DOCSLIB.ORG

X-Ray Properties of the Young Stellar And

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
X-Ray Properties of the Young Stellar And The Astronomical Journal, 123:1613–1628, 2002 March E # 2002. The American Astronomical Society. All rights reserved. Printed in U.S.A. X-RAY PROPERTIES OF THE YOUNG STELLAR AND SUBSTELLAR OBJECTS IN THE IC 348 CLUSTER: THE CHANDRA VIEW Thomas Preibisch Max-Planck-Institut fu¨r Radioastronomie, Auf dem Hu¨gel 69, D-53121 Bonn, Germany; [email protected] and Hans Zinnecker Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany; [email protected] Received 2001 October 2; accepted 2001 November 20 ABSTRACT We explore the X-ray properties of the young stellar and substellar objects in the open cluster IC 348 as seen in our deep Chandra X-Ray Observatory Advanced CCD Imaging Spectrometer image. First, we give identifications of all X-ray sources and determine upper limits for the X-ray luminosities of the undetected cluster members. Then we analyze the X-ray spectra of the young stellar objects, deriving plasma tempera- tures between 0.7 and 3 keV for the T Tauri stars in IC 348 and higher temperatures, between 3 and 7 keV, for flaring sources and two embedded young stellar objects. We find several large X-ray flares, in some of which a clear hardening of the X-ray spectra during the flare peak is seen. Next we use the exceptional opti- cal, infrared, and X-ray data set of this cluster to study various correlations and their implications, and to dis- cuss new answers to some long-standing questions related to X-ray emission from young (sub)stellar objects. The X-ray luminosities of the young low-mass stars are strongly correlated to the stellar bolometric luminosi- À4 ties (LX 10 Â Lbol). Also, a good correlation between X-ray luminosity and stellar mass is found 2 (LX / M ). For the weak-line T Tauri stars we find a tight correlation between X-ray activity and chromo- 0:8 spheric activity ðLX / LH Þ, supporting the hypothesis that the chromosphere is heated by X-rays from the overlying corona. The observed X-ray properties of the brown dwarfs (and brown dwarf candidates) are very similar to those of late-type stars; we explain this behavior as the consequence of the fact that very young sub- stellar objects are still warm enough to maintain partially ionized atmospheres, which are capable of sustain- ing electrical currents, while in the cooler neutral atmospheres of L and T dwarfs such currents are shut off (hence no X-ray emission). Finally, we explore the difference between the X-ray luminosity functions of clas- sical and weak-line T Tauri stars. We find that the classical T Tauri stars in IC 348 seem to be on average less X-ray luminous than the weak-line T Tauri stars. However, we suggest that this apparent difference is caused by a selection effect: there is a strong detections bias against those weak-line T Tauri stars that are optically faint and hence X-ray faint; the population of classical T Tauri stars, on the other hand, is essentially com- pletely known because of its very prominent H emission. This conclusion is corroborated by another new result: when using a photometrically selected, magnitude-limited, complete sample of T Tauri stars and tak- ing the KÀL infrared excess as a tracer of circumstellar material, we find no evidence in IC 348 for a difference in X-ray properties of young stars with and without circumstellar matter, i.e., classical and ‘‘ naked ’’ T Tauri stars. Key words: low-mass, brown dwarfs — open clusters and associations: individual (IC 348) — stars: coronae — stars: pre–main-sequence — X-rays On-line material: machine-readable tables 1. INTRODUCTION Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory, in which we detected IC 348 is a very young stellar cluster in the Perseus molecular cloud complex. The cluster is exceptionally 215 individual X-ray sources. First results of this obser- vation have been reported in Preibisch & Zinnecker well studied in optical and infrared wavelengths (see Her- (2001, hereafter PZ01), including a comparison of the big 1998, hereafter H98; Scholz et al. 1999; Lada & Lada optical, infrared, and X-ray images. In this paper we 1995; Luhman et al. 1998, hereafter L98; Luhman 1999, present detailed information on the identification of the hereafter L99; Najita, Tiede, & Carr 2000, hereafter X-ray sources and study the X-ray properties of the N00). Spectral types are known for more than 200 stars, young stellar and substellar objects in IC 348, including H emission has been detected for more than 100 stars, their implications. and numerous substellar objects have been identified. The distance to IC 348 is 310 pc (H98), the mean age of the stars is 1.5 Myr, and their mean extinction