Soft X-ray Polarization in Thermal Magnetar Emission (2009)
Van Adelsberg, Matthew, Perna, Rosalba
Emission spectra from magnetars in the soft X-ray band likely contain a thermal component emerging directly from the neutron star surface. However, the lack of observed absorption-like features in...
Gravitational Lensing of Anisotropic Sources (2009)
Perna, Rosalba, Keeton, Charles R.
In strong gravitational lensing, the multiple images we see correspond to light rays that leave the source in slightly different directions. If the source emission is anisotropic, the images may...
The first outburst of the new magnetar candidate SGR 0501+4516 (2009)
Rea, Nanda, Israel, GianLuca, Turolla, Roberto, Esposito, Paolo, Mereghetti, Sandro, Gotz, Diego, ...
We report here on the outburst onset and evolution of the new Soft Gamma Repeater SGR 0501+4516. We monitored the new SGR with XMM-Newton starting on 2008 August 23, one day after the source became...
How rapidly do neutron stars spin at birth? (2008)
Soria, Roberto, Perna, Rosalba, Pooley, David, Stella, Luigi
We have studied the X-ray properties of ageing historical core-collapse supernovae in nearby galaxies, using archival data from Chandra, XMM-Newton and Swift. We found possible evidence of a young...
A direct measurement of the dust extinction curve in an intermediate-redshift galaxy (2008)
Heng, Kevin, Lazzati, Davide, Perna, Rosalba, Garnavich, Peter, Noriega-Crespo, Alberto, Bersier, David, ...
We present a proof-of-concept study that dust extinction curves can be extracted from the infrared (IR), optical, ultraviolet (UV), and X-ray afterglow observations of GRBs without assuming known...
The oldest X-ray supernovae: X-ray emission from 1941C, 1959D, 1968D (2008)
Soria, Roberto, Perna, Rosalba
We have studied the X-ray emission from four historical Type-II supernovae (the newly-discovered 1941C in NGC 4631 and 1959D in NGC 7331; and 1968D, 1980K in NGC 6946), using Chandra ACIS-S imaging....
X-ray flares, neutrino cooled disks, and the dynamics of late accretion in GRB engines (2008)
Lazzati, Davide, Perna, Rosalba, Begelman, Mitchell C.
We compute the average luminosity of X-ray flares as a function of time, for a sample of 10 long-duration gamma-ray burst afterglows. The mean luminosity, averaged over a timescale longer than the...
X-ray flares and their relation to the inner engine activity of GRBs (2008)
Lazzati, Davide, Morsony, Brian J., Perna, Rosalba, Begelman, Mitchell C.
Flares overlaid on the smooth power-law decay of Swift X-ray afterglows are rather common, appearing in roughly half the observed light curves. They are a manifestation of the late time activity of...
A Direct Measurement of the Dust Extinction Curve in an Intermediate-Redshift Galaxy (2008)
Heng, Kevin, Lazzati, Davide, Perna, Rosalba, Garnavich, Peter, Noriega-Crespo, Alberto, Bersier, David, ...
We present a proof-of-concept study that dust extinction curves can be extracted from the infrared (IR), optical, ultraviolet (UV) and X-ray afterglow observations of GRBs without assuming known...
Perna, Rosalba, Gotthelf, Eric V.
The temporal decay of the flux components of Transient Anomalous X-ray Pulsar XTE J1810-197 following its 2002 outburst presents a unique opportunity to probe the emission geometry of a magnetar....
Perna, Rosalba, Soria, Roberto, Pooley, Dave, Stella, Luigi
Traditionally, studies aimed at inferring the distribution of birth periods of neutron stars are based on radio surveys. Here we propose an independent method to constrain the pulsar spin periods at...
"Orphan" afterglows in the Universal Structured Jet Model for gamma-ray bursts (2007)
Rossi, Elena M., Perna, Rosalba, Daigne, Frédéric
The paucity of reliable achromatic breaks in Gamma-Ray Burst afterglow light curves motivates independent measurements of the jet aperture. Serendipitous searches of afterglows, especially at radio...
Instabilities in the time-dependent neutrino disc in Gamma-Ray Bursts (2007)
Janiuk, Agnieszka, Yuan, Ye-Fei, Perna, Rosalba, Di Matteo, Tiziana
We investigate the properties and evolution of accretion tori formed after the coalescence of two compact objects. At these extreme densities and temperatures, the accreting torus is cooled mainly by...
