DOCSLIB.ORG

Comparison of the Masses of Planetary Nebula Nuclei Derived from Different Methods

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Comparison of the Masses of Planetary Nebula Nuclei Derived from Different Methods ACTA ASTRONOMICA Vol. 43 (1993) pp. 371±380 Comparison of the Masses of Planetary Nebula Nuclei Derived from Different Methods by ; S.K. G o r n y 1;2 , R. Tylenda1 2 , and G.Stasi nska 2 1 Copernicus Astronomical Center, Chopina 12/18, PL-87100 ToruÂn, Poland 2 DAEC, Observatoire de Paris-Meudon, F-92195 Meudon CÂedex, France ABSTRACT We present some results of an extensive and uniform analysis of the planetary nebula nuclei from samples examined by Mendez et al. and Gathier and Pottasch. The present study uses distance independent diagrams. The theoretical tracks have been modi®ed so that they can be directly compared in the diagrams to the observed central star positions. From this comparison the central star masses have been derived. Our results are in contradiction with those from the above cited studies. Possible explanations of the differences are presented. 1. Introduction During recent years numerous studies of the masses of planetary nebula nuclei (PNN) have been undertaken. Most of the authors have come to more or less the same general conclusion, i.e. thatthe PNNmasses are concentrated around0.60M and have a strong cutoff at 0.55 M (SchonbernerÈ 1981, Kaler 1983, Heap and Augensen 1987, Szczerba 1987, 1990, Weidemann 1989, Tylenda and Stasinska 1989, Stasinska and Tylenda 1990, Kaler et al. 1990, Kaler and Jacoby 1990, 1991, Dopita and Meathernigham 1991, Tylenda et al. 1991, Zhang and Kwok 1993). The principal controversy concerns the proportion of massive PNN. Some authors ®nd that the number of PNN above 0.7 M is negligible (e.g. SchonbernerÈ 1981, Weidemann 1989, Tylenda et al. 1991), others obtain an important high-mass tail (e.g. Kaler et al. 1990, Kaler and Jacoby 1990, Dopita and Meathernigham 1991). However, there are authors who came to qualitatively different conclusions than the mentioned above. Mendez et al. (1988, 1990) have obtained PNN masses between 0.65 and 0.90 M for 80% of the objects in their sample. On the other hand, Gathier and Pottasch (1989, hereinafter GP) have constructed an observed H-R diagram from which it can be infered that 50-60% of their PNN have masses 372 A. A. about or below 0.55 M (similar conclusion has also been drawn in Pottasch 1984, Zijlstra and Pottasch 1989 and Pottasch and Acker 1989). The problem is important, since it arises from elaborated studies performed with a great care by their authors. Mendez et al. (1988, 1990) have analyzed the absorption line pro®les in the PNN spectra by means of stellar atmosphere models T g which allowed them to derive e and log These values when compared to the theoretical PNN models have resulted in the PNN masses. In their more recent study Mendez et al. (1992, hereinafter MKH) using a more elaborated version of the PNN model atmospheres have obtained, in most cases, somewhat higher values for the gravities which resulted in lower PNN masses. The problem, however, still remains serious since 80% of the PNN in MKH havemassesbetween 0.64 and 0.73 M which is signi®cantly higher than masses found in other studies and in GP in particular. GP use a rather classic method as they confront the observations to the theoret- ical models in the H-R diagram. The principal particularity and importance of this study is that it uses individually determined distances from Gathier (1987). The authors believe that their distances have an accuracy better than 40%. One can invoke two reasons of the discrepancy between the results of MKH and those of GP. One possibility arises from the fact that the two samples, in the bulk, contain different objects. Therefore it can be suggested that MKH have preferentially selected more luminous and more massive PNN whereas the sample of GP contains a large proportion of low mass objects (see e.g. GP, McCarthy et al. 1990). However, the results obtained in the two studies for two objects in common (NGC 3242 and NGC 7009) are signi®cantly different: the luminosities derived by MKH for these two PNN are factor 30 larger than in GP. The difference is obviously too large and cannot be reconciled within error bars quoted in the two studies. This fact prompts to consider another possibility, i.e. that the bulk of the difference between the PNN masses in MKH and those in GP results from different methods of analysis applied in the two studies. If this is the case then the implication would be that either the PNN masses of MKH are systematically overestimated or the PNN luminosities in GP are, at least for some objects, underestimated or both. This possibility has already been discussed by some authors (e.g. Szczerba 1990, Zhang and Kwok 1993, Tylenda 1993). This paper presents some results of an extensive and uniform analysis of the PN from both samples performed in order to ®nd if there are indications that the two samples are systematically different and in which sense. From basic observational data, such as PNN magnitudes, H ¯ux, radio ¯ux, PN diamaters, etc., we can construct different diagrams in which the observed objects can be compared between them as well as to the theoretical evolutionary models. From these diagrams we can estimate the PNN masses which when confronted to the masses of MKH and GP allows to draw conclusions. Vol. 43 373 2. Observational Parameters and Theoretical Tracks The distances to PN are one of the principal sources of uncertainties while comparing the theoretical PNN models to the observations. Therefore we have concentrated, in the present study, on diagrams using distance independent param- eters. The observational data, i.e. PN diameters, H ¯uxes, radio ¯uxes at 6 cm, HeII 4686 line intensities, central star magnitudes, expansion velocities, have been taken from the ESO-Strasbourg catalogue (Acker et al. 1992). These data have been processed in the usual manner to derive the following parameters: hydrogen T ( ) T ( ) Z Zanstra temperature, Z HI , helium Zanstra temperature, HeII , (both being obtained assuming that the star radiates as a blackbody), parameter f as de®ned T in Tylenda and Stasinska (1989), and radio brightness temperature, b . Then the f observed PNN have been compared to the model PNN on a log T (PNN) ± log T T T ( ) Z diagram and a log b ± log (PNN) diagram constructed separately for HI T ( ) and Z HeII . The PNN evolution for a given mass have been obtained from an interpolation procedure discribed in Stasinska and Tylenda (1993). The procedure is based on the tracks of SchonbernerÈ (1981, 1983) and BlockerÈ and SchonbernerÈ (1991). The tracks from SchonbernerÈ (1981, 1983) have been somewhat modi®ed so they have the zero-age point at the pulsation period of 50 days, similarly as in BlockerÈ and SchonbernerÈ (1991). In order to have theoretical tracks directly comparable to the observed objects in the diagrams, the model PNN have been treated similarily as in Tylenda et al. (1991) or Gorny et al. (1993). Thus we have assumed that each evolving PNN is surrounded by a spherically symmetric, uniform density nebula M V exp of a given mass, neb , expanding at a constant velocity, . The nebular shell thickness relative to the nebular radius is kept constant, and taken equal to 0.3. The star is assumed to radiate as a blackbody. Then the H and He ionization structure of the nebula can be obtained from the ionization equilibrium. This allows to calculate the Zanstra temperatures for the model PNN and the nebular radio brightness temperature. 3. Diagnostic Diagrams Figs. 1 ± 4 show the resultant diagrams. The objects from the MKH sample are represented by ®lled circles. Those from the GP sample are shown as open circles. Partly ®lled squares correspond to the two objects in common. For a number of objects we had only upper limits for HeII 4686. Hence the upper limits T ( ) for Z HeII in Figs. 2 and 4. Curves show the theoretical tracks for given PNN M = V = exp masses. They have been obtained adopting neb 0 2M and 20 km/s. As can be seen from Figs. 1 ± 4 there is a systematic difference in the positions on the diagramsbetweenthe sample of MKH and the sampleof GP. On the average, 374 A. A. T ( ) Fig. 1. The parameter, f against the hydrogen Zanstra temperature, Z HI . Filled circles ± objects from the MKH sample; open circles ± objects from the GP sample; partly ®lled squares ± objects in common; dashed curves ± theoretical tracks for PNN masses from 0.55 M to 0.69 M spaced by 0.01 M . T ( ) Fig. 2. The parameter, f against the helium Zanstra temperature, Z HeII . The same notation as in Fig. 1. Vol. 43 375 T ( ) Fig. 3. The radio brightness temperature, Tb , against the hydrogen Zanstra temperature, Z HI . The same notation as in Fig. 1. T ( ) Fig. 4. The radio brightness temperature, Tb , against the helium Zanstra temperature, Z HeII . The same notation as in Fig. 1. 376 A. A. the former shows lower Zanstra temperatures than the latter. This is certainly due to the observationalselection asMKH pickedup PNN with well developed absorption lines of H and He which takes place at lower effective temperatures. When confronting the observed positions to the theoretical tracks two general conclusions can be drawn from Figs. 1 ± 4. First, contrary to GP we see no PNN lying de®nitively below the track of 0.55 M . Second, the sample of GP lies, on average, within the tracks of higher PNN masses than that of MKH. This is in contradiction to what is expected if the ®ndings of GP and MKH are compared.
