scholarly journals Variable Spectra of IC 4997 and NGC 6572

1993 ◽  
Vol 155 ◽  
pp. 488-488
Author(s):  
Siek Hyung ◽  
Lawrence H. Aller ◽  
Walter A. Feibelman
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
Line Intensity ◽  
Planetary Nebula ◽  
Radiative Flux ◽  
Gradual Decrease ◽  
High Dispersion ◽  
Echelle Spectrograph

Variability of the [OIII]4363/4340 H γ ratio in IC 4007 was established in 1956 by William Liller and L.H. Aller who attributed the changes to a gradual decrease of electron density with time. Subsequent 4363/4340 ratio fluctuations negated this explanation. Ferland pointed out that small changes in the radiative flux of the Planetary nebula nucleus (PNN) could explains the variations. Our pervious study emphasized IUE observations, here we compare high dispersion spectra obtained with the Hamilton Echelle Spectrograph with previous measurements to asses line intensity variations. Emission line variability in PNN spectra as noted by Mendez et al. (1988) and by other for HeII 4686 in NGC 6572 may offer significant clues. PNN 4686 appeared by 1990 in IC 4997. Possibly both of these PNN may be evolving into Wolf-Rayet objects, but this development does not necessarily imply that the nebular excitation will increase with time.

scholarly journals Detailed Studies of IPHAS sources. II. Sab 19, a true planetary nebula and its mimic crossing the Perseus Arm.

2020 ◽  
Author(s):  
M A Guerrero ◽  
R Ortiz ◽  
L Sabin ◽  
G Ramos-Larios ◽  
E J Alfaro
Keyword(s):  
Radial Velocity ◽  
Emission Line ◽  
Planetary Nebula ◽  
Central Star ◽  
High Dispersion ◽  
Velocity Shift ◽  
Optical Images ◽  
External Shell ◽  
Low Mass ◽  
Perseus Arm

Abstract The INT Photometric Hα Survey (IPHAS) has provided us with a number of new-emission line sources, among which planetary nebulae (PNe) constitute an important fraction. Here we present a detailed analysis of the IPHAS nebula Sab 19 (IPHASX J055242.8+262116) based on radio, infrared, and optical images and intermediate- and high-dispersion longslit spectra. Sab 19 consists of a roundish 0.10 pc in radius double-shell nebula surrounded by a much larger 2.8 pc in radius external shell with a prominent H-shaped filament. We confirm the nature of the main nebula as a PN whose sub-solar N/O ratio abundances, low ionized mass, peculiar radial velocity, and low-mass central star allow us to catalog it as a type III PN. Apparently, the progenitor star of Sab 19 became a PN when crossing the Perseus Arm during a brief visit of a few Myr. The higher N/O ratio and velocity shift ≃40  km s−1 of the external shell with respect to the main nebula and its large ionized mass suggest that it is not truly associated with Sab 19, but it is rather dominated by a Strömgren zone in the interstellar medium ionized by the PN central star.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

THEORETICAL ELECTRON DENSITY AND TEMPERATURE SENSITIVE EMISSION LINE RATIOS FOR HELIUM-LIKE Si XIII COMPARED TO DITE TOKAMAK OBSERVATIONS

1989 ◽  
Vol 50 (C1) ◽  
pp. C1-559-C1-564
Author(s):  
F. P. KEENAN ◽  
R. BARNSLEY ◽  
J. DUNN ◽  
K. D. EVANS ◽  
S. M. McCANN ◽  
...  
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
Temperature Sensitive ◽  
Electron Density And Temperature

scholarly journals Physical Conditions in the Compact Planetary Nebula Sw St 1

1983 ◽  
Vol 103 ◽  
pp. 520-520
Author(s):  
M. Cohen ◽  
D.R. Flower ◽  
A. Goharji
Keyword(s):  
Electron Density ◽  
Planetary Nebula ◽  
Emission Measure ◽  
Emission Feature ◽  
Radio Observations ◽  
Physical Conditions ◽  
Infra Red ◽  
High Emission

Sw St 1 is a compact and possibly young planetary nebula which has been recently observed at infra red (Aitken et al., 1979) and radio (Kwok et al., 1981) wavelengths. In the 8-13 μm region, a silicate emission feature is observed, suggesting that the nebular envelope is oxygen rich. The high emission measure determined from the radio observations implies a large value for the electron density.

