DOCSLIB.ORG

Asteroseismology of the Β Cep Star HD 129929

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Asteroseismology of the Β Cep Star HD 129929 A&A 415, 241–249 (2004) Astronomy DOI: 10.1051/0004-6361:20034142 & c ESO 2004 Astrophysics Asteroseismology of the β Cep star HD 129929 I. Observations, oscillation frequencies and stellar parameters C. Aerts1, C. Waelkens1, J. Daszy´nska-Daszkiewicz1,3,, M.-A. Dupret2,4,, A. Thoul2,†, R. Scuflaire2, K. Uytterhoeven1, E. Niemczura3, and A. Noels2 1 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium 2 Institut d’Astrophysique et de G´eophysique, Universit´edeLi`ege, all´ee du Six Aoˆut 17, 4000 Li`ege, Belgium 3 Astronomical Institute of the Wrocław University, ul. Kopernika 11, 51-622 Wrocław, Poland 4 Instituto de Astrof´ısica de Andaluc´ıa-CSIC, Apartado 3004, 18080 Granada, Spain Received 1 August 2003 / Accepted 25 September 2003 Abstract. We have gathered and analysed a timeseries of 1493 high-quality multicolour Geneva photometric data of the B3V β Cep star HD 129929. The dataset has a time base of 21.2 years. The occurrence of a beating phenomenon is evident from the data. We find evidence for the presence of at least six frequencies, among which we see components of two frequency multiplets with an average spacing of ∼0.0121 c d−1 which points towards very slow rotation. This result is in agreement with new spectroscopic data of the star and also with previously taken UV spectra. We provide the amplitudes of the six frequencies in all seven photometric filters. The metal content of the star is Z = 0.018 ± 0.004. All these observational results will be used to perform detailed seismic modelling of this massive star in a subsequent paper. Key words. stars: oscillations – stars: variables: general – stars: individual: HD 129929 1. Introduction Waelkens & Rufener (1983). HD 129929 is not included in the list of runaway stars composed from HIPPARCOS data = The star HD 129929 (spectral type B3V, V mag 8.1) is quite (Lindblad et al. 1997). However, the new HIPPARCOS dis- a peculiar object, as it is situated at intermediate galactic lati- tance estimate requires a mean vertical velocity of “only” = ◦ tude with b 20.21 (Hill et al. 1974), which is unusual for 13 km s−1 should the star have formed in the galactic plane such a massive object. This is the reason why Rufener (1981) (where we have used the age estimate of 17 million years re- included it in the Geneva database as a standard, which led him cently found by Aerts et al. 2003). We compare this value with to discover its variability. our new estimate of the radial velocity of the star in Sect. 2. The parallax of HD 129929 has meanwhile been measured by HIPPARCOS, albeit with a large uncertainty. The mea- Waelkens & Rufener (1983) made the first detailed study sured π = 1.48 ± 1.03 corresponds to a distance estimate of of the variability of HD 129929 by means of Geneva photom- etry and found the star to vary triperiodically with frequen- some 675 parsec. This value leads to a distance of 233 par- −1 sec perpendicular to the Galactic plane, which is less than cies 6.460965, 6.979940 and 6.449041 c d . The amplitudes half the value derived earlier from multicolour photometry by of these three frequencies were found to range between 10 to 18 millimagnitudes. The star was hence classified as a new Send offprint requests to: M.-A. Dupret, e-mail: [email protected] β Cep star. More recently, Heynderickx (1992) also established Based on data gathered with the Swiss 0.7m telescope equipped three frequencies in a more extensive dataset that included the with the photometer P7 of the Geneva Observatory and with the one used by Waelkens & Rufener (1983). However, only two of FEROS spectrograph attached to the ESO 2.2 m telescope, both these are in common with those found by Waelkens & Rufener situated at La Silla in Chile; the reduced photometric multicolour data (1983) and moreover the values he lists are slightly different: are provided in Table 1, which is only available in electronic form at 6.98670, 6.45610 and 6.97697 c d−1. the CDS via anonymous ftp to With such closely spaced frequencies, HD 129929 is a cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/415/241 very interesting massive pulsating star to try and perform seis- Postdoctoral Fellow, Belgian Federal Office for Scientific, mic modelling, once the frequencies are firmly established and Technical and Cultural Affairs. the modes are well identified. This situation now occurs for Marie-Curie Postdoctoral Fellow, European Union. HD 129929 and the main results of our seismic study based † Chercheur Qualifi´e au Fonds National de la