scholarly journals HST spectrophotometric data of the central star of the Planetary Nebula LMC-N66

1997 ◽  
Vol 180 ◽  
pp. 126-127
Author(s):  
M. Peña ◽  
W.-R. Hamann ◽  
L. Koesterke ◽  
J. Maza ◽  
R.H. Méndez ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Central Star ◽  
Short Time Scale ◽  
Type I ◽  
Ionization Degree ◽  
Filamentary Structure ◽  
High Ionization ◽  
Spectrophotometric Data ◽  
History Of ◽  
Short Time

N66 (WS 35, SMP 83) is a Type I (He-N rich) PN in the LMC with a high ionization degree. It shows a bipolar morphology with a filamentary structure (Dopita et al. 1993). Its central star has shown very impressive changes, in short time scale, that have been investigated. Here we describe the history of these changes:

scholarly journals Twenty years of observations of PM 1-188: Its chemical abundances and extraordinary kinematics

2021 ◽  
Author(s):  
Miriam Peña ◽  
Liliana Hernández-Martínez ◽  
Francisco Ruiz-Escobedo
Keyword(s):  
Chemical Composition ◽  
Planetary Nebula ◽  
Central Star ◽  
Emission Lines ◽  
Type I ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Physical Conditions ◽  
The Past ◽  
Spectrophotometric Data

Abstract The analysis of 20 years of spectrophotometric data of the double shell planetary nebula PM 1-188 is presented, aiming to determine the time evolution of the emission lines and the physical conditions of the nebula, as a consequence of the systematic fading of its [WC 10] central star whose brightness has declined by about 10 mag in the past 40 years. Our main results include that the [O iii], [O ii], [N ii] line intensities are increasing with time in the inner nebula as a consequence of an increase in electron temperature from 11 000 K in 2005 to more than 14 000 K in 2018, due to shocks. The intensity of the same lines are decreasing in the outer nebula, due to a decrease in temperature, from 13 000 K to 7000 K, in the same period. The chemical composition of the inner and outer shells was derived and they are similar. Both nebulae present subsolar O, S and Ar abundances, while they are He, N and Ne rich. For the outer nebula the values are 12+log He/H = 11.13 ± 0.05, 12+log O/H = 8.04 ± 0.04, 12+log N/H = 7.87 ± 0.06, 12+log S/H = 7.18 ± 0.10 and 12+log Ar = 5.33 ± 0.16. The O, S and Ar abundances are several times lower than the average values found in disc non-Type I PNe, and are reminiscent of some halo PNe. From high resolution spectra, an outflow in the N-S direction was found in the inner zone. Position-velocity diagrams show that the outflow expands at velocities in the −150 to 100 km s−1 range, and both shells have expansion velocities of about 40 km s−1.

scholarly journals On the Short Time Scale Evolutionary History of the Contact Binary VW Cephei

1998 ◽  
Vol 11 (1) ◽  
pp. 396-396
Author(s):  
I. Pustylnik
Keyword(s):  
Evolutionary History ◽  
Light Curves ◽  
Published Data ◽  
Short Time Scale ◽  
Flare Activity ◽  
Considerable Portion ◽  
History Of ◽  
Contact Binary ◽  
Elongation Phase ◽  
Short Time

We study the short-time evolutionary history of the well-known contact binary VW Cep. Our analysis is based partly on the numerous UBV lightcurves obtained at Tartu Observatory, IUE spectra, and samples from the published data. Special attention is given to the effects of asymmetry of the light curves. A higher degree of asymmetry outside the eclipses along with the significant displacements of the brightness maxima in respect to the elongation phase is interpreted as evidence that a considerable portion of the flaring source is concentrated close to the neck connecting the components. We discuss the nature of asymmetry in terms of possible mass exchange and the flare activity and compare the results of our model computations with the record of orbital period variations over the last 60 years.

