DOCSLIB.ORG

Polarimetry of the Protoplanetary Nebula AFGL 2688 V

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Polarimetry of the Protoplanetary Nebula AFGL 2688 V View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by The University of North Carolina at Greensboro Astronomy Reports, Vol. 48, No. 4, 2004, pp. 288–300. Translated from Astronomicheski˘ıZhurnal, Vol. 81, No. 4, 2004, pp. 319–332. Original Russian Text Copyright c 2004 by Klochkova, Panchuk, Yushkin, Miroshnichenko. Polarimetry of the Protoplanetary Nebula AFGL 2688 V. G. Klochkova1,V. E. Panchuk 1,M. V. Yushkin 1,andA.S.Miroshnichenko2,3 1Special Astrophysical Observatory, Russian Academy of Sciences, Nizhni ˘ı Arkhyz, Karacha ˘ı -Cherkessian Republic, 357147 Russia 2Main Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, St. Petersburg, 196140 Russia 3Ritter Observatory, University of Toledo, Toledo, OH 43606–3390, USA Received September 10, 2003; in final form, November 10, 2003 Abstract—Our spectroscopic (with resolution R = 75 000) and spectropolarimetric (R = 15 000)obser- vations with the 6-m telescope of the Special Astrophysical Observatory have enabled us to distinguish photospheric and circumstellar features in the optical spectrum of the bipolar protoplanetary nebula AFGL 2688 for the first time. The linear polarization of the radiation was measured at 5000–6600 A.˚ The emission in the lines of the sodium doublet and the Swan bands is formed in the envelope, and the mechanism exciting the transitions is resonance fluorescence. We conclude that the circumstellar envelope has a low density. Features of the structure of the nebula are discussed based on published high-angular-resolution photometric and polarimetric (HST NICMOS) data. c 2004 MAIK “Nauka/Interperiodica”. 1. INTRODUCTION polarimetric data and present the results of new high- angular-resolution polarimetric observations aimed Mass loss on and after the asymptotic giant at distinguishing the radiation of the central star from branch (the AGB and post-AGB stages) is accom- that of the circumstellar envelope of AFGL 2688. panied by the formation of a gas and dust envelope. We selected this object, known (from broadband The angular size of this envelope can be below the polarimetry) for its high degree of polarization, for the resolution limit for ground-based telescopes. In this development of our method. case, asymmetry of the envelope can be detected from the presence of radiation polarized by scattering 2. OBSERVATIONS AND REDUCTION on the envelope’s dust component. The degree of polarization depends on the scattering conditions Since these are the first high-spectral-resolution and the extent to which the star providing the spectropolarimetric observations of a post-AGB ob- unpolarized light is obscured. The protoplanetary ject, the observational method requires some dis- cussion. Medium resolution is preferable for most nebula AFGL 2688 is one of three bipolar post-AGB spectropolarimetric observations, with the exception structures resolved by ground-based telescopes [1, of studies of magnetic main-sequence stars, when 2]. Thirty years ago, the optical image of the source measurement of the four Stokes parameters within was thought to represent a pair of compact blue the profiles of magnetically sensitive lines makes it galaxies, IV Zw 67, at a distance of 30 Mpc [3]. possible to map the stellar magnetic fields [7, 8]. In During the flights of the AFCRL rockets in 1975, a other cases, the spectral resolution is chosen based on source that was unusually bright at 10 and 20 µmand the fact that, since the polarization of spectral features was not present in the 2.2 µm catalog of Neugebauer is low, it is necessary to obtain signal-to-noise ratios and Leighton [4] was detected. The nebula’s optical for such features appreciably higher than the values image consists of two elliptical lobes with different characteristic of spectrophotometric measurements brightnesses elongated approximately north–south. of unpolarized light. Within the possibilities provided The central object illuminating the lobes is hidden by a single telescope, this can usually be achieved from the observer by a dark bridge, thought to be by reducing the spectral resolution, which is often a dust disk or torus. High-angular-resolution HST done without taking into consideration the ratio of the observations [5] have increased the number of objects line’s width to the detector’s resolution. A more de- similar to AFGL 2688 to nine. The parameters and tailed consideration shows that the problem cannot be atmospheric chemical composition of the central star solved so trivially; as an example, we consider the es- were determined in [6]. Here, we discuss published timation of the uncertainties of equivalent widths, W . 