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Full-Text Articles in Physical Sciences and Mathematics

Magnetospherically-Trapped Dust And A Possible Model For The Unusual Transits At Wd1145+017, J. Farihi, Ted Von Hippel, J. E. Pringle Aug 2019

Magnetospherically-Trapped Dust And A Possible Model For The Unusual Transits At Wd1145+017, J. Farihi, Ted Von Hippel, J. E. Pringle

Ted von Hippel

The rapidly evolving dust and gas extinction observed towardsWD1145+017 has opened a real-time window onto the mechanisms for destruction-accretion of planetary bodies onto white dwarf stars, and has served to underline the importance of considering the dynamics of dust particles around such objects. Here it is argued that the interaction between (charged) dust grains and the stellar magnetic field is an important ingredient in understanding the physical distribution of infrared emitting particles in the vicinity of such white dwarfs. These ideas are used to suggest a possible model for WD 1145+017 in which the unusual transit shapes are ...


Dust Production And Depletion In Evolved Planetary Systems, J. Farihi, Ted Von Hippel, Rik Van Lieshout, P.W. Cauley, Erik Dennihy, Et Al. Aug 2019

Dust Production And Depletion In Evolved Planetary Systems, J. Farihi, Ted Von Hippel, Rik Van Lieshout, P.W. Cauley, Erik Dennihy, Et Al.

Ted von Hippel

The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20 per cent peak-to-peak over 11.2 yr, and is consistent with ongoing dust production and depletion. It is hypothesized that the dust is produced via collisions associated with an evolving dust disc, temporarily increasing the emitting surface of warm debris, and is subsequently destroyed or assimilated within a few years. The variations are consistent with debris that does not change temperature, indicating that dust is produced and depleted within a fixed range of orbital radii. Gas produced in collisions may rapidly re-condense ...


A Tight Relation Between Spiral Arm Pitch Angle And Protplanetary Disk Mass, Si-Yue Yu, Luis C. Ho, Zhaohuan Zhu May 2019

A Tight Relation Between Spiral Arm Pitch Angle And Protplanetary Disk Mass, Si-Yue Yu, Luis C. Ho, Zhaohuan Zhu

Physics & Astronomy Faculty Publications

We use two-dimensional Fourier transformation to measure the pitch angle () of the dominant spiral Fourier mode of well-defined spiral arms in 13 protoplanetary disks, making use of near-infrared scattered-light images of AB Aur, SAO 206462, MWC 758, V1247 Ori, HD 142527, DZ Cha, LkHα 330, and HD 100453, and ALMA millimeter continuum images of Elias 2-27, IM Lup, AS 205, and HT Lup. We find that the measured pitch angle correlates strongly with disk mass (M D ), such that more massive protoplanetary disks have smaller pitch angles, following . Interestingly, four disks with a known companion (HD 142527, HD 100453, AS ...


Kinematic Links And The Coevolution Of Mhd Winds, Jets, And Inner Disks From A High-Resolution Optical [ [Oi] Survey, Andrea Banzatti, Ilaria Pascucci, Suzan Edwards, Min Fang, Uma Gorti, Mario Flock Jan 2019

Kinematic Links And The Coevolution Of Mhd Winds, Jets, And Inner Disks From A High-Resolution Optical [ [Oi] Survey, Andrea Banzatti, Ilaria Pascucci, Suzan Edwards, Min Fang, Uma Gorti, Mario Flock

Astronomy: Faculty Publications

We present a survey of optical [O I] emission at 6300 Å toward 65 T Tauri stars at the spectral resolution of ∼7 km s−1 . Past work identified a highly blueshifted velocity component (HVC) tracing microjets and a less blueshifted low-velocity component (LVC) attributed to winds. We focus here on the LVC kinematics to investigate links between winds, jets, accretion, and disk dispersal. We track the behavior of four types of LVC components: a broad and a narrow component (“BC” and “NC,” respectively) in LVCs that are decomposed into two Gaussians which typically have an HVC, and single-Gaussian LVC ...


