Peggy Varniere - Academia.edu (original) (raw)
Papers by Peggy Varniere
Astronomische Nachrichten
Binary black holes emit gravitational waves as they inspiral towards coalescence. Searches for el... more Binary black holes emit gravitational waves as they inspiral towards coalescence. Searches for electromagnetic counterparts to these gravitational waves rely on looking for common sources producing both signals. In this paper, we take a different approach: we investigate the impact of radiation zone effects, including retardation effects and gravitational wave propagation onto the circumbinary disk around stellarmass, spinning black holes, using general relativistic hydrodynamical simulations. Then we used a general relativistic ray-tracing code to extract its X-ray spectrum and lightcurve. This allowed us to show that radiation zone effects leave an imprint onto the disk, leading to quasi-periodic patterns in the X-ray lightcurve. The amplitude of the modulation is weak (<1%) but increases with time and is strongly dependent on the inclination angle.
American Astronomical Society Meeting Abstracts #227, 2016
HAL (Le Centre pour la Communication Scientifique Directe), Dec 1, 2015
Astronomy & Astrophysics, 2020
Context. The Rossby wave instability (RWI) has been proposed to explain the origin of the high-fr... more Context. The Rossby wave instability (RWI) has been proposed to explain the origin of the high-frequency quasi-periodic oscillations observed in the X-ray emission of astrophysical systems harbouring black holes. Recent numerical computations have proven that the RWI does exist in a general relativistic context and that its presence is associated with a time-variable X-ray emission from the disc. Aims. Using our new Numerical Observatory of Violent Accreting system, NOVAs, we explore the way the RWI impacts an accretion disc orbiting a spinning black hole under realistic astrophysical conditions. Our aim is to study the impact of the presence of the RWI in the very inner part of the accretion disc on known observables and explore some possibly new ones. Methods. We present the first full general relativistic hydrodynamical simulations of the RWI occurring at the last stable orbit of an accretion disc orbiting around a Kerr black-hole. Those simulations, coupled with a full general r...
Astronomy & Astrophysics, 2019
Context. The rather elusive high-frequency quasi-periodic oscillations (HFQPOs) observed in the X... more Context. The rather elusive high-frequency quasi-periodic oscillations (HFQPOs) observed in the X-ray light curve of black holes have been seen in a wide range of frequencies, even within one source. Also notable is the detection of “pairs” of HFQPOs with a close-to-integer ratio between the frequencies. Aims. The aim of this paper is to investigate some of the possible observables that we could obtain from the Rossby wave instability (RWI) active in the accretion disc surrounding the compact object. Methods. Using the newly developed GR-AMRVAC code able to follow the evolution of the RWI in a full general relativistic framework, we explore how RWI can reproduce observed HFQPO frequency ratios and whether or not it is compatible with observations. In order to model the emission coming from the disc we have linked our general relativistic simulations to the general relativistic ray-tracing GYOTO code and delivered synthetic observables that can be confronted with actual data from bin...
Astronomy & Astrophysics, 2016
Context. Quasi-periodic oscillations (QPOs) are a common feature of the power spectrum of X-ray b... more Context. Quasi-periodic oscillations (QPOs) are a common feature of the power spectrum of X-ray binaries. Currently it is not possible to unambiguously differentiate the large number of proposed models to explain these phenomena through existing observations. Aims. We investigate the observable predictions of a simple model that generates flux modulation: a spiral instability rotating in a thin accretion disk. This model is motivated by the accretion ejection instability (AEI) model for low-frequency QPOs (LFQPOs). We are particularly interested in the inclination dependence of the observables that are associated with this model. Methods. We develop a simple analytical model of an accretion disk, which features a spiral instability. The disk is assumed to emit blackbody radiation, which is ray-traced to a distant observer. We compute pulse profiles and power spectra as observed from infinity. Results. We show that the amplitude of the modulation associated with the spiral rotation is a strong function of inclination and frequency. The pulse profile is quasi-sinusoidal only at low inclination (face-on source). As a consequence, a higher-inclination geometry leads to a stronger and more diverse harmonic signature in the power spectrum. Conclusions. We present how the amplitude depends on the inclination when the flux modulation comes from a spiral in the disk. We also include new observables that could potentially differentiate between models, such as the pulse profile and the harmonic content of the power spectra of high-inclination sources that exhibit LFQPOs. These might be important observables to explore with existing and new instruments.
