomar Transient Factory
Monika D. Soraisam, Lars Bildsten, Maria R. Drout +5
Using data from the (intermediate) Palomar Transient Factory (iPTF), we characterize the time variability of ~500 massive stars in M31. Our sample is those stars which are spectral…
General relativistic orbital decay in a seven-minute-orbital-period eclipsing binary system
Kevin B. Burdge, Michael W. Coughlin, Jim Fuller +23
General relativity predicts that short orbital period binaries emit significant gravitational radiation, and the upcoming Laser Interferometer Space Antenna (LISA) is expected to d…
Thermonuclear .Ia Supernovae from Helium Shell Detonations: Explosion Models and Observables
Ken J. Shen, Daniel Kasen, Nevin N. Weinberg +2
During the early evolution of an AM CVn system, helium is accreted onto the surface of a white dwarf under conditions suitable for unstable thermonuclear ignition. The turbulent mo…
Thermal Structure and Radius Evolution of Irradiated Gas Giant Planets
Phil Arras, Lars Bildsten
We consider the thermal structure and radii of strongly irradiated gas giant planets over a range in mass and irradiating flux. The cooling rate of the planet is sensitive to the s…
Shocking and Mass Loss of Compact Donor Stars in Type Ia Supernovae
Tin Long Sunny Wong, Christopher White, Lars Bildsten
Type Ia supernovae arise from thermonuclear explosions of white dwarfs accreting from a binary companion. Following the explosion, the surviving donor star leaves at roughly its or…
Shock Breakout in 3-Dimensional Red Supergiant Envelopes
Jared A. Goldberg, Yan-fei Jiang, Lars Bildsten
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 cor…
Acoustic Signatures of the Helium Core Flash
Lars Bildsten, Bill Paxton, Kevin Moore +1
All evolved stars with masses M <2 solar masses undergo an initiating off-center helium core flash in their 0.48 solar mass He core as they ascend the red giant branch (RGB). This…
Mass Loss and Subsequent Thermal Evolution of Surviving Helium White Dwarfs Shocked by Thermonuclear Supernovae
Tin Long Sunny Wong, Lars Bildsten
Following a type Ia supernova (SN Ia) in a double white dwarf (WD) binary, a surviving WD companion leaves at its orbital velocity ,000 - 3,000 km/s. The Gaia mission ha…
Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
Bill Paxton, R. Smolec, Josiah Schwab +14
We 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…
An infrared census of R Coronae Borealis Stars II -- Spectroscopic classifications and implications for the rate of low-mass white dwarf mergers
Viraj R. Karambelkar, Mansi M. Kasliwal, Patrick Tisserand +18
We present results from a systematic infrared (IR) census of R Coronae Borealis (RCB) stars in the Milky Way, using data from the Palomar Gattini IR (PGIR) survey. R Coronae Boreal…
The Importance of Urca-process Cooling in Accreting ONe White Dwarfs
Josiah Schwab, Lars Bildsten, Eliot Quataert
We study the evolution of accreting oxygen-neon (ONe) white dwarfs (WDs), with a particular emphasis on the effects of the presence of the carbon-burning products $\mathrm{^{23}Na}…
The Effects of Magnetic Fields on the Dynamics of Radiation Pressure Dominated Massive Star Envelopes
Yan-Fei Jiang, Matteo Cantiello, Lars Bildsten +2
We use three dimensional radiation magneto-hydrodynamic simulations to study the effects of magnetic fields on the energy transport and structure of radiation pressure dominated ma…
Faint Cataclysmic Variables in Quiescence: Globular Cluster and Field Surveys
Dean M. Townsley, Lars Bildsten
Current evolutionary models imply that most Cataclysmic Variables (CVs) have P_orb<2 hours and are Dwarf Nova (DN) systems that are quiescent most of the time. Observations of near…
Fast and Luminous Transients from the Explosions of Long Lived Massive White Dwarf Merger Remnants
Jared Brooks, Josiah Schwab, Lars Bildsten +4
We study the evolution and final outcome of long-lived ( years) remnants from the merger of a He white dwarf (WD) with a more massive C/O or O/Ne WD. Using Modules f…
Identification of the Optical Counterpart of Fermi Black Widow Millisecond Pulsar PSR J1544+4937
Sumin Tang, David L. Kaplan, Sterl Phinney +10
We report the optical identification of the companion to the {\it Fermi} black widow millisecond pulsar PSR J1544+4937. We find a highly variable source on Keck LRIS images at the…
Diffusive Nuclear Burning of Helium on Neutron Stars
Philip Chang, Lars Bildsten, Phil Arras
Diffusive nuclear burning of H by an underlying material capable of capturing protons can readily consume H from the surface of neutron stars (NSs) during their early cooling histo…