is 3.5 mag (H98; L98). ROSAT X-ray observations of IC 348 were 2. Chandra Observations and Data Analysis presented by Preibisch, Zinnecker, & Herbig (1996, here- The Chandra observation of IC 348 was performed on after PZH96) and led to the discovery of 116 X-ray 2000 September 25, utilizing ACIS in its imaging configura- sources in a 2 diameter field of view. We have recently tion. The total exposure time was 52,956.8 s. The results pre- obtained a deep X-ray image of IC 348 with the sented in PZ01 can be summarized as follows: 1613 1614 PREIBISCH & ZINNECKER Vol. 123 TABLE 1 Chandra X-Ray Sources in IC 348 Source Identification SpT AV W(H ) kT LX CXOPZ- (2) (3) (mag) (A˚) (keV) (1028 ergs sÀ1) (1) (4) (5) (6) (7) J034346.9+321320 ... 2MASS ... 0.70 i ... ... 5.0 Æ 1.6 J034349.3+321040 ... H-IfA68 ... 1.74 i 2.0 ... 34.2 Æ 7.0 J034351.2+321309 ... L-22 G5 2.31 ... 2.1 Æ 0.3 472.0 Æ 40.3 J034351.5+321239 ... noCP ... ... ... ... ... J034353.3+320927 ... noCP ... ... ... ... ... Notes.—Table 1 is presented in its entirety in the electronic edition of the Astronomical Journal. A portion is shown here for guidance regarding its form and content. Columns: (1) Chandra X-ray source name as defined in Preibisch & Zinnecker 2001; the name contains the J2000.0 coordinates in the format HHMMSS.S+DDMMSS. (2) Identification with optical and/or infrared counterparts from the catalog of Herbig 1998 (H-), Luhman et al. 1998 or Luhman 1999 (L-), or Najita et al. 2000 (N-). Stars known to be foreground or background objects are marked with ‘‘ FG ’’ and ‘‘ BG ’’, respectively. If no cataloged counterpart is known, the entry ‘‘ 2MASS ’’ means that the X-ray source has a counterpart in the 2MASS point-source catalog, while ‘‘ noCP ’’ means that no optical or infrared counterpart could be found. Source CXOPZ-J034424.6+321349 is identified with a faint infrared source not included in the 2MASS catalog. (3) Spectral type of the counterpart. (4) Visual extinction of the counterpart; ‘‘ i ’’ indicates that the value was estimated from the near-infrared colors, and a colon indicates that, owing to a lack of fur- ther information, an extinction of 3.5 mag has been assumed. (5) Equivalent width of the H emission line. Negative values denote H absorption. (6) Plasma temperature determined in the fit of the X-ray spectrum. (7) Extinction corrected 0.2–10 keV band X-ray luminosity. 1. The number of individual X-ray sources detected was be rather uniform, we are confident that they are back- 215. ground objects. 2. About 80% of all known cluster members with masses In Table 1 we present a list of all X-ray sources with corre- between 0.15 and 2 M are seen as X-ray sources in our sponding identifications and further information about the Chandra image. stellar and X-ray properties. The determination of the 3. X-ray emission at levels of 1028 ergs sÀ1 was discov- extinction corrected X-ray luminosities (integrated over the ered from four of 13 known brown dwarfs and from three of 0.2–10 keV band) was based on the analysis of the X-ray 12 brown dwarf candidates in IC 348. spectra as described in x 5. 4. X-ray emission was also detected from two deeply embedded young stellar objects, presumably Class I proto- stars, south of the optical cluster center. 4. UPPER LIMITS FOR NONDETECTED The data analysis presented in this paper was performed CLUSTER MEMBERS with the CIAO 2.1.2 software package provided by the In Table 2 we present a list of all those known cluster Chandra X-Ray Center and is based on the Level 2 proc- members that were not detected as X-ray sources in our essed event list provided by the pipeline processing at the Chandra image. We determined upper limits to the count Chandra X-Ray Center. rates of these objects by counting the observed number of photons in source regions centered at their optical/ infrared positions and comparing them with the expected 3. IDENTIFICATIONS OF THE CHANDRA number of background photons determined from several X-RAY SOURCES large source-free background regions. We used the Baye- We searched for counterparts of the X-ray sources in the sian statistics method described by Kraft, Burrows, & member lists published in H98, L98, L99, and N00. For X- Nousek (1991) to determine the 90% confidence upper ray sources without a cataloged counterpart, we searched limits for their count rates. From these count-rate upper for optical counterparts on the red DSS plate and on our limits we computed upper limits for the extinction-cor- own deep optical images, and for infrared counterparts in rected X-ray luminosities in the 0.2–10 keV band assum- the 2MASS source catalog, in the 2MASS images, and in ing thermal plasma spectra with a temperature of kT =1 our own deep J- and K-band images1 of IC 348.