1063-7729/04/4804-0288$26.00 c 2004 MAIK “Nauka/Interperiodica” PROTOPLANETARY NEBULA AFGL 2688 289 (a) (b) 25 20 , % 15 p 10 5 0 36 38 40 42 44 46 36 38 40 42 44 46 mm Fig. 1. (a) Instrumental polarization, p, measured from spectra of the zero-polarization standard ζ Peg in the center of each order with number m [11]. (b) Polarization as a function of m from spectral measurements of the polarization standard HD 204827. The instrumental polarization has been subtracted. For equal numbers of counts, N, detected during an echelle spectrograph [9] converted into a spectropo- exposure per unit wavelength (Angstrom),˚ the uncer- larimeter [11]. Observing at the prime focus makes tainty in the equivalent width is inversely proportional it possible to avoid the effects of instrumental polar- to the square root of the spectral resolution, R,when ization produced at the third (flat) mirror of the 6-m the light detector’s pixel width, s, is larger than the telescope. We simultaneously recorded wavelengths line’s width, l [9]. Thus, if s>l, it is advantageous of 4950–6630 A.˚ The width of a pixel of the light to increase the spectral resolution, R, and not N,if detector (a CCD chip with 1160 × 1040 elements) the latter must be achieved by increasing the total corresponded to a radial-velocity interval of 7.7 km/s. exposure time. This statement is correct if the readout A broadband (600–700 nm) image of the nebula is noise is negligible (as is true for spectrophotometric shown in Fig. 1 of [1]. We observed the nebula’s observations). Thus, the most “economical” spectral northern lobe, with the slit center placed on the main resolution (for measurements of W )istheR value axis of the nebula (the line connecting the centers of providing a linear resolution equal to the spectral line the optical lobes), 5 from the nebula’s center, which width (s = l). is hidden by a dark bridge. The effective magnitude of the part of the image that fit into the slit was Post-AGB stars are surrounded by cool envelopes 15.5m. During each of the exposures, we rotated s<l with narrow lines, and the condition is satisfied the spectrograph to compensate for the rotation of only if R>60 000. For this reason, it is desirable the field that is characteristic of telescopes with to approach such resolutions if one wishes to use altitude–azimuth mounts. During the spectropolari- spectropolarimetric observations to separate the light metric observations, we kept the projection of the emitted by the star and envelope. Below, we show that slit perpendicular to the nebula’s main axis during increasing the spectral resolution by more than an one exposure, and turned it counterclockwise by 45◦ order of magnitude (from R<1000 to R = 15 000) relative to the first position during the next exposure. made it possible to obtain new spectrophotometric Examples of the resulting spectropolarimetric echelle information and enabled us to improve the model of images are shown in Fig. 7 of [11]. In addition to the AFGL 2688. However, it is more useful to study the target object, we observed standard stars for which wavelength dependence of the polarization detected photometric data indicated either high polarization for a number of post-AGB objects over a wide spectral (several percent) or no polarization (zero-polarization range [10] using medium-resolution spectra, since standards). The position of the crystal optical axes of such spectra can also be used to detect (but not the analyzer relative to the spectrograph’s elements measure) polarization effects in individual spectral was always the same. features. We reduced the echelle spectrophotometric im- Our high-spectral-resolution (R = 15 000) linear- ages with the ECHELLE software package of the polarization measurements were obtained at the MIDAS system using original algorithms tested for prime focus of the 6-m telescope of the Special the reduction of observations of polarization stan- Astrophysical Observatory (SAO) with the PFES dards [11, 12]. In particular, these algorithms make ASTRONOMY REPORTS Vol. 48 No. 4 2004 290 KLOCHKOVA et al. 2 λ r 1 0 80 60 , % p 40 20 0 110° θ 100° 90° 5580° 5600° 5620° λ, Å Fig. 2. Fragment of the spectrum (R = 15 000) of the central part of the northern lobe of the AFGL 2688 nebula near the C2 (1; 2) 5585.2 A˚ and (0; 1) 5635.5 A˚ Swan bands and graphs of the linear polarization and polarization position angle. it possible to remove effects due to the fact that the of the lens components of the spectrograph optics, spectrograph is not rigid, which appear when the this leads to a complex wavelength dependence for projected position angle of the slit is changed by 45◦, the instrumental polarization. Figure 1a shows the i.e., during rapid repositioning of the spectrograph. instrumental polarization measured for the centers A characteristic feature of spectropolarimetric obser- of the echelle orders during observations of zero- vations with an echelle spectrograph is the complex polarization standards. An example of correction for relation between the instrumental polarization and this relation is presented in Fig.