Dust Echoes from the Ambient Medium of Gamma-Ray Bursts (2007)
Heng, Kevin, Lazzati, Davide, Perna, Rosalba
Long gamma-ray bursts (GRBs) are likely associated with the collapse of massive stars, which produce dust and are born in dusty environments. Absorption and scattering of ultraviolet/X-ray photons...
X-ray flares and the duration of engine activity in gamma-ray bursts (2006)
Lazzati, Davide, Perna, Rosalba
The detection of bright X-ray flares superimposed on the regular afterglow decay in Swift gamma-ray bursts has triggered theoretical speculations on their origin. We study the temporal properties of...
Constraining the environment of GRB 990712 through emission line fluxes (2006)
Yoldas, Aybuke Kupcu, Greiner, Jochen, Perna, Rosalba
The energy output in the gamma-ray burst (GRB) prompt emission and afterglow phase is expected to photoionize the surrounding medium out to large radii. Cooling of this gas produces line emission,...
A Study of Compact Object Mergers as Short Gamma-ray Burst Progenitors (2006)
Belczynski, Krzysztof, Perna, Rosalba, Bulik, Tomasz, Kalogera, Vassiliki, Ivanova, Natalia, Lamb, Donald Q.
We present a theoretical study of double compact objects as potential short/hard gamma-ray burst (GRB) progenitors. An updated population synthesis code StarTrack is used to calculate properties of...
Flares in long and short Gamma-Ray Bursts: a common origin in a hyperaccreting accretion disk (2005)
Perna, Rosalba, Armitage, Philip J., Zhang, Bing
Early-time X-ray observations of GRBs with the Swift satellite have revealed a more complicated phenomenology than was known before. In particular, the presence of flaring activity on a wide range of...
On the spin-up/spin-down transitions in accreting X-ray binaries (2005)
Perna, Rosalba, Bozzo, Enrico, Stella, Luigi
Accreting X-Ray Binaries display a wide range of behaviours. Some of them are observed to spin up steadily, others to alternate between spin-up and spin-down states, sometimes superimposed on a...
Israel, GianLuca, Covino, Stefano, Mignani, Roberto, Stella, Luigi, Marconi, Gianni, Testa, Vincenzo, ...
The sky region including the Chandra position of SGR 1806-20 was monitored in the IR band during 2004, following its increased high energy bursting activity. Observations were performed using...
Afterglow Observations Shed New Light on the Nature of X-ray Flashes (2005)
Granot, Jonathan, Ramirez-Ruiz, Enrico, Perna, Rosalba
X-ray flashes (XRFs) and X-ray rich gamma-ray bursts (XRGRBs) share many observational characteristics with long duration GRBs, but the reason for which their prompt emission peaks at lower photon...
Volonteri, Marta, Perna, Rosalba
We investigate the consequences of a model of the assembly and growth of massive black holes from primordial seeds, remnants of the first generation of stars in a hierarchical structure formation...
Mesinger, Andrei, Perna, Rosalba, Haiman, Zoltan
Cosmological models that include suppression of the power spectrum of density fluctuations on small scales exhibit an exponential reduction of high-redshift, non-linear structures, including a...
Are all Gamma Ray Bursts like GRB 980425, GRB 030329 and GRB 031203? (2004)
Guetta, Dafne, Perna, Rosalba, Stella, Luigi, Vietri, Mario
We study the probability that three GRBs (980425, 030329, 031203) are found within z=0.17, given the luminosity functions consistent with the log N-log S relationship for classical cosmological...
Accretion flows in early-type galaxies and CMB experiments (2004)
Pierpaoli, Elena, Perna, Rosalba
We investigate the possible contribution from the emission of accretion flows around supermassive black holes in early type galaxies to current measurements of the Cosmic Microwave Background (CMB)...
Young Crab-like pulsars and luminous X-ray sources in starbursts and optically dull galaxies (2004)
Recent Chandra observations of nearby galaxies have revealed a number of ultraluminous X-ray sources (ULXs) with super-Eddington luminosities, away from the central regions of non-active galaxies....
