scholarly journals High Resolution Spectroscopy As a Tool for Luminosity Calibration

2002 ◽  
Vol 12 ◽  
pp. 676-679
Author(s):  
Ruth C. Peterson
Keyword(s):  
High Resolution ◽  
Reasonable Agreement ◽  
Empirical Relationship ◽  
Model Atmosphere ◽  
Stellar Mass ◽  
Physical Basis ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Chromospheric Emission ◽  
Advance Knowledge

AbstractRecent results are reviewed for two methods of luminosity calibration based on high-resolution spectroscopy. The first relies onTeff/loggdeterminations from model-atmosphere analyses based on high-resolution spectra. This method is physically well founded but operationally demanding, and requires advance knowledge of stellar mass. The second, W-B, stems from the empirical relationship between luminosity and the width of chromospheric emission lines first established by Wilson and Bappu. Its physical basis is only partially understood, however, and the calibration depends on stellar metallicity and on the choice of lines.BothTeff/loggand W-B easily distinguish cool dwarfs from cool giants. Generally reasonable agreement is found between distances derived from Hipparcos parallaxes and those inferred from the loggvalues derived for nearby dwarfs with relatively well-known Hipparcos parallaxes, σ(π)/π < 0.2. Constraining Hipparcos parallaxes star-by-star is not possible at present. Improvements are suggested for both approaches.

scholarly journals High-resolution spectroscopy of the high-velocity hot post-AGB star IRAS 18379–1707 (LS 5112)

2019 ◽  
Vol 491 (4) ◽  
pp. 4829-4842 ◽  
Author(s):  
N P Ikonnikova ◽  
M Parthasarathy ◽  
A V Dodin ◽  
S Hubrig ◽  
G Sarkar
Keyword(s):  
High Resolution ◽  
Model Atmosphere ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Atmospheric Parameters ◽  
Optical Counterpart ◽  
Chemical Abundances ◽  
Balmer Lines ◽  
Cno Abundances ◽  
First Time

ABSTRACT The high-resolution ($R\sim 48\, 000$) optical spectrum of the B-type supergiant LS 5112, identified as the optical counterpart of the post-AGB candidate IRAS 18379–1707 is analysed. We report the detailed identifications of the observed absorption and emission features in the wavelength range 3700–9200 Å for the first time. The absorption line spectrum has been analysed using non-LTE model atmosphere techniques to determine stellar atmospheric parameters and chemical composition. We estimate Teff = 18 000 ± 1000 K, log g = 2.25 ± 0.08, ξt = 10 ± 4 km s−1, and vsin i = 37 ± 6 km s−1, and the derived abundances indicate a metal-deficient ([M/H] ≈ −0.6) post-AGB star. Chemical abundances of eight different elements were obtained. The estimates of the CNO abundances in IRAS 18379–1707 indicate that these elements are overabundant with [(C + N + O)/S] = + 0.5 ± 0.2 suggesting that the products of helium burning have been brought to the surface as a result of third dredge-up on the AGB. From the absorption lines, we derived heliocentric radial velocity of Vr = −124.0 ± 0.4 km s−1. We have identified permitted emission lines of O i, N i, Na i, S ii, Si ii, C ii, Mg ii, and Fe iii. The nebula forbidden lines of [N i], [O i], [Fe ii], [N ii], [S ii], [Ni ii], and [Cr ii] have also been identified. The Balmer lines H α, H β, and H γ show P-Cygni behaviour clearly indicating post-AGB mass-loss process in the object with the wind velocity up to 170 km s−1.

