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Articles 61 - 90 of 179
Full-Text Articles in Astrophysics and Astronomy
Elastic Properties Of The Zintl Ferromagnet Yb14mnsb11, Sriparna Bhattacharya, D C. Marinescu, James R. Morris, Ivan A. Sergienko, Brian Sales, David Madrus, Veerle Keppens
Elastic Properties Of The Zintl Ferromagnet Yb14mnsb11, Sriparna Bhattacharya, D C. Marinescu, James R. Morris, Ivan A. Sergienko, Brian Sales, David Madrus, Veerle Keppens
Publications
We report measurements of the elastic moduli as a function of temperature (5–300) K and magnetic field (0–2 T) for the Zintl ferromagnet Yb14MnSb11, which is believed to be a rare example of an underscreened Kondo lattice. The elastic moduli measured below the Curie temperature in this complex ferromagnet exhibit unusual lattice stiffening that is independent of the magnetic field and can be adequately modeled using the Landau theory.
Herschel/Pacs Observations Of Young Sources In Taurus: The Far-Infrared Counterpart Of Optical Jets, L Podio, I Kamp, D Flower, C Howard, G Sandell, A Mora, G Aresu, Sean D. Brittain, W.R.F. Dent, C Pinte, G J. White
Herschel/Pacs Observations Of Young Sources In Taurus: The Far-Infrared Counterpart Of Optical Jets, L Podio, I Kamp, D Flower, C Howard, G Sandell, A Mora, G Aresu, Sean D. Brittain, W.R.F. Dent, C Pinte, G J. White
Publications
Context. Observations of the atomic and molecular line emission associated with jets and outflows emitted by young stellar objects provide sensitive diagnostics of the excitation conditions, and can be used to trace the various evolutionary stages they pass through as they evolve to become main sequence stars. Aims. To understand the relevance of atomic and molecular cooling in shocks, and how accretion and ejection efficiency evolves with the evolutionary state of the sources, we will study the far-infrared counterparts of bright optical jets associated with Class I and II sources in Taurus (T Tau, DG Tau A, DG Tau B, …
Topological Thermoelectric Effects In Spin-Orbit Coupled Electron- And Hole-Doped Semiconductors, E Dumitrescu, Chuanwei Zhang, D C. Marinescu, Sumanta Tewari
Topological Thermoelectric Effects In Spin-Orbit Coupled Electron- And Hole-Doped Semiconductors, E Dumitrescu, Chuanwei Zhang, D C. Marinescu, Sumanta Tewari
Publications
We compute the intrinsic contributions to the Berry-phase mediated anomalous Hall and Nernst effects in electron- and hole-doped semiconductors in the presence of an in-plane magnetic field as well as Rashba and Dresselhaus spin-orbit couplings. For both systems we find that the regime of chemical potential which supports the topological superconducting state in the presence of the superconducting proximity effect can be characterized by plateaus in the topological Hall and Nernst coefficients flanked by well-defined peaks marking the emergence of the topological regime. The plateaus arise from a clear momentum space separation between the region where the Berry curvature is …
Observations Of Herbig Ae/Be Stars With Herschel/Pacs. The Atomic And Molecular Contents Of Their Protoplanetary Discs, G Meeus, B Montesinos, I Mendigutia, I Kamp, W F. Thi, C Eiroa, C A. Grady, G Mathews, G Sandell, C. Martin-Zaidi, Sean D. Brittain, W.R.F. Dent, C Howard, F Menard, C Pinte, A Roberge, B Vandenbussche, J P. Williams
Observations Of Herbig Ae/Be Stars With Herschel/Pacs. The Atomic And Molecular Contents Of Their Protoplanetary Discs, G Meeus, B Montesinos, I Mendigutia, I Kamp, W F. Thi, C Eiroa, C A. Grady, G Mathews, G Sandell, C. Martin-Zaidi, Sean D. Brittain, W.R.F. Dent, C Howard, F Menard, C Pinte, A Roberge, B Vandenbussche, J P. Williams
Publications
