Shock Breakout from Type Ia Supernova (2009)
Piro, Anthony L., Chang, Philip, Weinberg, Nevin N.
The mode of explosive burning in Type Ia SNe remains an outstanding problem. It is generally thought to begin as a subsonic deflagration, but this may transition into a supersonic detonation (the...
The Dynamic X-ray Sky of the Local Universe (2009)
Soderberg, Alicia M., Grindlay, Jonathan E., Bloom, Joshua S., Gezari, Suvi, Piro, Anthony L., Belloni, Tomaso, ...
Over the next decade, we can expect time domain astronomy to flourish at optical and radio wavelengths. In parallel with these efforts, a dedicated transient "machine" operating at higher energies...
Convection during the Late Stages of Simmering in Type Ia Supernovae (2008)
Piro, Anthony L., Chang, Philip
Following unstable ignition of carbon, but prior to explosion, a white dwarf (WD) in a Type Ia supernova (SN Ia) undergoes a simmering phase. During this time, a central convective region grows and...
The Internal Shear of Type Ia Supernova Progenitors During Accretion and Simmering (2008)
A white dwarf (WD) gains substantial angular momentum during the accretion process that grows it toward a Chandrasekhar mass. It is therefore expected to be quickly rotating when it ignites as a Type...
The Turbulent Story of X-ray Bursts: Effects of Shear Mixing on Accreting Neutron Stars (2007)
Piro, Anthony L., Bildsten, Lars
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, focusing on the impact...
Neutronization During Type Ia Supernova Simmering (2007)
Piro, Anthony L., Bildsten, Lars
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 that weak interactions...
Turbulent Mixing in the Surface Layers of Accreting Neutron Stars (2007)
Piro, Anthony L., Bildsten, Lars
During accretion a neutron star (NS) is spun up as angular momentum is transported through its surface layers. We study the resulting differentially rotating profile, focusing on the impact this has...
Fragmentation of Collapsar Disks and the Production of Gravitational Waves (2006)
We argue that gravitational instability in the outer parts of collapsar disks may lead to fragmentation near the radius where helium photodisintegrates, because of the strong cooling provided by this...
X-ray binaries in Sculptor (2005)
Maccarone, Thomas J., Kundu, Arunav, Zepf, Stephen E., Piro, Anthony L., Bildsten, Lars
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 establishing them as...
The Energy Dependence of Neutron Star Surface Modes and X-ray Burst Oscillations (2005)
Piro, Anthony L., Bildsten, Lars
We calculate the photon energy dependence of the pulsed amplitude of neutron star (NS) surface modes. Simple approximations demonstrate that it depends most strongly on the bursting NS surface...
Shear Waves and Giant Flare Oscillations from Soft Gamma-Ray Repeaters (2005)
Recent observations of giant flares from soft gamma-ray repeaters have exhibited multiple 25-150 Hz oscillations. Frequencies in this range are expected for toroidal shear waves in a neutron star...
The discovery of X-ray binaries in the Sculptor Dwarf Spheroidal Galaxy (2005)
Maccarone, Thomas J., Kundu, Arunav, Zepf, Stephen E., Piro, Anthony L., Bildsten, Lars
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 $6\times10^{33}$ ergs/sec with optical counterparts...
White Dwarf Heating and Subsequent Cooling in Dwarf Nova Outbursts (2005)
Piro, Anthony L., Arras, Phil, Bildsten, Lars
We follow the time dependent thermal evolution of a white dwarf (WD) undergoing sudden accretion in a dwarf nova outburst, using both simulations and analytic estimates. The post-outburst lightcurve...
Surface Modes on Bursting Neutron Stars and X-ray Burst Oscillations (2005)
Piro, Anthony L., Bildsten, Lars
Accreting neutron stars (NSs) often show coherent modulations during type I X-ray bursts, called burst oscillations. We consider whether a nonradial mode can serve as an explanation for burst...
A Spreading Layer Origin for Dwarf Nova Oscillations (2004)
Piro, Anthony L., Bildsten, Lars
Dwarf nova outbursts often show coherent ($Q\sim10^4-10^6$) sinusoidal oscillations with the largest pulsed fraction in the extreme ultraviolet. Called dwarf nova oscillations (DNOs), they have...
Neutron Star Crustal Interface Waves (2004)
Piro, Anthony L., Bildsten, Lars
The eigenfrequencies of nonradial oscillations are a powerful probe of a star's interior structure. This is especially true when there exist discontinuities such as at the neutron star (NS)...
The Spreading Layer and Dwarf Nova Oscillations (2004)
Piro, Anthony L., Bildsten, Lars
We describe recent theoretical work on the final stage of accretion when material passes from an accretion disk onto a white dwarf surface. Our calculations focus on understanding the latitudinal...
Spreading of Accreted Material on White Dwarfs (2004)
Piro, Anthony L., Bildsten, Lars
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 comes into co-rotation...
Unstable Nonradial Oscillations on Helium Burning Neutron Stars (2003)
Piro, Anthony L., Bildsten, Lars
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 crust permeates the...
Transient X-ray Binaries in Elliptical Galaxies (2002)
Piro, Anthony L., Bildsten, Lars
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 generates this...