Evolution of a neutrino-cooled disc in Gamma-Ray Bursts (2004)
Janiuk, Agnieszka, Perna, Rosalba, Di Matteo, Tiziana, Czerny, Bozena
Rapid, hyper-Eddington accretion is likely to power the central engines of gamma-ray bursts (GRBs). In the extreme conditions of densities and temperatures the accreting torus is cooled by neutrino...
Perna, Rosalba, Gaensler, Bryan M.
Traditional searches for radio pulsars have targeted individual small regions such as supernova remnants or globular clusters, or have covered large contiguous regions of the sky. None of these...
Pulsars With Jets May Harbor Dynamically Important Accretion Disks (2003)
Blackman, Eric G., Perna, Rosalba
For many astrophysical sources with jets, there is evidence for the contemporaneous presence of disks. In contrast, pulsars such as the Crab and Vela show jets but have not yet revealed direct...
Unveiling the multi-wavelength phenomenology of Anomalous X-ray Pulsars (2003)
Israel, GianLuca, Stella, Luigi, Covino, Stefano, Campana, Sergio, Angelini, Lorella, Mignani, Roberto, ...
During 2002-2003 the number of IR-identified counterparts to the Anomalous X-ray Pulsars (AXPs) has grown to four (4U0142+614, 2E2259+584, 1E 1048-59 and 1RXS J170849-400910) out of the six assessed...
Chandra Observations of the Dwarf Nova WX Hyi in Quiescence (2003)
Perna, Rosalba, McDowell, Jonathan, Menou, Kristen, Raymond, John, Medvedev, Mikhail
We report Chandra observations of the dwarf nova WX Hyi in quiescence. The X-ray spectrum displays strong and narrow emission lines of N, O, Mg, Ne, Si, S and Fe. The various ionization states...
Bondi Accretion and the Problem of the Missing Isolated Neutron Stars (2003)
Perna, Rosalba, Narayan, Ramesh, Rybicki, George, Stella, Luigi, Treves, Aldo
A large number of neutron stars (NSs), ~10^9, populate the Galaxy, but only a tiny fraction of them is observable during the short radio pulsar lifetime. The majority of these isolated NSs, too cold...
Jets in GRBs: Tests and Predictions for the Structured Jet Model (2003)
Perna, Rosalba, Sari, Re'em, Frail, Dale
The two leading interpretations of achromatic breaks that are observed in the light curves of GRBs afterglow are (i) the manifestation of the edge of a jet, which has a roughly uniform energy profile...
Lazzati, Davide, Perna, Rosalba
We use the time-dependent photoionization and dust destruction code developed by Perna & Lazzati (2002) to study the time evolution of the medium in a dusty gaseous cloud illuminated by a bright...
Broadband Modeling of GRB 021004 (2002)
Heyl, Jeremy S., Perna, Rosalba
We present a broadband modeling of the afterglow of GRB 021004. The optical transient of this burst has been detected very early and densely sampled in several bands. Its light curve shows...
Perna, Rosalba, Lazzati, Davide, Fiore, Fabrizio
The interaction of a radiation field with a dusty medium is a relevant issue in several astrophysical contexts. We use the time-dependent photoionization code in a dusty medium developed by Perna &...
Neutrino trapping and accretion models for Gamma-Ray Bursts (2002)
Di Matteo, Tiziana, Perna, Rosalba, Narayan, Ramesh
Many models of Gamma Ray Bursts invoke a central engine consisting of a black hole of a few solar masses accreting matter from a disk at a rate of a fraction to a few solar masses per second. Popham...
Time-Dependent Photoionization in a Dusty Medium I: Code Description and General Results (2002)
Perna, Rosalba, Lazzati, Davide
We present a time-dependent photoionization code that combines self-consistently metal evolution and dust destruction under an intense X-ray UV radiation field. Firstly, we extend the mathematical...
We derive a fully relativistic, self-similar solution to describe the propagation of a shock along an exponentially decreasing atmosphere, in the limit of very large Lorentz factor. We solve the...
X-ray spectroscopy of gamma-ray bursts: the path to the progenitor (2002)
Lazzati, Davide, Perna, Rosalba, Ghisellini, Gabriele
Despite great observational and theoretical effort, the burst progenitor is still a mysterious object. It is generally accepted that one of the best ways to unveil its nature is the study of the...