Theoretical Modeling of the Thermal State of Accreting White Dwarfs Undergoing Classical Novae
Dean M. Townsley, Lars Bildsten
White dwarfs experience a thermal renaissance when they receive mass from a stellar companion in a binary. For accretion rates < 10^-8 Msun/yr, the freshly accumulated hydrogen/hel…
Helium White Dwarfs in Cataclysmic Variables
Ken J. Shen, Irit Idan, Lars Bildsten
Binary evolution predicts a population of helium core (M < 0.5 Msol) white dwarfs (WDs) that are slowly accreting hydrogen-rich material from low mass main sequence or brown dwarf…
Transient X-ray Binaries in Elliptical Galaxies
Anthony L. Piro, Lars Bildsten
Chandra observations of elliptical galaxies have revealed large numbers of Low Mass X-ray Binaries (LMXBs) accreting at rates above 10^-9 solar masses per year. One scenario which…
Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
Adam S. Jermyn, Evan B. Bauer, Josiah Schwab +19
We update the capabilities of the open-knowledge software instrument Modules for Experiments in Stellar Astrophysics (MESA). The new auto_diff module implements automatic different…
X-ray diagnostics of chemical composition of the accretion disk and donor star in ultra-compact X-ray binaries
Filippos Koliopanos, Marat Gilfanov, Lars Bildsten
Non-solar composition of the donor star in ultra-compact X-ray binaries may have a pronounced effect on the fluorescent lines appearing in their spectra due to reprocessing of prim…
Gravitational Waves from Low-Mass X-ray Binaries: a Status Report
Greg Ushomirsky, Lars Bildsten, Curt Cutler
We summarize the observations of the spin periods of rapidly accreting neutron stars. If gravitational radiation is responsible for balancing the accretion torque at the observed s…
Observations of Accreting Pulsars
Lars Bildsten, Deepto Chakrabarty, John Chiu +10
We summarize five years of continuous monitoring of accretion-powered pulsars with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory. Our 20-70…
Seismology of Rapidly Rotating Accreting White Dwarfs
Dean M. Townsley, Phil Arras, Lars Bildsten
A number of White Dwarfs (WDs) in cataclysmic binaries have shown brightness variations consistent with non-radial oscillations as observed in isolated WDs. A few objects have been…
Numerical Simulations of Convective 3-Dimensional Red Supergiant Envelopes
Jared A. Goldberg, Yan-Fei Jiang, Lars Bildsten
We explore the three-dimensional properties of convective, luminous (), Hydrogen-rich envelopes of Red Supergiants (RSGs) based on radiation hydrody…
A new class of pulsating hot subdwarfs
Thomas Kupfer, Evan B. Bauer, Kevin B. Burdge +22
Using high-cadence observations from the Zwicky Transient Facility at low Galactic latitudes, we have discovered a new class of pulsating, hot, compact stars. We have found four ca…
Morphology and Mach Number Dependence of Subsonic Bondi-Hoyle Accretion
Logan J. Prust, Hila Glanz, Lars Bildsten +2
We carry out three-dimensional computations of the accretion rate onto an object (of size and mass ) as it moves through a uniform medium at a subsonic speed $v_{…
Lithium Depletion in Fully Convective Pre-Main Sequence Stars
Lars Bildsten, Edward F. Brown, Christopher D. Matzner +1
We present an analytic calculation of the thermonuclear depletion of lithium in contracting, fully convective, pre-main sequence stars of mass M < 0.5 M_sun. Previous numerical wor…
The Asteroseismological Richness of RCB and dLHdC Stars
Tin Long Sunny Wong, Lars Bildsten
RCB stars are solar-mass objects that can exhibit large periods of extinction from dust ejection episodes. Many exhibit semiregular pulsations in the rang…
Carbon Detonation and Shock-Triggered Helium Burning in Neutron Star Superbursts
Nevin N. Weinberg, Lars Bildsten
The strong degeneracy of the 12C ignition layer on an accreting neutron star results in a hydrodynamic thermonuclear runaway, in which the nuclear heating time becomes shorter than…
Rapid Rotation and Nonradial Pulsations: Kappa-Mechanism Excitation of G-Modes in B Stars
Greg Ushomirsky, Lars Bildsten
Several classes of stars (most notably O and B main-sequence stars, as well as accreting white dwarfs and neutron stars) rotate quite rapidly, at spin frequencies greater than the…
The First Day of a Type Ia Supernova from a Double-Degenerate Binary
Gabriel Kumar, Logan J. Prust, Lars Bildsten
Supernovae in binary star systems involve a hydrodynamical interaction between the ejecta and a binary companion. This collision results in shock heating and a modified density str…