Recherche upon the multicolour photometry were summarized recently Scientifique, Belgium. in Aerts et al. (2003). They established firm evidence of the Article published by EDP Sciences and available at http://www.aanda.org or http://dx.doi.org/10.1051/0004-6361:20034142 242 C. Aerts et al.: Asteroseismology of HD 129929. I. Only high-quality data, with a typical individual error less than 5 mmag, were retained in our analysis. An example of the lightcurve in the Geneva V filter for an observing run of 11 days is shown in Fig. 2. It is evident from this graph that HD 129929 behaves multiperiodically and that large beating effects occur on a timescale of a week. Such beat periods are typical for multiperiodic β Cep stars. In order to confirm the important result that the star exhibits non-rigid rotation with a very low equatorial rotation velocity of some 2 km s−1 (Aerts et al. 2003), we have taken one high- resolution (wavelength step of 0.0298 Å)echelle ´ spectrum of HD 129929 with the FEROS spectrograph attached to the ESO 2.2 m telescope. We integrated over 2000 s to reach a signal- to-noise ratio of some 200 at 4550 Å. This spectrum leads to a radial velocity of 64±1kms−1, from which we derive a velocity Fig. 1. The spectral window of our photometric data of HD 129929. of 22 km s−1 perpendicular to the Galactic plane. This is largely sufficient to bring the star to its current position and suggests that it was kicked out of the Galactic plane, rather than having occurrence of core overshooting in the star with an overshoot- formed outside of the plane. If so, it must have been kicked ing parameter α = 0.1. Moreover, they have shown the star to ov when it was 10 million years old if we consider it to move with have non-rigid slow rotation. constant speed ever since. The current paper is the first one in a series of three de- We show some particular selected absorption lines of the voted to the in-depth physical interpretation of the variability spectrum in Fig. 3. We see that the star is indeed sharp-lined. of HD 129929. In this first paper we provide the full frequency + + content based on all available measurements of this star. We An upper limit of the overall (thermal pulsational rotational) broadening can be derived from the FWHM of the different show that at least six oscillation modes at millimagnitude level metal lines in the spectrum. This leads to a value of some are excited in HD 129929. Moreover, we compare the rotation −1 velocity predicted by Aerts et al. (2003) from the photometric 17 km s . Taking into account the thermal broadening of a B3V star (some 10 km s−1) and the fact that considerable pul- variability with a recently obtained high-resolution spectrum sational broadening must occur, the spectrum provides inde- of the star. Our extensive seismic study will be published in a pendent evidence for the slow rotation of the star. We find an subsequent paper in this series (Dupret et al. 2004, hereafter upper limit of ∼13 km s−1 (assuming no pulsational broaden- termed Paper II) while a detailed comparison between inde- v i pendent evolution and oscillation codes, with HD 1299929 as ing nor any turbulence) for sin which is compatible with the estimate of Ω R = 2kms−1 provided by Aerts et al. (2003). a case study, constitutes a third paper in the series (Daszy´nska- Daszkiewicz et al., in preparation, Paper III). Finally, we mention that some low-resolution IUE spectra of HD 129929 are publicly available and have led previously to a radial-velocity estimate of 66 km s−1 which is entirely com- 2. Observations patible with our new result. These UV spectra also already showed that the star is sharp-lined but the resolution of these ff In an e ort to resolve and understand the discrepant fre- data is much lower than that of our FEROSechelle ´ spectrum. quency determinations by Heynderickx (1992) and Waelkens & Rufener (1983), HD 129929 was kept in the long-term pro- gramme of photometric monitoring of variable B stars per- 3. Frequency analysis formed by the Institute of Astronomy of the University of Leuven with the 0.7 m Swiss photometric telescope. This tele- For seismic analyses of stars to be successful, accurate fre- scope was operational at the La Silla observatory until 1997. It quency determinations of as many oscillation modes as pos- was equipped with the Geneva multicolour photometer P7. sible have to be derived. Heynderickx (1992) already pointed Many members of the Institute of Astronomy gathered in out, on the basis of some 800 datapoints with a time base of total 1493 good-quality data points with a total time base of some 15 years, that the star has closely spaced frequencies.
