Does GD356 Have a Terrestrial Planetary Companion
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Red Giant Sun May Not Destroy Earth
Site Index Subscriptions Shop Newsletters HOME ANIMALS ENVIRONMENT HISTORY NEWS HOME ANIMAL NEWS ANCIENT WORLD ENVIRONMENT NEWS CULTURES NEWS SCIENCE & SPACE NEWS KIDS WEIRD NEWS MAPS NEWS Red Giant Sun May Not Destroy Earth PEOPLE & PLACES PHOTOGRAPHY Anne Minard for National Geographic News 15 Most Popular News Pages VIDEO September 14, 2007 WORLD MUSIC The first glimpse of a planet that survived its star's red giant phase is Photos in the News offering a glimmer of hope that Earth might make it past our sun's News Videos NATIONAL eventual expansion. GEOGRAPHIC MAGAZINE The newfound planet, dubbed V391 Pegasi b, is much larger than Earth but likely ADVERTISEMENT MAGAZINES orbited its star as closely as our planet orbits the sun (explore a virtual solar system). SHOP LATEST PHOTOS IN THE NEWS SUBSCRIPTIONS When the aging star mushroomed into a red Photo Gallery: Frozen Inca Mummy TV & FILM giant about a hundred times its previous size, Goes On Display V391 Pegasi b was pushed out to an orbit TRAVEL WITH US nearly twice as far away. OUR MISSION Solar Plane Sets Record, Makers Say "After this finding, we now know that planets with an orbital distance similar to the Earth can survive the red giant expansion of their parent Hubble Fans Dispute "Sharpest" Title Enlarge Photo stars," said lead author Roberto Silvotti of the National Institute of Astrophysics in Napoli, Italy. Printer Friendly • Catalog Quick "But this does not automatically mean that even More Photos in the News Shop Email to a Friend the Earth, much smaller and much more vulnerable [than V391 Pegasi b], will survive" our • Books & Atlases RELATED sun's expansion billions of years from now, he NATIONAL GEOGRAPHIC'S PHOTO OF THE DAY • Clothing & Future Universe Will "Stop said. -
Galactic Parameters Derived from Open-Cluster Data T
Astronomy Reports, Vol. 48, No. 2, 2004, pp. 103–107. Translated from Astronomicheski˘ı Zhurnal, Vol. 81, No. 2, 2004, pp. 124–128. Original Russian Text Copyright c 2004 by Gerasimenko. Galactic Parameters Derived from Open-Cluster Data T. P. Gerasimenko Astronomical Observatory, Ural State University, Yekaterinburg, Russia Received September 20, 2001; in final form, July 26, 2003 Abstract—The components U0 and V0 of the solar motion and the Oort constant A0 are determined using the data of a homogeneous open-cluster catalog with corrected distance moduli. The results are based on a sample of 146 open clusters with known radial velocities located in the Galactic plane (b<7◦)within 4 kpc of the Sun. The solar Galactocentric distance R0 is determined usingtwo kinematic methods. The followingresults are obtained: A0 =17.0 ± 0.9 km/s kpc, U0 =10.5 ± 1.0 km/s, V0 =11.5 ± 1.1 km/s, R0 =8.3 ± 0.3 pc. c 2004 MAIK “Nauka/Interperiodica”. 1. INTRODUCTION distance-modulus estimates from the Uniform Cata- logand those determined usingHipparcos trigono- One of the traditional areas of kinematic studies metric parallaxes [12]; the distance scale changed is the determination of the main Galactic parameters by −0.153m, independent of the cluster age. The required to construct theoretical equilibrium models: clusters span a fairly wide age interval. Clusters the gradient of the angular velocity (the Oort constant in different age groups are known to have different AO), the Oort constant B0, and the principal scale motions. Analysis of the rotation of the open-cluster parameter—the distance of the Sun from the Galactic subsystem revealed a small group among the young center, RO. -
Arxiv:2001.10147V1
Magnetic fields in isolated and interacting white dwarfs Lilia Ferrario1 and Dayal Wickramasinghe2 Mathematical Sciences Institute, The Australian National University, Canberra, ACT 2601, Australia Adela Kawka3 International Centre for Radio Astronomy Research, Curtin University, Perth, WA 6102, Australia Abstract The magnetic white dwarfs (MWDs) are found either isolated or in inter- acting binaries. The isolated MWDs divide into two groups: a high field group (105 − 109 G) comprising some 13 ± 4% of all white dwarfs (WDs), and a low field group (B < 105 G) whose incidence is currently under investigation. The situation may be similar in magnetic binaries because