PTF10iya: A short-lived, luminous flare from the nuclear region of a star-forming galaxy
S. Bradley Cenko, Joshua S. Bloom, S. R. Kulkarni +28
We present the discovery and characterisation of PTF10iya, a short-lived (dt ~ 10 d, with an optical decay rate of ~ 0.3 mag per d), luminous (M_g ~ -21 mag) transient source found…
Variability in the Thermal Emission from Accreting Neutron Star Transients
Edward F. Brown, Lars Bildsten, Philip Chang
The composition of the outer 100 m of a neutron star sets the heat flux that flows outwards from the core. For an accreting neutron star in an X-ray transient, the thermal quiescen…
An Accreting White Dwarf near the Chandrasekhar Limit in the Andromeda Galaxy
Sumin Tang, Lars Bildsten, William M. Wolf +13
The iPTF detection of the most recent outburst of the recurrent nova system RX J0045.4+4154 in the Andromeda Galaxy has enabled the unprecedented study of a massive ($M>1.3\ M_\odo…
The Effects of Curvature and Expansion on Helium Detonations on White Dwarf Surfaces
Kevin Moore, Dean Townsley, Lars Bildsten
Accreted helium layers on white dwarfs have been highlighted for many decades as a possible site for a detonation triggered by a thermonuclear runaway. In this paper, we find the m…
Rotational Evolution During Type I X-Ray Bursts
Andrew Cumming, Lars Bildsten
The rotation rates of six weakly-magnetic neutron stars accreting in low-mass X-ray binaries have most likely been measured by Type I X-ray burst observations with RXTE. The nearly…
The Ocean and Crust of a Rapidly Accreting Neutron Star: Implications for Magnetic Field Evolution and Thermonuclear Flashes
Edward F. Brown, Lars Bildsten
We investigate the atmosphere, ocean, and crust of neutron stars accreting at rates sufficiently high (typically in excess of the local Eddington limit) to stabilize the burning of…
Thermonuclear Burning on Rapidly Accreting Neutron Stars
Lars Bildsten
Neutron stars in mass-transferring binaries are accreting the hydrogen and helium rich matter from the surfaces of their companions. This article simply explains the physics associ…
Electron Captures on as a Trigger for Helium Shell Detonations
Evan B. Bauer, Josiah Schwab, Lars Bildsten
White dwarfs (WDs) that accrete helium at rates , such as those in close binaries with sdB stars, can accumulate large ($\gtrsim 0.1 \, M_\o…
On the Dramatic Spin-up/Spin-down Torque Reversals in Accreting Pulsars
Robert W. Nelson, Lars Bildsten, Deepto Chakrabarty +7
Dramatic torque reversals between spin up and spin down have been observed in half of the persistent X-ray pulsars monitored by the BATSE all-sky monitor on CGRO. Theoretical model…
The Last Three Minutes: Issues in Gravitational Wave Measurements of Coalescing Compact Binaries
Curt Cutler, Theocharis A. Apostolatos, Lars Bildsten +8
Gravitational-wave interferometers are expected to monitor the last three minutes of inspiral and final coalescence of neutron star and black hole binaries at distances approaching…
Gravitational Settling of ^{22}Ne in Liquid White Dwarf Interiors--Cooling and Seismological Effects
Christopher J. Deloye, Lars Bildsten
We assess the impact of the trace element ^{22}Ne on the cooling and seismology of a liquid C/O white dwarf (WD). Due to this elements' neutron excess, it sinks towards the interio…
The Thermal State of the Accreting White Dwarf in AM Canum Venaticorum Binaries
Lars Bildsten, Dean M. Townsley, Christopher J. Deloye +1
We calculate the heating and cooling of the accreting white dwarf (WD) in the ultracompact AM Canum Venaticorum (AM CVn) binaries and show that the WD can contribute significantly…
Hydrogen Burning on Accreting White Dwarfs: Stability, Recurrent Novae, and the Post-Novae Supersoft Source
William M. Wolf, Lars Bildsten, Jared Brooks +1
We examine the properties of white dwarfs (WDs) accreting hydrogen-rich matter in and near the stable burning regime of accretion rates as modeled by time-dependent calculations do…
A Search for Rapid Photometric Variability in Symbiotic Binaries
J. L. Sokoloski, Lars Bildsten, Wynn C. G. Ho
We report on our survey for rapid (time scale of minutes) photometric variability in symbiotic binaries. These binaries are becoming an increasingly important place to study accret…
X-ray Spectral Identification of Three Candidate Quiescent Low-Mass X-ray Binaries in the Globular Cluster NGC 6304
Sebastien Guillot, Robert E. Rutledge, Lars Bildsten +3
We report the search for low-mass X-ray binaries in quiescence (qLMXBs) in the globular cluster NGC 6304 using XMM observations. We present the spectral analysis leading to the ide…