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Open Access. Powered by Scholars. Published by Universities.®
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- Protoplanetary disks (4)
- White dwarfs (4)
- Circumstellar matter (3)
- Accretion (2)
- Astrochemistry (2)
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- Astronautics (2)
- Astronomy (2)
- Kelvin-Helmholtz instability (2)
- Magnetosheath (2)
- Science (2)
- Star clusters and associations (2)
- Stars: individual (HD 100546) (2)
- Stars: pre-main sequence (2)
- Technology (2)
- 5-D brane model (1)
- 5-D brane world model (1)
- Accretion disks (1)
- Accretion disks - stars: flare - stars: formation - stars: individual (V1647 Ori) - stars: winds (1)
- Activity: Stars (1)
- Alfvén Mach number (1)
- And astronomy (En-ergetic particles) (1)
- Astrophysics (1)
- Be (1)
- Boundary layers (1)
- Bow shock (1)
- CME ejecta (1)
- Cataclysmic variables – X-rays: binaries – stars: individual: M31N 2010-10f – globular clusters: individual: Bol 126 (1)
- Coronal mass ejections (1)
- Cosmology (1)
- Cusp (1)
Articles 1 - 30 of 33
Full-Text Articles in Physical Sciences and Mathematics
Three X-Ray Transients In M31 Oberserved With Swift, R. Voss, W. Pietsch, F. Haberl, H. Stiele, J. Greiner, G. Sala, Dieter H. Hartmann, D. Hatzidimitriou
Three X-Ray Transients In M31 Oberserved With Swift, R. Voss, W. Pietsch, F. Haberl, H. Stiele, J. Greiner, G. Sala, Dieter H. Hartmann, D. Hatzidimitriou
Publications
Aims.The purpose of this study is to find transient X-ray sources in M 31, and to investigate and classify their nature.Methods.Three X-ray transients were observed with Swift. For each of the three X-ray transients we use the Swift X-ray and opticaldata together with observations from XMM-Newton and Chandra to investigate the lightcurves and the spectra of the outburst, andthereby to identify the source types. Results.The outburst of XMMU J004215.8+ 411924 lasted for about one month. The source had a hard power-law spectrum with aphoton index of 1.6. It was previously identified as a Be/X-ray binary based on the optical identification …
Supernova Neutrino Nucleosynthesis Of Light Elements With Neutrino Oscillations, Takashi Yoshida, Toshitaka Kajino, Hidekazu Yokomakura, Keiichi Kimura, Akira Takamura, Dieter H. Hartmann
Supernova Neutrino Nucleosynthesis Of Light Elements With Neutrino Oscillations, Takashi Yoshida, Toshitaka Kajino, Hidekazu Yokomakura, Keiichi Kimura, Akira Takamura, Dieter H. Hartmann
Publications
Light element synthesis in supernovae through neutrino-nucleus interactions, i.e., the ν-process, is affected by neutrino oscillations in the supernova environment. There is a resonance of 13-mixing in the O/C layer, which increases the rates of charged-current ν-process reactions in the outer He-rich layer. The yields of 7Li and 11B increase by about a factor of 1.9 and 1.3, respectively, for a normal mass hierarchy and an adiabatic 13-mixing resonance, compared to those without neutrino oscillations. In the case of an inverted mass hierarchy and a non-adiabatic 13-mixing resonance, the increase in the 7Li and 11B yields is much smaller. Observations …
Mapping Of The Quasi-Periodic Oscillations At The Flank Magnetopause Into The Ionosphere, E. R. Dougal, K. Nykyri, T. W. Moore
Mapping Of The Quasi-Periodic Oscillations At The Flank Magnetopause Into The Ionosphere, E. R. Dougal, K. Nykyri, T. W. Moore
Publications
We have estimated the ionospheric location, area, and travel time of quasi-periodic oscillations originating from the magnetospheric flanks. This was accomplished by utilizing global and local MHD models and Tsyganenko semi-empirical magnetic field model on multiple published and four new cases believed to be caused by the Kelvin– Helmholtz Instability. Finally, we used auroral, magnetometer, and radar instruments to observe the ionospheric signatures. The ionospheric magnetic latitude determined using global MHD and Tsyganenko models ranged from 58.3–80.2 degrees in the Northern Hemisphere and −59.6 degrees to −83.4 degrees in the Southern Hemisphere. The ionospheric magnetic local time ranged between 5.0–13.8 …