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 Exploring the stellar properties of M dwarfs with high-resolution spectroscopy from the optical to the near-infrared

2018 ◽  
Vol 620 ◽  
pp. A180 ◽  
Author(s):  
A. S. Rajpurohit ◽  
F. Allard ◽  
S. Rajpurohit ◽  
R. Sharma ◽  
G. D. C. Teixeira ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Spectral Synthesis ◽  
Model Atmosphere ◽  
High Resolution Spectroscopy ◽  
Cloud Formation ◽  
M Dwarfs ◽  
Near Infrared Spectra ◽  
The Galaxy ◽  
Stellar Properties

Context. Being the most numerous and oldest stars in the galaxy, M dwarfs are objects of great interest for exoplanet searches. The presence of molecules in their atmosphere complicates our understanding of their atmospheric properties. But great advances have recently been made in the modeling of M dwarfs due to the revision of solar abundances. Aims. We aim to determine stellar parameters of M dwarfs using high resolution spectra (R ∼ 90 000) simultaneously in the visible and the near-infrared. The high resolution spectra and broad wavelength coverage provide an unique opportunity to understand the onset of dust and cloud formation at cool temperatures. Furthermore, this study will help in understanding the physical processes which occur in a cool atmospheres, particularly, the redistribution of energy from the optical to the near-infrared. Methods. The stellar parameters of M dwarfs in our sample have been determined by comparing the high resolution spectra both in the optical and in the near-infrared simultaneously observed by CARMENES with the synthetic spectra obtained from the BT-Settl model atmosphere. The detailed spectral synthesis of these observed spectra both in the optical and in the near-infrared helps to understand the missing continuum opacity. Results. For the first time, we derive fundamental stellar parameters of M dwarfs using the high resolution optical and near-infrared spectra simultaneously. We determine Teff, log g and [M/H] for 292 M dwarfs of spectral type M0 to M9, where the formation of dust and clouds are important. The derived Teff for the sample ranges from 2300 to 4000 K, values of log g ranges from 4.5 ≤ logg ≤ 5.5 and the resulting metallicity ranges from −0.5 ≤ [M/H] ≤ +0.5. We have also explored the possible differences in Teff, log g and [M/H] by comparing them with other studies of the same sample of M dwarfs.

scholarly journals New Chandra/HST-STIS Results on Seyfert I AGN: Photoionized Outflows

2003 ◽  
Vol 214 ◽  
pp. 259-264
Author(s):  
Barry McKernan ◽  
Tahir Yaqoob
Keyword(s):  
High Resolution ◽  
Column Density ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Type I ◽  
Ionization State ◽  
X Ray ◽  
Spectral Signatures

We present soft X-ray results from observations with Chandra (HETGS) of the Seyfert I AGN NGC 4593 and Mrk 509. We discuss the photoionized outflows associated with Seyfert I AGN in terms of their absorption spectral signatures and discuss their kinematics, column density and ionization state. We discuss the link between UV and X-ray absorbers in Mrk 509 (which was simultaneously observed with Chandra and HST-STIS). We also briefly discuss the possibility of absorption due to neutral Fe embedded in the warm absorber of NGC 4593 versus an interpretation of the data in terms of soft X-ray relativistic emission lines. We conclude with a summary of what is being learnt about warm absorbers in type I AGN from high resolution spectroscopy.

scholarly journals Hidden in Plain Sight: A double-lined White Dwarf Binary 26 pc away and a Distant Cousin

2021 ◽  
Author(s):  
Mukremin Kilic ◽  
A Bédard ◽  
P Bergeron
Keyword(s):  
High Resolution ◽  
Orbital Period ◽  
White Dwarf ◽  
White Dwarfs ◽  
Model Atmosphere ◽  
High Resolution Spectroscopy ◽  
Low Mass ◽  
Orbital Periods ◽  
Velocity Changes ◽  
Cool White Dwarfs

Abstract We present high-resolution spectroscopy of two nearby white dwarfs with inconsistent spectroscopic and parallax distances. The first one, PG 1632+177, is a 13th magnitude white dwarf only 25.6 pc away. Previous spectroscopic observations failed to detect any radial velocity changes in this star. Here, we show that PG 1632+177 is a 2.05 d period double-lined spectroscopic binary (SB2) containing a low-mass He-core white dwarf with a more-massive, likely CO-core white dwarf companion. After L 870-2, PG 1632+177 becomes the second closest SB2 white dwarf currently known. Our second target, WD 1534+503, is also an SB2 system with an orbital period of 0.71 d. For each system, we constrain the atmospheric parameters of both components through a composite model-atmosphere analysis. We also present a new set of NLTE synthetic spectra appropriate for modeling high-resolution observations of cool white dwarfs, and show that NLTE effects in the core of the Hα line increase with decreasing effective temperature. We discuss the orbital period and mass distribution of SB2 and eclipsing double white dwarfs with orbital constraints, and demonstrate that the observed population is consistent with the predicted period distribution from the binary population synthesis models. The latter predict more massive CO + CO white dwarf binaries at short (<1 d) periods, as well as binaries with several day orbital periods; such systems are still waiting to be discovered in large numbers.