Load more

Recommended publications
  • Expansion Patterns and Parallaxes for Planetary Nebulae? D
    A&A 609, A126 (2018) Astronomy DOI: 10.1051/0004-6361/201731788 & c ESO 2018 Astrophysics Expansion patterns and parallaxes for planetary nebulae? D. Schönberner1, B. Balick2, and R. Jacob1 1 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany e-mail: [email protected] 2 Astronomy Department, University of Washington, Seattle, WA 98195, USA e-mail: [email protected] Received 17 August 2017 / Accepted 25 September 2017 ABSTRACT Aims. We aim to determine individual distances to a small number of rather round, quite regularly shaped planetary nebulae by combining their angular expansion in the plane of the sky with a spectroscopically measured expansion along the line of sight. Methods. We combined up to three epochs of Hubble Space Telescope imaging data and determined the angular proper motions of rim and shell edges and of other features. These results are combined with measured expansion speeds to determine individual distances by assuming that line of sight and sky-plane expansions are equal. We employed 1D radiation-hydrodynamics simulations of nebular evolution to correct for the difference between the spectroscopically measured expansion velocities of rim and shell and of their respective shock fronts. Results. Rim and shell are two independently expanding entities, driven by different physical mechanisms, although their model- based expansion timescales are quite similar. We derive good individual distances for 15 objects, and the main results are as follows: (i) distances derived
    [Show full text]
  • Planetary Nebulae
    Planetary Nebulae A planetary nebula is a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives. The term "planetary nebula" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. The mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energizes the shell of nebulous gas around the central star, appearing as a bright colored planetary nebula at several discrete visible wavelengths. Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances. In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies.
    [Show full text]
  • A Basic Requirement for Studying the Heavens Is Determining Where In
    Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun­ damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short).
    [Show full text]
  • On the Evolutionary Status of WR-Type Planetary Nebula Nuclei R
    ACTA ASTRONOMICA Vol. 43 (1993) pp. 389±396 On the Evolutionary Status of WR-type Planetary Nebula Nuclei by R. Tylenda and S.K. G o r n y Copernicus Astronomical Center, Chopina 12/18, PL-87100 ToruÂn, Poland ABSTRACT The planetary nebula nuclei showing WR-type spectra constitute a unique class of the central stars: they are He-burners. This work presents preliminary results of a study analyzing the observational characteristics of the WR-type nuclei and their nebulae. The existing He-burning models cannot account for the observations of the WR-type nuclei. In the discussion we consider two scenaria: (i) WR-type nuclei are single stars; (ii) WR phenomenon is an evolutionary phase of binary systems. 1. Introduction The planetary nebula nuclei (PNN) showing Wolf-Rayet features in their spectra constitue a unique class of the central stars. This class includes, at present, about 50 objects and all of them are of WC-type (Tylenda et al. 1993). Their strong winds imply that these stars have active shell sources. This and the fact that their atmospheres are hydrogen-poor (Mendez 1991) imply that the WR-type PNN are burning helium. It is, thus, the only class of PNN for which we know the nuclear burning mode. We have undertaken an extensive study of the WR-type PNN in order to better understand their evolutionary status. This paper presents some preliminary results. 2. Observed Samples From the list of WR-type PNN in Tylenda et al. (1993) we have selected a sample of 30 objects for which we have found necessary observational data (e.g.
    [Show full text]
  • Gravity Distances of Planetary Nebulae Ii. Application to a Sample of Galactic Objects
    GRAVITY DISTANCES OF PLANETARY NEBULAE II. APPLICATION TO A SAMPLE OF GALACTIC OBJECTS J. O. CAZETTA and W. J. MACIEL Instituto Astronômico e Geofísico da USP, Av. Miguel Stefano 4200, 04301-904 São Paulo SP, Brazil (Received 7 April 1999; accepted 28 October 1999) 1. Introduction The main results on the difficult problem of distance determination for planetary nebulae in the last few years derive from the application of trigonometric parallaxes (Harris et al. 1997), radio expansion method (Hajian et al., 1993, 1995) and Hippar- cos distances (Pottasch and Acker 1998, see also Terzian, 1993, 1997). However, these methods are necessarily restricted to a few objects, which remain a small fraction of the known population of galactic PN, estimated as around 1800 true and possible PN (Acker 1997). Therefore, there is still a need for the development of statistical methods, which may be applicable to a larger number of objects, even though at the cost of a lower accuracy. One such method is the so-called gravity distance method, proposed by Maciel and Cazetta (1997, hereafter referred to as Paper I). According to this method, an approximate range of progenitor masses can be attributed to the different PN types of the Peimbert classification scheme (Peimbert 1978, Peimbert and Torres- Peimbert 1983). Using theoretical initial mass-final mass relationships, the central star mass can be obtained. On the other hand, relations involving the surface gravity as a function of the central star temperature can also be derived for a given stellar mass, so that the luminosities of the central stars are obtained.