The Disk Substructures At High Angular Resolution Project (Dsharp). I. Motivation, Sample, Calibration, And Overview, Sean M. Andrews, Jane Huang, Laura M. Pérez, Andrea Isella, Cornelis P. Dullemond, Nicolás T. Kurtovic, Viviana V. Guzmán, John M. Carpenter, David J. Wilner, Shangjia Zhang, Zhaohuan Zhu, Tilman Birstiel, Xue-Ning Bai, Myriam Benisty, A. Meredith Hughes, Karin I. Öberg, Luca Ricci Dec 2018

The Disk Substructures At High Angular Resolution Project (Dsharp). I. Motivation, Sample, Calibration, And Overview, Sean M. Andrews, Jane Huang, Laura M. Pérez, Andrea Isella, Cornelis P. Dullemond, Nicolás T. Kurtovic, Viviana V. Guzmán, John M. Carpenter, David J. Wilner, Shangjia Zhang, Zhaohuan Zhu, Tilman Birstiel, Xue-Ning Bai, Myriam Benisty, A. Meredith Hughes, Karin I. Öberg, Luca Ricci

Physics & Astronomy Faculty Publications

We introduce the Disk Substructures at High Angular Resolution Project (DSHARP), one of the initial Large Programs conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The primary goal of DSHARP is to find and characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetary disks, using very high resolution (~0 035, or 5 au, FWHM) observations of their 240 GHz (1.25 mm) continuum emission. These data provide a first homogeneous look at the small-scale features in disks that are directly relevant to the planet formation process, quantifying their prevalence, morphologies, spatial scales ...


The Disk Substructures At High Angular Resolution Project (Dsharp). V. Interpreting Alma Maps Of Protoplanetary Disks In Terms Of A Dust Model, Tilman Birnstiel, Cornelis P. Dullemond, Zhaohuan Zhu, Sean M. Andrews, Xue-Ning Bai, David J. Wilner, John M. Carpenter, Jane Huang, Andrea Isella, Myriam Benisty, Laura M. Pérez, Shangjia Zhang Dec 2018

The Disk Substructures At High Angular Resolution Project (Dsharp). V. Interpreting Alma Maps Of Protoplanetary Disks In Terms Of A Dust Model, Tilman Birnstiel, Cornelis P. Dullemond, Zhaohuan Zhu, Sean M. Andrews, Xue-Ning Bai, David J. Wilner, John M. Carpenter, Jane Huang, Andrea Isella, Myriam Benisty, Laura M. Pérez, Shangjia Zhang

Physics & Astronomy Faculty Publications

The Disk Substructures at High Angular Resolution Project (DSHARP) is the largest homogeneous high-resolution (~0 035, or ~5 au) disk continuum imaging survey with the Atacama Large Millimeter/submillimeter Array (ALMA) so far. In the coming years, many more disks will be mapped with ALMA at similar resolution. Interpreting the results in terms of the properties and quantities of the emitting dusty material is, however, a very non-trivial task. This is in part due to the uncertainty in the dust opacities, an uncertainty that is not likely to be resolved any time soon. It is also partly due to the ...


Gaps And Rings In An Alma Survey Of Disks In The Taurus Star-Forming Region, Feng Long, Paola Pinilla, Gregory J. Herczeg, Daniel Harsono, Giovanni Dipierro, Ilaria Pascucci, Nathan Hendler, Marco Tazzari, Enrico Ragusa, Colette Salyk, Suzan Edwards, Giuseppe Lodato, Gerrit Van De Plas, Doug Johnstone, Yao Liu, Yann Boehler, Sylvie Cabrit, Carlo F. Manara, Francois Menard, Gijs D. Mulders, Brunella Nisini, William J. Fischer, Elisabetta Rigliaco, Andrea Banzatti, Henning Avenhaus, Michael Gully-Santiago Dec 2018

Gaps And Rings In An Alma Survey Of Disks In The Taurus Star-Forming Region, Feng Long, Paola Pinilla, Gregory J. Herczeg, Daniel Harsono, Giovanni Dipierro, Ilaria Pascucci, Nathan Hendler, Marco Tazzari, Enrico Ragusa, Colette Salyk, Suzan Edwards, Giuseppe Lodato, Gerrit Van De Plas, Doug Johnstone, Yao Liu, Yann Boehler, Sylvie Cabrit, Carlo F. Manara, Francois Menard, Gijs D. Mulders, Brunella Nisini, William J. Fischer, Elisabetta Rigliaco, Andrea Banzatti, Henning Avenhaus, Michael Gully-Santiago

Astronomy: Faculty Publications

Rings are the most frequently revealed substructure in ALMA dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. This subsample of disks is selected from a high-resolution (∼ 0.1200) ALMA 1.33 mm survey of 32 disks in the Taurus star-forming region, which was designed to cover a wide range of sub-mm brightness and to be unbiased to previously known substructures. While axisymmetric rings and gaps are common within our sample, spiral patterns and high contrast azimuthal asymmetries ...