We observed a sample of 20 representative Herbig Ae/Be stars and 5 A-type debris discs with PACS onboard Herschel, as part of the GAS in Protoplanetary Systems (GASPS) project. The observations were done in spectroscopic mode, and cover the far-infrared lines of [O i], [C ii], CO, CH+, H2O, and OH. We have a [Oi] 63 μm detection rate of 100% for the Herbig Ae/Be and 0% for the debris discs. The [Oi] 145 μm line is only detected in 25% and CO J = 18–17 in 45% (and fewer cases for higher J transitions) of the Herbig Ae/Be stars, …
Energetic Feedback And 26al From Massive Stars And Their Supernovae In The Carina Region, R. Voss, P. Martin, R. Diehl, J. S. Vink, Dieter H. Hartmann, T. Preibisch
Energetic Feedback And 26al From Massive Stars And Their Supernovae In The Carina Region, R. Voss, P. Martin, R. Diehl, J. S. Vink, Dieter H. Hartmann, T. Preibisch
Publications
We study the populations of massive stars in the Carina region and their energetic feedback and ejection of 26Al. Methods. We did a census of the stellar populations in young stellar clusters within a few degrees of the Carina nebula. For each star we estimated the mass, based on the spectral type and the host cluster age. We used population synthesis to calculate the energetic feedback and ejection of 26Al from the winds of the massive stars and their supernova explosions. We used 7 years of INTEGRAL observations to measure the 26Al signal from the region. Results. The INTEGRAL 26Al …
Weak Localization In A Lateral Superlattice With Rashba And Dresselhaus Spin-Orbit Interaction, D C. Marinescu, Andrei Manolescu
Weak Localization In A Lateral Superlattice With Rashba And Dresselhaus Spin-Orbit Interaction, D C. Marinescu, Andrei Manolescu
Publications
We calculate the weak localization (WL) correction to the conductivity of a lateral superlattice (LSL) with Rashba (R)-Dresselhaus (D) spin-orbit interaction (SOI). The superlattice is modeled as a sequence of parallel wires that support tunneling between adjacent sites, leading to the formation of extended Bloch states along its axis and a miniband in the energy spectrum. Our results, obtained by calculating the eigenvalues of the Cooperon operator in the diffusion approximation, indicate that the electron dephasing rate that determines the antilocalization correction is enhanced by a term proportional with the LSL potential and the bandwidth. Within the same formalism, the …
Bl Lacertae Objects Beyond Redshift 1.3 - Uv-To-Nir Photometry And Photometric Redshift For Fermi/Lat Blazars, A. Rau, P. Schady, J. Greiner, M. Salvato, M. Ajello, E. Bottacini, N. Gehrels, P.M. J. Afonso, J. Elliott, R Filgas, D A. Kann, S Klose, T Krühler, M Nardini, A Nicuesa Guelbenzu, F Olivares E., A Rossi, V Sudilovsky, A C. Updike, Dieter H. Hartmann
Bl Lacertae Objects Beyond Redshift 1.3 - Uv-To-Nir Photometry And Photometric Redshift For Fermi/Lat Blazars, A. Rau, P. Schady, J. Greiner, M. Salvato, M. Ajello, E. Bottacini, N. Gehrels, P.M. J. Afonso, J. Elliott, R Filgas, D A. Kann, S Klose, T Krühler, M Nardini, A Nicuesa Guelbenzu, F Olivares E., A Rossi, V Sudilovsky, A C. Updike, Dieter H. Hartmann
Publications
Context.Observations of the γ -ray sky with Fermi led to significant advances towards understanding blazars, the most extreme classof Active Galactic Nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whosesample has always suff ered from a severe redshift incompleteness due to the quasi-featureless optical spectra.Aims.Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LACFermi/LAT cataloge.Methods.For 103 Fermi/LAT blazars, photometric redshifts using spectral energy distribution fitting have been obtained. The pho-tometry includes 13 broad-band filters from the far ultraviolet …
Cxom31 J004253.1+411422: The First Ultraluminous X-Ray Transient In M 31, A. Kaur, M. Henze, F. Haberl, W. Pietsch, J. Greiner, A. Rau, Dieter H. Hartmann, G. Sala, M. Hernanz
Cxom31 J004253.1+411422: The First Ultraluminous X-Ray Transient In M 31, A. Kaur, M. Henze, F. Haberl, W. Pietsch, J. Greiner, A. Rau, Dieter H. Hartmann, G. Sala, M. Hernanz
Publications