Short GRBs and Mergers of Compact Objects: Observational Constraints (2002)
Perna, Rosalba, Belczynski, Krzysztof
GRB data accumulated over the years have shown that the distribution of their time duration is bimodal. While there is some evidence that long bursts are associated with star-forming regions, nothing...
Hydrogen-Poor Disks in Compact X-Ray Binaries (2001)
Menou, Kristen, Perna, Rosalba, Hernquist, Lars
We show that accretion disks in several compact X-ray binaries with hydrogen-depleted donors are likely subject to a thermal ionization instability, unless they are strongly irradiated. These disks...
Lazzati, Davide, Perna, Rosalba
We investigate through dedicated numerical simulations the evolution of the soft X-ray absorption properties of a cloud surrounding a gamma-ray burst source. We show that the absorption properties of...
Di Matteo, Tiziana, Perna, Rosalba, Abel, Tom, Rees, Martin J.
Absorption or emission against the cosmic microwave background radiation (CMB) may be observed in the redshifted 21cm line if the spin temperature of the neutral intergalactic medium prior to...
Time dependent photoionization opacities in dense Gamma-Ray Burst environments (2001)
Lazzati, Davide, Perna, Rosalba, Ghisellini, Gabriele
The recent detection of a transient absorption feature in the X-ray prompt emission of GRB 990705 showed the importance of such observations in the understanding of gamma-ray bursts and their...
X-ray emission from middle-aged pulsars (2001)
Perna, Rosalba, Heyl, Jeremy, Hernquist, Lars
We present a simple, unified model which accounts for properties of the X-ray emission from the three middle-aged pulsars PSR 1055-52, PSR 0656+14 and PSR 0630+18 (Geminga). The X-ray radiation from...
Gamma-ray Burst Remnants: How can we find them? (2001)
By now there is substantial evidence that Gamma-Ray Bursts (GRBs) originate at cosmological distances from very powerful explosions. The interaction between a GRB and its surrounding environment has...
Scintillation as a Probe of the Intergalactic Medium (2001)
Ferrara, Andrea, Perna, Rosalba
Most of the baryons in the low-redshift universe reside in a warm/hot component which is difficult to detect with standard absorption/emission line techniques. We propose to use quasar refractive...
Accretion-Assisted Spindown of Young Radio Pulsars (2001)
Menou, Kristen, Perna, Rosalba, Hernquist, Lars
We present a model for the spindown of young radio pulsars in which the neutron star loses rotational energy not only by emitting magnetic dipole radiation but also by torquing a surrounding...
Anomalous X-ray Pulsars and Soft gamma-ray Repeaters: Spectral Fits and the Magnetar Model (2001)
Perna, Rosalba, Heyl, Jeremy, Hernquist, Lars, Juett, Adrienne, Chakrabarty, Deepto
The energy source powering the X-ray emission from anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) is still uncertain. In one scenario, the presence of an ultramagnetized neutron...
Stability and Evolution of Supernova Fallback Disks (2001)
Menou, Kristen, Perna, Rosalba, Hernquist, Lars
We show that thin accretion disks made of Carbon or Oxygen are subject to the same thermal ionization instability as Hydrogen and Helium disks. We argue that the instability applies to disks of any...
Disks irradiated by beamed radiation from compact objects (2000)
Perna, Rosalba, Hernquist, Lars
We examine the reprocessing of X-ray radiation from compact objects by accretion disks when the X-ray emission from the star is highly beamed. The reprocessed flux for various degrees of beaming and...
X-Ray Lines from Hot Flows around White Dwarfs. Application to SS Cygni (2000)
Menou, Kristen, Perna, Rosalba, Raymond, John
Rather than accreting via a disk, some White Dwarfs (WDs) in quiescent Dwarf Novae (DN) could accrete via an Advection-Dominated Accretion Flow (ADAF) possibly responsible for the X-ray...
Consequences of Interstellar Absorption for Models of Anomalous X-ray Pulsars (2000)
Perna, Rosalba, Heyl, Jeremy, Hernquist, Lars
We examine properties of thermal radiation emitted by strongly magnetized neutron stars (NSs). In particular, we show that the pulsation amplitudes of the energy-integrated flux are an increasing...