Load more

Recommended publications
  • A Review on Substellar Objects Below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs Or What?
    geosciences Review A Review on Substellar Objects below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs or What? José A. Caballero Centro de Astrobiología (CSIC-INTA), ESAC, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain; [email protected] Received: 23 August 2018; Accepted: 10 September 2018; Published: 28 September 2018 Abstract: “Free-floating, non-deuterium-burning, substellar objects” are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups, and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. In this paper, their nomenclature, history of discovery, sites of detection, formation mechanisms, and future directions of research are reviewed. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST. Keywords: planetary systems; stars: brown dwarfs; stars: low mass; galaxy: solar neighborhood; galaxy: open clusters and associations 1. Introduction I can’t answer why (I’m not a gangstar) But I can tell you how (I’m not a flam star) We were born upside-down (I’m a star’s star) Born the wrong way ’round (I’m not a white star) I’m a blackstar, I’m not a gangstar I’m a blackstar, I’m a blackstar I’m not a pornstar, I’m not a wandering star I’m a blackstar, I’m a blackstar Blackstar, F (2016), David Bowie The tenth star of George van Biesbroeck’s catalogue of high, common, proper motion companions, vB 10, was from the end of the Second World War to the early 1980s, and had an entry on the least massive star known [1–3].
    [Show full text]
  • List of Bright Nebulae Primary I.D. Alternate I.D. Nickname
    List of Bright Nebulae Alternate Primary I.D. Nickname I.D. NGC 281 IC 1590 Pac Man Neb LBN 619 Sh 2-183 IC 59, IC 63 Sh2-285 Gamma Cas Nebula Sh 2-185 NGC 896 LBN 645 IC 1795, IC 1805 Melotte 15 Heart Nebula IC 848 Soul Nebula/Baby Nebula vdB14 BD+59 660 NGC 1333 Embryo Neb vdB15 BD+58 607 GK-N1901 MCG+7-8-22 Nova Persei 1901 DG 19 IC 348 LBN 758 vdB 20 Electra Neb. vdB21 BD+23 516 Maia Nebula vdB22 BD+23 522 Merope Neb. vdB23 BD+23 541 Alcyone Neb. IC 353 NGC 1499 California Nebula NGC 1491 Fossil Footprint Neb IC 360 LBN 786 NGC 1554-55 Hind’s Nebula -Struve’s Lost Nebula LBN 896 Sh 2-210 NGC 1579 Northern Trifid Nebula NGC 1624 G156.2+05.7 G160.9+02.6 IC 2118 Witch Head Nebula LBN 991 LBN 945 IC 405 Caldwell 31 Flaming Star Nebula NGC 1931 LBN 1001 NGC 1952 M 1 Crab Nebula Sh 2-264 Lambda Orionis N NGC 1973, 1975, Running Man Nebula 1977 NGC 1976, 1982 M 42, M 43 Orion Nebula NGC 1990 Epsilon Orionis Neb NGC 1999 Rubber Stamp Neb NGC 2070 Caldwell 103 Tarantula Nebula Sh2-240 Simeis 147 IC 425 IC 434 Horsehead Nebula (surrounds dark nebula) Sh 2-218 LBN 962 NGC 2023-24 Flame Nebula LBN 1010 NGC 2068, 2071 M 78 SH 2 276 Barnard’s Loop NGC 2149 NGC 2174 Monkey Head Nebula IC 2162 Ced 72 IC 443 LBN 844 Jellyfish Nebula Sh2-249 IC 2169 Ced 78 NGC Caldwell 49 Rosette Nebula 2237,38,39,2246 LBN 943 Sh 2-280 SNR205.6- G205.5+00.5 Monoceros Nebula 00.1 NGC 2261 Caldwell 46 Hubble’s Var.
