scholarly journals Long-term photospheric instabilities and envelopes dynamics in the post-AGB binary system 89 Herculis

2020 ◽  
Vol 500 (1) ◽  
pp. 926-941
Author(s):  
M Gangi ◽  
M Giarrusso ◽  
M Munari ◽  
C Ferrara ◽  
C Scalia ◽  
...  
Keyword(s):  
High Resolution ◽  
Binary System ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
High Resolution Spectroscopy ◽  
Time Interval ◽  
Radial Velocity Curve ◽  
Morphological Variations ◽  
Upper Level

ABSTRACT We present a long-term optical spectroscopic study of the post-asymptotic giant branch (AGB) binary system 89 Herculis, with the aim to characterize the relationship between photospheric instabilities and dynamics in the close circumstellar environment of the system. This study is based on spectra acquired with the high-resolution Catania Astrophysical Observatory Spectropolarimeter and archive data, covering a time interval between 1978 and 2018. We find long-term changes in the radial velocity curve of the system, occurring mostly in amplitude, which correlate with the variability observed in the blueshifted absorption component of the P Cygni-like H α profile. Two possible scenarios are discussed. We also find strong splitting in the s-process elements of Ba ii 6141.713- and 6496.898-Å  lines, with short-term morphological variations. A Gaussian decomposition of such profiles allows us to distinguish four shell components, two expanding and two infalling toward the central star, which are subject to the orbital motion of the system and are not affected by the long-term instabilities. Finally, we find that the numerous metal lines in emission could originate in regions of a structured circumbinary disc that have sizes proportional to the energy of the corresponding upper level transition Eup. This study demonstrates the potential of long-term high-resolution spectroscopy in linking together the instability processes occurring during the late evolutionary stages of post-AGBs and the subsequent phase of PNe.

scholarly journals GIARPS High-resolution Observations of T Tauri stars (GHOsT)

2020 ◽  
Vol 643 ◽  
pp. A32
Author(s):  
M. Gangi ◽  
B. Nisini ◽  
S. Antoniucci ◽  
T. Giannini ◽  
K. Biazzo ◽  
...  
Keyword(s):  
High Resolution ◽  
Complex Structure ◽  
Central Star ◽  
T Tauri Stars ◽  
Resolving Power ◽  
High Resolution Spectroscopy ◽  
Young Stellar Objects ◽  
Clear Correlation ◽  
Low Velocity ◽  
T Tauri

Context. Disk winds play a fundamental role in the evolution of protoplanetary systems. The complex structure and dynamics can be investigated through the emission of atomic and molecular lines detected in high-resolution optical/IR spectra of young stellar objects. Despite their great importance, however, studies connecting the atomic and molecular components are lacking so far. Aims. In the framework of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, we aim to characterize the atomic and molecular winds in a sample of classical T Tauri stars (CTTs) of the Taurus-Auriga region, focusing on a statistical analysis of the kinematic properties of the [O I] 630 nm and H2 2.12 μm lines and their mutual relationship. Methods. We analyzed the flux calibrated [O I] 630 nm and H2 2.12 μm lines in a sample of 36 CTTs observed at the Telescopio Nazionale Galileo with the HARPS-N spectrograph (resolving power of R = 115 000) and with the GIANO spectrograph (R = 50 000). We decomposed the line profiles into different kinematic Gaussian components and focused on the most frequently detected component, the narrow low-velocity (vp < 20 km s−1) component (NLVC). Results. We found that the H2 line is detected in 17 sources (~50% detection rate), and [O I] is detected in all sources but one. The NLV components of the H2 and [O I] emission are kinematically linked, with a strong correlation between the peak velocities and the full widths at half maximum of the two lines. Assuming that the line width is dominated by Keplerian broadening, we found that the [O I] NVLC originates from a disk region between 0.05 and 20 au and that of H2 in a region from 2 and 20 au. We also found that H2 is never detected in sources where [O I] originates in regions below 1 au, as well as in sources of early (~F-G) spectral type with a luminosity >1 L⊙. Moreover, in seven sources, both H2 and [O I] have clear blueshifted peaks and prominent [O I] high-velocity components. These components have also been detected in sources with no relevant centroid shift. Finally, we did not find any clear correlation between vp of the H2 and [O I] NVLC and the outer disk inclination. This result is in line with previous studies. Conclusions. Our results suggest that molecular and neutral atomic emission in disk winds originate from regions that might overlap, and that the survival of molecular winds in disks strongly depends on the gas exposure to the radiation from the central star. The presence of jets does not necessarily affect the kinematics of the low-velocity winds. Our results demonstrate the potential of wide-band high-resolution spectroscopy in linking tracers of different manifestations of the same phenomenon.