scholarly journals When nature tries to trick us

2018 ◽  
Vol 619 ◽  
pp. A84 ◽  
Author(s):  
Henri M. J. Boffin ◽  
David Jones ◽  
Roger Wesson ◽  
Yuri Beletsky ◽  
Brent Miszalski ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Binary Star ◽  
Central Star ◽  
Equal Mass ◽  
Type I ◽  
Eclipsing Binary ◽  
Common Envelope ◽  
Bright Object ◽  
F Stars ◽  
Central Stars

Bipolar planetary nebulae (PNe) are thought to result from binary star interactions and, indeed, tens of binary central stars of PNe have been found, in particular using photometric time-series that allow for the detection of post-common envelope systems. Using photometry at the NTT in La Silla we have studied the bright object close to the centre of PN M 3-2 and found it to be an eclipsing binary with an orbital period of 1.88 days. However, the components of the binary appear to be two A or F stars, of almost equal mass, and are therefore too cold to be the source of ionisation of the nebula. Using deep images of the central star obtained in good seeing conditions, we confirm a previous result that the central star is more likely much fainter, located 2″ away from the bright star. The eclipsing binary is thus a chance alignment on top of the planetary nebula. We also studied the nebular abundance and confirm it to be a Type I PN.

scholarly journals A Detailed Study of the Galactic Planetary Nebula G 258-15.7

1993 ◽  
Vol 155 ◽  
pp. 384-384
Author(s):  
P. Leisy ◽  
M. Dennefeld
Keyword(s):  
Planetary Nebula ◽  
Central Star ◽  
Striking Feature ◽  
Subsequent Paper ◽  
Type I ◽  
Significant Difference ◽  
Two Sides ◽  
Galactic Planetary Nebula

The galactic Planetary Nebula G 258-15.7 is a large, bright nebula well suited for a detailed study. Known since Wray (1966), its morphology presents several blobs and ansae, generally associated with type I nebulae, and could be described as “late-butterfly” type according to the classification by Balick (1989). The central star has been classified as hydrogen-deficient by Mendez et al. (1985). Spectroscopy of the two main blobs shows a clear overabundance in He and N, with a marginally significant difference between the two sides. The most striking feature is the jet-like structure appearing on the [OIII]/Halpha picture (Fig. 1), the “jets” being located within the main blobs seen on the monochromatic images. A detailed appraisal of all the data will be presented in a subsequent paper.

scholarly journals Thermal and Density Structures and Elemental Abundances in the Bipolar PN Mz 3

2003 ◽  
Vol 209 ◽  
pp. 377-378
Author(s):  
Y. Zhang ◽  
X.-W. Liu
Keyword(s):  
Fine Structure ◽  
Planetary Nebula ◽  
Far Infrared ◽  
Central Star ◽  
Type I ◽  
Ionized Gas ◽  
Elemental Abundances ◽  
Angular Extent ◽  
Salient Features ◽  
Fine Structure Lines

Mz 3 is a young bipolar planetary nebula (PN) with lobes extending over ~ 50 arcsec on the sky. It consists of a bright core, two approximately spherical bipolar lobes and two outer large filamentary bipolar nebulae. The salient features of Mz 3 are more easily studied than other bipolar nebula because of its large angular extent. It is very bright in the far-infrared. There is an extended shell of warm dust surrounding the central star. And the bipolar lobes are filled with hot ionized gas. Cohen et al. (1978) found that Mz 3 is He-rich. Based on the LWS observations of the far-IR fine-structure lines, Liu et al. (2001) derived a high N/O ratio in Mz 3 and identified the bipolar nebula as a Type-I PN.

scholarly journals Chandra observations of the planetary nebula IC 4593

2020 ◽  
Vol 494 (3) ◽  
pp. 3784-3789
Author(s):  
J A Toalá ◽  
M A Guerrero ◽  
L Bianchi ◽  
Y-H Chu ◽  
O De Marco
Keyword(s):  
Planetary Nebula ◽  
Careful Analysis ◽  
Central Star ◽  
Stellar Atmosphere ◽  
Hot Stars ◽  
Imaging Spectrometer ◽  
Ccd Imaging ◽  
X Ray ◽  
High Ionization ◽  
Thin Plasma

