Detecting Differential Rotation and Starspot Evolution on the M Dwarf GJ 1243 with Kepler James R
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Starspot Temperature Along the HR Diagram
Mem. S.A.It. Suppl. Vol. 9, 220 Memorie della c SAIt 2006 Supplementi Starspot temperature along the HR diagram K. Biazzo1, A. Frasca2, S. Catalano2, E. Marilli2, G. W. Henry3, and G. Tasˇ 4 1 Department of Physics and Astronomy, University of Catania, via Santa Sofia 78, 95123 Catania, e-mail: [email protected] 2 INAF - Catania Astrophysical Observatory, via S. Sofia 78, 95123 Catania, Italy 3 Tennessee State University - Center of Excellence in Information Systems, 330 10th Ave. North, Nashville, TN 37203-3401 4 Ege University Observatory - 35100 Bornova, Izmir˙ , Turkey Abstract. The photospheric temperature of active stars is affected by the presence of cool starspots. The determination of the spot configuration and, in particular, spot temperatures and sizes, is important for understanding the role of the magnetic field in blocking the convective heating flux inside starspots. It has been demonstrated that a very sensitive di- agnostic of surface temperature in late-type stars is the depth ratio of weak photospheric absorption lines (e.g. Gray & Johanson 1991, Catalano et al. 2002). We have shown that it is possible to reconstruct the distribution of the spots, along with their sizes and tempera- tures, from the application of a spot model to the light and temperature curves (Frasca et al. 2005). In this work, we present and briefly discuss results on spot sizes and temperatures for stars in various locations in the HR diagram. Key words. Stars: activity - Stars: variability - Stars: starspot 1. Introduction Table 1. Star sample. Within a large program aimed at studying the behaviour of photospheric surface inhomo- Star Sp. -
Star Systems in the Solar Neighborhood up to 10 Parsecs Distance
Vol. 16 No. 3 June 15, 2020 Journal of Double Star Observations Page 229 Star Systems in the Solar Neighborhood up to 10 Parsecs Distance Wilfried R.A. Knapp Vienna, Austria [email protected] Abstract: The stars and star systems in the solar neighborhood are for obvious reasons the most likely best investigated stellar objects besides the Sun. Very fast proper motion catches the attention of astronomers and the small distances to the Sun allow for precise measurements so the wealth of data for most of these objects is impressive. This report lists 94 star systems (doubles or multiples most likely bound by gravitation) in up to 10 parsecs distance from the Sun as well over 60 questionable objects which are for different reasons considered rather not star systems (at least not within 10 parsecs) but might be if with a small likelihood. A few of the listed star systems are newly detected and for several systems first or updated preliminary orbits are suggested. A good part of the listed nearby star systems are included in the GAIA DR2 catalog with par- allax and proper motion data for at least some of the components – this offers the opportunity to counter-check the so far reported data with the most precise star catalog data currently available. A side result of this counter-check is the confirmation of the expectation that the GAIA DR2 single star model is not well suited to deliver fully reliable parallax and proper motion data for binary or multiple star systems. 1. Introduction high proper motion speed might cause visually noticea- The answer to the question at which distance the ble position changes from year to year. -
Abstracts Connecting to the Boston University Network