Dust Production And Depletion In Evolved Planetary Systems, J. Farihi, Ted Von Hippel, Rik Van Lieshout, P.W. Cauley, Erik Dennihy, Et Al. Aug 2018

Dust Production And Depletion In Evolved Planetary Systems, J. Farihi, Ted Von Hippel, Rik Van Lieshout, P.W. Cauley, Erik Dennihy, Et Al.

Publications

The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20 per cent peak-to-peak over 11.2 yr, and is consistent with ongoing dust production and depletion. It is hypothesized that the dust is produced via collisions associated with an evolving dust disc, temporarily increasing the emitting surface of warm debris, and is subsequently destroyed or assimilated within a few years. The variations are consistent with debris that does not change temperature, indicating that dust is produced and depleted within a fixed range of orbital radii. Gas produced in collisions may rapidly re-condense ...


Revealing The Structure Of The Outer Disks Of Be Stars, Robert Klement, Anthony C. Carciofi, Thomas Rivinius, Lynn D. Matthews, Rodrigo G. Vieira, Richard Ignace, Jon E. Bjorkman, B. C. Mota, Daniel M. Faes, A. D. Bratcher, M. Cure, Stanislav Stefl Aug 2018

Revealing The Structure Of The Outer Disks Of Be Stars, Robert Klement, Anthony C. Carciofi, Thomas Rivinius, Lynn D. Matthews, Rodrigo G. Vieira, Richard Ignace, Jon E. Bjorkman, B. C. Mota, Daniel M. Faes, A. D. Bratcher, M. Cure, Stanislav Stefl

Richard Ignace

Context. The structure of the inner parts of Be star disks (≲ 20 stellar radii) is well explained by the viscous decretion disk (VDD) model, which is able to reproduce the observable properties of most of the objects studied so far. The outer parts, on the other hand, are not observationally well-explored, as they are observable only at radio wavelengths. A steepening of the spectral slope somewhere between infrared and radio wavelengths was reported for several Be stars that were previously detected in the radio, but a convincing physical explanation for this trend has not yet been provided.

Aims. We test ...


The Alma Early Science View Of Fuor/Exor Objects - V. Continuum Disc Masses And Sizes, Lucas Cieza, Dary Ruiz-Rodriguez, Sebastian Perez, Simon Casassus, Jonathan P. Williams, Alice Zurlo, David A. Principe, Antonio Hales, Jose L. Prieto, John J. Tobin, Zhaohuan Zhu, Sebastian Marino Nov 2017

The Alma Early Science View Of Fuor/Exor Objects - V. Continuum Disc Masses And Sizes, Lucas Cieza, Dary Ruiz-Rodriguez, Sebastian Perez, Simon Casassus, Jonathan P. Williams, Alice Zurlo, David A. Principe, Antonio Hales, Jose L. Prieto, John J. Tobin, Zhaohuan Zhu, Sebastian Marino

Physics & Astronomy Faculty Publications

Low-mass stars build a significant fraction of their total mass during short outbursts of enhanced accretion known as FUor and EXor outbursts. FUor objects are characterized by a sudden brightening of ∼5 mag at visible wavelengths within 1 yr and remain bright for decades. EXor objects have lower amplitude outbursts on shorter time-scales. Here we discuss a 1.3 mm Atacama Large Millimeter/submillimeter Array (ALMA) mini-survey of eight outbursting sources (three FUors, four EXors, and the borderline object V1647 Ori) in the Orion Molecular Cloud. While previous papers in this series discuss the remarkable molecular outflows observed in the ...


Magnetospherically-Trapped Dust And A Possible Model For The Unusual Transits At Wd1145+017, J. Farihi, Ted Von Hippel, J. E. Pringle Aug 2017

Magnetospherically-Trapped Dust And A Possible Model For The Unusual Transits At Wd1145+017, J. Farihi, Ted Von Hippel, J. E. Pringle

Publications

The rapidly evolving dust and gas extinction observed towardsWD1145+017 has opened a real-time window onto the mechanisms for destruction-accretion of planetary bodies onto white dwarf stars, and has served to underline the importance of considering the dynamics of dust particles around such objects. Here it is argued that the interaction between (charged) dust grains and the stellar magnetic field is an important ingredient in understanding the physical distribution of infrared emitting particles in the vicinity of such white dwarfs. These ideas are used to suggest a possible model for WD 1145+017 in which the unusual transit shapes are ...