Astronomy & Astrophysics, 2016
Context. While nobody would deny the presence of quasi-periodic oscillations in the power density... more Context. While nobody would deny the presence of quasi-periodic oscillations in the power density spectrum of black hole binaries nor their importance in the understanding of the mechanisms powering the X-ray emissions, the possible impact on the time-averaged disk energy spectrum from the phenomenon responsible for quasi-periodic oscillations is largely ignored in models of sources emission. Aims. Here we investigate the potential impact of such a structure on the resultant energy spectrum. Methods. Using data from the well-documented outbursts of XTE J1550-564, we looked at possible hints that the presence of quasiperiodic oscillations actually impacts the energy spectrum emitted by the source. In particular, we look at the evolution of the relation between the inner disk radius and the inner disk temperature obtained from fits to the spectral data. We then test this further by developing a simple model to simulate the spectrum of a disk with a structure mimicking quasi-periodic oscillations that are increasing in strength simulated results to those obtained from real data. Results. We detect a similar departure in the inner radius-inner temperature curve coming from the standard fit of our simulated observations as is seen in XTE J1550-564 data. We interpret our results as evidence that the structure at the origin of the quasi-periodic oscillations impacts the energy spectrum. Conclusions. Furthermore, in states with significant disk emission the inaccuracy of the determination of the disk parameters increases with the strength of quasi-periodic oscillations, an increase that then renders the value given by the fit unreliable for strong quasiperiodic oscillations.
SPIE Proceedings, 2016
The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M... more The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m 2 effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
Astrobiology, 2010
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Monthly Notices of the Royal Astronomical Society
Accreting binary black holes (BBHs) are multimessenger sources, emitting copious electromagnetic ... more Accreting binary black holes (BBHs) are multimessenger sources, emitting copious electromagnetic (EM) and gravitational waves. One of their most promising EM signatures is the light-curve modulation caused by a strong unique and extended azimuthal overdensity structure orbiting at the inner edge of the circumbinary disc (CBD), dubbed ‘lump’. In this paper, we investigate the origin of this structure using 2D general-relativistic (GR) hydrodynamical simulations of a CBD in an approximate BBH space–time. First, we use the symmetric mass-ratio case to study the transition from the natural m = 2 mode to m = 1. The asymmetry with respect to m = 2 grows exponentially, pointing to an instability origin. We indeed find that the CBD edge is prone to a (magneto)hydrodynamical instability owing to the disc edge density sharpness: the Rossby Wave Instability (RWI). The RWI criterion is naturally fulfilled at the CBD edge and we report the presence of vortices, which are typical structures of th...
Monthly Notices of the Royal Astronomical Society
Accreting supermassive binary black holes (SMBBHs) are potential targets for multimessenger astro... more Accreting supermassive binary black holes (SMBBHs) are potential targets for multimessenger astronomy as they emit gravitational waves (GW) while their environment emits electromagnetic (EM) waves. In order to get the most out of a joint GW–EM detection we first need to obtain theoretically predicted EM signals unambiguously linked to BBHs. In that respect, this is the first of a series of papers dedicated to accreting pre-merger BBHs and their associated EM observables. Here, we extend our Numerical Observatory of Violent Accreting systems, e-NOVAs, to any space–time. Unlike previous studies, almost exclusively focused on the inner regions, we investigated the impact of the BBH on its outer circumbinary disc, located in the radiation (or wave) zone, after implementing an approximate analytical space–time of spinning, inspiralling BBHs in e-NOVAs. We follow the formation of a weak spiral structure in disc density arising from the retardation effects in the radiation zone metric. Sim...
Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray
The presence of QPOs in the Power Density Spectra of x-ray binaries is quite ubiquitous and is of... more The presence of QPOs in the Power Density Spectra of x-ray binaries is quite ubiquitous and is often modeled as a hot structure orbiting in the disk. While we have been using timing and PDS to determine the presence and explore the possible origin of QPOs, they are, up to now, absent from the spectral analysis. Here we are using a simple analytical model to mimic the hot structure of several QPO models in order to determine their impact on the energy spectrum. Introduction • When looking at the Power Density Spectrum of microquasars the most striking features are the presence of Quasi-Periodic Oscillations. Those Low-Frequency (< 30Hz) and High-Frequency (> 40Hz) QPOs cannot be neglected, indeed, the LFQPO alone can have a rms of up to 30%. Models often describe them as a warm/hot structure orbiting the disk. ! important timing feature that modulates the X-ray flux. • Nevertheless, when looking at the same data through the energy spectrum the disk is considered smooth with a m...
Proceedings of 25th Texas Symposium on Relativistic Astrophysics — PoS(Texas 2010), 2011
We present a detailed calculation of the mechanism by which the Accretion-Ejection Instability ca... more We present a detailed calculation of the mechanism by which the Accretion-Ejection Instability can extract accretion energy and angular momentum from a magnetized disk, and redirect them to its corona. In a disk threaded by a poloidal magnetic field of the order of equipartition with the gas pressure, the instability is composed of a spiral wave (analogous to galactic ones) and a Rossby vortex. The mechanism detailed here describes how the vortex, twisting the footpoints of field lines threading the disk, generates Alfven waves propagating to the corona. We find that this is a very efficient mechanism, providing to the corona (where it could feed a jet or a wind) a substantial fraction of the accretion energy.
With 2D hydrodynamical simulations of disks perturbed externally by stars, brown dwarfs or planet... more With 2D hydrodynamical simulations of disks perturbed externally by stars, brown dwarfs or planets we investigate possible scenarios that can account for the spiral structure in circumstellar disks. We consider two scenarios, spiral structure driven by an external bound planet or low mass star and that excited by a previous stellar close encounter or flyby. We find that both scenarios produce morphology similar to that observed in the outer disks of HD 141569A and HD 100546; moderately open 2-armed outer spiral structure. The outer two-armed spiral structure observed in the disk of HD 141569A is qualitatively reproduced with tidal perturbations from its companion binary HD 141569B,C on a prograde orbit near periapse. Our simulation accounts for the outer spiral arms, but is less successful than the secular model of Augereau and Papaloizou at matching the lopsidedness or asymmetry of the disk edge at 300AU. The disk has been previously truncated by the tidal force from the binary. A ...
We present computational results showing eccentricity growth in the inner portions of a protoplan... more We present computational results showing eccentricity growth in the inner portions of a protoplanetary disc. We attribute this to the evolving surface density of the disc. The planet creates a gap, which adjusts the balance between the 3:1 (eccentricity exciting) and 2:1 (eccentricity damping) resonances. The eccentricity of the inner disc can rise as high as 0.3, which is sufficient to cause it to be accreted onto the star. This offers an alternative mechanism for producing the large holes observed in the discs of CoKu Tau/4, GM Aur and DM Tau.
We study the effects of an annular gap induced by an embedded proto-planet on disk scattered ligh... more We study the effects of an annular gap induced by an embedded proto-planet on disk scattered light images and the infrared spectral energy distribution. We find that the outer edge of a gap is brighter in the scattered light images than a similar location in a gap-free disk. The stellar radiation that would have been scattered by material within in the gap is instead scattered by the disk wall at the outer edge of the gap, producing a bright ring surrounding the dark gap in the images. Given sufficient resolution, such gaps can be detected by the presence of this bright ring in scattered light images. A gap in a disk also changes the shape of the SED. Radiation that would have been absorbed by material in the gap is instead reprocessed by the outer gap wall. This leads to a decrease in the SED at wavelengths corresponding to the temperature at the radius of the missing gap material and a corresponding flux increase at longer wavelengths corresponding to the temperature of the outer ...