    [Show full text]
  • Catalogue of Excitation Classes P for 750 Galactic Planetary Nebulae
    Catalogue of Excitation Classes p for 750 Galactic Planetary Nebulae Name p Name p Name p Name p NeC 40 1 Nee 6072 9 NeC 6881 10 IC 4663 11 NeC 246 12+ Nee 6153 3 NeC 6884 7 IC 4673 10 NeC 650-1 10 Nee 6210 4 NeC 6886 9 IC 4699 9 NeC 1360 12 Nee 6302 10 Nee 6891 4 IC 4732 5 NeC 1501 10 Nee 6309 10 NeC 6894 10 IC 4776 2 NeC 1514 8 NeC 6326 9 Nee 6905 11 IC 4846 3 NeC 1535 8 Nee 6337 11 Nee 7008 11 IC 4997 8 NeC 2022 12 Nee 6369 4 NeC 7009 7 IC 5117 6 NeC 2242 12+ NeC 6439 8 NeC 7026 9 IC 5148-50 6 NeC 2346 9 NeC 6445 10 Nee 7027 11 IC 5217 6 NeC 2371-2 12 Nee 6537 11 Nee 7048 11 Al 1 NeC 2392 10 NeC 6543 5 Nee 7094 12 A2 10 NeC 2438 10 NeC 6563 8 NeC 7139 9 A4 10 NeC 2440 10 NeC 6565 7 NeC 7293 7 A 12 4 NeC 2452 10 NeC 6567 4 Nee 7354 10 A 15 12+ NeC 2610 12 NeC 6572 7 NeC 7662 10 A 20 12+ NeC 2792 11 NeC 6578 2 Ie 289 12 A 21 1 NeC 2818 11 NeC 6620 8 IC 351 10 A 23 4 NeC 2867 9 NeC 6629 5 Ie 418 1 A 24 1 NeC 2899 10 Nee 6644 7 IC 972 10 A 30 12+ NeC 3132 9 NeC 6720 10 IC 1295 10 A 33 11 NeC 3195 9 NeC 6741 9 IC 1297 9 A 35 1 NeC 3211 10 NeC 6751 9 Ie 1454 10 A 36 12+ NeC 3242 9 Nee 6765 10 IC1747 9 A 40 2 NeC 3587 8 NeC 6772 9 IC 2003 10 A 41 1 NeC 3699 9 NeC 6778 9 IC 2149 2 A 43 2 NeC 3918 9 NeC 6781 8 IC 2165 10 A 46 2 NeC 4071 11 NeC 6790 4 IC 2448 9 A 49 4 NeC 4361 12+ NeC 6803 5 IC 2501 3 A 50 10 NeC 5189 10 NeC 6804 12 IC 2553 8 A 51 12 NeC 5307 9 NeC 6807 4 IC 2621 9 A 54 12 NeC 5315 2 NeC 6818 10 Ie 3568 3 A 55 4 NeC 5873 10 NeC 6826 11 Ie 4191 6 A 57 3 NeC 5882 6 NeC 6833 2 Ie 4406 4 A 60 2 NeC 5879 12 NeC 6842 2 IC 4593 6 A
    [Show full text]
  • Study of Electron Density in Planetary Nebulae
    A&A 382, 282–290 (2002) Astronomy DOI: 10.1051/0004-6361:20011621 & c ESO 2002 Astrophysics Study of electron density in planetary nebulae A comparison of different density indicators M. V. F. Copetti1,2 and B. C. Writzl1 1 Laborat´orio de An´alise Num´erica e Astrof´ısica, Departamento de Matem´atica, Universidade Federal de Santa Maria, 97119-900 Santa Maria, RS, Brazil 2 Physics Department, University of Cincinnati, Cincinnati OH 45221-0011, USA Received 29 August 2001 / Accepted 7 November 2001 Abstract. We present a comparison of electron density estimates for planetary nebulae based on different emission- line ratios. We have considered the density indicators [O ii]λ3729/λ3726, [S ii]λ6716/λ6731, [Cl iii]λ5517/λ5537, [Ar iv]λ4711/λ4740, C iii]λ1906/λ1909 and [N i]λ5202/λ5199. The observational data were extracted from the literature. We have found systematic deviations from the density homogeneous models, in the sense that: Ne(N i) ∼< Ne(O ii) <Ne(S ii, C iii, Cl iii or Ar iv)andNe(S ii) ≈ Ne(C iii) ≈ Ne(Cl iii) ≈ Ne(Ar iv). We argue that the lower [O ii] density estimates are likely due to errors in the atomic parameters used. Key words. ISM: planetary nebulae 1. Introduction have found the opposite, i.e., [O ii] densities systemati- cally higher than [S ii] ones. More recently, Keenan et al. The electron density, Ne, is one of the key physical pa- (1996, 1997, 1999), based on data from the series of high rameters needed to characterise a planetary nebula. Some spectral resolution observations of planetary nebulae by density assessment is necessary to confidently derive the Hyung, Aller and collaborators (see references in Sect.