scholarly journals Different long-term trends of the oxygen red 630.0 nm line nightglow intensity as the result of lowering the ionosphere F2 layer

2008 ◽  
Vol 26 (8) ◽  
pp. 2069-2080 ◽  
Author(s):  
N. B. Gudadze ◽  
G. G. Didebulidze ◽  
L. N. Lomidze ◽  
G. Sh. Javakhishvili ◽  
M. A. Marsagishvili ◽  
...  
Keyword(s):  
Electron Density ◽  
Line Intensity ◽  
Peak Height ◽  
Height Distribution ◽  
Theoretical Simulation ◽  
Type Layer ◽  
Long Term Trends ◽  
The Mean ◽  
Long Term Trend

Abstract. Long-term observations of total nightglow intensity of the atomic oxygen red 630.0 nm line at Abastumani (41.75° N, 42.82° E) in 1957–1993 and measurements of the ionosphere F2 layer parameters from the Tbilisi ionosphere station (41.65° N, 44.75° E) in 1963–1986 have been analyzed. It is shown that a decrease in the long-term trend of the mean annual red 630.0 nm line intensity from the pre-midnight value (+0.770±1.045 R/year) to its minimum negative value (−1.080±0.670 R/year) at the midnight/after midnight is a possible result of the observed lowering of the peak height of the ionosphere F2 layer electron density hmF2 (−0.455±0.343 km/year). A theoretical simulation is carried out using a simple Chapman-type layer (damping in time) for the height distribution of the F2 layer electron density. The estimated values of the lowering in the hmF2, the increase in the red line intensity at pre-midnight and its decrease at midnight/after midnight are close to their observational ones, when a negative trend in the total neutral density of the upper atmosphere and an increase in the mean northward wind (or its possible consequence – a decrease in the southward one) are assumed.

scholarly journals Radial-velocity search and statistical studies for short-period planets in the Pleiades open cluster

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Takuya Takarada ◽  
Bun’ei Sato ◽  
Masashi Omiya ◽  
Yasunori Hori ◽  
Michiko S Fujii
Keyword(s):  
Radial Velocity ◽  
Open Cluster ◽  
Open Clusters ◽  
Occurrence Rate ◽  
High Dispersion ◽  
Echelle Spectrograph ◽  
Upper Limit ◽  
Stringent Constraint ◽  
Short Period ◽  
Statistical Studies

Abstract We report on a radial-velocity search for short-period planets in the Pleiades open cluster. We observed 30 Pleiades member stars at the Okayama Astrophysical Observatory with the High Dispersion Echelle Spectrograph. To evaluate and mitigate the effects of stellar activity on radial-velocity (RV) measurements, we computed four activity indicators (full width at half maximum, Vspan, Wspan, and SHα). Among our sample, no short-period planet candidates were detected. Stellar intrinsic RV jitter was estimated to be 52 m s−1, 128 m s−1, and 173 m s−1 for stars with $v$ sin i of 10 km s−1, 15 km s−1, and 20 km s−1, respectively. We determined the planet occurrence rate from our survey and set the upper limit to 11.4% for planets with masses 1–13 MJUP and period 1–10 d. To set a more stringent constraint on the planet occurrence rate, we combined the result of our survey with those of other surveys targeting open clusters with ages in the range 30–300 Myr. As a result, the planet occurrence rate in young open clusters was found to be less than 7.4%, 2.9%, and 1.9% for planets with an orbital period of 3 d and masses of 1–5, 5–13, and 13–80 MJUP, respectively.

scholarly journals High-Dispersion Spectroscopy of the Brightest Emission-Line Stars of the Magellanic Clouds

1986 ◽  
Vol 116 ◽  
pp. 247-248 ◽  
Author(s):  
O. Stahl ◽  
B. Wolf ◽  
M. de Groot ◽  
C. Leitherer
Keyword(s):  
Emission Line ◽  
Wavelength Range ◽  
Spectral Resolution ◽  
Magellanic Clouds ◽  
High Dispersion

We present an atlas of high dispersion spectra of 24 of the brightest peculiar emission-line stars of the Magellanic Clouds.Our spectra cover the wavelength range from 3600 to 4900 Å. They have been obtained from 1970 to 1984 with the coudé spectrograph of the ESO 1.52 m telescope at La Silla, Chile. The spectral resolution is 0.4 Å for most of the spectra and 0.2 Å for the very brightest stars. Up to 11 spectra are available for one star. In addition, we have done UBVRIJHK(LM) photometry at several epochs of all stars of our sample.