scholarly journals Search for He I airglow emission from the hot Jupiter τ Boo b

2020 ◽  
Vol 641 ◽  
pp. A161
Author(s):  
Y. Zhang ◽  
I. A. G. Snellen ◽  
P. Mollière ◽  
F. J. Alonso-Floriano ◽  
R. K. Webb ◽  
...  
Keyword(s):  
High Resolution ◽  
Rest Frame ◽  
Emission Feature ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Transmission Spectra ◽  
Hot Jupiters ◽  
Line Widths ◽  
Calar Alto ◽  
Metastable Triplet State

Context. It has been suggested that the helium absorption line at 10 830 Å that originates from the metastable triplet state 23S is an excellent probe for the extended atmospheres of hot Jupiters and their hydrodynamic escape processes. It has recently been detected in the transmission spectra of a handful of planets. The isotropic reemission will lead to helium airglow that may be observable at other orbital phases. Aims. We investigate the detectability of He I emission at 10 830 Å in the atmospheres of exoplanets using high-resolution spectroscopy. This would provide insights into the properties of the upper atmospheres of close-in gas giants. Methods. We estimated the expected strength of He I emission in hot Jupiters based on their transmission signal. We searched for the He I 10 830 Å emission feature in τ Boo b in three nights of high-resolution spectra taken by CARMENES at the 3.5m Calar Alto telescope. The spectra from each night were corrected for telluric absorption, sky emission lines, and stellar features, and were shifted to the planetary rest frame to search for the emission. Results. The He I emission is not detected in τ Boo b at a 5σ contrast limit of 4 × 10−4 for emission line widths of >20 km s−1. This is about a factor 8 above the expected emission level (assuming a typical He I transit absorption of 1% for hot Jupiters). This suggests that targeting the He I emission with well-designed observations using upcoming instruments such as VLT/CRIRES+ and E-ELT/HIRES is possible.

Energy Transfer Between Two Sites in Nd3+:KLiYF5

1993 ◽  
Vol 329 ◽  
Author(s):  
H. Weidner ◽  
P. L. Summers ◽  
R. E. Peale ◽  
B. H. T. Chai
Keyword(s):  
Energy Transfer ◽  
High Resolution ◽  
Radiative Transfer ◽  
Transfer Rate ◽  
Selective Excitation ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Line Intensities ◽  
Lithium Yttrium Fluoride ◽  
Site Selective

AbstractHigh resolution spectroscopy of Nd3+ in Potassium Lithium Yttrium Fluoride (KLiYF5 ) at ≤80 K reveals two crystal-field sites which are equally populated independent of concentration. Site selective excitation of photoluminescence distinguishes each site's contribution to the spectra. The analysis of integrated line intensities reveals a bidirectional energy transfer between Nd3+ ions in different sites. A rapid increase in transfer rate with increasing Nd concentration is explained only if non-radiative transfer via exchange interaction contributes strongly to the effect. The observed relative decrease with increasing concentration of those emission lines which overlap strongly with opposite-site absorption lines implies that radiative transfer is also important. The energy transfer strongly depends on temperature (2 K – 80 K) which indicates the participation of phonons.

High‐Resolution Spectroscopy of Faint Emission Lines in the Orion Nebula

2000 ◽  
Vol 129 (1) ◽  
pp. 229-246 ◽  
Author(s):  
J. A. Baldwin ◽  
E. M. Verner ◽  
D. A. Verner ◽  
G. J. Ferland ◽  
P. G. Martin, ◽  
...  
Keyword(s):  
High Resolution ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Orion Nebula
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