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
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
Publications
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
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 axisymmetric …
Broadband Monitoring Tracing The Evolution Of The Jet And Disk In The Black Hole Candidate X-Ray Binary Maxi J1659-152, A. J. Horst, P. A. Curran, J. C. A. Miller-Jones, J. D. Linford, J. Gorosabel, D. M. Russell, A. De Ugarte Postigo, A. A. Lundgren, G. B. Taylor, D Maitra, S Guziy, T M. Belloni, C Kouveliotou, P G. Jonker, A Kamble, Z Paragi, J Homan, E Kuulkers, J Granot, D Altamirano, M M. Buxton, A Castro-Tirado, R P. Fender, M A. Garrett, N Gehrels, Dieter H. Hartmann, J A. Kennea, H A. Krimm, V Mangano, E Ramirez-Ruiz, P Romano, R.A.M.J. Wijers, R Wijnands, Y J. Yang
Broadband Monitoring Tracing The Evolution Of The Jet And Disk In The Black Hole Candidate X-Ray Binary Maxi J1659-152, A. J. Horst, P. A. Curran, J. C. A. Miller-Jones, J. D. Linford, J. Gorosabel, D. M. Russell, A. De Ugarte Postigo, A. A. Lundgren, G. B. Taylor, D Maitra, S Guziy, T M. Belloni, C Kouveliotou, P G. Jonker, A Kamble, Z Paragi, J Homan, E Kuulkers, J Granot, D Altamirano, M M. Buxton, A Castro-Tirado, R P. Fender, M A. Garrett, N Gehrels, Dieter H. Hartmann, J A. Kennea, H A. Krimm, V Mangano, E Ramirez-Ruiz, P Romano, R.A.M.J. Wijers, R Wijnands, Y J. Yang
Publications
MAXI J1659−152 was discovered on 2010 September 25 as a new X-ray transient, initially identified as a gamma-ray burst, but was later shown to be a new X-ray binary with a blackhole as the most likely compact object. Dips in the X-ray light curves have revealed that MAXI J1659−152 is the shortest period black hole candidate identified to date. Here we present the results of a large observing campaign at radio, submillimetre, near-infrared (nIR), optical and ultraviolet (UV) wavelengths. We have combined this very rich data set with the available X-ray observations to compile a broad-band picture of the evolution …
A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk
A Bayesian Approach To Deriving Ages Of Individual Field White Dwarfs, Erin M. O'Malley, Ted Von Hippel, David A. Van Dyk
Publications
We apply a self-consistent and robust Bayesian statistical approach to determine the ages, distances, and zero-age main sequence (ZAMS) masses of 28 field DA white dwarfs (WDs) with ages of approximately 4–8 Gyr. Our technique requires only quality optical and near-infrared photometry to derive ages with <15% uncertainties, generally with little sensitivity to our choice of modern initial–final mass relation. We find that age, distance, and ZAMS mass are correlated in a manner that is too complex to be captured by traditional error propagation techniques. We further find that the posterior distributions of age are often asymmetric, indicating that the …
Near-Infrared Spectroscopic Study Of V1647 Ori, Sean D. Brittain, T W. Rettig, Theodore Simon, Erika L. Gibb, Joseph Liskowsky
Near-Infrared Spectroscopic Study Of V1647 Ori, Sean D. Brittain, T W. Rettig, Theodore Simon, Erika L. Gibb, Joseph Liskowsky
Publications
We present new high-resolution infrared echelle spectra of V1647 Ori, the young star that illuminates McNeil's nebula. From the start, V1647 Ori has been an enigmatic source that has defied classification, in some ways resembling eruptive stars of the FUor class and in other respects the EXor variables. V1647 Ori underwent an outburst in 2003 before fading back to its pre-outburst brightness in 2006. In 2008, it underwent a new outburst. In this paper we present high-resolution K-band and M-band spectra from the W. M. Keck Observatory that were acquired during the 2008 outburst. We compare the spectra to spectra …
Nitrogen Abundances And The Distance Moduli Of The Pleiades And Hyades, Blake Miller, Jeremy R. King, Yu Chen, Ann Merchant Boesgaard
Nitrogen Abundances And The Distance Moduli Of The Pleiades And Hyades, Blake Miller, Jeremy R. King, Yu Chen, Ann Merchant Boesgaard
