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ATTENTION MICROFICHE USER, the Original Document from Which ATTENTION MICROFICHE USER, The original document from which this microfiche was made was found to contain some imperfection or imperfections that reduce full comprehension or some of the text despite the good technical quality of the microfiche itself. The imperfections may be: - missing or illegible pages/figures; - wrong pagination; - poor overall printing quality, etc... We normally refuse to microfiche such a document and request a replacement document (or page) from the national INIS Centre concerned. However, our experience shows that many months pass before such documents are replaced. Sometimes the Centre is not able to supply a better copy or, in some cases, the pages that were supposed to be missing correspond to a wrong pagination only. We feel that it is better to proceed with distributing the microfiche made of these documents than to withold them till the imperfections are removed. 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The original document from which this microfiche has been prepared has these imperfections: missing pagesmgu»8i numbered: \ ————— wrong pagination poor overall printing quality combinations of the above other INIS Clearinghouse IAEA P.O. Box 100 A-1400, Vienna-AUSTRIA \ ^^"[OOJoT- fMC.TH.33D2- THESE PRESENTEE A L'UNIVERSITE PARIS VII POUR OBTENIR LE GRADE DE DOCTEUR ES SCIENCES PHYSIQUES par Isabel le GRENIER LES RAYONS GAMMA , TRACEURS OU MILIEU INTERSTELLAIRE ET MESSAGERS DES PULSARS ET AUTRES OBJETS ENERGETIQUES Soutenue le 24 mars 1988 devant la Commission d'Examen composée de: MM. A. BRAHIC Président L. GOUGUENHEIM Rapporteur J. PAUL R. PELLAT G. VEDRENNE J. AUDOUZE Examinateur P.GOLDREICH J. HEYVAERTS » THESE PRESENTEE A L'UNIVERSITE PARIS VII POUR OBTENIR LE GRADE DE DOCTEUR ES SCIENCES PHYSIQUES par Isabelle GRENIER LES RAYONS GAMNA,TRACEURS DU HILIEU INTERSTELLAIRE ET MESSAGERS DES PULSARS ET AUTRES OBJETS ENERGETIQUES Soutenue le 24 mars 1968 devant la Commission d'Examen composée de: MM. A. BRAHIC Président L. GOUGUENHEIM Rapporteur J. PAUL " R. PELLAT G. VEDRENNE J. AUOOUZE Examinateur P.GOLDREICH " J. HEYVAERTS " " Joy -in looking and compteh&nding lt> natwiz'i moat beMUl£ut gli-t " MJbvU Einitzin AVANT PROPOS En premier lieu, je tiens à remercier vivement tous les membres du jury qui m'ont fait l'honneur et la joie d'accepter de juger ce travail; André BRAHIC pour avoir bien accepté d'assurer la présidence du jury, Lucienne GOUGUENHEIM, Jacques PAUL, René PELLAT et Gilbert VEDRENNE qui ont bien voulu être les rapporteurs de cette thèse ainsi que Jean AUDOUZE, Peter COLDREICH et Jean HEYVAERTS pour avoir accepté de faire partie du jury. Ce mémoire est le fruit de travaux menés depuis l'été 1983 en astronomie gamma. L'interprétation des données m'a permis d'aborder des domaines aussi variés que l'étude du milieu interstellaire en gamma, radio, millimétrique ou infra-rouge et la physique des pulsars et des restes de supernovae. J'ai pu ainsi m'initier à plusieurs techniques d'observation et à quelques aspects théoriques. L'essentiel de ces travaux a eu pour cadre le Service d'Astrophysique du Centre d'Etudes Nucléaires de Saclay. Aussi voudrais-je exprimer ma gratitude à Daniel CRIBIER, Alain RAVIART, Charles RYTER et Catherine CESARSKY pour n'avoir accueillie et offert la possibilité d'apprendre le métier de chercheur dans des domaines aussi variés et actifs de l'astronomie moderne. J'ai particulièrement apprécié l'ambiance chaleureuse du service. Les nombreuses discussions que j'ai eues avec tous ont été pour moi un encouragement constant. J'aimerais tous les remercier vivement. L'un des charmes de l'astrophysique est de pouvoir nouer de nombreuses collaborations au niveau international. COS-B fut une excellente carte de visite dans ce donaine et, grâce à elle, j'ai pu rencontrer en particulier Wim HEEMSEN, Andy STRONG and Andy POLLOCK. Je voudrais les remercier de m'avoir transmis "l'art" de déjouer les pièges de COS-B et du maximum de vraisemblance. Cette thèse doit beaucoup à leur amitié. Le défaut majeur de l'astronomie spatiale est de ne percevoir le ciel qu'au bout d'un ordinateur. Aussi aimerais-je remercier Patrick THADDEUS de la confiance qu'il m'a témoignée en mettant à ma disposition le télescope millimétrique de Columbia. Il m'a ainsi permis de connaître l'excitation (et les rigueurs) des observations "en direct". Un grand merci également aux