Revealing The Structure Of The Outer Disks Of Be Stars, Robert Klement, Anthony C. Carciofi, Thomas Rivinius, Lynn D. Matthews, Rodrigo G. Vieira, Richard Ignace, Jon E. Bjorkman, B. C. Mota, Daniel M. Faes, A. D. Bratcher, M. Cure, Stanislav Stefl May 2017

Revealing The Structure Of The Outer Disks Of Be Stars, Robert Klement, Anthony C. Carciofi, Thomas Rivinius, Lynn D. Matthews, Rodrigo G. Vieira, Richard Ignace, Jon E. Bjorkman, B. C. Mota, Daniel M. Faes, A. D. Bratcher, M. Cure, Stanislav Stefl

ETSU Faculty Works

Context. The structure of the inner parts of Be star disks (≲ 20 stellar radii) is well explained by the viscous decretion disk (VDD) model, which is able to reproduce the observable properties of most of the objects studied so far. The outer parts, on the other hand, are not observationally well-explored, as they are observable only at radio wavelengths. A steepening of the spectral slope somewhere between infrared and radio wavelengths was reported for several Be stars that were previously detected in the radio, but a convincing physical explanation for this trend has not yet been provided.

Aims. We test ...


Narrow Na And K Absorption Lines Toward T Tauri Stars: Tracing The Atomic Envelope Of Molecular Clouds, I. Pascucci, Suzan Edwards, M Heyer, E. Rigliaco, L. Hillenbrand, U. Gorti, D. Hollenbach, M. N. Simon Nov 2015

Narrow Na And K Absorption Lines Toward T Tauri Stars: Tracing The Atomic Envelope Of Molecular Clouds, I. Pascucci, Suzan Edwards, M Heyer, E. Rigliaco, L. Hillenbrand, U. Gorti, D. Hollenbach, M. N. Simon

Astronomy: Faculty Publications

We present a detailed analysis of narrow Na I and K I absorption resonance lines toward nearly 40 T Tauri stars in Taurus with the goal of clarifying their origin. The Na I λ5889.95 line is detected toward all but one source, while the weaker K I λ7698.96 line is detected in about two-thirds of the sample. The similarity in their peak centroids and the significant positive correlation between their equivalent widths demonstrate that these transitions trace the same atomic gas. The absorption lines are present toward both disk and diskless young stellar objects, which excludes cold gas ...


Characterizing The Rigidly Rotating Magnetosphere Stars Hd 345439 And Hd 23478, J. P. Wisniewski, S. D. Chojnowski, James R. A. Davenport, J. Bartz, J. Pepper, D. G. Whelan, S. S. Eikenberry, J. R. Lomax, S. R. Majewski, N. D. Richardson Sep 2015

Characterizing The Rigidly Rotating Magnetosphere Stars Hd 345439 And Hd 23478, J. P. Wisniewski, S. D. Chojnowski, James R. A. Davenport, J. Bartz, J. Pepper, D. G. Whelan, S. S. Eikenberry, J. R. Lomax, S. R. Majewski, N. D. Richardson

Physics & Astronomy

The SDSS III APOGEE survey recently identified two new σ Ori E type candidates, HD 345439 and HD 23478, which are a rare subset of rapidly rotating massive stars whose large (kGauss) magnetic fields confine circumstellar material around these systems. Our analysis of multi-epoch photometric observations of HD 345439 from the Kilodegree Extremely Little Telescope, Wide Angle Search for Planets, and ASAS surveys reveals the presence of a ~0.7701 day period in each data set, suggesting the system is among the faster known σ Ori E analogs. We also see clear evidence that the strength of Hα, H ...


Probing Stellar Accretion With Mid-Infrared Hydrogen Lines, Elisabetta Rigliaco, Ilaria Pascucci, Gaspard Duchene, Suzan Edwards, D. R. Ardila, C. Grady, Ignacio Imendigutía, Benjamín Montesinos, Gijs D. Mulders, Joan R. Najita, J. Carpenter, Elise Furlan, Uma Gorti, Rowin Meijerink, M. R. Meyer Feb 2015

Probing Stellar Accretion With Mid-Infrared Hydrogen Lines, Elisabetta Rigliaco, Ilaria Pascucci, Gaspard Duchene, Suzan Edwards, D. R. Ardila, C. Grady, Ignacio Imendigutía, Benjamín Montesinos, Gijs D. Mulders, Joan R. Najita, J. Carpenter, Elise Furlan, Uma Gorti, Rowin Meijerink, M. R. Meyer

Astronomy: Faculty Publications

In this paper we investigate the origin of the mid-infrared (IR) hydrogen recombination lines for a sample of 114 disks in different evolutionary stages (full, transitional, and debris disks) collected from the Spitzer archive. We focus on the two brighter H I lines observed in the Spitzer spectra, the H I (7-6) at 12.37 μm and the H I (9-7) at 11.32 μm. We detect the H I (7-6) line in 46 objects, and the H I (9-7) in 11. We compare these lines with the other most common gas line detected in Spitzer spectra, the [Ne II ...