Publications
Recent reanalyses of HIPPARCOS parallax data confirm a previously noted discrepancy with the Pleiades distance modulus estimated from main-sequence fitting in the color-magnitude diagram. One proposed explanation of this distance modulus discrepancy is a Pleiades He abundance that is significantly larger than the Hyades value. We suggest that, based on our theoretical and observational understanding of Galactic chemical evolution, nitrogen abundances may serve as a proxy for helium abundances of disk stars. Utilizing high-resolution near-UV Keck/HIRES spectroscopy, we determine N abundances in the Pleiades and Hyades dwarfs from NH features in the λ3330 region. While our Hyades N abundances show …
Gas Lines From The 5-Myr Old Optically Thin Disk Around Hd141569a, W F. Thi, C Pinte, E Pantin, J C. Augereau, G Meeus, F Menard, C Martin-Zaidi, P Woitke, P Riviere-Marichalar, I Kamp, A Carmona, G Sandell, C Eiroa, W Dent, B Montesinos, G Aresu, R Meijerink, M Spaans, G White, D Ardila, J Lebreton, I Mendigutia, Sean D. Brittain
Gas Lines From The 5-Myr Old Optically Thin Disk Around Hd141569a, W F. Thi, C Pinte, E Pantin, J C. Augereau, G Meeus, F Menard, C Martin-Zaidi, P Woitke, P Riviere-Marichalar, I Kamp, A Carmona, G Sandell, C Eiroa, W Dent, B Montesinos, G Aresu, R Meijerink, M Spaans, G White, D Ardila, J Lebreton, I Mendigutia, Sean D. Brittain
Publications
At the distance of 99-116 pc, HD141569A is one of the nearest HerbigAe stars that is surrounded by a tenuous disk, probably in transition between a massive primordial disk and a debris disk. We observed the fine-structure lines of OI at 63 and 145 micron and the CII line at 157 micron with the PACS instrument onboard the Herschel Space Telescope as part of the open-time large programme GASPS. We complemented the atomic line observations with archival Spitzer spectroscopic and photometric continuum data, a ground-based VLT-VISIR image at 8.6 micron, and 12CO fundamental ro-vibrational and pure rotational J=3-2 observations. We …
Moving Objects In The Hubble Ultra Deep Field, Mukremin Kilic, Alexandros Gianninas, Ted Von Hippel
Moving Objects In The Hubble Ultra Deep Field, Mukremin Kilic, Alexandros Gianninas, Ted Von Hippel
Publications
We identify proper motion objects in the Hubble Ultra Deep Field (UDF) using the optical data from the original UDF program in 2004 and the near-infrared data from the 128 orbit UDF 2012 campaign. There are 12 sources brighter than I = 27 mag that display >3σ significant proper motions. We do not find any proper motion objects fainter than this magnitude limit. Combining optical and near-infrared photometry, we model the spectral energy distribution of each point-source using stellar templates and state-of-the-art white dwarf models. For I ≤ 27 mag, we identify 23 stars with K0-M6 spectral types and two …
Book Review: Heart Of Darkness: Unraveling The Mysteries Of The Invisible Universe, T. D. Oswalt
Book Review: Heart Of Darkness: Unraveling The Mysteries Of The Invisible Universe, T. D. Oswalt
Publications
This document is Dr. Oswalt’s review of Heart of Darkness : Unraveling the Mysteries of the Invisible Universe by Jeremiah P. Ostriker and Simon Mitton Princeton, 2013 299p, 9780691134307 $27.95, 9781400844647 $27.95
Impact Of Mhd Shock Physics On Magnetosheath Symmetry And Kelvin-Helmholtz Instability, K. Nykyri
Impact Of Mhd Shock Physics On Magnetosheath Symmetry And Kelvin-Helmholtz Instability, K. Nykyri
Publications
We have performed 13 three-dimensional global magnetohydrodynamic (MHD) simulations of the magnetosheath plasma and magnetic field properties for Parker spiral (PS) and ortho-Parker spiral interplanetary magnetic field (IMF) orientations corresponding to a wide range of solar wind plasma conditions. To study the growth of the Kelvin-Helmholtz instability on the dawn and dusk flank magnetopause, we have performed 26 local two-dimensional MHD simulations, with the initial conditions taken from global simulations on both sides of the velocity shear layer at the dawn-dusk terminator. These simulations indicate that while the MHD physics of the fast shocks does not directly lead to strong …