AIP Conference Proceedings, 2005
ABSTRACT
Astronomische Nachrichten
Binary black holes emit gravitational waves as they inspiral towards coalescence. Searches for el... more Binary black holes emit gravitational waves as they inspiral towards coalescence. Searches for electromagnetic counterparts to these gravitational waves rely on looking for common sources producing both signals. In this paper, we take a different approach: we investigate the impact of radiation zone effects, including retardation effects and gravitational wave propagation onto the circumbinary disk around stellarmass, spinning black holes, using general relativistic hydrodynamical simulations. Then we used a general relativistic ray-tracing code to extract its X-ray spectrum and lightcurve. This allowed us to show that radiation zone effects leave an imprint onto the disk, leading to quasi-periodic patterns in the X-ray lightcurve. The amplitude of the modulation is weak (<1%) but increases with time and is strongly dependent on the inclination angle.
American Astronomical Society Meeting Abstracts #227, 2016
HAL (Le Centre pour la Communication Scientifique Directe), Dec 1, 2015
Astronomy & Astrophysics, 2020
Context. The Rossby wave instability (RWI) has been proposed to explain the origin of the high-fr... more Context. The Rossby wave instability (RWI) has been proposed to explain the origin of the high-frequency quasi-periodic oscillations observed in the X-ray emission of astrophysical systems harbouring black holes. Recent numerical computations have proven that the RWI does exist in a general relativistic context and that its presence is associated with a time-variable X-ray emission from the disc. Aims. Using our new Numerical Observatory of Violent Accreting system, NOVAs, we explore the way the RWI impacts an accretion disc orbiting a spinning black hole under realistic astrophysical conditions. Our aim is to study the impact of the presence of the RWI in the very inner part of the accretion disc on known observables and explore some possibly new ones. Methods. We present the first full general relativistic hydrodynamical simulations of the RWI occurring at the last stable orbit of an accretion disc orbiting around a Kerr black-hole. Those simulations, coupled with a full general r...
Astronomy & Astrophysics, 2019
Context. The rather elusive high-frequency quasi-periodic oscillations (HFQPOs) observed in the X... more Context. The rather elusive high-frequency quasi-periodic oscillations (HFQPOs) observed in the X-ray light curve of black holes have been seen in a wide range of frequencies, even within one source. Also notable is the detection of “pairs” of HFQPOs with a close-to-integer ratio between the frequencies. Aims. The aim of this paper is to investigate some of the possible observables that we could obtain from the Rossby wave instability (RWI) active in the accretion disc surrounding the compact object. Methods. Using the newly developed GR-AMRVAC code able to follow the evolution of the RWI in a full general relativistic framework, we explore how RWI can reproduce observed HFQPO frequency ratios and whether or not it is compatible with observations. In order to model the emission coming from the disc we have linked our general relativistic simulations to the general relativistic ray-tracing GYOTO code and delivered synthetic observables that can be confronted with actual data from bin...
Astronomy & Astrophysics, 2016
Context. Quasi-periodic oscillations (QPOs) are a common feature of the power spectrum of X-ray b... more Context. Quasi-periodic oscillations (QPOs) are a common feature of the power spectrum of X-ray binaries. Currently it is not possible to unambiguously differentiate the large number of proposed models to explain these phenomena through existing observations. Aims. We investigate the observable predictions of a simple model that generates flux modulation: a spiral instability rotating in a thin accretion disk. This model is motivated by the accretion ejection instability (AEI) model for low-frequency QPOs (LFQPOs). We are particularly interested in the inclination dependence of the observables that are associated with this model. Methods. We develop a simple analytical model of an accretion disk, which features a spiral instability. The disk is assumed to emit blackbody radiation, which is ray-traced to a distant observer. We compute pulse profiles and power spectra as observed from infinity. Results. We show that the amplitude of the modulation associated with the spiral rotation is a strong function of inclination and frequency. The pulse profile is quasi-sinusoidal only at low inclination (face-on source). As a consequence, a higher-inclination geometry leads to a stronger and more diverse harmonic signature in the power spectrum. Conclusions. We present how the amplitude depends on the inclination when the flux modulation comes from a spiral in the disk. We also include new observables that could potentially differentiate between models, such as the pulse profile and the harmonic content of the power spectra of high-inclination sources that exhibit LFQPOs. These might be important observables to explore with existing and new instruments.
