scholarly journals HD 93795: a late-B supergiant star with a square circumstellar nebula

2019 ◽  
Vol 492 (2) ◽  
pp. 2383-2392 ◽  
Author(s):  
V V Gvaramadze ◽  
A Y Kniazev ◽  
N Castro ◽  
I Y Katkov
Keyword(s):  
Spectral Analysis ◽  
Binary System ◽  
Emission Line ◽  
Main Sequence ◽  
Stellar Atmosphere ◽  
Optical Spectra ◽  
Large Telescope ◽  
Space Telescope ◽  
Supergiant Star ◽  
First Time

ABSTRACT We report the discovery of a square axisymmetric circumstellar nebula around the emission-line star HD 93795 in the archival Spitzer Space Telescope 24 $\rm{\mu m}$ data. We classify HD 93795 as a B9 Ia star using optical spectra obtained with the Southern African Large Telescope (SALT). A spectral analysis carried out with the stellar atmosphere code fastwind indicates that HD 93795 only recently left the main sequence and is evolving redward for the first time. We discuss possible scenarios for the origin of the nebula and suggest that HD 93795 was originally a binary system and that the nebula was formed because of the merger of the binary components. We also discuss a discrepancy between distance estimates for HD 93795 based on the Gaia data and the possible membership of this star of the Car OB1 association, and conclude that HD 93795 could be at the same distance as Car OB1.

scholarly journals Tomography of cool giant and supergiant star atmospheres

2020 ◽  
Vol 642 ◽  
pp. A235
Author(s):  
Kateryna Kravchenko ◽  
Markus Wittkowski ◽  
Alain Jorissen ◽  
Andrea Chiavassa ◽  
Sophie Van Eck ◽  
...  
Keyword(s):  
Mass Loss ◽  
Stellar Atmosphere ◽  
Asymptotic Giant Branch ◽  
Quantitative Relation ◽  
Dynamical Models ◽  
Disk Model ◽  
Tomographic Method ◽  
Supergiant Star ◽  
Mira Type Stars ◽  
First Time

Context. Asymptotic giant branch (AGB) stars are characterized by substantial mass loss, however the mechanism behind it not yet fully understood. The knowledge of the structure and dynamics of AGB-star atmospheres is crucial to better understanding the mass loss. The recently established tomographic method, which relies on the design of spectral masks containing lines that form in given ranges of optical depths in the stellar atmosphere, is an ideal technique for this purpose. Aims. We aim to validate the capability of the tomographic method in probing different geometrical depths in the stellar atmosphere and recovering the relation between optical and geometrical depth scales. Methods. We applied the tomographic method to high-resolution spectro-interferometric VLTI/AMBER observations of the Mira-type AGB star S Ori. The interferometric visibilities were extracted at wavelengths contributing to the tomographic masks and fitted to those computed from a uniform disk model. This allows us to measure the geometrical extent of the atmospheric layer probed by the corresponding mask. We then compared the observed atmospheric extension with others measured from available 1D pulsation CODEX models and 3D radiative-hydrodynamics CO5BOLD simulations. Results. While the average optical depths probed by the tomographic masks in S Ori decrease (with ⟨log τ0⟩ = −0.45, − 1.45, and − 2.45 from the innermost to the central and outermost layers), the angular diameters of these layers increase, from 10.59 ± 0.09 mas through 11.84 ± 0.17 mas, up to 14.08 ± 0.15 mas. A similar behavior is observed when the tomographic method is applied to 1D and 3D dynamical models. Conclusions. This study derives, for the first time, a quantitative relation between optical and geometrical depth scales when applied to the Mira star S Ori, or to 1D and 3D dynamical models. In the context of Mira-type stars, knowledge of the link between the optical and geometrical depths opens the way to deriving the shock-wave propagation velocity, which cannot be directly observed in these stars.

scholarly journals NLTE spectroscopic analysis of the 3He anomaly in subluminous B-type stars

2018 ◽  
Vol 618 ◽  
pp. A86 ◽  
Author(s):  
D. Schneider ◽  
A. Irrgang ◽  
U. Heber ◽  
M. F. Nieva ◽  
N. Przybilla
Keyword(s):  
Main Sequence ◽  
Spectroscopic Analysis ◽  
Stellar Atmosphere ◽  
Atomic Diffusion ◽  
Horizontal Branch ◽  
Line Profiles ◽  
Main Sequence Stars ◽  
Sdb Stars ◽  
Non Local ◽  
First Time