First Magnetic Seismology Of The Cme Reconnection Outflow Layer In The Low Corona With 2.5-D Mhd Simulations Of The Kelvin-Helmholtz Instability, Katariina Nykyri, Claire Foullon
First Magnetic Seismology Of The Cme Reconnection Outflow Layer In The Low Corona With 2.5-D Mhd Simulations Of The Kelvin-Helmholtz Instability, Katariina Nykyri, Claire Foullon
Publications
For conditions observed in the low corona, we perform 2.5-D magnetohydrodynamic (MHD) simulations of the Kelvin-Helmholtz instability (KHI) at the surface of a coronal mass ejection (CME). We match the observed time development of the KHI with simulated growth from 110 MHD experiments representing a parametric range of realistic magnetic field strengths and orientations and two key values of the velocity shear, ΔV, inferred from observations. The results are field strengths Be≈ 8–9 G and Bs≈ 10–11 G in the CME reconnection outflow layer and the surrounding sheath, respectively, for ΔV≈770kms−1; for nearly perpendicular orientation (1° tilt) of Bs with …
The Statistical Mapping Of Magnetosheath Plasma Properties Based On Themis Measurements In The Magnetosheath Interplanetary Medium Reference Frame, A. P. Dimmock, K. Nykyri
The Statistical Mapping Of Magnetosheath Plasma Properties Based On Themis Measurements In The Magnetosheath Interplanetary Medium Reference Frame, A. P. Dimmock, K. Nykyri
Publications
The magnetosheath operates as a natural filter between the solar wind and the magnetospheric plasma. As a result of this, the magnetosheath plays a crucial role in the plasma momentum and energy transport from the interplanetary medium into the magnetosphere. Statistical studies of the magnetosheath are difficult due to the dynamic nature of the terrestrial bow shock and the magnetopause. As a result of this, the spatial and temporal dependence of magnetosheath plasma properties under varying solar wind conditions is still not completely understood. We present a study of magnetosheath plasma properties using 5 years of THEMIS and OMNI data …
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
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
Publications
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 mean …
Mechanisms Of Field-Aligned Current Formation In Magnetic Reconnection, Xuanye Ma, Antonius Otto
Mechanisms Of Field-Aligned Current Formation In Magnetic Reconnection, Xuanye Ma, Antonius Otto
Publications
Satellite observations provide strong evidence for the generation of significant field-aligned currents (FACs) during magnetic reconnection. Reconnection of antiparallel magnetic field does not generate FACs in magnetohydrodynamics (MHD) due to coplanarity in MHD shocks. However, a guide magnetic field and a sheared velocity component are almost always present at the magnetopause and their absence is a singular case. It is illustrated that the presence of these noncoplanar fields requires FACs. Contrary to intuition, such currents are generated more efficiently for a small guide field and are more likely to be a result of the redistribution of already present FACs for …
Field Localization And Mass Generation In An Alternative 5-Dimensional Brane Model, Preston Jones, Doug Singleton, Gerardo Muñoz, Triyanta
Field Localization And Mass Generation In An Alternative 5-Dimensional Brane Model, Preston Jones, Doug Singleton, Gerardo Muñoz, Triyanta
Publications
This proceedings is from a talk given at the APS DPF 2013 on a 5- dimensional brane world model. This alternative brane world model is formally related but physically distinct from the Randall-Sundrum brane world model. The spin dependent localization of 5D fields for the alternative model are different and in some ways superior to the RandallSundrum. The alternative model also exhibits a cutoff in the localization of massive scalar fields not seen in the Randall-Sundrum model. This revision includes a correction to the integrand for the scalar field action appearing in the principle reference [1].
