DOCSLIB.ORG

Contributions to High Energy Γ-Ray Astronomy Jean-Philippe Lenain

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Contributions to High Energy Γ-Ray Astronomy Jean-Philippe Lenain Contributions to high energy γ-ray astronomy Jean-Philippe Lenain To cite this version: Jean-Philippe Lenain. Contributions to high energy γ-ray astronomy: Active galactic nuclei and leptonic cosmic rays. From H.E.S.S. to CTA. High Energy Astrophysical Phenomena [astro-ph.HE]. Sorbonne Université UPMC, 2018. tel-01740556 HAL Id: tel-01740556 https://tel.archives-ouvertes.fr/tel-01740556 Submitted on 22 Mar 2018 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. Contributions to high energy γ-ray astronomy Active galactic nuclei and leptonic cosmic rays From H.E.S.S. to CTA Jean-Philippe LENAIN Laboratoire de Physique Nucléaire et de Hautes Énergies Sorbonne Université, CNRS/IN2P3 Mémoire présenté en vue de l’obtention de l’ Habilitation à diriger des recherches de Sorbonne Université Spécialité: Physique Soutenue le 19 Février 2018 devant le jury composé de: Wystan BENBOW — Rapporteur Frédéric DAIGNE — Examinateur Kumiko KOTERA — Examinatrice Benoît LOTT — Rapporteur Tanguy PIEROG — Examinateur Jérôme RODRIGUEZ — Rapporteur January 30, 2018 À Maud, Lysandre & Abigail c Jorge Cham Contents Contents vii List of Figures ix List of Acronyms xi Acknowledgments xiii Preamble xv 1 High energy emission in AGN1 1.1 Introduction1 1.1.1 The AGN phenomenology and zoology1 1.1.2 The link between AGN and ultra high energy cosmic rays6 1.2 The H.E.S.S. experiment and the future CTA observatory7 1.2.1 The H.E.S.S. experiment8 1.2.2 The CTA observatory9 1.3 Some studies on high energy emission in active galactic nuclei 11 1.3.1 High energy γ-ray emission from radio-quiet systems 11 1.3.2 First H.E.S.S. II results on AGN: the case of PKS 2155 304 − and PG 1553+113 in monoscopic mode 16 1.4 Towards time-domain high-energy astrophysics 20 1.4.1 Flaring AGN at (very) high energies 21 1.4.2 FLaapLUC: a pipeline for the generation of prompt alerts on transient Fermi-LAT γ-ray sources 25 2 From the sky to the ground: characterising the instrument perfor- mances 31 2.1 High Energy Stereoscopic System 32 2.1.1 The H.E.S.S. simulations & analysis frameworks 32 2.1.2 H.E.S.S. II performances 33 2.1.3 Run-wise simulations 37 vii Contents 2.1.4 H.E.S.S. I upgraded cameras 41 2.2 Two specific studies on the response of the future CTA: observations with Moon light, and site related studies 49 2.2.1 High altitude site 51 2.2.2 Performances under Moon light 53 2.3 Conclusion 55 3 Cosmic-ray electron-positron spectrum 57 3.1 Context & motivation 57 3.2 Updated cosmic-ray e± spectrum with H.E.S.S. 58 4 Prospects 63 Bibliography 67 Appendices 83 A Selected publications 85 A.1 FLaapLUC: A pipeline for the generation of prompt alerts on transient Fermi-LAT γ-ray sources 86 A.2 Cloud ablation by a relativistic jet and the extended flare in CTA 102 in 2016 and 2017 93 A.3 Gamma-ray blazar spectra with H.E.S.S. II mono analysis: The case of PKS 2155 304 and PG 1553+113 102 − A.4 The 2012 flare of PG 1553+113 seen with H.E.S.S. and Fermi-LAT 115 A.5 Seyfert 2 galaxies in the GeV band: jets and starburst 129 B Curriculum Vitæ 137 C Publication list 141 Abstract 156 viii List of Figures 1.1 Composite image of the radio galaxy 3C 3482 1.2 Schematic representation of an AGN SED3 1.3 Schematics of the AGN classification model4 1.4 SED of a sample of blazars5 1.5 All particle cosmic ray spectrum7 1.6 Hillas diagram8 1.7 A view of the H.E.S.S. array9 1.8 Artist rendering of CTA 10 1.9 TS maps of NGC 1068 and NGC 4945 from Fermi-LAT data 13 1.10 Relationship between SN rate, total gas mass and γ-ray luminosity for a few systems 14 1.11 SED of NGC 1068 15 1.12 Excess maps of events in the directions of PKS 2155 304 and PG 1553+113 − with H.E.S.S. II mono 16 1.13 Observed high energy SED of PKS 