Several B-type main-sequence stars show chemical peculiarities. A particularly striking class are the 3He stars, which exhibit a remarkable enrichment of 3He with respect to 4He. This isotopic anomaly has also been found in blue horizontal branch (BHB) and subdwarf B (sdB) stars, which are helium-core burning stars of the extreme horizontal branch. Recent surveys uncovered 11 3He sdBs. The 3He anomaly is not due to thermonuclear processes, but caused by atomic diffusion in the stellar atmosphere. Using a hybrid local/non-local thermodynamic equilibrium (LTE/NLTE) approach for B-type stars, we analyzed high-quality spectra of two known 3He BHBs and nine known 3He sdBs to determine their isotopic helium abundances and 4He/3He abundance ratios. We redetermined their atmospheric parameters and analyzed selected He I lines, including λ4922 Å and λ6678 Å, which are very sensitive to 4He/3He. Most of the 3He sdBs cluster in a narrow temperature strip between 26000 K and 30000 K and are helium deficient in accordance with previous LTE analyses. BD+48° 2721 is reclassified as a BHB star because of its low temperature (Teff = 20700 K). Whereas 4He is almost absent (4He/3He < 0.25) in most of the known 3He stars, other sample stars show abundance ratios up to 4He/3He ∼2.51. A search for 3He stars among 26 candidate sdBs from the ESO SPY survey led to the discovery of two new 3He sdB stars (HE 0929–0424 and HE 1047–0436). The observed helium line profiles of all BHBs and of three sdBs are not matched by chemically homogeneous atmospheres, but hint at vertical helium stratification. This phenomenon has been seen in other peculiar B-type stars, but is found for the first time for sdBs. We estimate helium to increase from the outer to the inner atmosphere by factors ranging from 1.4 (SB 290) up to 8.0 (BD+48° 2721).

scholarly journals THE FIRST DETAILED ANALYSIS ON THE ASTROPHYSICAL PROPERTIES OF THE ECCENTRIC BINARY V990 HER

2021 ◽  
Vol 57 (2) ◽  
pp. 363-379
Author(s):  
E. Kiran ◽  
V. Bakiş ◽  
H. Bakiş ◽  
Ö. L. Değirmenci
Keyword(s):  
Binary System ◽  
Detailed Analysis ◽  
Internal Structure ◽  
Orbital Period ◽  
Spectroscopic Data ◽  
Main Sequence ◽  
Physical Parameters ◽  
Apsidal Motion ◽  
Structure Constants ◽  
First Time

We present accurate physical parameters of the eccentric binary system V990 Her which has an orbital period of P=8.193315±0.000003 days using its photometric and spectroscopic data. The physical parameters of the components were derived as Teff1=8000±200 K, Teff2=7570±200 K, M1=2.01±0.07 Mʘ, M2=1.83±0.03 Mʘ, R1=2.22±0.02 Rʘ, R2=2.12±0.01 Rʘ, log(L1/Lʘ)=1.25±0.04, log(L2/Lʘ)=1.12±0.05. Our findings revealed that both components are slightly evolved from the zero-age main sequence with an age of 6.3×108 years. We estimated an apsidal motion with a period of U=14683±2936 years in the system and the internal structure constants of the components were derived for the first time.

scholarly journals Spitzer Observations of M33 & M83 and the Hot Star, Hii Region Connection

2006 ◽  
Vol 2 (S235) ◽  
pp. 328-328
Author(s):  
R. Rubin ◽  
J. Simpson ◽  
S. Colgan ◽  
R. Dufour ◽  
R. Citron ◽  
...  
Keyword(s):  
Emission Line ◽  
Stellar Atmosphere ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Spitzer Space Telescope ◽  
Space Telescope ◽  
Hii Region

AbstractEmission-line observations made with the Spitzer Space Telescope are used to test the predicted ionizing spectral energy distributions of various stellar atmosphere models.