Csi 2264: Characterizing Young Stars In Ngc 2264 With Short-Duration, Periodic Flux Dips In Their Light Curves, John Stauffer, Ann Marie Cody, Pauline Mcginnis, Luisa Rebull, Lynne A. Hillenbrand, Neal. J. Turner, John Carpenter, Peter Plavchan, Sean Carey, Susan Terebey, Maria Morales-Calderon, Silvia H.P. Alencar, Jerome Bouvier, Laura Venuti, Lee Hartmann, Nuria Calvet, Giushi Micela, Ettore Flaccomio, Inseok Song, R. A. Gutermuth, David Barrado, Frederick J. Vrba, Kevin Covey, Debbie Padgett, William Herbst, Edward Gillen, Wladimir Lyra, Marcelo Medeiros Guimaraes, Herve Bouy, Fabio Favata Jan 2015

Csi 2264: Characterizing Young Stars In Ngc 2264 With Short-Duration, Periodic Flux Dips In Their Light Curves, John Stauffer, Ann Marie Cody, Pauline Mcginnis, Luisa Rebull, Lynne A. Hillenbrand, Neal. J. Turner, John Carpenter, Peter Plavchan, Sean Carey, Susan Terebey, Maria Morales-Calderon, Silvia H.P. Alencar, Jerome Bouvier, Laura Venuti, Lee Hartmann, Nuria Calvet, Giushi Micela, Ettore Flaccomio, Inseok Song, R. A. Gutermuth, David Barrado, Frederick J. Vrba, Kevin Covey, Debbie Padgett, William Herbst, Edward Gillen, Wladimir Lyra, Marcelo Medeiros Guimaraes, Herve Bouy, Fabio Favata

Robert A. Gutermuth

We identify nine young stellar objects (YSOs) in the NGC 2264 star-forming region with optical CoRoT light curves exhibiting short-duration, shallow periodic flux dips. All of these stars have infrared excesses that are consistent with their having inner disk walls near the Keplerian co-rotation radius. The repeating photometric dips have FWHMs generally less than 1 day, depths almost always less than 15%, and periods (3 < P < 11 days) consistent with dust near the Keplerian co-rotation period. The flux dips vary considerably in their depth from epoch to epoch, but usually persist for several weeks and, in two cases, were present in data collected in successive years. For several of these stars, we also measure the photospheric rotation period and find that the rotation and dip periods are the same, as predicted by standard "disk-locking" models. We attribute these flux dips to clumps of material in or near the inner disk wall, passing through our line of sight to the stellar photosphere. In some cases, these dips are also present in simultaneous Spitzer IRAC light curves at 3.6 and 4.5 microns. We characterize the properties of these dips, and compare the stars with light curves exhibiting this behavior to other classes of YSOs in NGC 2264. A number of physical mechanisms could locally increase the dust scale height near the inner disk wall, and we discuss several of those mechanisms; the most plausible mechanisms are either a disk warp due to interaction with the stellar magnetic field or dust entrained in funnel-flow accretion columns arising near the inner disk wall.


The Hα Spectroscopy Of Classical B-Emission Stars, Jessie M. Silaj Dec 2014

The Hα Spectroscopy Of Classical B-Emission Stars, Jessie M. Silaj

Electronic Thesis and Dissertation Repository

Classical B-emission (Be) stars are rapidly-rotating, massive stars that possess a dense, equatorial, gaseous disk. The presence of a disk was first inferred from the Balmer series emission that these stars exhibit, and Hα emission lines remain both a hallmark observational feature and one of the key diagnostics in determining the physical conditions within the disk.

In the first chapter of this thesis, we investigate the possible role of line-driven winds in disk formation. To test if line-driven winds could supply enough material to account for the equatorial disk, we check for the presence of Hα emission in the models ...