2155 304 and PG 1553+113 observed − with Fermi-LAT and H.E.S.S. II mono 17 1.14 Intrinsic high energy SED of PKS 2155 304 and PG 1553+113 derived − from Fermi-LAT and H.E.S.S. II mono observations 18 1.15 Sensitivities of CTA and Fermi-LAT with respect to integration time 20 1.16 Activity subsequent from cloud ablation by the relativistic jet in CTA 102 23 1.17 Light curves of PKS 1510 089 in 2015 24 − 1.18 Comparison of FLaapLUC and a likelihood analysis for PKS 2155 304 27 − 1.19 FLaapLUC false alarm trigger rate 28 1.20 Example light curve from FLaapLUC on PKS 0736+01 28 1.21 Results of the follow-up likelihood analysis automatically launched by FLaapLUC on PKS 0736+01 29 2.1 Illustration of the classical massive simulation framework 32 2.2 Sketch of the different H.E.S.S. II reconstruction and analysis modes 34 2.3 Example of a H.E.S.S. II effective area after analysis cuts 34 2.4 Differential sensitivity of H.E.S.S. II in the combined mode 35 ix List of Figures 2.5 Effet of the shower propagation discretisation step in the Čerenkov light distribution 36 2.6 Influence of the shower propagation discretisation on the effective areas 37 2.7 Illustration of the run-wise simulation framework 38 2.8 Measured NSB rate for an observation of the Galactic centre with CT5 39 2.9 Energy distribution comparisons between run-wise simulations, classical Monte Carlo simulations and data 39 2.10 Comparison between run-wise simulations and data of the squared angular distance (Θ2) to the source position, for PKS 2155 304 40 − 2.11 Crab extension as measured with H.E.S.S., overlaid on a Chandra image in X-rays 40 2.12 Layout of the trigger sectors in H.E.S.S. cameras 42 2.13 Sector trigger patterns 43 2.14 Next-neighbour trigger patterns 44 2.15 Pixel pattern that would fire a 2-NN trigger, but not a 4-NN one 44 2.16 3-NN trigger pattern overlapping between two drawers 44 2.17 Effect of the next-neighbour trigger on γ rays 46 2.18 Same as Fig. 2.17 for simulated protons 47 2.19 Effect of the pixel amplitude threshold on γ rays, for the N-majority trigger, under different NSB rates 48 2.20 Schematic view of the 13 equivalent cost arrays considered for the Prod1 Monte Carlo simulations in CTA 50 2.21 Comparison of the sensitivity for the different CTA array candidates for an altitude of 3700 m 52 2.22 Comparison of the sensitivity for the different CTA array candidates under Moon light 54 3.1 H.E.S.S. observations used for the derivation of the electron spectrum 59 3.2 Electron/proton discrimination with the model reconstruction 59 3.3 High energy electron and positron spectrum 61 x List of Acronyms AGN active galactic nucleus BLR broad line region CAT Čerenkov Array at Themis CMB cosmic microwave background CTA Čerenkov Telescope Array EBL extragalactic background light EIC external inverse Compton EGI European Grid Infrastructure FSRQ flat spectrum radio quasar GRMHD general-relativistic magnetohydrodynamics GZK Greisen-Zatsepin-Kuzmin H.E.S.S. High Energy Stereoscopic System HBL high-frequency-peaked BL Lac object HE high energy HEGRA High Energy Gamma-Ray Astronomy IACT imaging atmospheric Čerenkov telescope IBL intermediate-frequency-peaked BL Lac object LBL low-frequency-peaked BL Lac object LST large-sized telescope MAGIC Major Atmospheric Gamma-Ray Imaging Čerenkov MST medium-sized telescope NAG noyau actif de galaxie NSB night sky background PMT photomultiplier tube PSF point spread function SED spectral energy distribution SSC synchrotron self-Compton SST small-sized telescope ToO target of opportunity VERITAS Very Energetic Radiation Imaging Telescope Array System VHE very high energy xi Acknowledgements First and foremost, my thanks goes to the member of the jury, Wystan Benbow, Frédéric Daigne, Kumiko Kotera, Benoît Lott, Tanguy Pierog and Jérôme Rodriguez, for accepting this charge. I would like to warmly thank my colleagues from the