    [Show full text]
  • Open Clusters
    Open Clusters Open clusters (also known as galactic clusters) are of tremendous importance to the science of astronomy, if not to astrophysics and cosmology generally. Star clusters serve as the "laboratories" of astronomy, with stars now all at nearly the same distance and all created at essentially the same time. Each cluster thus is a running experiment, where we can observe the effects of composition, age, and environment. We are hobbled by seeing only a snapshot in time of each cluster, but taken collectively we can understand their evolution, and that of their included stars. These clusters are also important tracers of the Milky Way and other parent galaxies. They help us to understand their current structure and derive theories of the creation and evolution of galaxies. Just as importantly, starting from just the Hyades and the Pleiades, and then going to more distance clusters, open clusters serve to define the distance scale of the Milky Way, and from there all other galaxies and the entire universe. However, there is far more to the study of star clusters than that. Anyone who has looked at a cluster through a telescope or binoculars has realized that these are objects of immense beauty and symmetry. Whether a cluster like the Pleiades seen with delicate beauty with the unaided eye or in a small telescope or binoculars, or a cluster like NGC 7789 whose thousands of stars are seen with overpowering wonder in a large telescope, open clusters can only bring awe and amazement to the viewer. These sights are available to all.
    [Show full text]
  • December 2019 BRAS Newsletter
    A Monthly Meeting December 11th at 7PM at HRPO (Monthly meetings are on 2nd Mondays, Highland Road Park Observatory). Annual Christmas Potluck, and election of officers. What's In This Issue? President’s Message Secretary's Summary Outreach Report Asteroid and Comet News Light Pollution Committee Report Globe at Night Member’s Corner – The Green Odyssey Messages from the HRPO Friday Night Lecture Series Science Academy Solar Viewing Stem Expansion Transit of Murcury Edge of Night Natural Sky Conference Observing Notes: Perseus – Rescuer Of Andromeda, or the Hero & Mythology Like this newsletter? See PAST ISSUES online back to 2009 Visit us on Facebook – Baton Rouge Astronomical Society Baton Rouge Astronomical Society Newsletter, Night Visions Page 2 of 25 December 2019 President’s Message I would like to thank everyone for having me as your president for the last two years . I hope you have enjoyed the past two year as much as I did. We had our first Members Only Observing Night (MOON) at HRPO on Sunday, 29 November,. New officers nominated for next year: Scott Cadwallader for President, Coy Wagoner for Vice- President, Thomas Halligan for Secretary, and Trey Anding for Treasurer. Of course, the nominations are still open. If you wish to be an officer or know of a fellow member who would make a good officer contact John Nagle, Merrill Hess, or Craig Brenden. We will hold our annual Baton Rouge “Gastronomical” Society Christmas holiday feast potluck and officer elections on Monday, December 9th at 7PM at HRPO. I look forward to seeing you all there. ALCon 2022 Bid Preparation and Planning Committee: We’ll meet again on December 14 at 3:00.pm at Coffee Call, 3132 College Dr F, Baton Rouge, LA 70808, UPCOMING BRAS MEETINGS: Light Pollution Committee - HRPO, Wednesday December 4th, 6:15 P.M.