Load more

Recommended publications
  • Opacity Effects on Pulsations of Main-Sequence A-Type Stars
    atoms Article Opacity Effects on Pulsations of Main-Sequence A-Type Stars Joyce A. Guzik * ID , Christopher J. Fontes and Chris Fryer ID Los Alamos National Laboratory, Los Alamos, NM 87545, USA; [email protected] (C.J.F.); [email protected] (C.F.) * Correspondence: [email protected] Received: 10 April 2018; Accepted: 11 May 2018 ; Published: 4 June 2018 Abstract: Opacity enhancements for stellar interior conditions have been explored to explain observed pulsation frequencies and to extend the pulsation instability region for B-type main-sequence variable stars. For these stars, the pulsations are driven in the region of the opacity bump of Fe-group elements at ∼200,000 K in the stellar envelope. Here we explore effects of opacity enhancements for the somewhat cooler main-sequence A-type stars, in which p-mode pulsations are driven instead in the second helium ionization region at ∼50,000 K. We compare models using the new LANL OPLIB vs. LLNL OPAL opacities for the AGSS09 solar mixture. For models of two solar masses and effective temperature 7600 K, opacity enhancements have only a mild effect on pulsations, shifting mode frequencies and/or slightly changing kinetic-energy growth rates. Increased opacity near the bump at 200,000 K can induce convection that may alter composition gradients created by diffusive settling and radiative levitation. Opacity increases around the hydrogen and 1st He ionization region (∼13,000 K) can cause additional higher-frequency p modes to be excited, raising the possibility that improved treatment of these layers may result in prediction of new modes that could be tested by observations.
    [Show full text]
  • An Asteroseismic Study of the Beta Cephei Star 12 Lacertae: Multisite
    Mon. Not. R. Astron. Soc. 000, 1–15 (2002) Printed 31 October 2018 (MN LATEX style file v2.2) An asteroseismic study of the β Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling M. Desmet1⋆, M. Briquet1†, A. Thoul2‡, W. Zima1, P. De Cat3, G. Handler4, I. Ilyin5, E. Kambe6, J. Krzesinski7, H. Lehmann8, S. Masuda9, P. Mathias10, D. E. Mkrtichian11, J. Telting12, K. Uytterhoeven13, S. L. S. Yang14 and C. Aerts1,15 1 Institute of Astronomy - KULeuven, Celestijnenlaan 200D, 3001 Leuven, Belgium 2 Institut d’Astrophysique et de G´eophysique de l’Universit´ede Li`ege, 17, All´ee du 6 Aoˆut, 4000 Li`ege, Belgium 3 Koninklijke Sterrenwacht van Belgi¨e, Ringlaan 3, 1180 Brussel, Belgium 4 Institut f¨ur Astronomie, Universist¨at Wien, T¨urkenschanzstrasse 17, 1180 Wien, Austria 5 Astrophysical Institute Potsdam, An der Sternwarte 16 D-14482 Potsdam, Germany 6 Okayama Astrophysical Observatory, National Astronomical Observatory, Kamogata, Okayama 719-0232, Japan 7 Mt. Suhora Observatory, Cracow Pedagogical University, Ul. Podchorazych 2, 30-084 Cracow, Poland 8 Karl-Schwarzschild-Observatorium, Th¨uringer Landessternwarte, 7778 Tautenburg, Germany 9 Tokushima Science Museum, Asutamu Land Tokushima, 45 - 22 Kibigadani, Nato, Itano-cho, Itano-gun, Tokushima 779-0111, Japan 10 UNS, CNRS, OCA, Campus Valrose, UMR 6525 H. Fizeau, F-06108 Nice Cedex 2, France 11 Astronomical Observatory of Odessa National University, Marazlievskaya, 1v, 65014 Odessa, Ukraine 12 Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain 13 Instituto de Astrof´ısica de Canarias, Calle Via L´actea s/n, 38205 La Laguna (TF, Spain) 14 Department of Physics and Astronomy, Universtity of Victoria, Victoria, BC V8W 3P6, Canada 15 Department of Astrophysics, University of Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands Accepted 2008.