H.E.S.S. collaboration, for all these years of fruitful exchanges, discussions, collaborations, hard work, and friendships. Many thanks goes to Catherine Boisson, Hélène Sol and Andreas Zech, for bringing me in this field, for their trust, support and friendship, since the time of my PhD studies. I am indebted to lots of people from the H.E.S.S. collaboration and the CTA consortium. I would not venture to provide an exhaustive list, but I reserve special mentions for (in no special order): Mathieu de Naurois, Santiago Pita, Bruno Khélifi, Arache Djannati-Ataï, Michael Punch, Markus Holler, Fabian Schüssler, Jonathan Biteau, Martin Raue, Wystan Benbow, Berrie Giebels, Gilles Henri, Jean-François Glicenstein, Yvonne Becherini, Heike Prokoph, Stefan Wagner, Michael Zacharias, Pol Bordas, Vincent Marandon, Lucie Gérard, Gabriele Cologna, Emma de Oña Wilhelmi, Andrew Taylor, David Sanchez, Gianluca Giavitto, Carlo Romoli, Manuel Meyer, Nukri Komin, François Brun, Pierre Brun, Frank Rieger, Justine Devin, Léa Jouvin, Arnim Balzer, Michael Gajdus, Joachim Hahn, Yves Gallant, Steve Fegan, Aldée Charbonnier, Stefan Ohm, Matthieu Renaud, Stefan Klepser, Karl Kosack, Susumu Inoue, Fabio Acero, Christian Farnier, Thierry Stolarczyk, Clementina Medina, Armand Fiasson.
Load more

Recommended publications
  • X-Ray Flux and Spectral Variability of Blazar H 2356-309
    galaxies Article X-ray Flux and Spectral Variability of Blazar H 2356-309 Kiran A. Wani and Haritma Gaur * Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India; [email protected] * Correspondence: [email protected] Received: 6 July 2020; Accepted: 31 July 2020; Published: date Abstract: We present the results of timing and spectral analysis of the blazar H 2356-309 using XMM-Newton observations. This blazar is observed during 13 June 2005–24 December 2013 in total nine observations. Five of the observations show moderate flux variability with amplitude 1.7–2.2%. We search for the intra-day variability timescales in these five light curves, but did not find in any of them. The fractional variability amplitude is generally lower in the soft bands than in the hard bands, which is attributed to the energy dependent synchrotron emission. Using the hardness ratio analysis, we search for the X-ray spectral variability along with flux variability in this source. However, we did not find any significant spectral variability on intra-day timescales. We also investigate the X-ray spectral curvature of blazar H 2356-309 and found that six of our observations are well described by the log parabolic model with α = 1.99–2.15 and β = 0.03–0.18. Three of our observations are well described by power law model. The break energy of the X-ray spectra varies between 1.97–2.31 keV. We investigate the correlation between various parameters that are derived from log parabolic model and their implications are discussed.
    [Show full text]
  • Relativistic Jets in Active Galactic Nuclei Und Microquasars
    SSRv manuscript No. (will be inserted by the editor) Relativistic Jets in Active Galactic Nuclei and Microquasars Gustavo E. Romero · M. Boettcher · S. Markoff · F. Tavecchio Received: date / Accepted: date Abstract Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly un- derstood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravi- tational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by γ-ray emission observed from many jet sources) and the physical processes responsible for this particle accelera- tion; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet colli- mation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially Gustavo E. Romero Instituto Argentino de Radioastronoma (IAR), C.C. No. 5, 1894, Buenos Aires, Argentina E-mail: [email protected] M. Boettcher Centre for Space Research, Private Bag X6001, North-West University, Potchef- stroom, 2520, South Africa E-mail: [email protected] S.