    [Show full text]
  • GEORGE HERBIG and Early Stellar Evolution
    GEORGE HERBIG and Early Stellar Evolution Bo Reipurth Institute for Astronomy Special Publications No. 1 George Herbig in 1960 —————————————————————– GEORGE HERBIG and Early Stellar Evolution —————————————————————– Bo Reipurth Institute for Astronomy University of Hawaii at Manoa 640 North Aohoku Place Hilo, HI 96720 USA . Dedicated to Hannelore Herbig c 2016 by Bo Reipurth Version 1.0 – April 19, 2016 Cover Image: The HH 24 complex in the Lynds 1630 cloud in Orion was discov- ered by Herbig and Kuhi in 1963. This near-infrared HST image shows several collimated Herbig-Haro jets emanating from an embedded multiple system of T Tauri stars. Courtesy Space Telescope Science Institute. This book can be referenced as follows: Reipurth, B. 2016, http://ifa.hawaii.edu/SP1 i FOREWORD I first learned about George Herbig’s work when I was a teenager. I grew up in Denmark in the 1950s, a time when Europe was healing the wounds after the ravages of the Second World War. Already at the age of 7 I had fallen in love with astronomy, but information was very hard to come by in those days, so I scraped together what I could, mainly relying on the local library. At some point I was introduced to the magazine Sky and Telescope, and soon invested my pocket money in a subscription. Every month I would sit at our dining room table with a dictionary and work my way through the latest issue. In one issue I read about Herbig-Haro objects, and I was completely mesmerized that these objects could be signposts of the formation of stars, and I dreamt about some day being able to contribute to this field of study.
    [Show full text]
  • Cycle 9 Approved Programs
    Cycle 9 Approved Programs TYPE OF SCIENCE FIRST NAME LAST NAME INSTITUTION COUNTRY TITLE PROPOSAL CATEGORY A Morphological and Multicolor HST Survey for Ultrafaint Quasars, Sampling A Scott Anderson AR University of Washington United States AGN Broad Redshift Range Antonio Aparicio GO Instituto de Astrofi sica de Canarias Spain GAL Phoenix: "halo/disk" structures in dwarf galaxies John Bahcall GO Institute for Advanced Study United States HS Observing the next nearby supernova Ultraviolet Spectroscopy of Hot Horizontal-Branch Stars in the Globular Cluster Bradford Behr GO California Institute of Technology United States HS M13 David Bennett GO University of Notre Dame United States SP Confirmation of Black Hole, Planetary, and Binary Microlensing Events Klaus P. Beuermann GO Universitaets-Sternwarte Goettingen Germany HS FGS parallaxes of magnetic CVs Luciana Bianchi GO The Johns Hopkins University United States SP The Massive Star Content of NGC 6822 Torsten Boeker SNAP Space Telescope Science Institute United States GAL A Census of Nuclear Star Clusters in Late-Type Spiral Galaxies Ann Boesgaard GO Institute for Astronomy, University of Hawaii United States CS The Nucleosynthesis of Boron - Benchmarks for the Galactic Disk Howard Bond GO Space Telescope Science Institute United States CS WFPC2 Observations of Astrophysically Important Visual Binaries Howard Bond GO Space Telescope Science Institute United States HS Sakurai's Novalike Object: Real-Time Monitoring of a Stellar Thermal Pulse Amanda Bosh AR Lowell Observatory United States
    [Show full text]
  • Arxiv:2105.09338V2 [Astro-Ph.GA] 16 Jun 2021
    Draft version June 18, 2021 Typeset using LATEX twocolumn style in AASTeX63 Stars with Photometrically Young Gaia Luminosities Around the Solar System (SPYGLASS) I: Mapping Young Stellar Structures and their Star Formation Histories Ronan Kerr,1 Aaron C. Rizzuto,1, ∗ Adam L. Kraus,1 and Stella S. R. Offner1 1Department of Astronomy, University of Texas at Austin 2515 Speedway, Stop C1400 Austin, Texas, USA 78712-1205 (Accepted May 16, 2021) ABSTRACT Young stellar associations hold a star formation record that can persist for millions of years, revealing the progression of star formation long after the dispersal of the natal cloud. To identify nearby young stellar populations that trace this progression, we have designed a comprehensive framework for the identification of young stars, and use it to identify ∼3×104 candidate young stars within a distance of 333 pc using Gaia DR2. Applying the HDBSCAN clustering algorithm to this sample, we identify 27 top-level groups, nearly half of which have little to no presence in previous literature. Ten of these groups have visible substructure, including notable young associations such as Orion, Perseus, Taurus, and Sco-Cen. We provide a complete subclustering analysis on all groups with substructure, using age estimates to reveal each region's star formation history. The patterns we reveal include an apparent star formation origin for Sco-Cen along a semicircular arc, as well as clear evidence for sequential star formation moving away from that arc with a propagation speed of ∼4 km s−1 (∼4 pc Myr−1). We also identify earlier bursts of star formation in Perseus and Taurus that predate current, kinematically identical active star-forming events, suggesting that the mechanisms that collect gas can spark multiple generations of star formation, punctuated by gas dispersal and cloud regrowth.