Evidence Of A Mira-Like Tail And Bow Shock About The Semi-Regular Variable V Cvn From Four Decades Of Polarization Measurements., Hilding Neilson, Richard Ignace, Beverly Smith, Gary Henson, Alyssa Adams Aug 2014

Evidence Of A Mira-Like Tail And Bow Shock About The Semi-Regular Variable V Cvn From Four Decades Of Polarization Measurements., Hilding Neilson, Richard Ignace, Beverly Smith, Gary Henson, Alyssa Adams

ETSU Faculty Works

Polarization is a powerful tool for understanding stellar atmospheres and circumstellar environments. Mira and semi-regular variable stars have been observed for decades and some are known to be polarimetrically variable, however, the semi-regular variable V Canes Venatici displays an unusually large, unexplained amount of polarization. We present ten years of optical polarization observations obtained with the HPOL instrument, supplemented by published observations spanning a total interval of about forty years for V CVn. We find that V CVn shows large polarization variations ranging from 1 - 6%. We also find that for the past forty years the position angle measured for ...


Evidence Of A Mira-Like Tail And Bow Shock About The Semi-Regular Variable V Cvn From Four Decades Of Polarization Measurements., Hilding R. Neilson, Richard Ignace, Beverly J. Smith, Gary Henson, Alyssa M. Adams Aug 2014

Evidence Of A Mira-Like Tail And Bow Shock About The Semi-Regular Variable V Cvn From Four Decades Of Polarization Measurements., Hilding R. Neilson, Richard Ignace, Beverly J. Smith, Gary Henson, Alyssa M. Adams

Richard Ignace

Polarization is a powerful tool for understanding stellar atmospheres and circumstellar environments. Mira and semi-regular variable stars have been observed for decades and some are known to be polarimetrically variable, however, the semi-regular variable V Canes Venatici displays an unusually large, unexplained amount of polarization. We present ten years of optical polarization observations obtained with the HPOL instrument, supplemented by published observations spanning a total interval of about forty years for V CVn. We find that V CVn shows large polarization variations ranging from 1 - 6%. We also find that for the past forty years the position angle measured for ...


Dust Stratification In Young Circumstellar Disks, Terrence Rettig, Sean D. Brittain, Theodore Simon, Erika Gibb, Dinshaw S. Balsara, David A. Tilley, Craig Kulesa Aug 2014

Dust Stratification In Young Circumstellar Disks, Terrence Rettig, Sean D. Brittain, Theodore Simon, Erika Gibb, Dinshaw S. Balsara, David A. Tilley, Craig Kulesa

Sean D Brittain

We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S, RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO, and C18O, as well as broad emission lines of gas-phase 12CO. The narrow absorption lines of CO are shown to originate from the colder circumstellar gas. We find that the line-of-sight gas column densities resulting from the CO absorption lines are much higher than expected for the measured extinction for each source and suggest the gas/dust ratio is measuring the dust settling and/or grain coagulation in these extended disks. We ...


Co Line Emission And Absorption From The Hl Tauri Disk-Where Is All The Dust?, Sean D. Brittain, Terrence W. Rettig, Theodore Simon, Craig Kulesa Aug 2014

Co Line Emission And Absorption From The Hl Tauri Disk-Where Is All The Dust?, Sean D. Brittain, Terrence W. Rettig, Theodore Simon, Craig Kulesa

Sean D Brittain

We present high-resolution infrared spectra of HL Tau, a heavily embedded young star. The spectra exhibit broad emission lines of 12CO gas-phase molecules, as well as narrow absorption lines of 12CO, 13CO, and C18O. The broad emission lines of vibrationally excited 12CO are dominated by the hot (T ~ 1500 K) inner disk. The narrow absorption lines of CO are found to originate from the circumstellar gas at a temperature of ~100 K. The 12CO column density for this cooler material [(7.5 ± 0.2) × 1018 cm-2] indicates a large column of absorbing gas along the line of sight. In dense ...


Warm Gas In The Inner Disks Around Young Intermediate-Mass Stars, Sean D. Brittain, Theodore Simon, Joan R. Najita, Terrence W. Rettig Aug 2014

Warm Gas In The Inner Disks Around Young Intermediate-Mass Stars, Sean D. Brittain, Theodore Simon, Joan R. Najita, Terrence W. Rettig

Sean D Brittain

The characterization of gas in the inner disks around young stars is of particular interest because of its connection to planet formation. In order to study the gas in inner disks, we have obtained high-resolution K- and M-band spectroscopy of 14 intermediate-mass young stars. In sources that have optically thick inner disks, i.e., E(K-L)>1, our detection rate of the rovibrational CO transitions is 100%, and the gas is thermally excited. Of the five sources that do not have optically thick inner disks, we only detect the rovibrational CO transitions from HD 141569. In this case, we show ...