    [Show full text]
  • Index to JRASC Volumes 61-90 (PDF)
    THE ROYAL ASTRONOMICAL SOCIETY OF CANADA GENERAL INDEX to the JOURNAL 1967–1996 Volumes 61 to 90 inclusive (including the NATIONAL NEWSLETTER, NATIONAL NEWSLETTER/BULLETIN, and BULLETIN) Compiled by Beverly Miskolczi and David Turner* * Editor of the Journal 1994–2000 Layout and Production by David Lane Published by and Copyright 2002 by The Royal Astronomical Society of Canada 136 Dupont Street Toronto, Ontario, M5R 1V2 Canada www.rasc.ca — [email protected] Table of Contents Preface ....................................................................................2 Volume Number Reference ...................................................3 Subject Index Reference ........................................................4 Subject Index ..........................................................................7 Author Index ..................................................................... 121 Abstracts of Papers Presented at Annual Meetings of the National Committee for Canada of the I.A.U. (1967–1970) and Canadian Astronomical Society (1971–1996) .......................................................................168 Abstracts of Papers Presented at the Annual General Assembly of the Royal Astronomical Society of Canada (1969–1996) ...........................................................207 JRASC Index (1967-1996) Page 1 PREFACE The last cumulative Index to the Journal, published in 1971, was compiled by Ruth J. Northcott and assembled for publication by Helen Sawyer Hogg. It included all articles published in the Journal during the interval 1932–1966, Volumes 26–60. In the intervening years the Journal has undergone a variety of changes. In 1970 the National Newsletter was published along with the Journal, being bound with the regular pages of the Journal. In 1978 the National Newsletter was physically separated but still included with the Journal, and in 1989 it became simply the Newsletter/Bulletin and in 1991 the Bulletin. That continued until the eventual merger of the two publications into the new Journal in 1997.
    [Show full text]
  • Inference for Stellar Opacities from Seismic Studies of the Hybrid Β Cep/SPB Pulsators
    EPJ Web of Conferences 152, 06005 (2017) DOI: 10.1051/ epjconf/201715206005 Wide-Field Variability Surveys: A 21st Century Perspective Inference for stellar opacities from seismic studies of the hybrid β Cep/SPB pulsators Przemysław Walczak1,, Jadwiga Daszynska-Daszkiewicz´ 1, and Alexey Pamyatnykh2 1Astronomical Institute Wrocław University, ul. Kopernika 11, 51-622 Wrocław, Poland 2Nicolaus Copernicus Astronomical Center Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland Abstract. We present a comprehensive seismic study of the three pulsating stars of β Cep/SPB type: ν Eridani, 12 Lacertae and γ Pegasi. Models with the modified mean opacity profile are constructed in order to account for both the observed frequency range and the values of some individual frequencies. To decrease the number of possible so- lutions, we make use of the non-adiabatic parameter f , whose value is very sensitive to subphotospheric layers where pulsations are driven. This complex seismic modelling shows the need for a significant modification of the opacity profile. 1 Introduction The hybrid pulsators, exhibiting oscillations both in low order p/g modes and high order g modes, pose a challenge for pulsation theory because the range of their observed frequencies cannot be explained by standard models. To overcome this problem an increase of the opacity at the certain depths was postulated by many authors (i.e., [1–3]). This approach is justified by recent experiments ([4]), where higher than predicted opacities of iron and nickel were measured. Here we analyse the three well known hybrid β Cep/SPB pulsators: ν Eri (HD 29248), γ Peg (HD 886) and 12 Lac (HD 214993).