    [Show full text]
  • 7.5 X 11.5.Threelines.P65
    Cambridge University Press 978-0-521-19267-5 - Observing and Cataloguing Nebulae and Star Clusters: From Herschel to Dreyer’s New General Catalogue Wolfgang Steinicke Index More information Name index The dates of birth and death, if available, for all 545 people (astronomers, telescope makers etc.) listed here are given. The data are mainly taken from the standard work Biographischer Index der Astronomie (Dick, Brüggenthies 2005). Some information has been added by the author (this especially concerns living twentieth-century astronomers). Members of the families of Dreyer, Lord Rosse and other astronomers (as mentioned in the text) are not listed. For obituaries see the references; compare also the compilations presented by Newcomb–Engelmann (Kempf 1911), Mädler (1873), Bode (1813) and Rudolf Wolf (1890). Markings: bold = portrait; underline = short biography. Abbe, Cleveland (1838–1916), 222–23, As-Sufi, Abd-al-Rahman (903–986), 164, 183, 229, 256, 271, 295, 338–42, 466 15–16, 167, 441–42, 446, 449–50, 455, 344, 346, 348, 360, 364, 367, 369, 393, Abell, George Ogden (1927–1983), 47, 475, 516 395, 395, 396–404, 406, 410, 415, 248 Austin, Edward P. (1843–1906), 6, 82, 423–24, 436, 441, 446, 448, 450, 455, Abbott, Francis Preserved (1799–1883), 335, 337, 446, 450 458–59, 461–63, 470, 477, 481, 483, 517–19 Auwers, Georg Friedrich Julius Arthur v. 505–11, 513–14, 517, 520, 526, 533, Abney, William (1843–1920), 360 (1838–1915), 7, 10, 12, 14–15, 26–27, 540–42, 548–61 Adams, John Couch (1819–1892), 122, 47, 50–51, 61, 65, 68–69, 88, 92–93,
    [Show full text]
  • Binocular Challenges
    This page intentionally left blank Cosmic Challenge Listing more than 500 sky targets, both near and far, in 187 challenges, this observing guide will test novice astronomers and advanced veterans alike. Its unique mix of Solar System and deep-sky targets will have observers hunting for the Apollo lunar landing sites, searching for satellites orbiting the outermost planets, and exploring hundreds of star clusters, nebulae, distant galaxies, and quasars. Each target object is accompanied by a rating indicating how difficult the object is to find, an in-depth visual description, an illustration showing how the object realistically looks, and a detailed finder chart to help you find each challenge quickly and effectively. The guide introduces objects often overlooked in other observing guides and features targets visible in a variety of conditions, from the inner city to the dark countryside. Challenges are provided for viewing by the naked eye, through binoculars, to the largest backyard telescopes. Philip S. Harrington is the author of eight previous books for the amateur astronomer, including Touring the Universe through Binoculars, Star Ware, and Star Watch. He is also a contributing editor for Astronomy magazine, where he has authored the magazine’s monthly “Binocular Universe” column and “Phil Harrington’s Challenge Objects,” a quarterly online column on Astronomy.com. He is an Adjunct Professor at Dowling College and Suffolk County Community College, New York, where he teaches courses in stellar and planetary astronomy. Cosmic Challenge The Ultimate Observing List for Amateurs PHILIP S. HARRINGTON CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao˜ Paulo, Delhi, Dubai, Tokyo, Mexico City Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521899369 C P.