Context. We seek clarification of the nature of X-ray sources detected in M 31. Here we focus on CXOM31 J004253.1+411422, the brightness of which suggests that it belongs to the class of ultraluminous X-ray sources. Aims. We determine the X-ray properties of sources detected in the XMM-Newton/Chandra monitoring program. We investigate spectral properties and search for periodic or quasi-periodic oscillations. Methods. A multicomponent model was applied to the spectra obtained from XMM-Newton data to evaluate the relative contributions from thermal and nonthermal emission. The time dependence of this ratio was evaluated over a period of forty days. We simultaneously fit …
Loft: The Observatory For X-Ray Timing, M. Feroci, J. W. Den Herder, E. Bozzo, D. Barret, S. Brandt, M. Hernanz, M. Van Der Klis, M. Pohl, A. Santangelo, L Stella, A Watts, J Wilms, S Zane
Loft: The Observatory For X-Ray Timing, M. Feroci, J. W. Den Herder, E. Bozzo, D. Barret, S. Brandt, M. Hernanz, M. Van Der Klis, M. Pohl, A. Santangelo, L Stella, A Watts, J Wilms, S Zane
Publications
The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor …
Measuring The Stellar Accretion Rates Of Herbig Ae/Be Stars, Brian Donehew, Sean D. Brittain
Measuring The Stellar Accretion Rates Of Herbig Ae/Be Stars, Brian Donehew, Sean D. Brittain
Publications
The accretion rate of young stars is a fundamental characteristic of these systems.While accretion onto T Tauri stars has been studied extensively, little work has been done on measuring the accretion rate of their intermediate-mass analogs, the Herbig Ae/Be stars. Measuring the stellar accretion rate of Herbig Ae/Bes is not straightforward both because of the dearth of metal absorption lines available for veiling measurements and the intrinsic brightness of Herbig Ae/Be stars at ultraviolet wavelengths where the brightness of the accretion shock peaks. Alternative approaches to measuring the accretion rate of young stars by measuring the luminosity of proxies such …
Lithium In The Upper Centaurus Lupus And Lower Centaurus Crux Subgroups Of Scorpius-Centaurus, Eric J. Bubar, Marc Schaeuble, Jeremy R. King, Eric E. Mamajek, John R. Stauffer
Lithium In The Upper Centaurus Lupus And Lower Centaurus Crux Subgroups Of Scorpius-Centaurus, Eric J. Bubar, Marc Schaeuble, Jeremy R. King, Eric E. Mamajek, John R. Stauffer
Publications
We utilize spectroscopically derived model atmosphere parameters and the Li i λ6104 subordinate line and the λ6708 doublet to derive lithium abundances for 12 members of the Upper Centaurus Lupus and Lower Centaurus Crux subgroups of the Scorpius–Centaurus OB Association. The results indicate any intrinsic Li scatter in our 0.9–1.4 M stars is limited to ∼0.15 dex, consistent with the lack of dispersion in 1.0 M stars in the 100 Myr Pleiades and 30–50 Myr IC 2391 and 2602 clusters. Both ab initio uncertainty estimates and the derived abundances themselves indicate that the λ6104 line yields abundances with equivalent or …
Electronic Charge And Spin Density Distribution In A Quantum Ring With Spin-Orbit And Coulomb Interactions, Csaba Daday, Andrei Manolescu, D C. Marinescu, Vidar Gudmundsson
Electronic Charge And Spin Density Distribution In A Quantum Ring With Spin-Orbit And Coulomb Interactions, Csaba Daday, Andrei Manolescu, D C. Marinescu, Vidar Gudmundsson
Publications
Charge and spin density distributions are studied within a nanoring structure endowed with Rashba and Dresselhaus spin-orbit interactions (SOIs). For a small number of electrons, in the presence of an external magnetic field and of the Coulomb interaction, the energy spectrum of the system is calculated through an exact numerical diagonalization procedure. The eigenstates thus determined are used to estimate the charge and spin densities around the ring. We find that when more than two electrons are considered, the charge density deformations induced by SOIs are dramatically flattened by the Coulomb repulsion, while the spin density deformations are amplified.