    [Show full text]
  • JOHN R. THORSTENSEN Address
    CURRICULUM VITAE: JOHN R. THORSTENSEN Address: Department of Physics and Astronomy Dartmouth College 6127 Wilder Laboratory Hanover, NH 03755-3528; (603)-646-2869 [email protected] Undergraduate Studies: Haverford College, B. A. 1974 Astronomy and Physics double major, High Honors in both. Graduate Studies: Ph. D., 1980, University of California, Berkeley Astronomy Department Dissertation : \Optical Studies of Faint Blue X-ray Stars" Graduate Advisor: Professor C. Stuart Bowyer Employment History: Department of Physics and Astronomy, Dartmouth College: { Professor, July 1991 { present { Associate Professor, July 1986 { July 1991 { Assistant Professor, September 1980 { June 1986 Research Assistant, Space Sciences Lab., U.C. Berkeley, 1975 { 1980. Summer Student, National Radio Astronomy Observatory, 1974. Summer Student, Bartol Research Foundation, 1973. Consultant, IBM Corporation, 1973. (STARMAP program). Honors and Awards: Phi Beta Kappa, 1974. National Science Foundation Graduate Fellow, 1974 { 1977. Dorothea Klumpke Roberts Award of the Berkeley Astronomy Dept., 1978. Professional Societies: American Astronomical Society Astronomical Society of the Pacific International Astronomical Union Lifetime Publication List * \Can Collapsed Stars Close the Universe?" Thorstensen, J. R., and Partridge, R. B. 1975, Ap. J., 200, 527. \Optical Identification of Nova Scuti 1975." Raff, M. I., and Thorstensen, J. 1975, P. A. S. P., 87, 593. \Photometry of Slow X-ray Pulsars II: The 13.9 Minute Period of X Persei." Margon, B., Thorstensen, J., Bowyer, S., Mason, K. O., White, N. E., Sanford, P. W., Parkes, G., Stone, R. P. S., and Bailey, J. 1977, Ap. J., 218, 504. \A Spectrophotometric Survey of the A 0535+26 Field." Margon, B., Thorstensen, J., Nelson, J., Chanan, G., and Bowyer, S.
    [Show full text]
  • A Basic Requirement for Studying the Heavens Is Determining Where In
    Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun­ damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short).
    [Show full text]
  • Cadas Transit October 2014
    October Transit 2014 The Newsletter of the Cleveland and Darlington Astronomical Society Page: 1 Header picture: The Sombrero Galaxy (M104) Cover Picture: The Veil Nebula Source: hubblesite.org Taken by: Jurgen Schmoll Next Meeting: Contents: Friday 10th October 7:15pm Editorial Page 2 At Wynyard Planetarium The Decay of the Life in the Sky – 3: Benik Markarian (By Rod Cuff) Page 3 Universe India’s MOM Snaps Spectacular Portrait of New Home Page 6 By Prof. Ruth Gregory Durham University Members Photos Page 8 The Transit Quiz (Neil Haggath) Page 10 Answers to last month’s quiz Page 11 Meetings Calendar Page 12 October Transit 2014 The Newsletter of the Cleveland and Darlington Astronomical Society Page: 2 Editorial Welcome to the October issue of Transit. This month we struggled for articles, but many thanks to Rod Cuff for completing the 3rd in his Life in the Skies series of articles. Thanks also to Jurgen Schmoll, Michael Tiplady and John McCue for their images. We have also reproduced an article from Universe Today (with their kind permission) on the arrival of India’s first interplanetary spacecraft. Any photo’s or articles for next month would be most welcome, but I would also like to ask you the readers what you would like to see in future issues of Transit. Does anyone want to see articles for beginners, or more about practical subjects , finding your way round the night sky, Astronomical History, Current News. Any comments or suggestions would be most welcome. Regards Jon Mathieson Email: [email protected] Phone: +44 7545 641 287 Address: 12 Rushmere, Marton, Middlesbrough, TS8 9XL New Members Dutch astronomer Frans Snik of the European Southern Observatory (ESO) has built his own version of the E-ELT using Lego.