    [Show full text]
  • Alma Survey of Circumstellar Disks in the Young Stellar Cluster Ic 348
    Mon. Not. R. Astron. Soc. 000, 1–?? (2018) Printed 22 May 2018 (MN LATEX style file v2.2) ALMA SURVEY OF CIRCUMSTELLAR DISKS IN THE YOUNG STELLAR CLUSTER IC 348 D. Ruíz-Rodríguez, 1;2? L. A. Cieza,3;4 J. P. Williams,5 S. M. Andrews,6 D. A. Principe,7 C. Caceres,8;12 H. Canovas,9 S. Casassus,3;10 M. R. Schreiber,3;11;12 and J. H. Kastner1 1Chester F. Carlson Center for Imaging Science, School of Physics & Astronomy, and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester NY 14623 USA. 2Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia 3Millenium Nucleus “Protoplanetary discs in ALMA Early Science", Chile. 4Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile. 5Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI, 96822, USA. 6Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA. 7Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 8Departamento de Ciencias Fisicas, Facultad de Ciencias Exactas, Universidad Andres Bello. Av. Fernandez Concha 700, Las Condes, Santiago, Chile. 9European Space Astronomy Centre (ESA), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain. 10Universidad de Chile, Camino el Observatorio 1515, Santiago, Chile. 11Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, 2360102 Valparaíso, Chile. 12Núcleo Milenio Formación Planetaria - NPF, Universidad de Valparaiso, Av. Gran Bretaña 1111, Valparaiso, Chile. ABSTRACT We present a 1.3 mm continuum survey of the young (2-3 Myr) stellar cluster IC 348, which lies at a distance of 310 pc, and is dominated by low-mass stars (M? ∼ 0.1-0.6 M ).
    [Show full text]
  • Exploring the Low-Mass Initial Mass Function in Young Clusters and Star-Forming Regions Andrew Burgess
    Exploring the Low-Mass Initial Mass Function in Young Clusters and Star-Forming Regions Andrew Burgess To cite this version: Andrew Burgess. Exploring the Low-Mass Initial Mass Function in Young Clusters and Star-Forming Regions. Astrophysics [astro-ph]. Université de Grenoble, 2010. English. tel-00576460 HAL Id: tel-00576460 https://tel.archives-ouvertes.fr/tel-00576460 Submitted on 14 Mar 2011 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. UNIVERSITE´ DE GRENOBLE THESE` pour obtenir le grade de DOCTEUR DE L’UNIVERSITE´ DE GRENOBLE Sp´ecialit´e: ASTROPHYSIQUE ET MILIEUX DILUES´ Arrˆet´es minist´eriels du 7 aoˆut 2006 pr´esent´ee et soutenue publiquement par A.S.M.BURGESS le 15i`eme decembre´ 2010 Exploring the Low-Mass Initial Mass Function in Young Clusters and Star-Forming Regions1 - Exploration de la fonction de faible masse initiale dans les amas jeunes et les regions´ de formation stellaire Th`ese dirig´ee par Jerome Bouvier et coridig´ee par Estelle Moraux JURY M. Jean-Louis MONIN Pr´esident Mme. France ALLARD Rapporteur M. Eduardo MARTIN´ Rapporteur M. J´erˆome BOUVIER Examinateur M. Nicolas LODIEU Examinateur Mme.