Field Localization And The Nambu-Jona-Lasinio Mass Generation Mechanism In An Alternative 5-Dimensional Brane Model, Preston Jones, Gerardo Muñoz, Douglas Singleton, Triyanta
Field Localization And The Nambu-Jona-Lasinio Mass Generation Mechanism In An Alternative 5-Dimensional Brane Model, Preston Jones, Gerardo Muñoz, Douglas Singleton, Triyanta
Publications
We consider a five-dimensional brane world model with a single brane which is distinct from the well known Randall-Sundrum model. We discuss the similarities and differences between our brane model and the Randall-Sundrum brane model. In particular we focus on the localization of five-dimensional fields with different spins—spin 0, spin 1 / 2 , and spin 1—to the brane, and a self-consistent mass-generation mechanism. We find that the brane model studied here has different (and in some cases superior) localization properties for fields/particles with different spins to the brane, as compared to the original five-dimensional brane models. In addition this …
Magnetic Field Generation In A Jet-Sheath Plasma Via The Kinetic Kelvin-Helmholtz Instability, K.-I. Nishikawa, P. Hardee, B. Zhang, I. Dutan, M. Medvedev, E. J. Choi, K. W. Min, J. Niemiec, Y. Mizuno, A Nordlund, J T. Frederiksen, H Sol, M Pohl, Dieter H. Hartmann
Magnetic Field Generation In A Jet-Sheath Plasma Via The Kinetic Kelvin-Helmholtz Instability, K.-I. Nishikawa, P. Hardee, B. Zhang, I. Dutan, M. Medvedev, E. J. Choi, K. W. Min, J. Niemiec, Y. Mizuno, A Nordlund, J T. Frederiksen, H Sol, M Pohl, Dieter H. Hartmann
Publications
We have investigated the generation of magnetic fields associated with velocity shear between an unmagne-tized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by ki-netic shear (Kelvin–Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin– Helmholtz instability (KKHI) of our jet-sheath configura-tion is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse …
Measuring The Evolutionary Rate Of Cooling Of Zz Ceti, Anjum S. Mukadam, Ted Von Hippel, Et Al.
Measuring The Evolutionary Rate Of Cooling Of Zz Ceti, Anjum S. Mukadam, Ted Von Hippel, Et Al.