Detailed Abundances Of The Solar Twins 16 Cygni And B Cygni: Constraining Planet Formation Models, Simon C. Schuler, Katia Cunha, Verne V. Smith, Luan Ghezzi, Jeremy R. King, Constantine P. Deliyannis, Ann Merchant Boesgaard
Detailed Abundances Of The Solar Twins 16 Cygni And B Cygni: Constraining Planet Formation Models, Simon C. Schuler, Katia Cunha, Verne V. Smith, Luan Ghezzi, Jeremy R. King, Constantine P. Deliyannis, Ann Merchant Boesgaard
Publications
Results of a detailed abundance analysis of the solar twins 16 Cyg A and 16 Cyg B based on high-resolution, high signal-to-noise ratio echelle spectroscopy are presented. 16 Cyg B is known to host a giant planet while no planets have yet been detected around 16 Cyg A. Stellar parameters are derived directly from our high-quality spectra, and the stars are found to be physically similar, with ΔTeff = +43 K, Δ log g =−0.02 dex, and Δξ = +0.10 km s−1 (in the sense of A − B), consistent with previous findings. Abundances of 15 elements are derived and …
X-Ray Monitoring Of Classical Novae In The Central Region Of M 31 Iii. Autumn And Winter 2007/2008 And 2008/2009, M. Henze, W. Pietsch, F. Haberl, M. Hernanz, G. Sala, D. Hartzidimitriou, M. Della Velle, A. Rau, Dieter H. Hartmann, V. Burwitz
X-Ray Monitoring Of Classical Novae In The Central Region Of M 31 Iii. Autumn And Winter 2007/2008 And 2008/2009, M. Henze, W. Pietsch, F. Haberl, M. Hernanz, G. Sala, D. Hartzidimitriou, M. Della Velle, A. Rau, Dieter H. Hartmann, V. Burwitz
Publications
Context. Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of the galaxy M 31. Aims. We performed a dedicated monitoring of the M 31 central region with XMM-Newton and Chandra between Nov. 2007 and Feb. 2008 and between Nov. 2008 and Feb. 2009, respectively, to find SSS counterparts of CNe, determine the duration of their SSS phase, and derive physical outburst parameters. Methods. We systematically searched our data for X-ray counterparts of CNe, determined their X-ray light curves and characterised their spectra using blackbody fits and white dwarf (WD) atmosphere models. Additionally, …
Helical Antiferromagnetic Ordering In The Lowest Landau Level Of A Semiconductor Superlattice, Liqiu Zheng, D C. Marinescu
Helical Antiferromagnetic Ordering In The Lowest Landau Level Of A Semiconductor Superlattice, Liqiu Zheng, D C. Marinescu
Publications
When subjected to a tilted magnetic field, the ground state of a semiconductor superlattice (SL) with two identical quantum wells per unit cell is shown to exhibit different magnetic configurations that are dependent on the strength and direction of the field and the SL characteristics. Intra- and interunit cell tunneling between the wells, assumed to be infinitely attractive, generate an energy miniband structure of the lowest Landau level that, in cooperation with the Zeeman splitting, creates, at certain points in the momentum space, an energy difference between opposite-spin single-particle states that can be overcome by the Coulomb interaction. Within the …
Nova M31n 2007-12b: Supersoft X-Rays Reveal An Intermediate Polar?, W. Pietsch, M. Henze, F. Haberl, M. Hernanz, G. Sala, Dieter H. Hartmann, M. Della Valle
Nova M31n 2007-12b: Supersoft X-Rays Reveal An Intermediate Polar?, W. Pietsch, M. Henze, F. Haberl, M. Hernanz, G. Sala, Dieter H. Hartmann, M. Della Valle
Publications