the bright accretion discs in low field systems hide the photosphere of their WDs thus preventing the study of their magnetic fields’ strength and structure. Considerable research has been devoted to the vexed question on the origin of magnetic fields. One hypothesis is that WD magnetic fields are of fossil origin, that is, their progenitors are the magnetic main-sequence Ap/Bp stars and magnetic flux is conserved during their evolution. The other hypothesis is that magnetic fields arise from binary interaction, through differential rotation, during common envelope evolution. If the two stars merge the end product is a single high-field MWD. If close binaries survive and the primary develops a strong field, they may later evolve into the arXiv:2001.10147v1 [astro-ph.SR] 28 Jan 2020 magnetic cataclysmic variables (MCVs). The recently discovered population of hot, carbon-rich WDs exhibiting an incidence of magnetism of up to about 70% and a variability from a few minutes to a couple of days may support the [email protected] [email protected] [email protected] Preprint submitted to Journal of LATEX Templates January 29, 2020 merging binary hypothesis. -
The Fate of Planets
The Fate of Planets Eva Villaver Universidad Autónoma de Madrid, Dpto. Física Teórica, Módulo 15, Facultad de Ciencias, Campus de Cantoblanco, 28049 Madrid, Spain. e-mail: [email protected] Abstract. As a star evolves off the Main Sequence, it endures major structural changes that are capable of determining the fate of the planets orbiting it. Throughout its evolution along the Red Giant Branch, the star increases its radius by two orders of magnitude. Later, during the Asymptotic Giant Branch, it loses most of its initial mass. Finally, during the Planetary Nebulae phase, it emits intense radiation before ultimately beginning its fade as a white dwarf. We show how the several competing processes (stellar mass-loss, gravitational and frictional drag, tidal forces, planet accretion and evaporation) affect the survival of planets around evolved stars. Keywords: Planets, Evolved Stars, Giant and White Dwarf stars PACS: 97.82.j, 97.10.Me, 97.20.Li PLANET'S FATE BEYOND THE MAIN SEQUENCE The Red Giant Branch Phase Once the nuclear burning has been exhausted in the core, low- and intermediate mass stars evolve into the Red Giant Branch (RGB) phase. During the RGB, hydrogen burning continues in a shell outside the helium core, which now, devoid of energy sources, is contracting and heating up. The stellar evolution timescales (in the absence of significant mass loss) are set by the rate of consumption of the nuclear fuel. As the core contracts the envelope expands and cools. The stellar effective temperature decreases while the star’s radius and luminosity increase. There are several competing processes that affect the orbital distance between the star and the planet as the star evolves off the Main Sequence (MS): the changes in the mass of both the planet and the star (M˙p and M˙∗ respectively), the gravitational and frictional drag (Fg and Ff ), and the tidal force. -
Hot Subdwarf Stars in Close-Up View: Orbits, Rotation, Abundances and Masses of Their Unseen Companions
Hot Subdwarf Stars in Close-up View: Orbits, Rotation, Abundances and Masses of their Unseen Companions Den Naturwissenschaftlichen Fakult¨aten der Friedrich-Alexander-Universit¨at Erlangen-N¨urnberg zur Erlangung des Doktorgrades vorgelegt von Stephan Geier aus Stadtsteinach Als Dissertation genehmigt von den Naturwissenschaftlichen Fakult¨aten der Universit¨at Erlangen-N¨urnberg Tag der m¨undlichen Pr¨ufung: 18. M¨arz 2009 Vositzender der Promotionskommission: Prof. Dr. E. B¨ansch Erstberichterstatter: Prof. Dr. U. Heber Zweitberichterstatter: Prof. Dr. P. Podsiadlowski, University of Oxford Drittberichterstatter: Prof. Dr. K. Werner, Universit¨at T¨ubingen Contents 1 Hot subdwarf stars: A review 9 1.1 Generalproperties ............................... .... 9 1.2 Single star formation and evolution scenarios . ............ 10 1.3 Hot subdwarf binaries: Observations, formation and evolution........... 12 1.4 Pulsating hot subdwarfs and asteroseismology . ............ 15 1.5 Hot subdwarf atmospheres and diffusion processes . .......... 20 1.6 Hot subdwarfs and extrasolar planets . ......... 21 1.7 Hotsubdwarfsashyper-velocitystars . ........ 