    [Show full text]
  • Pos(NLS1)058 Ce of Broad Emission Lines in Their Ds Reveals Strong Similarities in the Ant Differences (E.G
    BL Lac objects with optical jets: PKS 2201+044, 3C 371 and PKS 0521-365. PoS(NLS1)058 E∗. Liuzzo Istituto di Radioastronomia-INAF-Bologna (Italy) E-mail: [email protected] R. Falomo Osservatorio Astronomico di Padova-INAF (Italy) A. Treves Università dell’Insubria (Como-Italy), associated to INAF and INFN We investigate the properties of the three BL Lac objects, PKS 2201+044, 3C 371 and PKS 0521- 365, that exhibit prominent optical jets. We present high resolution near-IR images of the jet of the first two, obtained with an innovative adaptive-optics system (MAD) at ESO VLT telescope. Comparison of the jet in the optical, radio, NIR and X-ray bands reveals strong similarities in the morphology. A common property of these sources is the presence of broad emission lines in their optical spectra at variance with the typical featureless spectrum of the nearby BL Lac objects. Despite some resemblances (e.g. in the radio type), significant differences (e.g. in the central black hole masses and radio structures) with radio-loud NLS1s are found. Narrow-Line Seyfert 1 Galaxies and their place in the Universe - NLS1, April 04-06, 2011 Milan Italy ∗Speaker. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/ BL Lac objects with optical jets. E 1. Introduction Radio loud (RL) Active Galactic Nuclei (AGN), in the contrary to their radio quiet (RQ) counterparts, show prominent jets mainly observable in the radio band. Blazars, including BL Lac objects and flat-spectrum radio quasars (FSRQs), are an important class of RL AGNs in which jets are relativistic and beamed in the observing direction.
    [Show full text]
  • Is the Massive Star Cluster Westerlund 2 Double? - a High Resolution Multi-Band Survey with the Hubble Space Telescope
    Formation, evolution, and survival of massive star clusters Proceedings IAU Symposium No. 316, 2015 c International Astronomical Union 2017 C. Charbonnel & A. Nota, eds. doi:10.1017/S1743921315008972 Is the massive star cluster Westerlund 2 double? - A high resolution multi-band survey with the Hubble Space Telescope Peter Zeidler1,2, Antonella Nota2,3, Elena Sabbi2, Eva K. Grebel1, Monica Tosi5, Alceste Z. Bonanos4, Anna Pasquali1, Carol Christian2 and Selma E. de Mink6 1 Astronomisches Rechen-Institut, Zentrum f¨ur Astronomie der Universit¨at Heidelberg, M¨onchhofstr. 12-14, 69120 Heidelberg, Germany email: [email protected] 2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 3 ESA, SRE Operations Devision 4 IAASARS, National Observatory of Athens, GR-15326 Penteli, Greece 5 INAF - Osservatorio Astronomico di Bologna 6 Astronomical Institute Anton Pannekoek, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The Netherlands Abstract. Westerlund 2 (Wd2) is one of the most massive young star clusters known in the Milky Way. The close proximity (4.16 kpc) to the Sun, and the young age (2.0 Myr) allow us to study star formation in detail at a high spatial resolution. We present results from our recent deep multi-band survey in the optical and near-infrared obtained with the Hubble Space Telescope. We demonstrated that, as expected, the region is affected by significant differential reddening with a median value of E(B − V )g =1.87 mag. The distance was inferred from the dereddened color-magnitude diagrams using Padova isochrones. Analyzing the spatial distribution of stars we found that Wd2 consists of two sub-clumps, namely the main cluster of Westerlund 2 and a less well populated clump located to the North.