Context. In the central part of M 31, a high number of optical novae can be targeted within the field of view of the XMM-Newton EPIC and Chandra HRC-I X-ray detectors. A special monitoring program of the area has allowed us to investigate supersoft emission of individual novae in detail and perform a statistical analysis of the sample. Aims. For the He/N nova M31N 2007-12b, we aimed to constrain the time of appearance of a supersoft source (SSS) and the duration of the SSS state as well as determine the spectral and time variability while the source was bright. Methods. …
Thermal Conductance Of A Two-Channel Kondo Model, C P. Moca, A Roman, D C. Marinescu
Thermal Conductance Of A Two-Channel Kondo Model, C P. Moca, A Roman, D C. Marinescu
Publications
A theory of thermal transport in a two-channel Kondo system, such as the one formed by a small quantum dot coupled to two leads and to a larger dot, is formulated. The interplay of the two screening constants allow an exploration of the Fermi liquid and non-Fermi liquid regimes. By using analytical, as well as numerical, renormalization group methods, we study the temperature dependence of the thermal conductance and the Lorentz number. We find that in the low-temperature limit, the Lorentz number attains its universal value, irrespective of the nature of the ground state.
Ro-Vibrational Co Detected In The Β Pictoris Circumstellar Disk, Matthew R. Troutman, Kenneth H. Hinkle, Joan R. Najita, Terrence W. Rettig, Sean D. Brittain
Ro-Vibrational Co Detected In The Β Pictoris Circumstellar Disk, Matthew R. Troutman, Kenneth H. Hinkle, Joan R. Najita, Terrence W. Rettig, Sean D. Brittain
Publications
We present high-resolution near-infrared spectra of β Pictoris—a nearby young star with a debris disk. Fundamental low-J CO absorption lines are detected and strict upper limits are placed on the flux of v = 2–1 low-J CO emission lines. The limit on the UV fluorescent emission flux in the v = 2–1 lines is used to place a tight constraint on the inner extent of the CO gas. Assuming Hi is the primary collision partner, the sub-thermal population of the low-J v = 0 rotational levels constrains the density of the gas in the disk to nH = (2.5+7.1 −1.2)×105 …
Grips - Gamma-Ray Imaging, Polarimetry And Spectroscopy, Jochen Greiner, Karl Mannheim, Felix Aharonian, Marco Ajello, Lajos G. Balaz, Guido Barbiellini, Ronaldo Bellazzini, Shawn Bishop, Gennady S. Bisnoyatij-Kogan, Steven Boggs, Andrej Bykov, Guido Dicocco, Roland Diehl, Dominik Elsasser, Suzanne Foley, Claes Fransson, Neil Gehrels, Lorraine Hanlon, Dieter H. Hartmann
Grips - Gamma-Ray Imaging, Polarimetry And Spectroscopy, Jochen Greiner, Karl Mannheim, Felix Aharonian, Marco Ajello, Lajos G. Balaz, Guido Barbiellini, Ronaldo Bellazzini, Shawn Bishop, Gennady S. Bisnoyatij-Kogan, Steven Boggs, Andrej Bykov, Guido Dicocco, Roland Diehl, Dominik Elsasser, Suzanne Foley, Claes Fransson, Neil Gehrels, Lorraine Hanlon, Dieter H. Hartmann
Publications
We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range (COMPTEL, INTEGRAL; see Fig. 1). The Gamma-Ray Imaging, Polarimetry and Spectroscopy (“GRIPS”) mission addresses fundamental questions in ESA’s Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, vio-lent Universe, exploring a unique energy window. We propose to investigate γ-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of …