23 1.8 Hot subdwarfs and globular clusters . ........ 24 1.9 Hot subdwarfs and the UV-upturn in early-type galaxies . ........... 25 1.10 Hot subdwarf stars, supernovae and cosmology . ........... 26 2 Hot subdwarf stars in close binary systems: Previous work and new discov- eries 30 2.1 Generalstatistics ............................... ..... 30 2.2 Determination of hot subdwarf and companion masses in close binaries . 33 2.3 Orbital parameters of new close binary subdwarfs . ........... 34 2.3.1 Target selection, observations and data reduction . ........... 35 2.3.2 Radial velocity measurements, power spectra and RV curves........ 35 2.3.3 Constraints on the nature of the unseen companions . ......... 36 2.3.4 Results .................................... -
Pulsating Components in Binary and Multiple Stellar Systems---A
Research in Astron. & Astrophys. Vol.15 (2015) No.?, 000–000 (Last modified: — December 6, 2014; 10:26 ) Research in Astronomy and Astrophysics Pulsating Components in Binary and Multiple Stellar Systems — A Catalog of Oscillating Binaries ∗ A.-Y. Zhou National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; [email protected] Abstract We present an up-to-date catalog of pulsating binaries, i.e. the binary and multiple stellar systems containing pulsating components, along with a statistics on them. Compared to the earlier compilation by Soydugan et al.(2006a) of 25 δ Scuti-type ‘oscillating Algol-type eclipsing binaries’ (oEA), the recent col- lection of 74 oEA by Liakos et al.(2012), and the collection of Cepheids in binaries by Szabados (2003a), the numbers and types of pulsating variables in binaries are now extended. The total numbers of pulsating binary/multiple stellar systems have increased to be 515 as of 2014 October 26, among which 262+ are oscillating eclipsing binaries and the oEA containing δ Scuti componentsare updated to be 96. The catalog is intended to be a collection of various pulsating binary stars across the Hertzsprung-Russell diagram. We reviewed the open questions, advances and prospects connecting pulsation/oscillation and binarity. The observational implication of binary systems with pulsating components, to stellar evolution theories is also addressed. In addition, we have searched the Simbad database for candidate pulsating binaries. As a result, 322 candidates were extracted. Furthermore, a brief statistics on Algol-type eclipsing binaries (EA) based on the existing catalogs is given. We got 5315 EA, of which there are 904 EA with spectral types A and F. -
WASP-33: the First Delta Scuti Exoplanet Host Star
Astronomy & Astrophysics manuscript no. ms c ESO 2018 November 1, 2018 Letter to the Editor WASP-33: The first δ Scuti exoplanet host star E. Herrero1, J.C. Morales1, I. Ribas1, and R. Naves2 1 Institut de Ci`encies de l’Espai (CSIC-IEEC), Campus UAB, Facultat de Ci`encies, Torre C5 parell, 2a pl, 08193 Bellaterra, Spain, e-mail: [email protected], [email protected], [email protected] 2 Observatori Montcabrer, C/Jaume Balmes, 24, Cabrils, Spain, e-mail: [email protected] Received ¡date¿ / Accepted ¡date¿ ABSTRACT We report the discovery of photometric oscillations in the host star of the exoplanet WASP-33 b (HD 15082). The data were obtained in the R band in both transit and out-of-transit phases from the 0.3-m telescope and the Montcabrer Observatory and the 0.8-m telescope at the Montsec Astronomical Observatory. Proper fitting and subsequent removal of the transit signal reveals stellar photometric variations with a semi-amplitude of about 1 mmag. The detailed analysis of the periodogram yields a structure of significant signals around a frequency of 21 cyc d−1, which is typical of δ Scuti-type variable stars. An accurate study of the power spectrum reveals a possible commensurability with the planet orbital motion with a factor of 26, but this remains to be confirmed with additional time-series data that will permit the identification of the significant frequencies. These findings make WASP-33 the first transiting exoplanet host star with δ Sct variability and a very interesting candidate to search for star-planet interactions. -
An Upper Limit to Coronal X-Rays from Single, Magnetic White Dwarfs