20th Cambridge Workshop: Cool Stars, Stellar Systems, and the Sun July 29 - Aug 3, 2018 Boston / Cambridge, USA Abstracts Connecting to the Boston University Network 1. Select network ”BU Guest (unencrypted)” 2. Once connected, open a web browser and try to navigate to a website. You should be redirected to https://safeconnect.bu.edu:9443 for registration. If the page does not automatically redirect, go to bu.edu to be brought to the login page. 3. Enter the login information: Guest Username: CoolStars20 Password: CoolStars20 Click to accept the conditions then log in. ii Foreword Our story starts on January 31, 1980 when a small group of about 50 astronomers came to- gether, organized by Andrea Dupree, to discuss the results from the new high-energy satel- lites IUE and Einstein. Called “Cool Stars, Stellar Systems, and the Sun,” the meeting empha- sized the solar stellar connection and focused discussion on “several topics … in which the similarity is manifest: the structures of chromospheres and coronae, stellar activity, and the phenomena of mass loss,” according to the preface of the resulting, “Special Report of the Smithsonian Astrophysical Observatory.” We could easily have chosen the same topics for this meeting. Over the summer of 1980, the group met again in Bonas, France and then back in Cambridge in 1981. Nearly 40 years on, I am comfortable saying these workshops have evolved to be the premier conference series for cool star research. Cool Stars has been held largely biennially, alternating between North America and Europe. Over that time, the field of stellar astro- physics has been upended several times, first by results from Hubble, then ROSAT, then Keck and other large aperture ground-based adaptive optics telescopes. -
HOW to CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, and RADIUS Andrew W
The Astrophysical Journal, 804:64 (38pp), 2015 May 1 doi:10.1088/0004-637X/804/1/64 © 2015. The American Astronomical Society. All rights reserved. HOW TO CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, AND RADIUS Andrew W. Mann1,2,8,9, Gregory A. Feiden3, Eric Gaidos4,5,10, Tabetha Boyajian6, and Kaspar von Braun7 1 University of Texas at Austin, USA; [email protected] 2 Institute for Astrophysical Research, Boston University, USA 3 Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden 4 Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822, USA 5 Max Planck Institut für Astronomie, Heidelberg, Germany 6 Department of Astronomy, Yale University, New Haven, CT 06511, USA 7 Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff, AZ, USA Received 2015 January 6; accepted 2015 February 26; published 2015 May 4 ABSTRACT Precise and accurate parameters for late-type (late K and M) dwarf stars are important for characterization of any orbiting planets, but such determinations have been hampered by these stars’ complex spectra and dissimilarity to the Sun. We exploit an empirically calibrated method to estimate spectroscopic effective temperature (Teff) and the Stefan–Boltzmann law to determine radii of 183 nearby K7–M7 single stars with a precision of 2%–5%. Our improved stellar parameters enable us to develop model-independent relations between Teff or absolute magnitude and radius, as well as between color and Teff. The derived Teff–radius relation depends strongly on [Fe/H],as predicted by theory. -
The Solar Neighborhood XXXVII: the Mass-Luminosity Relation for Main Sequence M Dwarfs 1
The Solar Neighborhood XXXVII: The Mass-Luminosity Relation for Main Sequence M Dwarfs 1 G. F. Benedict2, T. J. Henry3;11, O. G. Franz4, B. E. McArthur2, L. H. Wasserman4, Wei-Chun Jao5;11, P. A. Cargile6, S. B. Dieterich 7;11, A. J. Bradley8, E. P. Nelan9, and A. L. Whipple10 ABSTRACT We present a Mass-Luminosity Relation (MLR) for red dwarfs spanning a range of masses from 0.62 M to the end of the stellar main sequence at 0.08 M . The relation is based on 47 stars for which dynamical masses have been determined, primarily using astrometric data from Fine Guidance Sensors (FGS) 3 and 1r, white-light interferometers on the Hubble Space Telescope (HST), and radial velocity data from McDonald Observatory. For our HST/FGS sample of 15 binaries, component mass errors range from 0.4% to 4.0% with a median error of 1.8%. With these and masses from other sources, we construct a V -band MLR for the lower main sequence with 47 stars, and a K-band MLR with 45 stars with fit residuals half of those of the V -band. We use GJ 831 AB as an example, obtaining an absolute trigonometric par- allax, πabs = 125:3 ± 0:3 milliseconds of arc, with orbital elements yielding MA = 0:270 ± 0:004M and MB = 0:145 ± 0:002M . The mass precision rivals that derived for eclipsing binaries. 2McDonald Observatory, University of Texas, Austin, TX 78712 3RECONS Institute, Chambersburg, PA 17201 4Lowell Observatory, 1400 West Mars Hill Rd., Flagstaff, AZ 86001 5Dept. -