scholarly journals Chemodynamics of green pea galaxies – I. Outflows and turbulence driving the escape of ionizing photons and chemical enrichment

2020 ◽  
Vol 494 (3) ◽  
pp. 3541-3561 ◽  
Author(s):  
L Hogarth ◽  
R Amorín ◽  
J M Vílchez ◽  
G F Hägele ◽  
M Cardaci ◽  
...  
Keyword(s):  
Emission Line ◽  
Indirect Evidence ◽  
Young Star ◽  
High Dispersion ◽  
H Ii Regions ◽  
Ionized Gas ◽  
Narrow Component ◽  
Radiation Fields ◽  
Hard Radiation ◽  
Green Pea

ABSTRACT We investigate the ionized gas kinematics, physical properties, and chemical abundances of Sloan Digital Sky Survey J142947, a Green Pea galaxy at redshift z∼ 0.17 with strong, double-peak Ly α emission and indirect evidence of Lyman continuum (LyC) leakage. Using high-dispersion spectroscopy, we perform a multicomponent analysis of emission-line profiles. Our model consistently fits all lines as a narrow component with intrinsic velocity dispersion σ ∼ 40 km s−1, and two broader blue-shifted components with σ ∼ 90 and ∼ 250 km s−1. We find electron densities and temperatures, ionization conditions, and direct O/H and N/O abundances for each component. A highly ionized, metal-poor, young and compact starburst dominates narrow emission, showing evidence of hard radiation fields and elevated N/O. The blue-shifted broader components are consistent with highly turbulent, possibly clumpy ionized gas at the base of a strong photoionized outflow, which accounts for ≳50 per cent of the integrated emission-line fluxes. The outflow is dense and metal-enriched compared to the H ii regions, with expansion velocities larger than those obtained from UV interstellar absorption lines under standard assumptions. Some of these metals may be able to escape, with outflows loading factors comparable to those found in high-z galaxies of similar SFR/Area. Our findings depict a two-stage starburst picture; hard radiation fields from young star clusters illuminate a turbulent and clumpy ISM that has been eroded by SNe feedback. Whilst UV data suggest an extended Ly α halo with high average H i column density, LyC photons could only escape from SDSS J142947 through low H i density channels or filaments in the ISM approaching density-bounded conditions, traced by outflowing gas.

scholarly journals Variable Winds in Early-B Hypergiants

1999 ◽  
Vol 169 ◽  
pp. 222-229
Author(s):  
Bernhard Wolf ◽  
Thomas Rivinius
Keyword(s):  
Mass Loss ◽  
Terminal Velocity ◽  
Spectral Lines ◽  
High Mass ◽  
High Dispersion ◽  
Echelle Spectrograph ◽  
Variability Pattern ◽  
Evolutionary Phase ◽  
High Mass Loss ◽  
Wind Velocities

AbstractEarly-B hypergiants belong to the most luminous stars in the Universe. They are characterized by high mass-loss rates (Ṁ ≈ 10−5Mʘyr−1) and low terminal wind velocities (v∞ʘ400 kms−1) implying very dense winds. They represent a short-lived evolutionary phase and are of particular interest for evolutionary theories of massive stars with mass loss. Due to their high luminosity they play a key role in connection with the “wind momentum - luminosity relation”. Among the main interesting characteristics of early-B hypergiants are the various kinds of photometric and spectroscopic variations. In several recent campaigns our group has performed extensive high dispersion spectroscopy of galactic early-B hypergiants with our fiber-fed echelle spectrograph FLASH/HEROS at the ESO-50 cm telescope. The main outcome was that their dense winds behave hydrodynamically differently to the less luminous supergiants of comparable spectral type. Outwardly accelerated propagating discrete absorption components of the P Cyg-type lines are the typical features rather than rotationally modulated line profile variations. These discrete absorptions could be traced in different spectral lines from photospheric velocities up to 75% of the terminal velocity. The stellar absorption lines show a pulsation-like radial velocity variability pattern lasting up to two weeks as the typical time scale. The radius variations connected with this pulsation-like motions are correlated with the emission height of the P Cyg-type profiles.

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