J. Astrophys. Astr. (1993) 14, 141–143 An Upper Limit to Coronal X-rays from Single, Magnetic White Dwarfs 1 1 2 Rob Cavallo , Keith A. Arnaud & Virginia Trimble Astronomy Department, University of Maryland, College Park MD 20742 USA 1 Also Code 666, Goddard Space Flight Center, Greenbelt MD 20771 USA 2 Also Physics Department, University of California, Irvine CA 92717 Received 1993 August 19; accepted 1993 September 28 Abstract. Pointed ROSAT PSPC exposures of 9277 and 6992 sec, directed toward the nearby, single, cool, magnetic white dwarfs GR 290 and EG 250 yielded no counts significantly above the expected background rate. The corresponding flux limits (for an assumed source temperature of l keV) are 1.0 and 1.7 × 10 –14erg cm–2 s–1, within the 0.1–2.5 keV bandpass of the instrument (99% confidence limits). This is more than an order of magnitude below the tentative detection level (for GR 290) and limits (for four other similar stars) obtained from archival Einstein data in 1991. The corresponding limits on coronal electron density are comparable with those implied if cyclotron emission is not responsible for any of the features observed in the optical spectra of magnetic white dwarfs. X-ray data currently provide no evidence for the existence of coronae around these stars. A final long observation (25,000 sec of GD 356) is scheduled for later this year on ROSAT, along with coordinated EUVE observations. Key words: White dwarfs—stellar coronae—X-ray emission 1. Introduction Motivated by theoretical considerations (Zheleznyakov & Litvinchuk 1985; Serber 1990) and by the preponderance of magnetic systems among known cataclysmic variable X-ray sources, Arnaud et al. -
Limits on Unresolved Planetary Companions to White Dwarf
Limits on Unresolved Planetary Companions to White Dwarf Remnants of 14 Intermediate-Mass Stars Mukremin Kilic1,4, Andrew Gould2, and Detlev Koester3 ABSTRACT We present Spitzer IRAC photometry of white dwarf remnants of 14 stars with M =3 − 5 M⊙. We do not detect mid-infrared excess around any of our targets. By demanding a 3σ photometric excess at 4.5 µm for unresolved companions, we rule out planetary mass companions down to 5, 7, or 10 MJ for 13 of our targets based on the Burrows et al. (2003) substellar cooling models. Combined with previous IRAC observations of white dwarf remnants of intermediate-mass stars, we rule out ≥ 10MJ companions around 40 white dwarfs and ≥ 5MJ companions around 10 white dwarfs. Subject headings: infrared: stars — planetary systems — stars: low-mass, brown dwarfs — white dwarfs 1. INTRODUCTION Radial velocity, transit, and microlensing searches are succesful in finding planets around stars less massive than 2M⊙ (see Udry & Santos 2007; Marcy et al. 2005; Gould 2009; Mazeh 2009, and references therein). However, these techniques have limitations for higher mass stars. The main problem is that intermediate- and high-mass stars are big, they are rare, and they do not have many usable lines for radial velocity studies. The short (≤ 1 Gyr) main-sequence lifetimes of intermediate-mass stars and the small radii of the remnant white arXiv:0909.2038v2 [astro-ph.SR] 18 Sep 2009 dwarfs (WDs) imply that the planetary systems around massive stars can be effectively studied after the hosts have been transformed into WDs (Ignace 2001; Burleigh et al. -
Magnetic Fields at the Surfaces of Stars
THE The Astron AstrophysRev (1992) 4:35-77 ASTRONOMY AND ASTROPHYSICS REVIEW Springer-Verlag 1992 Magnetic fields at the surfaces of stars J.D. Landstreet Department of Astronomy, University of Western Ontario, London, Ontario, Canada N6A 3K7 Observatoire Midi-Pyr6n6es, 14, ave. Edouard-Belin, F-31400 Toulouse, France Summary. Magnetic fields have now been detected in stars in several parts of the Hertzsprung-Russell diagram. Roughly dipolar fields ranging in strength between 3 • 102 and 3 x 104 G are found in many chemically peculiar A and B main sequence stars. Dipolar fields are also found in some 2-3% of white dwarfs, but with strengths between 1 • 106 and 5 • 108 G. In both these types of stars, the observed fields vary as the underlying star turns, but do not change in a secular manner. In solar- type stars, structurally complex fields of a few kG are found with filling factors of the order of 0.1 to 0.8. Further indirect evidence of fields in cool main sequence stars is provided by detection of visible and ultraviolet line emission (chromospheric activity), x radiation (coronal matter), and giant starspots. In this review, we survey the observations of stellar magnetism in all these types of stars, as well as efforts to model the observed magnetic fields and associated photospheric peculiarities and activity. Key words: Magnetic field - Stars: activity of- Stars: magnetic field - Stars: peculiar A - Stars: white dwarf 1. Introduction Magnetic fields are now known to occur in a wide variety of types of stars. The first detection of a stellar field occurred nearly a century ago, when Hale (1908) observed the magnetic splitting of spectral lines in sunspots. -