Publications
We have finally measured the evolutionary rate of cooling of the pulsating hydrogen atmosphere (DA) white dwarf ZZ Ceti (Ross 548), as reflected by the drift rate of the 213.13260694 s period. Using 41 yr of time-series photometry from 1970 November to 2012 January, we determine the rate of change of this period with time to be dP/dt = (5.2 ± 1.4) × 10–15 s s–1 employing the O – C method and (5.45 ± 0.79) × 10–15 s s–1 using a direct nonlinear least squares fit to the entire lightcurve. We adopt the dP/dt obtained …
A Spectroscopic Analysis Of The Eclipsing Short-Period Binary V505 Persei And The Origin Of The Lithium Dip, Patrick Baugh, Jeremy R. King, Constantine P. Deliyannis, Ann Merchant Boesgaard
A Spectroscopic Analysis Of The Eclipsing Short-Period Binary V505 Persei And The Origin Of The Lithium Dip, Patrick Baugh, Jeremy R. King, Constantine P. Deliyannis, Ann Merchant Boesgaard
Publications
As a test of rotationally-induced mixing causing the well-known Li dip in older mid-F dwarfs in the local Galactic disk, we utilize high-resolution and -S/N Keck/HIRES spectroscopy to measure the Li abundance in the components of the ∼1 Gyr, [Fe/H]= −0.15 eclipsing short-period binary V505 Per. We find A(Li) ∼ 2.7 ± 0.1 and 2.4 ± 0.2 in the Teff∼6500 and 6450K primary and sec-ondary components, respectively. Previous Teff determinations and uncertainties suggest that each component is located in the midst of the Li dip. If so, their A(Li) are ≥2–5 times larger than A(Li) detections and upper limits observed …
70 Da White Dwarfs Identified In Lamost Pilot Survey, J. K. Zhao, A. L. Luo, Terry D. Oswalt, G. Zhao
70 Da White Dwarfs Identified In Lamost Pilot Survey, J. K. Zhao, A. L. Luo, Terry D. Oswalt, G. Zhao
Publications
We present a spectroscopically identified catalog of 70 DA white dwarfs (WDs) from the LAMOST pilot survey. Thirty-five are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogs. The effective temperature and gravity of these WDs are estimated by Balmer lines fitting. Most of them are hot WDs. The cooling times and masses of these WDs are estimated by interpolation in theoretical evolution tracks. The peak of the mass distribution is found to be ∼0.6M, which is consistent with prior work in the literature. The distances of these WDs are estimated using the method …
Tracers Of Chromospheric Structure. I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, A. L. Luo, L. Y. Zhang
Tracers Of Chromospheric Structure. I. Ca Ii H&K Emission Distribution Of 13,000 F, G, And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, A. L. Luo, L. Y. Zhang
Publications
We present chromospheric activity index SHK measurements for over 13,000 F, G, and K disk stars with high signal-to-noise ratio (>60) spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopic sample. A parameter δS is defined as the difference between SHK and a “zero” emission line fitted by several of the most inactive stars. The SHK indices of subgiant stars tend to be much lower than dwarfs, which provide a way to distinguish dwarfs and giants with relatively low-resolution spectra. Cooler stars are generally more active and display a larger scatter than …
Tracers Of Chromospheric Structure. I. Caii H&K Emission Distribution Of 13000 F, G And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, L. Y. Zhang
Tracers Of Chromospheric Structure. I. Caii H&K Emission Distribution Of 13000 F, G And K Stars In Sdss Dr7 Spectroscopic Sample, J. K. Zhao, T. D. Oswalt, G. Zhao, Q. H. Lu, L. Y. Zhang
Publications
We present chromospheric activity index SHK measurements for over 13,000 F, G and K disk stars with high signal-to-noise ratio (> 60) spectra in the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopic sample. A parameter S is defined as the difference between SHK and a ‘zero’ emission line fitted by several of the most inactive stars. The SHK indices of subgiant stars tend to be much lower than dwarfs, which provide a way to distinguish dwarfs and giants with relatively low resolution spectra. Cooler stars are generally more active and display a larger scatter than hotter stars. …
X-Ray Source Variability Study Of The M31 Central Field Using Chandra Hrc-1, F. Hofmann, W. Pietsch, M. Henze, F. Haberl, R. Sturm, M. Della Valle, Dieter H. Hartmann, D. Hatzidimitriou
X-Ray Source Variability Study Of The M31 Central Field Using Chandra Hrc-1, F. Hofmann, W. Pietsch, M. Henze, F. Haberl, R. Sturm, M. Della Valle, Dieter H. Hartmann, D. Hatzidimitriou
Publications