    [Show full text]
  • DECEMBER 2009 OBSERVER Inside the Happy Holidays! Observer
    THE DENVER OBSERVER DECEMBER 2009 OBSERVER Inside the Happy Holidays! Observer President’s Corner........................... 2 Society Directory............................. 2 Letter #om Ginny Kramer................ 3 $Easy View Mount%.......................... 4 Colorado Astronomy Day.................. 5 School of Mines Telescope................. 6 Holiday Potluck.............................. 7 Schedule of Events.............. back page Calendar 2..................................................... Full moon 8...................................... Last quarter moon HEART AND SOUL FOR THE HOLIDAYS 12................................................... Hanukkah In Cassiopeia, IC 1805, the Heart (right), and IC 1848, the Soul (left), were imaged at the Dark 14.......................................... Winter Solstice Site with a 110-mm Mamiya RZ lens at f/5.6 on an SBIG ST-2000XM ccd camera. Joe shot 16................................................. New moon 20 minute LRGB plus 30 minutes Ha narrowband exposures, with five-minute sub- exposures. 24.................................... First quarter moon Image copyright 2009 Joe Gafford 25........................................... Christmas Day DECEMBER SKIES by Dennis Cochran hey say that Mars is coming and Jupiter’s going, and Cygnus the The Red Planet rises at 10 P.M. as the month begins and by 8 P.M. after T Swan is diving into the northwest, standing the Northern Cross Christmas. The opposition of Mars (when it’s closest to Earth) happens upright on the evening horizon. Our favorite double star, Albi- January 27, 2010, so January and February will be the best months for reo, will be buried in the twilight—or twilit—trees. As Jupiter becomes viewing the world to which we have paid so much attention over the an evening dropout, (although still visible), Saturn rises at midnight. years. This time around it’s not as near as before, and consequently, not as By mid-month, Neptune will be a moon’s width above Jupiter.
    [Show full text]
  • Cosmography of OB Stars in the Solar Neighbourhood⋆
    A&A 584, A26 (2015) Astronomy DOI: 10.1051/0004-6361/201527058 & c ESO 2015 Astrophysics Cosmography of OB stars in the solar neighbourhood? H. Bouy1 and J. Alves2 1 Centro de Astrobiología, INTA-CSIC, Depto Astrofísica, ESAC Campus, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain e-mail: [email protected] 2 Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria Received 25 July 2015 / Accepted 6 October 2015 ABSTRACT We construct a 3D map of the spatial density of OB stars within 500 pc from the Sun using the Hipparcos catalogue and find three large-scale stream-like structures that allow a new view on the solar neighbourhood. The spatial coherence of these blue streams and the monotonic age sequence over hundreds of parsecs suggest that they are made of young stars, similar to the young streams that are conspicuous in nearby spiral galaxies. The three streams are 1) the Scorpius to Canis Majoris stream, covering 350 pc and 65 Myr of star formation history; 2) the Vela stream, encompassing at least 150 pc and 25 Myr of star formation history; and 3) the Orion stream, including not only the well-known Orion OB1abcd associations, but also a large previously unreported foreground stellar group lying only 200 pc from the Sun. The map also reveals a remarkable and previously unknown nearby OB association, between the Orion stream and the Taurus molecular clouds, which might be responsible for the observed structure and star formation activity in this cloud complex. This new association also appears to be the birthplace of Betelgeuse, as indicated by the proximity and velocity of the red giant.
    [Show full text]
  • CONSTELLATION PERSEUS the Constellation Perseus Is a Constellation in the Northern Sky Which Was Named After the Greek Mythological Hero Perseus
    CONSTELLATION PERSEUS The constellation Perseus is a constellation in the northern sky which was named after the Greek mythological hero Perseus. It is located in the northern celestial hemisphere near several other constellations named after ancient Greek legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it is still among the 88 modern constellations as defined by the International Astronomical Union GENERAL Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, and Triangulum to the west. Some star atlases during the early 19th century also depicted Perseus holding onto the head of the Medusa, whose asterism was named together as Perseus et Caput Medusae, however, this never came into popular usage. The galactic plane of the Milky Way passes through Perseus but is mostly obscured by molecular clouds. The constellation's brightest star is the yellow-white supergiant Alpha Persei (also called Mirfak or Mirphak), which shines at magnitude 1.79. It and many of the surrounding stars are members of an open cluster known as the Alpha Persei Cluster. The best-known star, however, is Algol (Beta Persei), linked with ominous legends because of its variability, which is noticeable to the naked eye. Rather than being an intrinsically variable star, it is an eclipsing Perseus carrying the head of Medusa the Gorgon, as depicted in binary. Other notable star systems in Perseus Urania's Mirror, a set of cards published in London c.1825 include X Persei, a binary system containing a neutron star, and GK Persei, a nova that peaked at magnitude 0.2 in 1901.
    [Show full text]