Post-Main-Sequence Planetary System Evolution Rsos.Royalsocietypublishing.Org Dimitri Veras
Post-main-sequence planetary system evolution rsos.royalsocietypublishing.org Dimitri Veras Department of Physics, University of Warwick, Coventry CV4 7AL, UK Review The fates of planetary systems provide unassailable insights Cite this article: Veras D. 2016 into their formation and represent rich cross-disciplinary Post-main-sequence planetary system dynamical laboratories. Mounting observations of post-main- evolution. R. Soc. open sci. 3: 150571. sequence planetary systems necessitate a complementary level http://dx.doi.org/10.1098/rsos.150571 of theoretical scrutiny. Here, I review the diverse dynamical processes which affect planets, asteroids, comets and pebbles as their parent stars evolve into giant branch, white dwarf and neutron stars. This reference provides a foundation for the Received: 23 October 2015 interpretation and modelling of currently known systems and Accepted: 20 January 2016 upcoming discoveries. 1. Introduction Subject Category: Decades of unsuccessful attempts to find planets around other Astronomy Sun-like stars preceded the unexpected 1992 discovery of planetary bodies orbiting a pulsar [1,2]. The three planets around Subject Areas: the millisecond pulsar PSR B1257+12 were the first confidently extrasolar planets/astrophysics/solar system reported extrasolar planets to withstand enduring scrutiny due to their well-constrained masses and orbits. However, a retrospective Keywords: historical analysis reveals even more surprises. We now know that dynamics, white dwarfs, giant branch stars, the eponymous celestial body that Adriaan van Maanen observed pulsars, asteroids, formation in the late 1910s [3,4]isanisolatedwhitedwarf(WD)witha metal-enriched atmosphere: direct evidence for the accretion of planetary remnants. These pioneering discoveries of planetary material around Author for correspondence: or in post-main-sequence (post-MS) stars, although exciting, Dimitri Veras represented a poor harbinger for how the field of exoplanetary e-mail: [email protected] science has since matured. -
A Chandra Search for Coronal X Rays from the Cool White Dwarf GD
DRAFT 2006.09.19: ApJ to be submitted A Chandra Search for Coronal X Rays from the Cool White Dwarf GD 356 Martin C. Weisskopf1, Kinwah Wu2, Virginia Trimble3,4, Stephen L. O’Dell5, Ronald F. Elsner5, Vyacheslav E. Zavlin5,6, and Chryssa Kouveliotou5 ABSTRACT We report observations with the Chandra X-ray Observatory of the single, cool, magnetic white dwarf GD 356. For consistent comparison with other X-ray observations of single white dwarfs, we also re-analyzed archival ROSAT data for GD 356 (GJ 1205), G 99-47 (GR 290 = V1201 Ori), GD 90, G 195-19 (EG250 = GJ 339.1), and WD 2316+123 and archival Chandra data for LHS 1038 (GJ 1004) and GD 358 (V777 Her). Our Chandra observation detected no X rays from GD 356, setting the most restrictive upper limit to the X-ray luminosity from 25 −1 any cool white dwarf — LX < 6.0×10 erg s , at 99.7% confidence, for a 1- keV thermal-bremsstrahlung spectrum. The corresponding limit to the electron 11 −3 density is n0 < 4.4×10 cm . Our re-analysis of the archival data confirmed the non-detections reported by the original investigators. We discuss the implications of our and prior observations on models for coronal emission from white dwarfs. For magnetic white dwarfs, we emphasize the more stringent constraints imposed by cyclotron radiation. In addition, we describe (in an appendix) a statistical methodology for detecting a source and for constraining the strength of a source, which applies even when the number of source or background events is small.