Simulation Of Relativistic Jets And Associated Self-Consistent Radiation, K.-I. Nishikawa, E. J. Choi, K. Min, P. Hardee, Y. Mizuno, C. Zhang, J. Niemiec, M. Medvedev, A. Norlund, J Frederiksen, M Pohl, H Sol, Dieter H. Hartmann, G J. Fishman
Simulation Of Relativistic Jets And Associated Self-Consistent Radiation, K.-I. Nishikawa, E. J. Choi, K. Min, P. Hardee, Y. Mizuno, C. Zhang, J. Niemiec, M. Medvedev, A. Norlund, J Frederiksen, M Pohl, H Sol, Dieter H. Hartmann, G J. Fishman
Publications
Plasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a par-tially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection behind the shock. Our initial …
Abundances Of Stars With Planets: Trends With Condensation Temperature, Simon C. Schuler, Davin Flateau, Katia Cunha, Jeremy R. King, Luan Ghezzi, Verne V. Smith
Abundances Of Stars With Planets: Trends With Condensation Temperature, Simon C. Schuler, Davin Flateau, Katia Cunha, Jeremy R. King, Luan Ghezzi, Verne V. Smith
Publications
Precise abundances of 18 elements have been derived for 10 stars known to host giant planets from high signal-to-noise ratio, high-resolution echelle spectroscopy. Internal uncertainties in the derived abundances are typically 0.05 dex. The stars in our sample have all been previously shown to have abundances that correlate with the condensation temperature (Tc) of the elements in the sense of increasing abundances with increasing Tc; these trends have been interpreted as evidence that the stars may have accreted H-depleted planetary material. Our newly derived abundances also correlate positively with Tc, although slopes of linear least-square fits to the [m/H]–Tc relations …
Measurements Of Mass Accretion Rates In Herbig Ae/Be Stars, Brian Donehew
Measurements Of Mass Accretion Rates In Herbig Ae/Be Stars, Brian Donehew
All Dissertations
Herbig Ae/Be stars(HAeBes) are young stellar objects of spectral class F2 through B0, with the central star often surrounded by a circumstellar disk of gas and dust. They are the higher mass analogs to T Tauri stars. The interaction between the star and the disk is not well understood, nor is the disk structure. The central star will often accrete mass from the disk, and the mass accretion rate is an important parameter for modeling the disk structure and evolution. The methods for measuring mass accretion rates of T Tauri stars are generally not applicable to HAeBe stars. As such, …
Nonadiabatic Generation Of A Pure Spin Current In A One-Dimensional Quantum Ring With Spin-Orbit Interaction, Marian Nita, D C. Marinescu, Andrei Manolescu, Vidar Gudmundsson
Nonadiabatic Generation Of A Pure Spin Current In A One-Dimensional Quantum Ring With Spin-Orbit Interaction, Marian Nita, D C. Marinescu, Andrei Manolescu, Vidar Gudmundsson
Publications
We demonstrate the theoretical possibility of obtaining a pure spin current in a 1D ring with spin-orbit interaction by irradiation with a nonadiabatic, two-component terahertz laser pulse, whose spatial asymmetry is reflected by an internal phase difference φ. The solutions of the equation of motion for the density operator are obtained for a spin-orbit coupling linear in the electron momentum (Rashba) and they are used to calculate the time-dependent charge and spin currents. We find that there are critical values of φ at which the charge current disappears, while the spin current reaches a maximum or a minimum value.