Gamma-ray burst afterglows as probes of galactic and intergalactic dust (2000)
Perna, Rosalba, Aguirre, Anthony
The amount and properties of high-redshift galactic and intergalactic (IG) dust are largely unknown, but could be investigated using multi-wavelength photometry of high-z objects that have a known...
X-ray Line Diagnostics of Hot Accretion Flows around Black Holes (2000)
Perna, Rosalba, Raymond, John, Narayan, Ramesh
We compute X-ray emission lines from thermal plasma in hot accretion flows. We show that line profiles are strong probes of the gas dynamics, and we present line-ratio diagnostics which are sensitive...
Synchrotron Emission from Hot Accretion Flows and the Cosmic Microwave Background Anisotropy (2000)
Perna, Rosalba, Di Matteo, Tiziana
Current estimates of number counts of radio sources in the frequency range where the most sensitive Cosmic Microwave Background (CMB) experiments are carried out significantly under-represent sources...
Testing the multiple supernovae versus gamma-ray burst scenarios for giant HI supershells (2000)
The energy source of the giant HI supershells in nearby galaxies and in our own is still an unsettled issue. Proposed scenarios for production of near-complete ringlike supershells are multiple...
Emission Spectra of Fallback Disks Around Young Neutron Stars (1999)
Perna, Rosalba, Hernquist, Lars, Narayan, Ramesh
The nature of the energy source powering anomalous X-ray pulsars is uncertain. Proposed scenarios involve either an ultramagnetized neutron star, or accretion onto a neutron star. We consider the...
Identifying Gamma-Ray Burst Remnants in Nearby Galaxies (1999)
Perna, Rosalba, Raymond, John, Loeb, Abraham
We study the spectral signatures arising from cooling and recombination of an interstellar medium whose equilibrium state has been altered over \sim 100 pc by the radiation of a Gamma-Ray Burst (GRB)...
Theoretical studies of gamma-ray bursts /--a thesis presented by Rosalba Perna. (1999)
Thesis (Ph. D., Department of Physics)--Harvard University, 1999.
Constraining the Beaming of Gamma-Ray Bursts With Radio Surveys (1998)
The degree of beaming in Gamma-Ray Bursts (GRBs) is currently unknown. The uncertainty in the gamma-ray beaming angle, theta, leaves the total energy release (proportional to theta^2) and the event...
Are HI Supershells the Remnants of Gamma-Ray Bursts? (1998)
Gamma-Ray Bursts (GRBs) are thought to originate at cosmological distances from the most powerful explosions in the Universe. If GRBs are not beamed then the distribution of their number as a...
X-Ray Absorption by the Hot Intergalactic Medium (1998)
The current census of observed baryons in the local Universe is still missing a significant fraction of them according to standard Big-Bang nucleosynthesis. Numerical simulations predict that most of...
The discovery of Gamma-Ray Burst (GRB) afterglows revealed a new class of variable sources at optical and radio wavelengths. At present, the environment and precise redshift of the detected...
Microlensing of $\gamma$-Ray Burst Afterglows (1997)
The afterglow of a cosmological Gamma-Ray Burst (GRB) should appear on the sky as a narrow emission ring of radius 3x10^{16}cm(t/day)^{5/8} which expands faster than light. After a day, the ring...
Probing the Mass Fraction of MACHOs in Extragalactic Halos (1997)
Current microlensing searches calibrate the mass fraction of the Milky Way halo which is in the form of Massive Compact Halo Objects (MACHOs). We show that surveys like the Sloan Digital Sky Survey...
Effects of Dust on Gravitational Lensing by Spiral Galaxies (1997)
Perna, Rosalba, Loeb, Abraham, Bartelmann, Matthias
Gravitational lensing of an optical QSO by a spiral galaxy is often counteracted by dust obscuration, since the line-of-sight to the QSO passes close to the center of the galactic disk. The dust in...
Identifying Microlensing by Binaries (1997)
Di Stefano, Rosanne, Perna, Rosalba
The microlensing monitoring programs have studied large numbers of standard light curves which seem to be due to lensing by a dark point mass. Theory predicts that many microlensing events should...
Microlensing of Quasars By Stars In Their Damped Lyman alpha Absorbers (1997)
The damped Lyman alpha absorbers (DLAs) in quasar spectra are believed to be the progenitors of present-day disk galaxies. We examine the probability for microlensing of background quasars by stars...