Load more

Recommended publications
  • Kuchner, M. & Seager, S., Extrasolar Carbon Planets, Arxiv:Astro-Ph
    Extrasolar Carbon Planets Marc J. Kuchner1 Princeton University Department of Astrophysical Sciences Peyton Hall, Princeton, NJ 08544 S. Seager Carnegie Institution of Washington, 5241 Broad Branch Rd. NW, Washington DC 20015 [email protected] ABSTRACT We suggest that some extrasolar planets . 60 ML will form substantially from silicon carbide and other carbon compounds. Pulsar planets and low-mass white dwarf planets are especially good candidate members of this new class of planets, but these objects could also conceivably form around stars like the Sun. This planet-formation pathway requires only a factor of two local enhancement of the protoplanetary disk’s C/O ratio above solar, a condition that pileups of carbonaceous grains may create in ordinary protoplanetary disks. Hot, Neptune- mass carbon planets should show a significant paucity of water vapor in their spectra compared to hot planets with solar abundances. Cooler, less massive carbon planets may show hydrocarbon-rich spectra and tar-covered surfaces. The high sublimation temperatures of diamond, SiC, and other carbon compounds could protect these planets from carbon depletion at high temperatures. arXiv:astro-ph/0504214v2 2 May 2005 Subject headings: astrobiology — planets and satellites, individual (Mercury, Jupiter) — planetary systems: formation — pulsars, individual (PSR 1257+12) — white dwarfs 1. INTRODUCTION The recent discoveries of Neptune-mass extrasolar planets by the radial velocity method (Santos et al. 2004; McArthur et al. 2004; Butler et al. 2004) and the rapid development 1Hubble Fellow –2– of new technologies to study the compositions of low-mass extrasolar planets (see, e.g., the review by Kuchner & Spergel 2003) have compelled several authors to consider planets with chemistries unlike those found in the solar system (Stevenson 2004) such as water planets (Kuchner 2003; Leger et al.
    [Show full text]
  • 1 Towards a Molecular Inventory of Protostellar
    TOWARDS A MOLECULAR INVENTORY OF PROTOSTELLAR DISCS Glenn J White (1), Mark A. Thompson (1), C.V. Malcolm Fridlund (2), Monica Huldtgren White (3) (1) University of Kent, UK, [email protected] (2) ESTEC, NL, (3) Stockholm Observatory, Sweden Abstract solid, atomic and ionised material in the pre- planetary environment. The chemical environment in circumstellar discs is a unique diagnostic of the thermal, physical and Details of the survey chemical environment. In this paper we examine the structure of star formation regions giving rise to low We are carrying out a survey of nearby star mass stars, and the chemical environment inside formation regions to them, and the circumstellar discs around the developing stars. • Search in the optical/IR region for triggered/induced solar-type star formation. Introduction We measure the boundary conditions, such as external pressure of ionised gas that Life develops from a sequence of organic chemical triggering the star formation using radio processes that develop sufficient complexity to lead observations, and from molecular line to mutating and self-replicating sentient organisms. tracers, estimate the internal pressure in the Cellular structures, formed following selective molecular gas. evolution along the Tree of Life, emerged from the • Characterise the properties of the central reactions amongst these simple organic compounds, protostellar core and protostellar discs at which were derived from cosmically abundant submm, mid and near-IR wavelengths, by elements and molecules that are abundant in space. measuring the spectral energy distributions Much of this early chemical inventory was delivered and the atomic and molecular inventory of a to the surfaces of planets, including the Earth, during sample of circumstellar discs the early phase of massive cometary bombardment of • Measure the chemical inventory of gas- the earth - e.g.