ABSTRACT The Advanced CCD Imaging Spectrometer (ACIS-S) camera on board the Chandra X-ray Observatory has been used to discover a hot bubble in the planetary nebula (PN) IC 4593, the most distant PN detected by Chandra so far. The data are used to study the distribution of the X-ray-emitting gas in IC 4593 and to estimate its physical properties. The hot bubble has a radius of ∼2 arcsec and is found to be confined inside the optically bright innermost cavity of IC 4593. The X-ray emission is mostly consistent with that of an optically thin plasma with temperature kT ≈ 0.15 keV (or TX ≈ 1.7 × 106 K), electron density ne ≈ 15 cm−3, and intrinsic X-ray luminosity in the 0.3–1.5 keV energy range LX = 3.4 × 1030 erg s−1. A careful analysis of the distribution of hard (E >0.8 keV) photons in IC 4593 suggests the presence of X-ray emission from a point source likely associated with its central star (CSPN). If this was the case, its estimated X-ray luminosity would be LX, CSPN = 7 × 1029 erg s−1, fulfilling the log(LX, CSPN/Lbol) ≈ −7 relation for self-shocking winds in hot stars. The X-ray detection of the CSPN helps explain the presence of high-ionization species detected in the ultraviolet spectra as predicted by stellar atmosphere models.

AI and HCI: Two Fields Divided by a Common Focus

AI Magazine ◽  
2009 ◽  
Vol 30 (4) ◽  
pp. 48 ◽  
Author(s):  
Jonathan Grudin
Keyword(s):  
Time Scale ◽  
Short Time Scale ◽  
Intelligent Behavior ◽  
History Of ◽  
Short Time ◽  
Competition For Resources

Although AI and HCI explore computing and intelligent behavior and the fields have seen some cross-over, until recently there was not very much. This article outlines a history of the fields that identifies some of the forces that kept the fields at arm’s length. AI was generally marked by a very ambitious, long-term vision requiring expensive systems, although the term was rarely envisioned as being as long as it proved to be, whereas HCI focused more on innovation and improvement of widely-used hardware within a short time-scale. These differences led to different priorities, methods, and assessment approaches.  A consequence was competition for resources, with HCI flourishing in AI winters and moving more slowly when AI was in favor. The situation today is much more promising, in part because of platform convergence: AI can be exploited on widely-used systems.

Molecular Hydrogen Emission from the Cometary Globules in the Helix Nebula (NGC 7293)

2003 ◽  
Vol 209 ◽  
pp. 275-276
Author(s):  
J. R. Walsh ◽  
N. Ageorges
Keyword(s):  
Central Region ◽  
Planetary Nebula ◽  
Molecular Hydrogen ◽  
Direct Evidence ◽  
Central Star ◽  
Small Distance ◽  
Ionization Front ◽  
The Sun ◽  
Hydrogen Emission ◽  
High Ionization

The discovery of many dense, dusty condensations in the Helix Nebula, NGC 7293, by Meaburn et al. (1992) was the first direct evidence of the real inhomogeneity of the medium of a planetary nebula. On account of the small distance of the Helix nebula from the Sun (~200pc), the knots (cometary globules) can be resolved from the ground and studied in detail from HST imaging (O'Dell & Handron, 1996). The condensations typically have a projected diameter of <2″ and hence sizes of <6 x 1015 cm. The condensations consist of a dusty core, visible as absorption against the background high ionization central region of the nebula for the foreground globules, and with a bow-shaped ionization front, strong in low ionization emission. The emission is displaced in the direction towards the central star, often with an outwardly-directed radial tail.

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