    [Show full text]
  • Arxiv:1907.10541V1 [Astro-Ph.GA] 24 Jul 2019 Possibly Even Completely Destroy a Planet-Forming Disc
    ! # Perspective Planet formation in clusters Susanne Pfalzner Figure 1: Environmental effects on protoplanetary discs. a) HST image of an externally photo-evaporated disc (credit: NASA/ESA) and b) simulation result of the effect of a stellar flyby. For both questions still no definite answer exists, but there has been considerable progress during past years. One well-tested method in science is to separate the ob- The central parameter is the \stellar density" since it de- ject of interest from its surroundings and look at it in termines both the frequency and the strength of the ex- isolation. The advantage is that unimportant information ternal influence. This applies equally to radiation as to is removed and the true properties of the object are seen gravitational interactions. Sparse stellar groups like Cha I more clearly. However, sometimes the influences of the consist of just a few dozens of stars, whereas dense groups surroundings actually determine the properties of an ob- like NGC 3603 and Trumpler 14 can contain tens of thou- ject. In this case, not taking the environment into account sands of stars packed within less than 1 pc3. Even in 3 can lead to incomplete or even false conclusions. high-mass stellar groups (Mc > 10 M ) the average stel- lar densities vary over many orders of magnitude from In the context of planet formation this question arises to: < 0.1 M pc−3 to > 105 M pc−3 (Wolff et al. 2007). is it sufficient to study the nascent planetary system in iso- lation? Stars usually do not form in isolation but as part Even without large simulations it is intuitively obvious of a stellar group (Lada & Lada 2003, Porras 2003).
    [Show full text]
  • Diffuse Γ-Ray Emission in the Vicinity of Young Star Cluster Westerlund 2 Rui-Zhi Yang 1, Emma De Oña Wilhelmi2, and Felix Aharonian1,3
    A&A 611, A77 (2018) https://doi.org/10.1051/0004-6361/201732045 Astronomy & © ESO 2018 Astrophysics Diffuse γ-ray emission in the vicinity of young star cluster Westerlund 2 Rui-zhi Yang 1, Emma de Oña Wilhelmi2, and Felix Aharonian1,3 1 Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany e-mail: [email protected] 2 Institute for Space Sciences (CSIC–IEEC), Campus UAB, Carrer de Can Magrans s/n, 08193 Barcelona, Spain 3 Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland Received 4 October 2017 / Accepted 17 December 2017 ABSTRACT We report the results of our analysis of the publicly available data obtained by the Large Area Telescope (LAT) on board the Fermi satellite towards the direction of the young massive star cluster Westerlund 2. We found significant extended γ-ray emission in the vicinity of Westerlund 2 with a hard power-law energy spectrum extending from 1 to 250 GeV with a photon index of 2:0 ± 0:1. We argue that amongst several alternatives, the luminous stars in Westerlund 2 are likely sites of acceleration of particles responsible for the diffuse γ-ray emission of the surrounding interstellar medium. In particular, the young star cluster Westerlund 2 can provide sufficient non-thermal energy to account for the γ-ray emission. In this scenario, since the γ-ray production region is significantly larger than the area occupied by the star cluster, we conclude that the γ-ray production is caused by hadronic interactions of accelerated protons and nuclei with the ambient gas.
    [Show full text]
  • Jahresbericht 2010 Mitteilungen Der Astronomischen Gesellschaft 94 (2013), 583–627
    Jahresbericht 2010 Mitteilungen der Astronomischen Gesellschaft 94 (2013), 583–627 Potsdam Leibniz-Institut für Astrophysik Potsdam (AIP) An der Sternwarte 16, D-14482 Potsdam Tel. 03317499-0, Telefax: 03317499-267 E-Mail: [email protected] WWW: http://www.aip.de Beobachtungseinrichtungen Robotisches Observatorium STELLA Observatorio del Teide, Izaña E-38205 La Laguna, Teneriffa, Spanien Tel. +34 922 329 138 bzw. 03317499-633 LOFAR-Station DE604 Potsdam-Bornim D-14469 Potsdam Tel. 03317499-291, Telefax: 03317499-352 Observatorium für Solare Radioastronomie Tremsdorf D-14552 Tremsdorf Tel. 03317499-291, Telefax: 03317499-352 Sonnenobservatorium Einsteinturm Telegrafenberg, D-14473 Potsdam Tel. 0331288-2303/-2304, Telefax: 03317499-524 0 Allgemeines