10. Scientific Programme 10.1
10. SCIENTIFIC PROGRAMME 10.1. OVERVIEW (a) Invited Discourses Plenary Hall B 18:00-19:30 ID1 “The Zoo of Galaxies” Karen Masters, University of Portsmouth, UK Monday, 20 August ID2 “Supernovae, the Accelerating Cosmos, and Dark Energy” Brian Schmidt, ANU, Australia Wednesday, 22 August ID3 “The Herschel View of Star Formation” Philippe André, CEA Saclay, France Wednesday, 29 August ID4 “Past, Present and Future of Chinese Astronomy” Cheng Fang, Nanjing University, China Nanjing Thursday, 30 August (b) Plenary Symposium Review Talks Plenary Hall B (B) 8:30-10:00 Or Rooms 309A+B (3) IAUS 288 Astrophysics from Antarctica John Storey (3) Mon. 20 IAUS 289 The Cosmic Distance Scale: Past, Present and Future Wendy Freedman (3) Mon. 27 IAUS 290 Probing General Relativity using Accreting Black Holes Andy Fabian (B) Wed. 22 IAUS 291 Pulsars are Cool – seriously Scott Ransom (3) Thu. 23 Magnetars: neutron stars with magnetic storms Nanda Rea (3) Thu. 23 Probing Gravitation with Pulsars Michael Kremer (3) Thu. 23 IAUS 292 From Gas to Stars over Cosmic Time Mordacai-Mark Mac Low (B) Tue. 21 IAUS 293 The Kepler Mission: NASA’s ExoEarth Census Natalie Batalha (3) Tue. 28 IAUS 294 The Origin and Evolution of Cosmic Magnetism Bryan Gaensler (B) Wed. 29 IAUS 295 Black Holes in Galaxies John Kormendy (B) Thu. 30 (c) Symposia - Week 1 IAUS 288 Astrophysics from Antartica IAUS 290 Accretion on all scales IAUS 291 Neutron Stars and Pulsars IAUS 292 Molecular gas, Dust, and Star Formation in Galaxies (d) Symposia –Week 2 IAUS 289 Advancing the Physics of Cosmic -
Differential Rotation of Kepler-71 Via Transit Photometry Mapping of Faculae and Starspots
MNRAS 484, 618–630 (2019) doi:10.1093/mnras/sty3474 Advance Access publication 2019 January 16 Differential rotation of Kepler-71 via transit photometry mapping of faculae and starspots Downloaded from https://academic.oup.com/mnras/article-abstract/484/1/618/5289895 by University of Southern Queensland user on 14 November 2019 S. M. Zaleski ,1‹ A. Valio,2 S. C. Marsden1 andB.D.Carter1 1University of Southern Queensland, Centre for Astrophysics, Toowoomba 4350, Australia 2Center for Radio Astronomy and Astrophysics, Mackenzie Presbyterian University, Rua da Consolac¸ao,˜ 896 Sao˜ Paulo, Brazil Accepted 2018 December 19. Received 2018 December 18; in original form 2017 November 16 ABSTRACT Knowledge of dynamo evolution in solar-type stars is limited by the difficulty of using active region monitoring to measure stellar differential rotation, a key probe of stellar dynamo physics. This paper addresses the problem by presenting the first ever measurement of stellar differential rotation for a main-sequence solar-type star using starspots and faculae to provide complementary information. Our analysis uses modelling of light curves of multiple exoplanet transits for the young solar-type star Kepler-71, utilizing archival data from the Kepler mission. We estimate the physical characteristics of starspots and faculae on Kepler-71 from the characteristic amplitude variations they produce in the transit light curves and measure differential rotation from derived longitudes. Despite the higher contrast of faculae than those in the Sun, the bright features on Kepler-71 have similar properties such as increasing contrast towards the limb and larger sizes than sunspots. Adopting a solar-type differential rotation profile (faster rotation at the equator than the poles), the results from both starspot and facula analysis indicate a rotational shear less than about 0.005 rad d−1, or a relative differential rotation less than 2 per cent, and hence almost rigid rotation. -
Spectroscopy of Variable Stars