    [Show full text]
  • The Β Cep/SPB Star 12 Lacertae 3 of Metallicity: Z = 0.015 and Z = 0.010
    Mon. Not. R. Astron. Soc. 000, 1–?? () Printed 21 June 2018 (MN LATEX style file v2.2) The β Cep/SPB star 12 Lacertae: extended mode identification and complex seismic modelling J. Daszy´nska-Daszkiewicz1⋆, W. Szewczuk1† and P. Walczak1‡ 1Instytut Astronomiczny Uniwersytet Wroc lawski, Wroc law, Poland ABSTRACT Results of mode identification and seismic modelling of the β Cep/SBP star 12 Lac- ertae are presented. Using data on the multi-colour photometry and radial velocity variations, we determine or constrain the mode degree, ℓ, for all pulsational frequen- cies. Including the effects of rotation, we show that the dominant frequency, ν1, is most likely a pure ℓ = 1 mode and the low frequency, νA, is a dipole retrograde mode. We construct a set of seismic models which fit two pulsational frequencies corresponding to the modes ℓ = 0, p1 and ℓ = 1, g1 and reproduce also the complex amplitude of the bolometric flux variations, f, for both frequencies simultaneously. Some of these seismic models reproduce also the frequency νA, as a mode ℓ =1, g13 or g14, and its empirical values of f. Moreover, it was possible to find a model fitting the six 12 Lac frequencies (the first five and νA), only if the rotational splitting was calculated for a velocity of Vrot ≈ 75 km/s. In the next step, we check the effects of model atmo- spheres, opacity data, chemical mixture and opacity enhancement. Our results show that the OP tables are preferred and an increase of opacities in the Z−bump spoils the concordance of the empirical and theoretical values of f.
    [Show full text]
  • Highlights of Stellar Astrophysics
    Highlights of stellar astrophysics Pawe lPietrukowicz1 1. Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00{478 Warszawa, Poland This is a review on advances in stellar astrophysics achieved by astronomers affiliated to Polish astronomical institutions in years 2017 { 2019. Over the last three years Polish-based astronomers had a significant contribution to the development of stellar astrophysics. Undertaken investigations referred to the stellar objects on various stages of evolution, including normal stars, pre-main sequence stars, and evolved objects. Most of the published papers are on pulsating stars, their properties and applications to the galactic structure studies. Here, I present all important results from the years 2017 { 2019. 1 Studies of enigmatic star FU Orionis Pre-main sequence stars are difficult objects to study due to their irregular behaviour. FU Orionis represents a group of young stellar objects characterized by a rise in brightness by about 4 { 6 mag and slow decline several months after. Observations of FU Orionis gathered by MOST satellite continuously for 55 days and simultaneously obtained ground-based multi-colour data were compared to create a model of the object. Siwak et al. (2018), in the article entitled Insights into the inner regions of the FU Orionis disc, show that the observed light variations arise from rotational revolution of disc inhomogeneities located between 16 and 20 R . The variations are due to changing visibility of plasma tongues revolving in the magnetospheric gap or due to hotspots. 2 An important message from early-type main-sequence pulsators Bright pulsating B-type stars are among the targets of the Austrian-Canadian-Polish constellation of six BRITE nano-satellites.
    [Show full text]
  • NOT Annual Report 2009 (PDF)
    ANNUAL REPORT 2009 Globular cluster Globular cluster Messier 3 TELESCOPE NORDIC OPTICAL NORDIC OPTICAL TELESCOPE The Nordic Optical Telescope (NOT) is a modern 2.5-m telescope located at the Spanish Observa- torio del Roque de los Muchachos on the island of La Palma, Canarias, Spain. It is operated for the benefit of Nordic astronomy by theN ordic Optical Telescope Scientific Asso ciation (NOTSA), estab- lished by the national Research Councils of Den- mark, Finland, Norway, and Sweden, and the Uni- versity of Iceland. The chief governing body of NOTSA is the Council, which sets overall policy, approves the annual bud- gets and accounts, and appoints the Director and Astronomer-in-Charge. A Scienti fic and Technical Committee (STC) advises the Council on scientific and technical policy. An Observing Programmes Committee (OPC) of independent experts, appointed by the Council, performs peer review and scientific ranking of the observing proposals submitted. Based on the rank- Front cover: ing by the OPC, the Director prepares the actual The globular cluster Messier 3, imaged observing schedule. with the NOT and ALFOSC in blue, red and near-infrared light by Paul A. Wilson and Anders Thygesen. The Director has overall responsibility for the operation of NOTSA, including staffing, financial matters, external relations, and long-term planning. The staff on La Palma is led by the Deputy Director, who has authority to deal with all matters related to the daily operation of NOT. The members of the Council and committees and contact information to NOT are listed at the end of this report. The NOT Annual Reports for 2002-2009 are available at: http://www.not.iac.es/news/reports/ 1 CONTENT 2 THE STAFF 3 PREFacE 4 EVENTS IN 2009 5 SCIENCE HIGHLIGHTS 5 Cosmology, Formation and Evolution of Galaxies 13 Formation, Structure, and Evolution of Stars 19 Planetary systems in the Universe S 24 INSTRUMENTS 25 EDUCATION Paul A.