Detection Of Ch+ Emission From The Disc Around Hd 100546, W F. Thi, F Menard, G Meeus, C. Martin-Zaidi, P Woitke, E Tatulli, M Benisty, I Kamp, I Pascucci, C Pinte, C A. Grady, Sean D. Brittain, G J. White, C D. Howard, G Sandell, C Eiroa
Detection Of Ch+ Emission From The Disc Around Hd 100546, W F. Thi, F Menard, G Meeus, C. Martin-Zaidi, P Woitke, E Tatulli, M Benisty, I Kamp, I Pascucci, C Pinte, C A. Grady, Sean D. Brittain, G J. White, C D. Howard, G Sandell, C Eiroa
Publications
Despite its importance in the thermal balance of the gas and in the determination of primeval planetary atmospheres, the chemistry in protoplanetary discs remains poorly constrained with only a handful of detected species. We observed the emission from the disc around the Herbig Be star HD 100546 with the PACS instrument in the spectroscopic mode on board the Herschel Space Telescope as part of the GAS in Protoplanetary Systems (GASPS) programme and used archival data from the DIGIT programme to search for the rotational emission of CH+. We detected in both datasets an emission line centred at 72.16 μm that …
Water Depletion In The Disk Atmosphere Of Herbig Aebe Stars, D Fedele, I Pascucci, Sean D. Brittain, I Kamp, P Woitke, J P. Williams, W.R.F. Dent, W F. Thi
Water Depletion In The Disk Atmosphere Of Herbig Aebe Stars, D Fedele, I Pascucci, Sean D. Brittain, I Kamp, P Woitke, J P. Williams, W.R.F. Dent, W F. Thi
Publications
We present high-resolution (R ∼ 100,000) L-band spectroscopy of 11 Herbig AeBe stars with circumstellar disks. The observations were obtained with the VLT/CRIRES to detect hot water and hydroxyl radical emission linespreviously detected in disks around T Tauri stars. OH emission lines are detected toward four disks. The OH 2Π3/2 P4.5 (1+,1−) doublet is spectrally resolved as well as the velocity profile of each component of the doublet. Its characteristic double-peak profile demonstrates that the gas is in Keplerian rotation and points to an emitting region extending out to ∼15–30 AU. The OH emission correlates with disk geometry as it …
The Unusual Protoplanetary Disk Around The T Tauri Star Et Chamaeleontis, P Woitke, B Riaz, G Duchene, I Pascucci, A Ran Lyo, W.R.F. Dent, N Phillips, W F. Thi, F Menard, G J. Herczeg, E Bergin, A Brown, A Mora, I Kamp, G Aresu, Sean D. Brittain, I De Gregorio-Monsalvo, G Sandell
The Unusual Protoplanetary Disk Around The T Tauri Star Et Chamaeleontis, P Woitke, B Riaz, G Duchene, I Pascucci, A Ran Lyo, W.R.F. Dent, N Phillips, W F. Thi, F Menard, G J. Herczeg, E Bergin, A Brown, A Mora, I Kamp, G Aresu, Sean D. Brittain, I De Gregorio-Monsalvo, G Sandell
Publications
We present new continuum and line observations, along with modelling, of the faint (6−8) Myr old T Tauri star ETCha belonging to the η Chamaeleontis cluster. We have acquired Herschel/PACS photometric fluxes at 70 μm and 160 μm, as well as a detection of the [OI] 63 μm fine-structure line in emission, and derived upper limits for some other far-IR OI, CII, CO and o-H2O lines. These observations were carried out in the frame of the open time key programme GASPS, where ETCha was selected as one of the science demonstration phase targets. The Herschel data is complemented by new …
The Nature Of "Dark" Gamma-Ray Bursts, J. Greiner, T. Krühler, S. Klose, P. Afonso, C. Clemens, R. Filgas, Dieter H. Hartmann, A. Küpcü Yoldas, M. Nardini, F. Olivares E., A Rau, A Rossi, P Schady, A Updike