Spectroscopy of Variable Stars Steve B. Howell and Travis A. Rector The National Optical Astronomy Observatory 950 N. Cherry Ave. Tucson, AZ 85719 USA Introduction A Note from the Authors The goal of this project is to determine the physical characteristics of variable stars (e.g., temperature, radius and luminosity) by analyzing spectra and photometric observations that span several years. The project was originally developed as a The 2.1-meter telescope and research project for teachers participating in the NOAO TLRBSE program. Coudé Feed spectrograph at Kitt Peak National Observatory in Ari- Please note that it is assumed that the instructor and students are familiar with the zona. The 2.1-meter telescope is concepts of photometry and spectroscopy as it is used in astronomy, as well as inside the white dome. The Coudé stellar classification and stellar evolution. This document is an incomplete source Feed spectrograph is in the right of information on these topics, so further study is encouraged. In particular, the half of the building. It also uses “Stellar Spectroscopy” document will be useful for learning how to analyze the the white tower on the right. spectrum of a star. Prerequisites To be able to do this research project, students should have a basic understanding of the following concepts: • Spectroscopy and photometry in astronomy • Stellar evolution • Stellar classification • Inverse-square law and Stefan’s law The control room for the Coudé Description of the Data Feed spectrograph. The spec- trograph is operated by the two The spectra used in this project were obtained with the Coudé Feed telescopes computers on the left. -
The Milky Way Almost Every Star We Can See in the Night Sky Belongs to Our Galaxy, the Milky Way
The Milky Way Almost every star we can see in the night sky belongs to our galaxy, the Milky Way. The Galaxy acquired this unusual name from the Romans who referred to the hazy band that stretches across the sky as the via lactia, or “milky road”. This name has stuck across many languages, such as French (voie lactee) and spanish (via lactea). Note that we use a capital G for Galaxy if we are talking about the Milky Way The Structure of the Milky Way The Milky Way appears as a light fuzzy band across the night sky, but we also see individual stars scattered in all directions. This gives us a clue to the shape of the galaxy. The Milky Way is a typical spiral or disk galaxy. It consists of a flattened disk, a central bulge and a diffuse halo. The disk consists of spiral arms in which most of the stars are located. Our sun is located in one of the spiral arms approximately two-thirds from the centre of the galaxy (8kpc). There are also globular clusters distributed around the Galaxy. In addition to the stars, the spiral arms contain dust, so that certain directions that we looked are blocked due to high interstellar extinction. This dust means we can only see about 1kpc in the visible. Components in the Milky Way The disk: contains most of the stars (in open clusters and associations) and is formed into spiral arms. The stars in the disk are mostly young. Whilst the majority of these stars are a few solar masses, the hot, young O and B type stars contribute most of the light. -
Arxiv:1812.04626V2 [Astro-Ph.HE] 27 Jan 2019
Draft version January 29, 2019 Preprint typeset using LATEX style emulateapj v. 12/16/11 OPTICAL SPECTROSCOPY AND DEMOGRAPHICS OF REDBACK MILLISECOND PULSAR BINARIES Jay Strader1, Samuel J. Swihart1, Laura Chomiuk1, Arash Bahramian2, Christopher T. Britt3, C. C. Cheung4, Kristen C. Dage1, Jules P. Halpern5, Kwan-Lok Li6, Roberto P. Mignani7,8, Jerome A. Orosz9, Mark Peacock1, Ricardo Salinas10, Laura Shishkovsky1, Evangelia Tremou11 Draft version January 29, 2019 ABSTRACT We present the first optical spectroscopy of five confirmed (or strong candidate) redback millisecond pulsar binaries, obtaining complete radial velocity curves for each companion star. The properties of these millisecond pulsar binaries with low-mass, hydrogen-rich companions are discussed in the context of the 14 confirmed and 10 candidate field redbacks. We find that the neutron stars in redbacks have a median mass of 1:78 ± 0:09M with a dispersion of σ = 0:21 ± 0:09. Neutron stars with masses in excess of 2M are consistent with, but not firmly demanded by, current observations. Redback companions have median masses of 0:36 ± 0:04M with a scatter of σ = 0:15 ± 0:04M , and a tail possibly extending up to 0.7{0:9M . Candidate redbacks tend to have higher companion masses than confirmed redbacks, suggesting a possible selection bias against the detection of radio pulsations in these more massive candidate systems. The distribution of companion masses between redbacks and the less massive black widows continues to be strongly bimodal, which is an important constraint on evolutionary models for these systems. Among redbacks, the median efficiency of converting the pulsar spindown energy to γ-ray luminosity is ∼ 10%. -