    [Show full text]
  • 2015 in Living Color
    THE TEXAS STAR PARTY 2015 TELESCOPE OBSERVING CLUB BY JOHN WAGONER TEXAS ASTRONOMICAL SOCIETY OF DALLAS RULES AND REGULATIONS Welcome to the Texas Star Party's Telescope Observing Club. The purpose of this club is not to test your observing skills by throwing the toughest objects at you that are hard to see under any conditions, but to give you an opportunity to observe 25 showcase objects under the ideal conditions of these pristine West Texas skies, thus displaying them to their best advantage. The regular observing program is “In Living Color”. These are colorful objects consisting of single, double, & multiple stars and planetary nebula. Note any color you detect in your observing notes. You need to observe 25 objects of the 30 available to get your pin, but if you are using a smaller scope and have a little trouble with some of the objects, just mark it as “tried” and move on, and you will get credit for the object. If you detect a hint of color, please note this in your log. We are also bringing back “I Have No Idea Where I Am” from 2013. This is a list of 29 objects. Only 25 objects need be observed. That's it. Any size telescope can be used. All observations must be made at the Texas Star Party to qualify. All objects are within range of small (6”) to medium sized (10”) telescopes, and are available for observation between 9:00PM and 5:00AM any time during the TSP. Each person completing this list will receive an official Texas Star Party Telescope Observing Club lapel pin.
    [Show full text]
  • Making a Sky Atlas
    Appendix A Making a Sky Atlas Although a number of very advanced sky atlases are now available in print, none is likely to be ideal for any given task. Published atlases will probably have too few or too many guide stars, too few or too many deep-sky objects plotted in them, wrong- size charts, etc. I found that with MegaStar I could design and make, specifically for my survey, a “just right” personalized atlas. My atlas consists of 108 charts, each about twenty square degrees in size, with guide stars down to magnitude 8.9. I used only the northernmost 78 charts, since I observed the sky only down to –35°. On the charts I plotted only the objects I wanted to observe. In addition I made enlargements of small, overcrowded areas (“quad charts”) as well as separate large-scale charts for the Virgo Galaxy Cluster, the latter with guide stars down to magnitude 11.4. I put the charts in plastic sheet protectors in a three-ring binder, taking them out and plac- ing them on my telescope mount’s clipboard as needed. To find an object I would use the 35 mm finder (except in the Virgo Cluster, where I used the 60 mm as the finder) to point the ensemble of telescopes at the indicated spot among the guide stars. If the object was not seen in the 35 mm, as it usually was not, I would then look in the larger telescopes. If the object was not immediately visible even in the primary telescope – a not uncommon occur- rence due to inexact initial pointing – I would then scan around for it.
    [Show full text]
  • The 3-D Ionization Structure of the Planetary Nebula NGC6565
    1 Abstract. A detailed study of the planetary nebula NGC 6565 has been carried out on long-slit echellograms (λ/∆λ=60000, spectral range=λλ3900–7750A)˚ at six, equally spaced position angles. The expansion velocity field, the c(Hβ) distribution and the radial profile of the physical conditions (electron temperature and density) are obtained. The distance, radius, mass and filling factor of the nebula and the temperature and luminosity of the cen- tral star are derived. The radial ionization structure is analyzed using both the classical method and the photo- ionization code CLOUDY. Moreover, we present the spa- tial structure in a series of images from different directions, allowing the reader to “see” the nebula in 3-D. NGC 6565 results to be a young (2000–2500 years), patchy, optically thick triaxial ellipsoid (a=10.1 arcsec, a/b=1.4, a/c=1.7) projected almost pole-on. The matter close to major axis was swept-up by some accelerating agent (fast wind? ion- ization? magnetic fields?), forming two faint and asym- metric polar cups. A large cocoon of almost neutral gas completely embeds the ionized nebula. NGC 6565 is in a recombination phase, because of the luminosity drop of the massive powering star, which is reaching the white dwarf domain (logT∗ ≃5.08 K; logL∗/L⊙ ≃2.0). The stel- lar decline started about 1000 years ago, but the main nebula remained optically thin for other 600 years before the recombination phase occurred. In the near future the ionization front will re-grow, since the dilution factor due to the expansion will prevail on the slower and slower stel- lar decline.
    [Show full text]