membres de son équipe, Thomas DAME, Ronald HADDALENA et Sam PALMER, pour m'avoir enseigné les techniques de la radioastronomie millimétrique, même si je les soupçonne d'avoir été de très bons professeurs pour éviter d'être réveillés en pleine nuit par des questions du style "Pourquoi le télescope tourne-t-il à l'envers ou comment remonter à l'endroit la batterie de filtres et réaccorder le récepteur?", l'annonce des découvertes étant bien sûr toujours remise au lendemain matin. Je voudrais exprimer ma profonde reconnaissance à Jacques PAUL pour n'avoir spontanément accueillie et initiée à l'astronomie gamma. Sans son soutien, la méthode d'analyse spectrale n'aurait jamais vu le jour. Jacques m'a également appris à oublier les réflexes d'écolière et à ne pas restreindre un travail d'analyse de données à une publication de chiffres, mais à tenter chaque fois de percer les conséquences les plus diverses de ces nouveaux indices. Il m'a également démontré l'importance de la simplicité et de l'esprit critique dans un travail d'interprétation. Je me suis souvent appuyée sur ses vastes connaissances pour aller de l'avant. J'espère que son exemple m'incitera toujours à éviter l'écueil d'une trop grande spécialisation. François LEBRUN sait combien sa collaboration et son amitié me sont précieuses. Je voudrais le remercier plus particulièrement pour la patience avec laquelle il m'a enseigné l'art des statistiques. Malgré des rechutes fréquentes, je crois comprendre un peu mieux les effets malicieux du hasard. J'ai par dessus tout apprécié le jeu "d'avocat du diable" que nous avons souvent joué au cours d'interminables discussions. La plupart des travaux présentés ici sont nés de telles joutes. Elles m'ont appris la prudence et la remise en cause. Je voudrais enfin remercier mes parents d'avoir cru une gamine qui, en 1969, avait brusquement décidé de devenir astronome et de m'avoir ensuite toujours soutenue dans cette voie exotique. Sans M. LEQUEUX, instituteur à l'Kay les Roses qui m'a révélé les merveilles du ciel, et M. DUCROCQ qui m'a fait découvrir les rayons gamma, cette thèse n'aurait jamais existé. Mes sincères remerciements vont également à André pour ses conseils, ses encouragements et pour m'avoir communiqué une partie de son immense enthousiasme. TABLE DES MATIERES 1. INTRODUCTION 1.1 Petit Guide de la thèse 1.2 "Les Rayons de la Colère" 2. L'ASTRONOMIE GAMMA AVEC COS-B 2.1 Un télescope gamma 2.2 Quelques méthodes d'analyse a) analyse de l'émission gamma galactique b) recherche de sources gamma ponctuelles c) analyse temporelle et spectrale de sources isolées 3. LE MILIEU INTERSTELLAIRE 3.1 Les nuages moléculaires dans la Galaxie 3.2 Comparaison de traceurs du milieu interstellaire 4. LE RAYONNEMENT GAMMA GALACTIQUE DIFFUS 4.1 Les rayons gamma et le gaz interstellaire dans le disque galactique 4.2 Les rayons gamma et le gaz interstellaire dans Céphée - Cassiopée 5. L'EMISSION GAMMA DES PULSARS 5.1 Le pulsar du Crabe 5.2 Le pulsar des Voiles 6. PERSPECTIVES - I - INTRODUCTION " Vvwujjt. a. le m£me. cUiolt de i 'expumA que la \>iiUtt " CondoiceX - J - INTRODUCTION 1.1 PETIT GUIDE DE LA THESE Ce mémoire est le fruit de travaux menés depuis l'été 1963 sous la direction de Jacques PAUL au Service d'Astrophysique du Centre d'Etudes Nucléaires de Saclay. avec pour fil d'Ariane l'analyse du rayonnement gamma observé dans notre Galaxie par le satellite européen COS-B. Un tel rayonnement ayant deux origines distinctes dans la Galaxie, ce mémoire s'articule autour de deux thèmes principaux. Il s'agit tout d'abord de l'étude du milieu interstellaire en mettant à profit le fait que les rayons gamma diffus naissent de l'interaction des rayons cosmiques avec toute matière interstellaire. D'autres sources d'information ont également été utilisées dans cette étude, notamment les cartes de nuages moléculaires obtenues pendant plusieurs mois d'observations avec le télescope millimétrique de l'Université Columbia de New York. L'analyse détaillée de brillantes sources compactes de rayons gamma constitue l'autre thème du mémoire. Les photons gamma sont alorsexploités pour tenter de sonder les conditions physiques extrêmes qui gouvernent les objets très énergétiques tels que les pulsars. Il peut paraître étonnant de présenter une thèse sur les observations de COS-B treize ans après le lancement de celui-ci, alors que les 250 000 photons qu'il a recueillis ont déjà donné matière à cinq ou six thèses.
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