Spot Activity of the RS Canum Venaticorum Star Σ Geminorum⋆
A&A 562, A107 (2014) Astronomy DOI: 10.1051/0004-6361/201321291 & c ESO 2014 Astrophysics Spot activity of the RS Canum Venaticorum star σ Geminorum P. Kajatkari1, T. Hackman1,2, L. Jetsu1,J.Lehtinen1, and G.W. Henry3 1 Department of Physics, PO Box 64, 00014 University of Helsinki, 00014 Helsinki, Finland e-mail: [email protected] 2 Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland 3 Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209, USA Received 14 February 2013 / Accepted 6 November 2013 ABSTRACT Aims. We model the photometry of RS CVn star σ Geminorum to obtain new information on the changes of the surface starspot distribution, that is, activity cycles, differential rotation, and active longitudes. Methods. We used the previously published continuous period search (CPS) method to analyse V-band differential photometry ob- tained between the years 1987 and 2010 with the T3 0.4 m Automated Telescope at the Fairborn Observatory. The CPS method divides data into short subsets and then models the light-curves with Fourier-models of variable orders and provides estimates of the mean magnitude, amplitude, period, and light-curve minima. These light-curve parameters are then analysed for signs of activity cycles, differential rotation and active longitudes. d Results. We confirm the presence of two previously found stable active longitudes, synchronised with the orbital period Porb = 19.60, and found eight events where the active longitudes are disrupted. The epochs of the primary light-curve minima rotate with a shorter d period Pmin,1 = 19.47 than the orbital motion. -
Differential Rotation in Sun-Like Stars from Surface Variability and Asteroseismology
Differential rotation in Sun-like stars from surface variability and asteroseismology Dissertation zur Erlangung des mathematisch-naturwissenschaftlichen Doktorgrades “Doctor rerum naturalium” der Georg-August-Universität Göttingen im Promotionsprogramm PROPHYS der Georg-August University School of Science (GAUSS) vorgelegt von Martin Bo Nielsen aus Aarhus, Dänemark Göttingen, 2016 Betreuungsausschuss Prof. Dr. Laurent Gizon Institut für Astrophysik, Georg-August-Universität Göttingen Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany Dr. Hannah Schunker Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany Prof. Dr. Ansgar Reiners Institut für Astrophysik, Georg-August-Universität, Göttingen, Germany Mitglieder der Prüfungskommision Referent: Prof. Dr. Laurent Gizon Institut für Astrophysik, Georg-August-Universität Göttingen Max-Planck-Institut für Sonnensystemforschung, Göttingen Korreferent: Prof. Dr. Stefan Dreizler Institut für Astrophysik, Georg-August-Universität, Göttingen 2. Korreferent: Prof. Dr. William Chaplin School of Physics and Astronomy, University of Birmingham Weitere Mitglieder der Prüfungskommission: Prof. Dr. Jens Niemeyer Institut für Astrophysik, Georg-August-Universität, Göttingen PD. Dr. Olga Shishkina Max Planck Institute for Dynamics and Self-Organization Prof. Dr. Ansgar Reiners Institut für Astrophysik, Georg-August-Universität, Göttingen Prof. Dr. Andreas Tilgner Institut für Geophysik, Georg-August-Universität, Göttingen Tag der mündlichen Prüfung: 3 Contents 1 Introduction 11 1.1 Evolution of stellar rotation rates . 11 1.1.1 Rotation on the pre-main-sequence . 11 1.1.2 Main-sequence rotation . 13 1.1.2.1 Solar rotation . 15 1.1.3 Differential rotation in other stars . 17 1.1.3.1 Latitudinal differential rotation . 17 1.1.3.2 Radial differential rotation . 18 1.2 Measuring stellar rotation with Kepler ................... 19 1.2.1 Kepler photometry .