Context. The central field of the Andromeda galaxy (M 31) has been monitored, using the Chandra HRC-I detector (about 0.1-10 keV energy range) from 2006 to 2012 with the main aim to detect X-rays from optical novae. We present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Aims. Based on these observations, we studied the X-ray long-term variability of the source population and especially of X-ray binaries in M 31. Methods. We created a catalogue …
Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona, Claire Foullon, Erwin Verwichte, Katariina Nykyri, Markus J. Aschwanden, Iain G. Hannah
Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona, Claire Foullon, Erwin Verwichte, Katariina Nykyri, Markus J. Aschwanden, Iain G. Hannah
Publications
New capabilities for studying the Sun allow us to image for the first time the magnetic Kelvin–Helmholtz (KH) instability developing at the surface of a fast coronal mass ejecta (CME) less than 150 Mm above the solar surface. We conduct a detailed observational investigation of this phenomenon, observed off the east solar limb on 2010 November 3, in the EUV with SDO/AIA. In conjunction with STEREO-B/EUVI, we derive the CME source surface position. We ascertain the timing and early evolution of the CME outflow leading to the instability onset. We perform image and spectral analysis, exploring the CME plasma structuring …
Nature Of The Gas And Dust Around 51 Oph, W F. Thi, F Menard, G Meeus, A Carmona, P Riviere-Marichalar, J C. Augereau, I Kamp, P Woitke, C Pinte, I Mendigutia, C Eiroa, B Montesinos, Sean D. Brittain, W Dent
Nature Of The Gas And Dust Around 51 Oph, W F. Thi, F Menard, G Meeus, A Carmona, P Riviere-Marichalar, J C. Augereau, I Kamp, P Woitke, C Pinte, I Mendigutia, C Eiroa, B Montesinos, Sean D. Brittain, W Dent
Publications
Circumstellar disc evolution is paramount for the understanding of planet formation. The GASPS program aims at determining the circumstellar gas and solid mass around ~250 pre-main-sequence Herbig Ae and TTauri stars. We aim to understand the origin and nature of the circumstellar matter orbiting 51 Oph, a young (Myr) luminous B9.5 star. We obtained continuum and line observations with the PACS instrument on board the Herschel Space Observatory and continuum data at 1.2 mm with the IRAM 30m telescope. The SED and line fluxes were modelled using the physico-chemo radiative transfer code ProDiMo. We detected a strong emission by OI …
Asymmetry Of Magnetosheath Flows And Magnetopause Shape During Low Alfvén Mach Number Solar Wind, B. Lavraud, E. Larroque, E. Budnik, V. Génot, J. E. Borovsky, M. W. Dunlop, K. Nykyri, Et Al.
Asymmetry Of Magnetosheath Flows And Magnetopause Shape During Low Alfvén Mach Number Solar Wind, B. Lavraud, E. Larroque, E. Budnik, V. Génot, J. E. Borovsky, M. W. Dunlop, K. Nykyri, Et Al.
Publications
Previous works have emphasized the significant influence of the solar wind Alfvén Mach number (MA) on magnetospheric dynamics. Here we report statistical, observational results that pertain to changes in the magnetosheath flow distribution and magnetopause shape as a function of solar wind MA and interplanetary magnetic field (IMF) clock angle orientation. We use all Cluster 1 data in the magnetosheath during the period 2001–2010, using an appropriate spatial superposition procedure, to produce magnetosheath flow distributions as a function of location in themagnetosheath relative to the IMF and other parameters. The results demonstrate that enhanced flows in the magnetosheath are expected …
Supersoft X-Rays Reveal A Classical Nova In The M31 Globular Cluster Bol 126, M. Henze, W. Pietsch, F. Haberl, M. Della Valle, A. Riffeser, G. Sala, D. Hatzidimitriou, F. Hofmann, Dieter H. Hartmann, J. Koppenhoefer
Supersoft X-Rays Reveal A Classical Nova In The M31 Globular Cluster Bol 126, M. Henze, W. Pietsch, F. Haberl, M. Della Valle, A. Riffeser, G. Sala, D. Hatzidimitriou, F. Hofmann, Dieter H. Hartmann, J. Koppenhoefer
Publications
Context. Classical novae (CNe) represent the main class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M 31. Only three confirmed novae and three SSSs have been discovered in globular clusters (GCs) of any galaxy so far, of which one nova and two SSSs (including the nova) were found in M 31 GCs. Aims. To study the SSS state of CNe we carried out a high-cadence X-ray monitoring of the M 31 central area with XMM-Newton and Chandra. This project is supplemented by regular optical monitoring programmes at various observatories. Methods. We analysed X-ray and …