scholarly journals Signatures of pulsations and mass loss in the spectra of post-AGB stars

2011 ◽  
Vol 7 (S283) ◽  
pp. 526-527
Author(s):  
Laimons Začs ◽  
Julius Sperauskas ◽  
Aija Laure ◽  
Olesja Smirnova
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Mass Loss ◽  
Radial Velocity ◽  
High Resolution Spectroscopy ◽  
Agb Stars ◽  
Atomic Lines ◽  
Mass Ejection

AbstractThe results of high-resolution spectroscopy and radial velocity monitoringa are presented for selected post-AGB candidate stars. Time series of high-resolution spectra for HD235858 shows spliting of low-excitation atomic lines and significant changes in the intensity of C2 and CN lines originated in the extended atmosphere significantly affected by pulsations and outflow. Mass ejection was confirmed for cool R CrB candidate stars DY Per, V1983 Cyg, and V2074 Cyg.

scholarly journals The runaway supergiant HD 188209 (O9.5Iab): a binary or a pulsating star?

1999 ◽  
Vol 193 ◽  
pp. 69-70
Author(s):  
Garik Israelian ◽  
Artemio Herrero ◽  
E. Santolaya-Rey ◽  
A. Kaufer ◽  
F. Musaev ◽  
...  
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Mass Loss ◽  
Radial Velocity ◽  
Loss Rate ◽  
State Of The Art ◽  
Mass Loss Rate ◽  
Fundamental Parameters ◽  
Binary Nature ◽  
Period 2

We report radial velocity studies of photospheric absorption lines from spectral time series of the late O-type runaway supergiant HD 188209. Radial velocity variations with a quasi-period ∼ 2 days have been detected in high-resolution echelle spectra and most probably indicate that the supergiant is pulsating. Night-to-night variations in the position and strength of the central emission reversal of the Hα profile have been observed. The fundamental parameters of the star have been derived using state-of-the-art plane-parallel and unified non-LTE model atmospheres, these last including the mass-loss rate. The binary nature of this star is not suggested either from Hipparcos photometry or from radial-velocity curves.

scholarly journals The Structure of the HH39 Region

1987 ◽  
Vol 115 ◽  
pp. 340-341
Author(s):  
J. R. Walsh
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Proper Motion ◽  
High Velocity ◽  
Velocity Structure ◽  
The Other ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Bow Shocks ◽  
Hh Objects

HH39 is the group of Herbig-Haro (HH) objects associated with the young semi-stellar object R Monocerotis (R Mon) and the variable reflection nebula NGC 2261. An R CCD frame and a B prime focus plate of the region show a filament connecting NGC 2261 with HH39, confirming the association between R Mon and the HH objects. This filament is probably composed of emission material. The southern knot in HH39 has brightened over the last 20 years; its proper motion has been determined and is similar to that of the other knots. A total of 8 knots can be distinguished in HH39 surrounded by diffuse nebulosity. High resolution spectroscopy of the Hα and [N II] emission lines shows the spatial variation of the radial velocity structure over the largest knots (HH39 A and C). Distinct differences in excitation and velocity structure between the knots are apparent. The observations are compatible with the knots being high velocity ejecta from R Mon, decelerated by interaction with ambient material and with bow shocks on their front surfaces.

scholarly journals A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band

2020 ◽  
Vol 494 (1) ◽  
pp. 108-119 ◽  
Author(s):  
Rebecca K Webb ◽  
Matteo Brogi ◽  
Siddharth Gandhi ◽  
Michael R Line ◽  
Jayne L Birkby ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Semimajor Axis ◽  
Spectral Lines ◽  
Lapse Rate ◽  
High Spectral Resolution ◽  
High Resolution Spectroscopy ◽  
Spectral Signature ◽  
Orbital Inclination ◽  
L Band

ABSTRACT High-resolution spectroscopy ($R\, \geqslant \, 20\, 000$) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES ($R=100\, 000$) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 ${\mu {m}}$. We observe a weak (3.0σ, or S/N = 4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K band, we measure a detection significance of 8.4 σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken 3 yr apart, this points to the absence of strong radial-velocity anomalies due, e.g. to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of KP = (145.2 ± 2.0) km s−1 (1σ) and improve the error bars on this parameter by ∼70 per cent. However, we only marginally tighten constraints on orbital inclination ($66.2^{+3.7}_{-3.1}$ deg) and planet mass ($0.963^{+0.036}_{-0.031}$ Jupiter masses), due to the dominant uncertainties of stellar mass and semimajor axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterization via high-resolution spectroscopy.

scholarly journals Transiting exocomets detected in broadband light by TESS in the β Pictoris system

2019 ◽  
Vol 625 ◽  
pp. L13 ◽  
Author(s):  
S. Zieba ◽  
K. Zwintz ◽  
M. A. Kenworthy ◽  
G. M. Kennedy
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Light Curve ◽  
Frequency Analysis ◽  
Photometric Data ◽  
High Resolution Spectroscopy

Aims. We search for signs of falling evaporating bodies (FEBs, also known as exocomets) in photometric time series obtained for β Pictoris after fitting and removing its δ Scuti-type pulsation frequencies. Methods. Using photometric data obtained by the TESS satellite we determined the pulsational properties of the exoplanet host star β Pictoris through frequency analysis. We then pre-whitened the 54 identified δ Scuti p-modes and investigated the residual photometric time series for the presence of FEBs. Results. We identify three distinct dipping events in the light curve of β Pictoris over a 105-day period. These dips have depths from 0.5 to 2 millimagnitudes and durations of up to 2 days for the largest dip. These dips are asymmetric in nature and are consistent with a model of an evaporating comet with an extended tail crossing the disc of the star Conclusions. We present the first broadband detections of exocomets crossing the disc of β Pictoris, complementing the predictions made 20 years earlier by Lecavelier Des Etangs et al. (1999, A&A, 343, 916). No periodic transits are seen in this time series. These observations confirm the spectroscopic detection of exocomets in calcium H and K lines that have been seen in high resolution spectroscopy.