    [Show full text]
  • Observing Dust Grain Growth and Sedimentation in Circumstellar Discs Interpretations and Predictions of Their Observable Quantities in a Multi-Wavelength Approach
    Observing dust grain growth and sedimentation in circumstellar discs Interpretations and predictions of their observable quantities in a multi-wavelength approach Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftliche Fakult¨at der Christian-Albrechts Universit¨atzu Kiel vorgelegt von J¨urgenSauter Kiel, 2011 Referent : Prof. Dr. S. Wolf Koreferent: Prof. Dr. C. Dullemond Tag der m¨undlichen Pr¨ufung: 7. Juli 2011 Zum Druck genehmigt: 7. Juli 2011 gez. Prof. Dr. L. Kipp, Dekan To my growing family Abstract In the present thesis, the observational effects of dust grain growth and sedimentation in circumstellar discs are investigated. The growth of dust grains from some nanometres in diameter as found in the inter- stellar medium towards planetesimal bodies some meters in diameter is an important step in the formation of planets. However, this process is currently not entirely un- derstood. Especially, in the literature several `barriers' are discussed that apparently prohibit an effective growth of dust grains. Hence, it is of particular interest to compare theories and observational data in this respect. State-of-the-art radiative transfer techniques allow one to derive observable quantities from theoretical models that allow this comparison. In this thesis, generic tracers of dust grain growth in spatially high resolution multi-wavelength images are identified for the first time. Further, a possibility to detect a dust trapping mechanism for dust grains by local pressure maxima using the new interferometer, ALMA, is established. By fitting parametric models to new observations of the disc in the Bok globule CB 26, unexpected features of the system are revealed, such as a large inner void and the possibility to interpret the data without the need for grain growth.
    [Show full text]
  • The Dispersal of Planet-Forming Discs: Theory Confronts Observations Rsos.Royalsocietypublishing.Org Barbara Ercolano1,2, Ilaria Pascucci3,4
    The Dispersal of Planet-forming discs: Theory confronts Observations rsos.royalsocietypublishing.org Barbara Ercolano1;2, Ilaria Pascucci3;4 1Universitäts-Sternwarte München, Scheinerstr. 1, Research 81679 München, Germany 2Excellence Cluster Origin and Structure of the Article submitted to journal Universe, Boltzmannstr.2, 85748 Garching bei München, Germany 3Lunar and Planetary Laboratory, The University of Subject Areas: Arizona, Tucson, AZ 85721, USA Astrophysics 4Earths in Other Solar Systems Team, NASA Nexus Keywords: for Exoplanet System Science Protoplanetary Disks, Planet Formation Discs of gas and dust around Myr-old stars are a by-product of the star formation process and provide the raw material to form planets. Hence, their Author for correspondence: evolution and dispersal directly impact what type ercolanousm.lmu.de of planets can form and affect the final architecture of planetary systems. Here, we review empirical constraints on disc evolution and dispersal with special emphasis on transition discs, a subset of discs that appear to be caught in the act of clearing out planet-forming material. Along with observations, we summarize theoretical models that build our physical understanding of how discs evolve and disperse and discuss their significance in the context of the formation and evolution of planetary systems. By confronting theoretical predictions with observations, we also identify the most promising areas for future progress. ............ arXiv:1704.00214v2 [astro-ph.EP] 4 Apr 2017 c 2014 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/ by/4.0/, which permits unrestricted use, provided the original author and source are credited.
    [Show full text]
  • Pennsylvania Science Olympiad Southeast Regional Tournament 2013 Astronomy C Division Exam March 4, 2013
    PENNSYLVANIA SCIENCE OLYMPIAD SOUTHEAST REGIONAL TOURNAMENT 2013 ASTRONOMY C DIVISION EXAM MARCH 4, 2013 SCHOOL:________________________________________ TEAM NUMBER:_________________ INSTRUCTIONS: 1. Turn in all exam materials at the end of this event. Missing exam materials will result in immediate disqualification of the team in question. There is an exam packet as well as a blank answer sheet. 2. You may separate the exam pages. You may write in the exam. 3. Only the answers provided on the answer page will be considered. Do not write outside the designated spaces for each answer. 4. Include school name and school code number at the bottom of the answer sheet. Indicate the names of the participants legibly at the bottom of the answer sheet. Be prepared to display your wristband to the supervisor when asked. 5. Each question is worth one point. Tiebreaker questions are indicated with a (T#) in which the number indicates the order of consultation in the event of a tie. Tiebreaker questions count toward the overall raw score, and are only used as tiebreakers when there is a tie. In such cases, (T1) will be examined first, then (T2), and so on until the tie is broken. There are 12 tiebreakers. 6. When the time is up, the time is up. Continuing to write after the time is up risks immediate disqualification. 7. In the BONUS box on the answer sheet, name the gentleman depicted on the cover for a bonus point. 8. As per the 2013 Division C Rules Manual, each team is permitted to bring “either two laptop computers OR two 3-ring binders of any size, or one binder and one laptop” and programmable calculators.