Astronomy & Astrophysics, 2016
Context. While nobody would deny the presence of quasi-periodic oscillations in the power density... more Context. While nobody would deny the presence of quasi-periodic oscillations in the power density spectrum of black hole binaries nor their importance in the understanding of the mechanisms powering the X-ray emissions, the possible impact on the time-averaged disk energy spectrum from the phenomenon responsible for quasi-periodic oscillations is largely ignored in models of sources emission. Aims. Here we investigate the potential impact of such a structure on the resultant energy spectrum. Methods. Using data from the well-documented outbursts of XTE J1550-564, we looked at possible hints that the presence of quasiperiodic oscillations actually impacts the energy spectrum emitted by the source. In particular, we look at the evolution of the relation between the inner disk radius and the inner disk temperature obtained from fits to the spectral data. We then test this further by developing a simple model to simulate the spectrum of a disk with a structure mimicking quasi-periodic oscillations that are increasing in strength simulated results to those obtained from real data. Results. We detect a similar departure in the inner radius-inner temperature curve coming from the standard fit of our simulated observations as is seen in XTE J1550-564 data. We interpret our results as evidence that the structure at the origin of the quasi-periodic oscillations impacts the energy spectrum. Conclusions. Furthermore, in states with significant disk emission the inaccuracy of the determination of the disk parameters increases with the strength of quasi-periodic oscillations, an increase that then renders the value given by the fit unreliable for strong quasiperiodic oscillations.
SPIE Proceedings, 2016
The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M... more The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m 2 effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
Astrobiology, 2010
For guidance on citations see FAQs.
Monthly Notices of the Royal Astronomical Society
Accreting binary black holes (BBHs) are multimessenger sources, emitting copious electromagnetic ... more Accreting binary black holes (BBHs) are multimessenger sources, emitting copious electromagnetic (EM) and gravitational waves. One of their most promising EM signatures is the light-curve modulation caused by a strong unique and extended azimuthal overdensity structure orbiting at the inner edge of the circumbinary disc (CBD), dubbed ‘lump’. In this paper, we investigate the origin of this structure using 2D general-relativistic (GR) hydrodynamical simulations of a CBD in an approximate BBH space–time. First, we use the symmetric mass-ratio case to study the transition from the natural m = 2 mode to m = 1. The asymmetry with respect to m = 2 grows exponentially, pointing to an instability origin. We indeed find that the CBD edge is prone to a (magneto)hydrodynamical instability owing to the disc edge density sharpness: the Rossby Wave Instability (RWI). The RWI criterion is naturally fulfilled at the CBD edge and we report the presence of vortices, which are typical structures of th...
Monthly Notices of the Royal Astronomical Society
Accreting supermassive binary black holes (SMBBHs) are potential targets for multimessenger astro... more Accreting supermassive binary black holes (SMBBHs) are potential targets for multimessenger astronomy as they emit gravitational waves (GW) while their environment emits electromagnetic (EM) waves. In order to get the most out of a joint GW–EM detection we first need to obtain theoretically predicted EM signals unambiguously linked to BBHs. In that respect, this is the first of a series of papers dedicated to accreting pre-merger BBHs and their associated EM observables. Here, we extend our Numerical Observatory of Violent Accreting systems, e-NOVAs, to any space–time. Unlike previous studies, almost exclusively focused on the inner regions, we investigated the impact of the BBH on its outer circumbinary disc, located in the radiation (or wave) zone, after implementing an approximate analytical space–time of spinning, inspiralling BBHs in e-NOVAs. We follow the formation of a weak spiral structure in disc density arising from the retardation effects in the radiation zone metric. Sim...
Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray
The presence of QPOs in the Power Density Spectra of x-ray binaries is quite ubiquitous and is of... more The presence of QPOs in the Power Density Spectra of x-ray binaries is quite ubiquitous and is often modeled as a hot structure orbiting in the disk. While we have been using timing and PDS to determine the presence and explore the possible origin of QPOs, they are, up to now, absent from the spectral analysis. Here we are using a simple analytical model to mimic the hot structure of several QPO models in order to determine their impact on the energy spectrum. Introduction • When looking at the Power Density Spectrum of microquasars the most striking features are the presence of Quasi-Periodic Oscillations. Those Low-Frequency (< 30Hz) and High-Frequency (> 40Hz) QPOs cannot be neglected, indeed, the LFQPO alone can have a rms of up to 30%. Models often describe them as a warm/hot structure orbiting the disk. ! important timing feature that modulates the X-ray flux. • Nevertheless, when looking at the same data through the energy spectrum the disk is considered smooth with a m...
Proceedings of 25th Texas Symposium on Relativistic Astrophysics — PoS(Texas 2010), 2011
We present a detailed calculation of the mechanism by which the Accretion-Ejection Instability ca... more We present a detailed calculation of the mechanism by which the Accretion-Ejection Instability can extract accretion energy and angular momentum from a magnetized disk, and redirect them to its corona. In a disk threaded by a poloidal magnetic field of the order of equipartition with the gas pressure, the instability is composed of a spiral wave (analogous to galactic ones) and a Rossby vortex. The mechanism detailed here describes how the vortex, twisting the footpoints of field lines threading the disk, generates Alfven waves propagating to the corona. We find that this is a very efficient mechanism, providing to the corona (where it could feed a jet or a wind) a substantial fraction of the accretion energy.
With 2D hydrodynamical simulations of disks perturbed externally by stars, brown dwarfs or planet... more With 2D hydrodynamical simulations of disks perturbed externally by stars, brown dwarfs or planets we investigate possible scenarios that can account for the spiral structure in circumstellar disks. We consider two scenarios, spiral structure driven by an external bound planet or low mass star and that excited by a previous stellar close encounter or flyby. We find that both scenarios produce morphology similar to that observed in the outer disks of HD 141569A and HD 100546; moderately open 2-armed outer spiral structure. The outer two-armed spiral structure observed in the disk of HD 141569A is qualitatively reproduced with tidal perturbations from its companion binary HD 141569B,C on a prograde orbit near periapse. Our simulation accounts for the outer spiral arms, but is less successful than the secular model of Augereau and Papaloizou at matching the lopsidedness or asymmetry of the disk edge at 300AU. The disk has been previously truncated by the tidal force from the binary. A ...
We present computational results showing eccentricity growth in the inner portions of a protoplan... more We present computational results showing eccentricity growth in the inner portions of a protoplanetary disc. We attribute this to the evolving surface density of the disc. The planet creates a gap, which adjusts the balance between the 3:1 (eccentricity exciting) and 2:1 (eccentricity damping) resonances. The eccentricity of the inner disc can rise as high as 0.3, which is sufficient to cause it to be accreted onto the star. This offers an alternative mechanism for producing the large holes observed in the discs of CoKu Tau/4, GM Aur and DM Tau.
We study the effects of an annular gap induced by an embedded proto-planet on disk scattered ligh... more We study the effects of an annular gap induced by an embedded proto-planet on disk scattered light images and the infrared spectral energy distribution. We find that the outer edge of a gap is brighter in the scattered light images than a similar location in a gap-free disk. The stellar radiation that would have been scattered by material within in the gap is instead scattered by the disk wall at the outer edge of the gap, producing a bright ring surrounding the dark gap in the images. Given sufficient resolution, such gaps can be detected by the presence of this bright ring in scattered light images. A gap in a disk also changes the shape of the SED. Radiation that would have been absorbed by material in the gap is instead reprocessed by the outer gap wall. This leads to a decrease in the SED at wavelengths corresponding to the temperature at the radius of the missing gap material and a corresponding flux increase at longer wavelengths corresponding to the temperature of the outer ...
AIP Conference Proceedings, 2005
ABSTRACT