Co Emission In The Inner Disk Around Young Intermediate-Mass Stars, Matt L. Stevans, Sean D. Brittain Aug 2014

Co Emission In The Inner Disk Around Young Intermediate-Mass Stars, Matt L. Stevans, Sean D. Brittain

Sean D Brittain

We present observations that indicate viscous heating contributes significantly to the surface heating of the inner disk region (0.1-5 AU) around young intermediate-mass stars, Herbig AeBe stars, when the inner disk is optically thick. Brgamma flux is known to scale with accretion rate around young stars. We find a trend between Brgamma and CO emissivity, a tracer 1, 500 K gas in the gaseous atmospheres of less evolved inner disk regions in a sample of 25 Herbig AeBe stars, the higher mass analog of T Tauri stars. Evolved Herbig circumstellar disks do not follow this trend as closely. A ...


The Herschel View Of Gas In Protoplanetary Systems (Gasps). First Comparisons With A Large Grid Of Models, C Pinte, P Woitke, F Menard, G Duchene, I Kamp, G Meeus, G Mathews, C D. Howard, C A. Grady, W.-F. Thi, I Tilling, J.-C. Augereau, W.R.F. Dent, J M. Alacid, S Andrews, D R. Ardila, G Aresu, D Barrado, Sean D. Brittain, D R. Ciardi Aug 2014

The Herschel View Of Gas In Protoplanetary Systems (Gasps). First Comparisons With A Large Grid Of Models, C Pinte, P Woitke, F Menard, G Duchene, I Kamp, G Meeus, G Mathews, C D. Howard, C A. Grady, W.-F. Thi, I Tilling, J.-C. Augereau, W.R.F. Dent, J M. Alacid, S Andrews, D R. Ardila, G Aresu, D Barrado, Sean D. Brittain, D R. Ciardi

Sean D Brittain

The Herschel GASPS key program is a survey of the gas phase of protoplanetary discs, targeting 240 objects which cover a large range of ages, spectral types, and disc properties. To interpret this large quantity of data and initiate self-consistent analyses of the gas and dust properties of protoplanetary discs, we have combined the capabilities of the radiative transfer code MCFOST with the gas thermal balance and chemistry code ProDiMo to compute a grid of ≈300 000 disc models (DENT). We present a comparison of the first Herschel/GASPS line and continuum data with the predictions from the DENT grid ...


Accretion Variability Of Herbig Ae/Be Stars Observed By X-Shooter Hd 31648 And Hd 163296, I Mendigutia, Sean D. Brittain, C Eiroa, G Meeus, B Montesinos, A Mora, J Muzerolle, R D. Oudmaijer, E Rigliaco Aug 2014

Accretion Variability Of Herbig Ae/Be Stars Observed By X-Shooter Hd 31648 And Hd 163296, I Mendigutia, Sean D. Brittain, C Eiroa, G Meeus, B Montesinos, A Mora, J Muzerolle, R D. Oudmaijer, E Rigliaco

Sean D Brittain

This work presents X-Shooter/Very Large Telescope spectra of the prototypical, isolated Herbig Ae stars HD 31648 (MWC 480) and HD 163296 over five epochs separated by timescales ranging from days to months. Each spectrum spans over a wide wavelength range covering from 310 to 2475 nm. We have monitored the continuum excess in the Balmer region of the spectra and the luminosity of 12 ultraviolet, optical, and near-infrared spectral lines that are commonly used as accretion tracers for T Tauri stars. The observed strengths of the Balmer excesses have been reproduced from a magnetospheric accretion shock model, providing a ...


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 Aug 2014

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

Sean D Brittain

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 ...