    [Show full text]
  • Timescales of the Solar Protoplanetary Disk 233
    Russell et al.: Timescales of the Solar Protoplanetary Disk 233 Timescales of the Solar Protoplanetary Disk Sara S. Russell The Natural History Museum Lee Hartmann Harvard-Smithsonian Center for Astrophysics Jeff Cuzzi NASA Ames Research Center Alexander N. Krot Hawai‘i Institute of Geophysics and Planetology Matthieu Gounelle CSNSM–Université Paris XI Stu Weidenschilling Planetary Science Institute We summarize geochemical, astronomical, and theoretical constraints on the lifetime of the protoplanetary disk. Absolute Pb-Pb-isotopic dating of CAIs in CV chondrites (4567.2 ± 0.7 m.y.) and chondrules in CV (4566.7 ± 1 m.y.), CR (4564.7 ± 0.6 m.y.), and CB (4562.7 ± 0.5 m.y.) chondrites, and relative Al-Mg chronology of CAIs and chondrules in primitive chon- drites, suggest that high-temperature nebular processes, such as CAI and chondrule formation, lasted for about 3–5 m.y. Astronomical observations of the disks of low-mass, pre-main-se- quence stars suggest that disk lifetimes are about 3–5 m.y.; there are only few young stellar objects that survive with strong dust emission and gas accretion to ages of 10 m.y. These con- straints are generally consistent with dynamical modeling of solid particles in the protoplanetary disk, if rapid accretion of solids into bodies large enough to resist orbital decay and turbulent diffusion are taken into account. 1. INTRODUCTION chondritic meteorites — chondrules, refractory inclusions [Ca,Al-rich inclusions (CAIs) and amoeboid olivine ag- Both geochemical and astronomical techniques can be gregates (AOAs)], Fe,Ni-metal grains, and fine-grained ma- applied to constrain the age of the solar system and the trices — are largely crystalline, and were formed from chronology of early solar system processes (e.g., Podosek thermal processing of these grains and from condensation and Cassen, 1994).
    [Show full text]
  • Abstracts of Talks 1
    Abstracts of Talks 1 INVITED AND CONTRIBUTED TALKS (in order of presentation) Milky Way and Magellanic Cloud Surveys for Planetary Nebulae Quentin A. Parker, Macquarie University I will review current major progress in PN surveys in our own Galaxy and the Magellanic clouds whilst giving relevant historical context and background. The recent on-line availability of large-scale wide-field surveys of the Galaxy in several optical and near/mid-infrared passbands has provided unprecedented opportunities to refine selection techniques and eliminate contaminants. This has been coupled with surveys offering improved sensitivity and resolution, permitting more extreme ends of the PN luminosity function to be explored while probing hitherto underrepresented evolutionary states. Known PN in our Galaxy and LMC have been significantly increased over the last few years due primarily to the advent of narrow-band imaging in important nebula lines such as H-alpha, [OIII] and [SIII]. These PNe are generally of lower surface brightness, larger angular extent, in more obscured regions and in later stages of evolution than those in most previous surveys. A more representative PN population for in-depth study is now available, particularly in the LMC where the known distance adds considerable utility for derived PN parameters. Future prospects for Galactic and LMC PN research are briefly highlighted. Local Group Surveys for Planetary Nebulae Laura Magrini, INAF, Osservatorio Astrofisico di Arcetri The Local Group (LG) represents the best environment to study in detail the PN population in a large number of morphological types of galaxies. The closeness of the LG galaxies allows us to investigate the faintest side of the PN luminosity function and to detect PNe also in the less luminous galaxies, the dwarf galaxies, where a small number of them is expected.