scholarly journals High-resolution spectroscopy of two LBV cycles of HR Car

2003 ◽  
Vol 212 ◽  
pp. 243-244 ◽  
Author(s):  
Thomas Szeifert ◽  
Andreas Kaufer ◽  
Paul A. Crowther ◽  
Otmar Stahl ◽  
Chris Sterken
Keyword(s):  
High Resolution ◽  
Stellar Wind ◽  
Optical Spectra ◽  
High Resolution Spectroscopy ◽  
Luminous Blue Variables ◽  
Wide Part ◽  
Spectroscopic Monitoring ◽  
Wind Characteristics ◽  
Long Timescales

Luminous Blue Variables (LBVs or S Dor Variables) are showing characteristic variability of very long timescales of a decade and more. During their expansion and contraction phases, they move across a wide part of the H-R diagram with dramatic changes of their stellar wind characteristics, radius and temperature. We present results of our long-term spectroscopic monitoring campaigns for the galactic star HR Car with optical spectra taken over 13 years and two minimum and maximum phases observed during this time.

scholarly journals High-Resolution Spectroscopy of the Planetary Nebulae PM 1–242, PM 1–318 and PM 1–322

2010 ◽  
Vol 27 (2) ◽  
pp. 199-202 ◽  
Author(s):  
L. F. Miranda ◽  
R. Vázquez ◽  
M. A. Guerrero ◽  
C. B. Pereira ◽  
E. Iñiguez-Garín
Keyword(s):  
High Resolution ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Brightness Distribution ◽  
Physical Structure ◽  
High Resolution Spectroscopy

AbstractWe have recently confirmed the planetary nebula (PN) nature of PM 1–242, PM 1–318 and PM 1–322. Here we present high-resolution long-slit spectra of these three PNe in order to analyze their internal kinematics and to investigate their physical structure. PM 1–242 is a tilted ring and not an elliptical PN as suggested by direct images. The object is probably related to ring-like PNe and shows an unusual pointsymmetric brightness distribution in the ring. PM 1–318 is a pole-on elliptical PN, instead of a circular one as suggested by direct images. PM 1–322 is spatially unresolved and its spectrum shows large differences between the forbidden lines and Hα profiles, with the latter showing a double-peaked profile and relatively extended wings (FWZI ~325 km s−1). These properties are found in other PNe that are suspected to host a symbiotic central star.

scholarly journals Full orbital solution for the binary system in the northern Galactic disc microlensing event Gaia16aye

2020 ◽  
Vol 633 ◽  
pp. A98 ◽  
Author(s):  
Ł. Wyrzykowski ◽  
P. Mróz ◽  
K. A. Rybicki ◽  
M. Gromadzki ◽  
Z. Kołaczkowski ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Mass Function ◽  
Space Mission ◽  
Galactic Disc ◽  
Radial Velocity Curve ◽  
Orbital Parameters ◽  
Data Points ◽  
Binary Orbit

Gaia16aye was a binary microlensing event discovered in the direction towards the northern Galactic disc and was one of the first microlensing events detected and alerted to by the Gaia space mission. Its light curve exhibited five distinct brightening episodes, reaching up to I = 12 mag, and it was covered in great detail with almost 25 000 data points gathered by a network of telescopes. We present the photometric and spectroscopic follow-up covering 500 days of the event evolution. We employed a full Keplerian binary orbit microlensing model combined with the motion of Earth and Gaia around the Sun to reproduce the complex light curve. The photometric data allowed us to solve the microlensing event entirely and to derive the complete and unique set of orbital parameters of the binary lensing system. We also report on the detection of the first-ever microlensing space-parallax between the Earth and Gaia located at L2. The properties of the binary system were derived from microlensing parameters, and we found that the system is composed of two main-sequence stars with masses 0.57 ± 0.05 M⊙ and 0.36 ± 0.03 M⊙ at 780 pc, with an orbital period of 2.88 years and an eccentricity of 0.30. We also predict the astrometric microlensing signal for this binary lens as it will be seen by Gaia as well as the radial velocity curve for the binary system. Events such as Gaia16aye indicate the potential for the microlensing method of probing the mass function of dark objects, including black holes, in directions other than that of the Galactic bulge. This case also emphasises the importance of long-term time-domain coordinated observations that can be made with a network of heterogeneous telescopes.

scholarly journals Low-frequency photospheric and wind variability in the early-B supergiant HD 2905