scholarly journals Mass outflow of the X-ray emission line gas in NGC 4151

2020 ◽  
Vol 15 (S359) ◽  
pp. 131-135
Author(s):  
S. B. Kraemer ◽  
T. J. Turner ◽  
D. M. Crenshaw ◽  
H. R. Schmitt ◽  
M. Revalski ◽  
...  
Keyword(s):  
Emission Line ◽  
Total Mass ◽  
High Energy ◽  
Model Parameters ◽  
Zeroth Order ◽  
Space Telescope ◽  
X Ray ◽  
Ngc 4151 ◽  
Outflow Rate ◽  
Mass Outflow

AbstractWe have analyzed Chandra/High Energy Transmission Grating spectra of the X-ray emission line gas in the Seyfert galaxy NGC 4151. The zeroth-order spectral images show extended H- and He-like O and Ne, up to a distance r ˜ 200 pc from the nucleus. Using the 1st-order spectra, we measure an average line velocity ˜230 km s–1, suggesting significant outflow of X-ray gas. We generated Cloudy photoionization models to fit the 1st-order spectra; the fit required three distinct emission-line components. To estimate the total mass of ionized gas (M) and the mass outflow rates, we applied the model parameters to fit the zeroth-order emission-line profiles of Ne IX and Ne X. We determined an M ≍ 5.4 × 105Mʘ. Assuming the same kinematic profile as that for the [O III] gas, derived from our analysis of Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra, the peak X-ray mass outflow rate is approximately 1.8 Mʘ yr–1, at r ˜ 150 pc. The total mass and mass outflow rates are similar to those determined using [O III], implying that the X-ray gas is a major outflow component. However, unlike the optical outflows, the X-ray emitting mass outflow rate does not drop off at r > 100pc, which suggests that it may have a greater impact on the host galaxy.

scholarly journals Resolved Stellar Populations of the interacting galaxies of the M81 group

2016 ◽  
Vol 11 (S321) ◽  
pp. 22-24
Author(s):  
Sakurako Okamoto ◽  
Nobuo Arimoto ◽  
Annette M.N. Ferguson ◽  
Edouard J. Bernard ◽  
Mike J. Irwin ◽  
...  
Keyword(s):  
Main Sequence ◽  
Field Survey ◽  
State Of The Art ◽  
Young Stars ◽  
Interacting Galaxies ◽  
Wide Field ◽  
Red Giant ◽  
Tidal Streams ◽  
Stellar Associations ◽  
First Time

AbstractWe present the results from the state-of-the-art wide-field survey of the M81 galaxy group that we are conducting with Hyper Suprime-Cam on Subaru Telescope. Our photometry reaches about 2 mag below the tip of the red giant branch (RGB) and reveals the spatial distribution of both old and young stars over an area of 5°2around the M81. The young main-sequence (MS) stars closely follow the HI distribution and can be found in a stellar stream between M81 and NGC 3077 and in numerous outlying stellar associations. Our survey also reveals for the first time the very extended (>2 × R25) halos of RGB stars around M81, M82, and NGC 3077, as well as faint tidal streams that link these systems. The gravitational interactions between M81, M82 and NGC 3077 galaxies induced star formation in tidally stripped gas, and also significantly perturbed the older stellar components leading to disturbed halo morphologies.

scholarly journals Doppler Tomography in 2D and 3D of the X-ray Binary Cyg X-1 for June 2007

2011 ◽  
Vol 7 (S282) ◽  
pp. 201-202 ◽  
Author(s):  
O. I. Sharova ◽  
M. I. Agafonov ◽  
E. A. Karitskaya ◽  
N. G. Bochkarev ◽  
S. V. Zharikov ◽  
...  
Keyword(s):  
Binary System ◽  
Spectral Data ◽  
Inclination Angle ◽  
Tomographic Reconstruction ◽  
Orbital Plane ◽  
National Observatory ◽  
Doppler Tomography ◽  
X Ray ◽  
2D And 3D ◽  
First Time

AbstractThe 2D and 3D Doppler tomograms of X-ray binary system Cyg X-1 (V1357 Cyg) were reconstructed from spectral data for the line HeII 4686Å obtained with 2-m telescope of the Peak Terskol Observatory (Russia) and 2.1-m telescope of the Mexican National Observatory in June, 2007. Information about gas motions outside the orbital plane, using all of the three velocity components Vx, Vy, Vz, was obtained for the first time. The tomographic reconstruction was carried out for the system inclination angle of 45°. The equal resolution (50 × 50 × 50 km/s) is realized in this case, in the orbital plane (Vx, Vy) and also in the perpendicular direction Vz. The checkout tomograms were realized also for the inclination angle of 40° because of the angle uncertainty. Two versions of the result showed no qualitative discrepancy. Details of the structures revealed by the 3D Doppler tomogram were analyzed.