    [Show full text]
  • The Physics and Chemistry of Nebular Evolution 209
    Ciesla and Charnley: The Physics and Chemistry of Nebular Evolution 209 The Physics and Chemistry of Nebular Evolution F. J. Ciesla and S. B. Charnley NASA Ames Research Center Primitive materials in the solar system, found in both chondritic meteorites and comets, record distinct chemical environments that existed within the solar nebula. These environments would have been shaped by the dynamic evolution of the solar nebula, which would have affected the local pressure, temperature, radiation flux, and available abundances of chemical reactants. In this chapter we summarize the major physical processes that would have affected the chemis- try of the solar nebula and how the effects of these processes are observed in the meteoritic record. We also discuss nebular chemistry in the broader context of recent observations and chemical models of astronomical disks. We review recent disk chemistry models and discuss their applicability to the solar nebula, as well as their direct and potential relevance to meteor- itical studies. 1. INTRODUCTION ent facets of disk evolution may have been and discuss what effects this evolution may have had on nebular chemistry. Condensation calculations have been used as the basic (For example, we will discuss the effect of mass transport guides for understanding solar nebula chemistry over the through the solar nebula even though the driving mecha- last few decades. As reviewed by Ebel (2006), condensa- nism for this transport remains an area of ongoing research.) tion calculations provide information about the direction of It should be the goal of future studies and future generations chemical evolution, telling us what the end products would of meteoriticists, astronomers, and astrophysicists to im- be in a system given a constant chemical inventory, infinite prove upon the overviews provided here and make greater time, and ready access of all chemical species to one an- strides toward developing a coherent, unified model for the other.
    [Show full text]
  • Scientific World-Vol6-FINAL for PDF.Pmd
    FORMATION OF INTERSTELLAR BUBBLE: A TIME DEPENDENT NUMERICAL SIMULATION B. Aryal*, A. Devkota* and R. Weinberger** *Central Department of Physics, Tribhuvan University, Kirtipur, Nepal. **Institute of Astrophysics, Innsbruck University, Innsbruck, Austria. Abstract: We present results of the numerical simulations for the first 105 years of the development of spherically symmetric interstellar bubbles. We have assumed three phase interstellar medium (ISM) model and estimated the size of the interstellar bubbles (ISB). Our results are based on calculations including 106 virtual stellar wind particles. We discuss the result in the context of Asymptotic Giant Branch (AGB) star, Proto-Planetary Nebula (PPN) phase and Relativistic Wind (RW) star. The size of the ISB is found 0.14 pc to 9.03 pc in the case of AGB (Asymptotic Giant Branch) star. This size increases for the PPN and RW phase to 0.64 - 40.28 pc and 2.83 pc - 178.12 pc, respectively. It is found that the ISB can survive in the case of cold and warm interstellar medium. In the hot ISM, the ISB can not be formed due to the AGB wind. The bubble can survive in the case of PPN phase stellar wind for all kinds of the ISM. In addition, we found that the bubble can be formed in the case of RW when the ISM is hot. In the cold ISM, the ISB can not be formed due to the RW. In the warm ISM, bubble can be formed due to the relativistic (pulsar) wind if the mass loss rate is extremely high. In the warm ISM, the overall size of the bubble increases but do not exceed the recommended limit.
    [Show full text]
  • PO and PN in the Wind of the Oxygen-Rich AGB Star IK Tauri⋆
    A&A 558, A132 (2013) Astronomy DOI: 10.1051/0004-6361/201321349 & c ESO 2013 Astrophysics PO and PN in the wind of the oxygen-rich AGB star IK Tauri? E. De Beck1;2, T. Kaminski´ 1, N. A. Patel3, K. H. Young3, C. A. Gottlieb3, K. M. Menten1, and L. Decin2;4 1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: [email protected] 2 Instituut voor Sterrenkunde, Departement Natuurkunde en Sterrenkunde, Celestijnenlaan 200D, 3001 Heverlee, Belgium 3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS78, Cambridge, MA 02138, USA 4 Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, 1098 Amsterdam, The Netherlands Received 22 February 2013 / Accepted 13 September 2013 ABSTRACT Context. Phosphorus-bearing compounds have only been studied in the circumstellar environments of the asymptotic giant branch star IRC +10 216 and the protoplanetary nebula CRL 2688, both carbon-rich objects, and the oxygen-rich red supergiant VY CMa. The current chemical models cannot reproduce the high abundances of PO and PN derived from observations of VY CMa. No obser- vations have been reported of phosphorus in the circumstellar envelopes of oxygen-rich asymptotic giant branch stars. Aims. We aim to set observational constraints on the phosphorous chemistry in the circumstellar envelopes of oxygen-rich asymptotic giant branch stars, by focussing on the Mira-type variable star IK Tau. Methods. Using the IRAM 30 m telescope and the Submillimeter Array, we observed four rotational transitions of PN (J = 2−1; 3−2; 6−5; 7−6) and four of PO (J = 5=2−3=2; 7=2−5=2; 13=2−11=2; 15=2−13=2).