2018 ◽  
Vol 612 ◽  
pp. A40 ◽  
Author(s):  
S. Simón-Díaz ◽  
C. Aerts ◽  
M. A. Urbaneja ◽  
I. Camacho ◽  
V. Antoci ◽  
...  
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
High Performance ◽  
Low Frequency ◽  
High Resolution Spectroscopy ◽  
Photometric Variability ◽  
Wind Variability ◽  
Short Period ◽  
Convective Motions

Context. Despite important advances in space asteroseismology during the last decade, the early phases of evolution of stars with masses above ~15 M⊙ (including the O stars and their evolved descendants, the B supergiants) have been only vaguely explored up to now. This is due to the lack of adequate observations for a proper characterization of the complex spectroscopic and photometric variability occurring in these stars. Aim. Our goal is to detect, analyze, and interpret variability in the early-B-type supergiant HD 2905 (κ Cas, B1 Ia) using long-term, ground-based, high-resolution spectroscopy. Methods. We gather a total of 1141 high-resolution spectra covering some 2900 days with three different high-performance spectrographs attached to 1–2.6m telescopes at the Canary Islands observatories. We complement these observations with the hipparcos light curve, which includes 160 data points obtained during a time span of ~1200 days. We investigate spectroscopic variability of up to 12 diagnostic lines by using the zero and first moments of the line profiles. We perform a frequency analysis of both the spectroscopic and photometric dataset using Scargle periodograms. We obtain single snapshot and time-dependent information about the stellar parameters and abundances by means of the FASTWIND stellar atmosphere code. Results. HD 2905 is a spectroscopic variable with peak-to-peak amplitudes in the zero and first moments of the photospheric lines of up to 15% and 30 km s−1, respectively. The amplitude of the line-profile variability is correlated with the line formation depth in the photosphere and wind. All investigated lines present complex temporal behavior indicative of multi-periodic variability with timescales of a few days to several weeks. No short-period (hourly) variations are detected. The Scargle periodograms of the hipparcos light curve and the first moment of purely photospheric lines reveal a low-frequency amplitude excess and a clear dominant frequency at ~0.37 d−1. In the spectroscopy, several additional frequencies are present in the range 0.1–0.4 d−1. These may be associated with heat-driven gravity modes, convectively driven gravity waves, or sub-surface convective motions. Additional frequencies are detected below 0.1 d−1. In the particular case of Hα, these are produced by rotational modulation of a non-spherically symmetric stellar wind. Conclusions. Combined long-term uninterrupted space photometry with high-precision spectroscopy is the best strategy to unravel the complex low-frequency photospheric and wind variability of B supergiants. Three-dimensional (3D) simulations of waves and of convective motions in the sub-surface layers can shed light on a unique interpretation of the variability.

scholarly journals High-resolution spectroscopy of globular cluster post-Asymptotic Giant Branch stars

2004 ◽  
Vol 419 (3) ◽  
pp. 1123-1132 ◽  
Author(s):  
C. J. Mooney ◽  
W. R. J. Rolleston ◽  
F. P. Keenan ◽  
P. L. Dufton ◽  
J. V. Smoker ◽  
...  
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Asymptotic Giant Branch ◽  
High Resolution Spectroscopy ◽  
Asymptotic Giant Branch Stars ◽  
Giant Branch Stars

scholarly journals Long-term multicolour photometry and high-resolution spectroscopy of the two $\gamma\,$Doradus stars HD 12901 and HD 48501

2004 ◽  
Vol 415 (3) ◽  
pp. 1079-1088 ◽  
Author(s):  
C. Aerts ◽  
J. Cuypers ◽  
P. De Cat ◽  
M. A. Dupret ◽  
J. De Ridder ◽  
...  
Keyword(s):  
High Resolution ◽  
High Resolution Spectroscopy

scholarly journals The quest for magnetic massive stars in the Magellanic Clouds

2016 ◽  
Vol 12 (S329) ◽  
pp. 430-430
Author(s):  
Y. Nazé ◽  
S. Bagnulo ◽  
N. R. Walborn ◽  
N. Morrell ◽  
G. A. Wade ◽  
...  
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
High Resolution Spectroscopy ◽  
X Ray ◽  
Low Metallicity

AbstractThe Of?p category was introduced more than 40 years ago to gather several Galactic stars with some odd properties. Since 2000, spectropolarimetry, high-resolution spectroscopy, long-term photometry, and X-ray observations have revealed their nature: magnetic oblique rotators - they all have magnetic fields that confine their winds. Several Of?p stars have now been detected in the Magellanic Clouds, likely the prototypes of magnetic massive stars at low metallicity. This contribution will present the most recent photometric, spectroscopic, and spectropolarimetric data, along with the first modeling of these objects.

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