    [Show full text]
  • 1945Apj. . .102. .318S SIX-COLOR PHOTOMETRY of STARS III. THE
    .318S SIX-COLOR PHOTOMETRY OF STARS .102. III. THE COLORS OF 238 STARS OF DIFFERENT SPECTRAL TYPES* Joel Stebbins1 and A. E. Whiteord2 1945ApJ. Mount Wilson Observatory and Washburn Observatory Received June 8,1945 ABSTRACT Colors have been obtained for 238 stars of all spectral types from O to M by measuring intensities i six spectral regions from X 3530 to X 10,300 A (Tables 2 and 3). The early-type stars from O to B3 sho small dispersion in intrinsic color, but many are strongly affected by space reddening. A dozen late-tyx giants in low latitudes are likewise affected. The most marked effect of absolute magnitude is near spe< trum K0, where the colors of dwarfs, ordinary giants, and supergiants are all different {Fig. 1). The observed colors of the stars agree closely with the colors of a black body at suitable temperatur« (Fig. 2). The derived relative color temperatures are based upon the mean of ten stars of spectrum dG with an assumed temperature of 5500°K. On this scale the values are 23,000° for O stars, 11,000° for A( and 5950° for dGO. An alternative scale, with 6700° and spectrum dG2 for the sun, gives 140,000° fc O stars, 16,000° for A0, and 6900° for dGO (Table 7). A definitive zero point for the temperature seal has not been determined. The bluest O and B stars agree very well with each other, but there is still the possibility that all ai slightly affected by space reddening. A dozen bright stars of the Pleiades seem normal for their type.
    [Show full text]
  • First Results from the Echelle Spectrograph at the Trottier Observatory Howard Trottier February 2016 Overview
    First results from the echelle spectrograph at the Trottier Observatory Howard Trottier February 2016 Overview This is a report on the first results obtained at the Trottier Observatory using our new echelle spectrograph, which is designed primarily for high-resolution stellar spectroscopy. I’ve tried to write the report assuming relatively little physics and math background, intending for it to be used in some form in a second-year breadth course on observational astronomy that I’m developing for students from both the arts and the sciences. However the level of the report is somewhat uneven, with some parts using more sophisticated physics and math – though the math can usually be skipped entirely in favour of the interpretation of the results. Our spectrograph is made by a small company in France, Shelyak Instruments, and is called the “eShel” because of its “echelle” design.1 The basic design principles of echelles are reviewed later; for now, it’s enough to note that echelles are advantageous compared to other spectrometer designs because of their high resolution. Spectral resolution is characterized by the smallest possible wavelength interval δλ between two neighbouring spectral features that can be individually identified, as illustrated below for two emission lines. # Resolution is usually quoted in terms of a fractional measure R that is defined by # The eShel has a resolution R of about 10,000, meaning that it can distinguish between spectral features separated by about as little as 5,000 Angstroms/10,000 or 0.5Å, at a typical wavelength of optical light. The highest-resolution professional echelles have R above 1 The Shelyak webpage on the eShel is at http://www.shelyak.com/dossier.php?id_dossier=47.