scholarly journals A Possible Third Component in the L Dwarf Binary System DENIS-P J020529.0-115925 Discovered with theHubble Space Telescope

2005 ◽  
Vol 129 (1) ◽  
pp. 511-517 ◽  
Author(s):  
H. Bouy ◽  
E. L. Martín ◽  
W. Brandner ◽  
J. Bouvier
Keyword(s):  
Binary System ◽  
Space Telescope

scholarly journals The habitable zone of Kepler-16: impact of binarity and climate models

2018 ◽  
Vol 18 (1) ◽  
pp. 79-89 ◽  
Author(s):  
S. Y. Moorman ◽  
B. L. Quarles ◽  
Zh. Wang ◽  
M. Cuntz
Keyword(s):  
Binary System ◽  
Main Sequence ◽  
Climate Models ◽  
Main Sequence Star ◽  
Habitable Zone ◽  
Lagrangian Points ◽  
The Earth ◽  
Stable Solutions

AbstractWe continue to investigate the binary system Kepler-16, consisting of a K-type main-sequence star, a red dwarf and a circumbinary Saturnian planet. As part of our study, we describe the system's habitable zone based on different climate models. We also report on stability investigations for possible Earth-mass Trojans while expanding a previous study by B. L. Quarles and collaborators given in 2012. For the climate models, we carefully consider the relevance of the system's parameters. Furthermore, we pursue new stability simulations for the Earth-mass objects starting along the orbit of Kepler-16b. The eccentricity distribution as obtained prefers values close to circular, whereas the inclination distribution remains flat. The stable solutions are distributed near the co-orbital Lagrangian points, thus enhancing the plausibility that Earth-mass Trojans might be able to exist in the Kepler-16(AB) system.

scholarly journals Eclipsing spotted giant star with K2 and historical photometry

2018 ◽  
Vol 620 ◽  
pp. A189 ◽  
Author(s):  
K. Oláh ◽  
S. Rappaport ◽  
T. Borkovits ◽  
T. Jacobs ◽  
D. Latham ◽  
...  
Keyword(s):  
Binary System ◽  
Main Sequence ◽  
Rapid Evolution ◽  
Magnetic Activity ◽  
Primary Component ◽  
Physical Parameters ◽  
Giant Star ◽  
Eclipsing Binary ◽  
Giant Stars ◽  
Active Stars

Context. Stars can maintain their observable magnetic activity from the pre-main sequence (PMS) to the tip of the red giant branch. However, the number of known active giants is much lower than active stars on the main sequence (MS) since the stars spend only about 10% of their MS lifetime on the giant branch. Due to their rapid evolution it is difficult to estimate the stellar parameters of giant stars. A possibility for obtaining more reliable stellar parameters for an active giant arises when it is a member of an eclipsing binary system. Aims. We have discovered EPIC 211759736, an active spotted giant star in an eclipsing binary system during the Kepler K2 Campaign 5. The eclipsing nature allows us to much better constrain the stellar parameters than in most cases of active giant stars. Methods. We have combined the K2 data with archival HATNet, ASAS, and DASCH photometry, new spectroscopic radial velocity measurements, and a set of follow-up ground-based BVRCIC photometric observations, to find the binary system parameters as well as robust spot models for the giant at two different epochs. Results. We determined the physical parameters of both stellar components and provide a description of the rotational and long-term activity of the primary component. The temperatures and luminosities of both components were examined in the context of the Hertzsprung–Russell diagram. We find that both the primary and the secondary components deviate from the evolutionary tracks corresponding to their masses in the sense that the stars appear in the diagram at lower masses than their true masses. Conclusions. We further evaluate the proposition that traditional methods generally result in higher masses for active giants than what is indicated by stellar evolution tracks in the HR diagram. A possible reason for this discrepancy could be a strong magnetic field, since we see greater differences in more active stars.

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