    [Show full text]
  • Arxiv:2009.11122V1 [Astro-Ph.SR] 23 Sep 2020 02 Esr Ta.21) N La Ta.(00 Ru That Argue Hole
    Draft version September 24, 2020 Preprint typeset using LATEX style emulateapj v. 12/16/11 A NEW CANDIDATE LUMINOUS BLUE VARIABLE Donald F. Figer1,Francisco Najarro2, Maria Messineo3,J.Simon Clark4,Karl M. Menten5 Draft version September 24, 2020 ABSTRACT We identify IRAS 16115−5044, which was previously classified as a protoplanetary nebula (PPN), as a 5.75 candidate luminous blue variable (LBV). The star has high luminosity (∼>10 L⊙), ensuring supergiant status, has a temperature similar to LBVs, is photometrically and spectroscopically variable, and is surrounded by warm dust. Its near-infrared spectrum shows the presence of several lines of HI, HeI, FeII, Fe[II], MgII, and NaI with shapes ranging from pure absorption and P Cygni profiles to full emission. These characteristics are often observed together in the relatively rare LBV class of stars, of which only ≈20 are known in the Galaxy. The key to the new classification is the fact that we compute a new distance and extinction that yields a luminosity significantly in excess of those for post-AGB PPNe, for which the initial masses are <8 M⊙. Assuming single star evolution, we estimate an initial mass of ≈40 M⊙. Subject headings: Luminous blue variable stars (944) — Stellar evolution (1599) — Massive stars (732) — Supergiant stars (1661) — Infrared sources (793) — Stellar mass loss (1613) 1. INTRODUCTION In this paper, we demonstrate that IRAS16115−5044 Luminous blue variables (LBVs) have a distinct set of ob- (G332.2843-00.0002) has all the characteristics of LBVs, served characteristics (Conti 1984). They have luminosities confirming the claim in Messineo et al.
    [Show full text]
  • Accretion Processes Alessandro Morbidelli Cnrs, Observatoire De La Cote D’Azur, Nice, France
    ACCRETION PROCESSES ALESSANDRO MORBIDELLI CNRS, OBSERVATOIRE DE LA COTE D’AZUR, NICE, FRANCE Abstract In planetary science, accretion is the process in which solids agglomerate to form larger and larger objects and eventually planets are produced. The initial conditions are a disc of gas and microscopic solid particles, with a total mass of about 1% of the gas mass. These discs are routinely detected around young stars and are now imaged with the new generation of instruments. Accretion has to be effective and fast. Effective, because the original total mass in solids in the solar protoplanetary disk was probably of the order of ~ 300 Earth masses, and the mass incorporated into the planets is ~100 Earth masses. Fast, because the cores of the giant planets had to grow to tens of Earth masses in order to capture massive doses of hydrogen and helium from the disc before the dispersal of the latter, i.e. in a few millions of years. The surveys for extrasolar planets have shown that most stars have planets around them. Accretion is therefore not an oddity of the Solar System. However, the final planetary systems are very different from each other, and typically very different from the Solar System. Observations have shown that more than 50% of the stars have planets that don’t have analogues in the Solar System. Therefore the Solar System is not the typical specimen. Thus, models of planet accretion have to explain not only how planets form but also why the outcomes of the accretion history can be so diverse. There is probably not one accretion process but several, depending on the scale at which accretion operates.
    [Show full text]