The Nature Of "Dark" Gamma-Ray Bursts, J. Greiner, T. Krühler, S. Klose, P. Afonso, C. Clemens, R. Filgas, Dieter H. Hartmann, A. Küpcü Yoldas, M. Nardini, F. Olivares E., A Rau, A Rossi, P Schady, A Updike
Publications
Context. Thirteen years after the discovery of the first afterglows, the nature of dark gamma-ray bursts (GRB) still eludes explanation: while each long-duration GRB typically has an X-ray afterglow, optical/NIR emission is only seen for 40-60% of them. Aims. Here we use the afterglow detection statistics of the systematic follow-up observations performed with GROND since mid-2007 in order to derive the fraction of “dark bursts” according to different methods, and to distinguish between various scenarios for “dark bursts”. Methods. Observations were performed with the 7-channel “Gamma-Ray Optical and Near-infrared Detector” (GROND) at the 2.2m MPI/ESO telescope. We used the afterglow …
Origin: Metal Creation And Evolution From The Cosmic Dawn, J. W. Den Herder, L. Piro, T. Ohashi, C. Kouveliotou, Dieter H. Hartmann, J. Kaastra, L. Amati, M. I. Andersen, M. Arnaud, J.-L. Attéia
Origin: Metal Creation And Evolution From The Cosmic Dawn, J. W. Den Herder, L. Piro, T. Ohashi, C. Kouveliotou, Dieter H. Hartmann, J. Kaastra, L. Amati, M. I. Andersen, M. Arnaud, J.-L. Attéia
Publications
ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to …
The Swift/Fermi Grb 080928 From 1 Ev To 150 Kev, A. Rossi, S. Schulze, S. Klose, D. A. Kann, A. Rau, H. A. Krimm, G. Jóhannesson, A. Panaitescu, F. Yuan, P Ferrero, T Krühler, J Greiner, P Schady, S B. Pandey, L Amati, P.M.F. Afonso, C W. Akerlof, L A. Arnold, C Clemens, R Filgas, Dieter H. Hartmann
The Swift/Fermi Grb 080928 From 1 Ev To 150 Kev, A. Rossi, S. Schulze, S. Klose, D. A. Kann, A. Rau, H. A. Krimm, G. Jóhannesson, A. Panaitescu, F. Yuan, P Ferrero, T Krühler, J Greiner, P Schady, S B. Pandey, L Amati, P.M.F. Afonso, C W. Akerlof, L A. Arnold, C Clemens, R Filgas, Dieter H. Hartmann
Publications
We present the results of a comprehensive study of the gamma-ray burst 080928 and of its afterglow. GRB 080928 was a long burst detected by Swift/BAT and Fermi/GBM. It is one of the exceptional cases where optical emission had already been detected when the GRB itself was still radiating in the gamma-ray band. For nearly 100 s simultaneous optical, X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. In particular, we show that the SED during the main prompt emission phase agrees with synchrotron radiation. We …
Libstatmech And Applications To Astrophysics, Tianhong Yu
Libstatmech And Applications To Astrophysics, Tianhong Yu
All Theses
In this work an introduction to Libstatmech is presented and applications especially to astrophysics are discussed. Libstatmech is a C toolkit for computing the statistical mechanics of fermions and bosons, written on top of libxml and gsl (GNU Scientific Library). Calculations of Thomas-Fermi Screening model and Bose-Einstein Condensate based on libstatmech demonstrate the expected results. For astrophysics application, a simple Type Ia Supernovae model is established to run the network calculation with weak reactions, in which libstatmech contributes to compute the electron chemical potential and allows the weak reverse rates to be calculated from detailed balance. Starting with pure 12C …