    [Show full text]
  • 04/11/2011 RIA 35 PUBLICACIONES 2007 1. a Portrait of the Nucleus Of
    PUBLICACIONES 2007 1. A portrait of the nucleus of comet 67P/Churyumov-Gerasimenko Author(s): Lamy PL, Toth I, Davidsson BJR, et al. Source: SPACE SCIENCE REVIEWS Volume: 128 Issue: 1-4 Pages: 23-66 Published: 2007 ESA: Hubble ; ROSETTA (on-going studies) 2. Search for tidal dwarf galaxy candidates in a sample of ultraluminous infrared galaxies Author(s): Monreal-Ibero, A; Colina, L; Arribas, S, et al. Source: ASTRONOMY & ASTROPHYSICS Volume: 472 Pages: 421-433 Published: 2007 ESA: Hubble; INTEGRAL 3. Supermassive black holes in the Sbc spiral galaxies NGC 3310, NGC 4303 and NGC 4258 Author(s): Pastorini, G; Marconi, A; Capetti, A, et al. Source: ASTRONOMY & ASTROPHYSICS Volume: 469 Issue: 2 Pages: 405-U50 Published: JUL 2007 ESA: Hubble 4. HST/ACS observations of shell galaxies: inner shells, shell colours and dust Author(s): Sikkema, G; Carter, D; Peletier, RF, et al. Source: ASTRONOMY & ASTROPHYSICS Volume: 467 Issue: 3 Pages: 1011-U27 Published: JUN 2007 ESA: Hubble 5. Optical detection of the radio supernova SN 2000ft in the circumnuclear region of the luminous infrared galaxy NGC 7469 Author(s): Colina, L; Diaz-Santos, T; Alonso-Herrero, A, et al. Source: ASTRONOMY & ASTROPHYSICS Volume: 467 Issue: 2 Pages: 559-564 Published: MAY 2007 ESA: Hubble 6. HST and VLT observations of the symbiotic star Hen 2-147 - Its nebular dynamics, its Mira variable and its distance Author(s): Santander-Garcia, M; Corradi, RLM; Whitelock, PA, et al. Source: ASTRONOMY & ASTROPHYSICS Volume: 465 Issue: 2 Pages: 481-491 Published: 2007 ESA: Hubble . 04/11/2011 RIA 35 7. Black hole masses and Eddington ratios of AGNs at z < 1: Evidence of retriggering for a representative sample of X-ray-selected AGNs Ballo, L; Cristiani, S; Fasano, G, et al.
    [Show full text]
  • The Two Hybrid B-Type Pulsators: Ν Eridani and 12 Lacertae
    Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 31 October 2018 (MN LATEX style file v2.2) The two hybrid B-type pulsators: ν Eridani and 12 Lacertae W. A. Dziembowski1,2⋆ and A. A. Pamyatnykh1,3 1 Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland 2 Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland 3 Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya Str. 48, 109017 Moscow, Russia Accepted 000. Received 2007 June 000; in original form 2007 June 000 ABSTRACT The rich oscillation spectra determined for the two stars, ν Eridani and 12 Lacertae, present an interesting challenge to stellar modelling. The stars are hybrid objects showing a number of modes at frequencies typical for β Cep stars but also one mode at frequency typical for SPB stars. We construct seismic models of these stars considering uncertainties in opacity and element distribution. We also present estimate of the interior rotation rate and address the matter of mode excitation. We use both the OP and OPAL opacity data and find significant difference in the results. Uncertainty in these data remains a major obstacle in precise modelling of the objects and, in particular, in estimating the overshooting distance. We find evidence for significant rotation rate increase between envelope and core in the two stars. Instability of low-frequency g-modes was found in seismic models of ν Eri built with the OP data, but at frequencies higher than those measured in the star. No such instability was found in models of 12 Lac. We do not have yet a satisfactory explanation for low frequency modes.
    [Show full text]
  • A Summary of the Different Classes of Stellar Pulsators
    A Summary of the Different Classes of Stellar Pulsators A summary of all the classes of pulsating stars and their main properties as described in Chapter 2 is given in the tables below. This list originated from a combination of observational discoveries, measured stellar properties, and theoretical developments. Observers who found a new type of pulsator either named it after the prototype or gave the class a name according to the ob- served characteristics of the oscillations. Several pulsators, or even groups of pulsators, were afterwards found to originate from the same physical mech- anism and were thus merged into one and the same class. We sort this out here in Tables A.1 and A.2 in order to avoid further confusion on pulsating star nomenclature. The effective temperature and luminosity indicated in Tables A.1 and A.2 should be taken as rough indications only of the borders of instability strips. Often the theory is not sufficiently refined to consider these boundaries as final. Moreover, there is overlap between various classes where so-called hy- brid pulsators, whose oscillations are excited in two different layers and/or by two different mechanisms, occur. Finally, new discoveries are being made frequently, which then drive new theoretical developments possibly leading to new instability regions. The results from the future observing facilities as described in Chapter 8 will surely lead to new classes and/or subclasses with lower amplitudes compared to what is presently achievable. In the tables below, F stands for fundamental radial mode, FO for first radial overtone and S for strange mode oscillations.
    [Show full text]