High-Resolution Near-Infrared Spectroscopy Of Hd 100546. Ii. Analysis Of Variable Rovibrational Co Emission Lines, Sean D. Brittain, Joan Najita, John S. Carr, Joseph Liskowsky, Matthew R. Troutman, Greg W. Doppmann Aug 2014

High-Resolution Near-Infrared Spectroscopy Of Hd 100546. Ii. Analysis Of Variable Rovibrational Co Emission Lines, Sean D. Brittain, Joan Najita, John S. Carr, Joseph Liskowsky, Matthew R. Troutman, Greg W. Doppmann

Sean D Brittain

We present observations of rovibrational CO in HD 100546 from four epochs spanning 2003 January through 2010 December. We show that the equivalent widths of the CO lines vary during this time period with the v = 1–0 CO lines brightening more than the UV fluoresced lines from the higher vibrational states.While the spectroastrometric signal of the hot band lines remains constant during this period, the spectroastrometric signal of the v = 1–0 lines varies substantially. At all epochs, the spectroastrometric signals of the UV fluoresced lines are consistent with the signal one would expect from gas in an ...


Gas In The Protoplanetary Disc Of Hd 169142: Herschel's View, G Meeus, C Pinte, P Woitke, B Montesinos, I Mendigutia, P Riviere-Marichalar, C Eiroa, G S. Mathews, B Vandenbussche, C D. Howard, A Roberge, G Sandell, G Duchene, F Menard, C A. Grady, W.R.F. Dent, I Kamp, J C. Augereau, W F. Thi, I Tilling, J M. Alacid, S Andrews, D R. Ardila, G Aresu, D Barrado, Sean D. Brittain Aug 2014

Gas In The Protoplanetary Disc Of Hd 169142: Herschel's View, G Meeus, C Pinte, P Woitke, B Montesinos, I Mendigutia, P Riviere-Marichalar, C Eiroa, G S. Mathews, B Vandenbussche, C D. Howard, A Roberge, G Sandell, G Duchene, F Menard, C A. Grady, W.R.F. Dent, I Kamp, J C. Augereau, W F. Thi, I Tilling, J M. Alacid, S Andrews, D R. Ardila, G Aresu, D Barrado, Sean D. Brittain

Sean D Brittain

In an effort to simultaneously study the gas and dust components of the disc surrounding the young Herbig Ae star HD 169142, we present far-IR observations obtained with the PACS instrument onboard the Herschel Space Observatory. This work is part of the open time key program GASPS, which is aimed at studying the evolution of protoplanetary discs. To constrain the gas properties in the outer disc, we observed the star at several key gas-lines, including [OI] 63.2 and 145.5 mum, [CII] 157.7 mum, CO 72.8 and 90.2 mum, and o-H2O 78.7 and 179.5 ...


High-Resolution Near-Infrared Spectroscopy Of Hd 100546. I. Analysis Of Asymmetric Ro-Vibrational Oh Emission Lines, Joseph Liskowsky, Sean D. Brittain, Joan R. Najita, John S. Carr, Greg W. Doppman, Matthew R. Troutman Aug 2014

High-Resolution Near-Infrared Spectroscopy Of Hd 100546. I. Analysis Of Asymmetric Ro-Vibrational Oh Emission Lines, Joseph Liskowsky, Sean D. Brittain, Joan R. Najita, John S. Carr, Greg W. Doppman, Matthew R. Troutman

Sean D Brittain

We present observations of ro-vibrational OH and CO emission from the Herbig Be star HD 100546. The emission from both molecules arises from the inner region of the disk extending from approximately 13 AU from the central star. The velocity profiles of the OH lines are narrower than the velocity profile of the [O i] λ6300 line, indicating that the OH in the disk is not cospatial with the Oi. This suggests that the inner optically thin region of the disk is largely devoid of molecular gas. Unlike the ro-vibrational CO emission lines, the OH lines are highly asymmetric. We ...


High-Resolution Near-Infrared Spectroscopy Of Hd 100546. Ii. Analysis Of Variable Rovibrational Co Emission Lines, Sean D. Brittain, Joan Najita, John S. Carr, Joseph Liskowsky, Matthew R. Troutman, Greg W. Doppmann Nov 2013

High-Resolution Near-Infrared Spectroscopy Of Hd 100546. Ii. Analysis Of Variable Rovibrational Co Emission Lines, Sean D. Brittain, Joan Najita, John S. Carr, Joseph Liskowsky, Matthew R. Troutman, Greg W. Doppmann

Publications

We present observations of rovibrational CO in HD 100546 from four epochs spanning 2003 January through 2010 December. We show that the equivalent widths of the CO lines vary during this time period with the v = 1–0 CO lines brightening more than the UV fluoresced lines from the higher vibrational states.While the spectroastrometric signal of the hot band lines remains constant during this period, the spectroastrometric signal of the v = 1–0 lines varies substantially. At all epochs, the spectroastrometric signals of the UV fluoresced lines are consistent with the signal one would expect from gas in an ...