scholarly journals High-Resolution Radial Velocity and Hα Study of Proto-Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 354-354 ◽  
Author(s):  
B.J. Hrivnak ◽  
A.W. Woodsworth
Keyword(s):  
High Resolution ◽  
Physical Properties ◽  
Radial Velocity ◽  
Planetary Nebulae ◽  
Agb Stars ◽  
Binary Nature ◽  
Circumstellar Shells

We are engaged in a program to monitor radial velocity variability in proto-planetary nebulae (PPN). Observations are being made with the radial velocity spectrometer at the DAO, with a precision of ±0.5 km s−1. Radial velocity variability can arise from binary motion and/or pulsation in these post-AGB stars. The demonstration of a binary nature for some of these objects can have important implications for the understanding of their physical properties, and for the shaping of their circumstellar shells.

scholarly journals Results from six multiwavelength campaigns to study short-term FUV flux variability and phase-dependent mass loss in Be stars

1994 ◽  
Vol 162 ◽  
pp. 284-286
Author(s):  
Geraldine J. Peters
Keyword(s):  
High Resolution ◽  
Mass Loss ◽  
High Resolution Spectroscopy ◽  
Be Stars ◽  
Short Term ◽  
The Past ◽  
Flux Variability ◽  
Optical Region ◽  
Dependent Mass

During the past six years we have carried through seven multiwavelength, multisite campaigns to investigate the cause for short-term (rapid) photometric and spectroscopic variability in Be stars and assess its importance in driving the mass loss in these objects. These campaigns usually included simultaneous observations in the UV with the IUE and Voyager spacecraft and optical region with ground-based telescopes worldwide (photometry, high resolution spectroscopy, and polarimetry). Typically 10–25 observers from 5–9 countries participated. Stars that have been observed include λ Eri, ω Ori, o And, ∊ Cap, 28 Cyg, η Cen, 48 Lib, ζ Tau, ψ Per, and 2 Vul. We briefly summarize some of the results from the UV study here. Additional results from the ground-based data are given in other papers in this volume by D. Gies, M. Hahula, J. Percy, and D. McDavid.

The role of AGB stars in the evolution of globular clusters

2018 ◽  
Vol 14 (S343) ◽  
pp. 291-300
Author(s):  
Paolo Ventura ◽  
Franca D’Antona ◽  
Marcella Di Criscienzo ◽  
Flavia Dell’Agli ◽  
Marco Tailo
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Globular Clusters ◽  
State Of The Art ◽  
High Resolution Spectroscopy ◽  
Agb Stars ◽  
Light Elements ◽  
Original Population ◽  
Traditional Paradigm

AbstractThe results from high-resolution spectroscopy and accurate photometry have challenged the traditional paradigm that stars in globular clusters (GC) are simple stellar populations, rather suggesting that these structures harbor distinct groups of stars, differing in the chemical composition, particularly in the abundances of the light elements, from helium to silicon. Because this behavior is not shared by field stars, it is generally believed that some self-enrichment mechanism must have acted in GC, such that new stellar generations formed from the ashes of stars belonging to the original population. In this review, after presenting the state-of-the-art of the observations of GC stars, we discuss the possibility that the pollution of the intra-cluster medium was provided by the winds of AGB stars of initial mass above ∼3 M⊙. These objects evolve with time scales of 40 − 100 Myr and contaminate their surroundings with gas processed by p-capture nucleosynthesis, in agreement with the chemical patterns traced by GC stars.

scholarly journals Radial velocity follow-up for confirmation and characterization of transiting exoplanets

2008 ◽  
Vol 4 (S253) ◽  
pp. 129-139 ◽  
Author(s):  
François Bouchy ◽  
Claire Moutou ◽  
Didier Queloz ◽  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Space Mission ◽  
High Resolution Spectroscopy

AbstractRadial Velocity follow-up is essential to establish or exclude the planetary nature of a transiting companion as well as to accurately determine its mass. Here we present some elements of an efficient Doppler follow-up strategy, based on high-resolution spectroscopy, devoted to the characterization of transiting candidates. Some aspects and results of the radial velocity follow-up of the CoRoT space mission are presented in order to illustrate the strategy used to deal with the zoo of transiting candidates.

scholarly journals Transit Search for Exoplanets with the Vulcan Camera

2004 ◽  
Vol 202 ◽  
pp. 69-71
Author(s):  
Douglas A. Caldwell ◽  
W. J. Borucki ◽  
J. M. Jenkins ◽  
D. G. Koch ◽  
L. Webster ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Data Reduction ◽  
Extrasolar Planets ◽  
Galactic Plane ◽  
Variable Stars ◽  
Current Data ◽  
Eclipsing Binaries ◽  
High Resolution Spectroscopy ◽  
Nasa Ames Research

The NASA Ames Research Center's Vulcan photometer is being used in a search for close–in giant extrasolar planets. With our current data reduction system we achieve 0.2–0.8% hour–to–hour relative photometric precision on ∽ 6000 stars brighter than 13th magnitude. Three Galactic-plane fields have so far yielded hundreds of variable stars, including ∽ 50 eclipsing or interacting binaries per field. Several candidate detections have been followed up with radial velocity observations. High-resolution spectroscopy revealed many of the strongest candidates to be grazing eclipsing binaries.

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