Das Leibniz-Institut für Astrophysik Potsdam (AIP) ist eine Stiftung bürgerlichen Rechts zum Zweck der wissenschaftlichen Forschung auf dem Gebiet der Astrophysik. Als außer- universitäre Forschungseinrichtung ist es Mitglied der Leibniz-Gemeinschaft. Seinen For- schungsauftrag führt das AIP im Rahmen von nationalen und internationalen Kooperatio- nen aus. Die Beteiligung am Large Binocular Telescope auf dem Mt Graham in Arizona, dem größten optischen Teleskop der Welt, verdient hierbei besondere Erwähnung. Neben seinen Forschungsarbeiten profiliert sich das Institut zunehmend als Kompetenzzentrum im Bereich der Entwicklung von Forschungstechnologie. Vier gemeinsame Berufungen mit der Universität Potsdam und mehrere außerplanmäßige Professuren und Privatdozenturen an Universitäten in der Region und
    [Show full text]
  • 241 — 12 January 2013 Editor: Bo Reipurth ([email protected])
    THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar/planetary evolution and molecular clouds No. 241 — 12 January 2013 Editor: Bo Reipurth ([email protected]) 1 List of Contents The Star Formation Newsletter Interview ...................................... 3 My Favorite Object ............................ 5 Editor: Bo Reipurth [email protected] Perspective .................................... 7 Technical Editor: Eli Bressert Abstracts of Newly Accepted Papers .......... 10 [email protected] New Jobs ..................................... 42 Technical Assistant: Hsi-Wei Yen Meeting Announcements ...................... 44 [email protected] Upcoming Meetings .......................... 45 Editorial Board Short Announcements ........................ 47 Joao Alves Alan Boss Jerome Bouvier Lee Hartmann Cover Picture Thomas Henning Paul Ho The Cygnus X region is one of the richest known Jes Jorgensen regions of star formation in the Galaxy. Because Charles J. Lada of the high extinction to the region, it is rather Thijs Kouwenhoven unremarkable at optical wavelengths, but in the in- Michael R. Meyer frared the full scale of star formation activity is re- Ralph Pudritz vealed. The image shows a Spitzer mosaic, from Luis Felipe Rodr´ıguez the Spitzer Cygnus X Legacy Survey, of a region Ewine van Dishoeck several pc wide at the assumed distance of 1.7 kpc Hans Zinnecker (blue 3.6 µm, aqua 4.5 µm, green 8 µm, red 24 µm). The pillars and globules face towards the center of The Star Formation Newsletter is a vehicle for the Cygnus OB2 association, which harbors about fast distribution of information of interest for as- a hundred O stars and many thousands of young tronomers working on star and planet formation low mass stars.
    [Show full text]
  • Annual Report 2012: A
    Research Institute Leiden Observatory (Onderzoekinstituut Sterrewacht Leiden) Annual Report Sterrewacht Leiden Faculty of Mathematics and Natural Sciences Leiden University Niels Bohrweg 2 Postbus 9513 2333 CA Leiden 2300 RA Leiden The Netherlands http://www.strw.leidenuniv.nl Cover: During the past 10 years, characterization of exoplanet atmospheres has been confined to transiting planets. Now, thanks to a particular observational technique and to a novel data analysis designed by astronomers of Leiden Observatory, it is possible to study the atmospheres of planets that do not transit, which represent the majority of known exoplanets. The first of its kind now to be characterized is τ Bo¨otisb (artist impression on the cover). Due to the very high resolution of the CRIRES spectrograph at the VLT, it was possible to detect molecular absorption from CO at 2.3 micron in the dayside spectrum of this planet, and to measure the Doppler shift due to its motion along the orbit. This yielded the planet mass and the orbital inclination, which were unknown before. Recently, using this technique also CO from 51 Pegasi b (the first planet discovered around a main-sequence star), and HD 189733 b were successfully detected. Ultimately, using ground- based high-resolution spectroscopy on the next-generation of telescopes (such as E-ELT) biomarkers may be detected in terrestrial planets orbiting M-dwarfs. An electronic version of this annual report is available on the web at http://www.strw.leidenuniv.nl/research/annualreport.php Production Annual Report 2012: A. van der Tang, E. Gerstel, A.S. Abdullah, K.M. Maaskant, J.
    [Show full text]