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1. Meaningful Improvement in General Health Outcomes with Guselkumab Treatment for Psoriatic Arthritis: Patient-Reported Outcomes Measurement Information System-29 Results from a Phase 3 Study

Author

Orbai, A-M, Coates, LC, Deodhar, A, Helliwell, PS, Ritchlin, CT, Leibowitz, E, Kollmeier, AP, Hsia, EC, Xu, XL, Sheng, S, Jiang, Y, Liu, Y, and Han, C

Subjects
Sleep Wake Disorders, Treatment Outcome, Arthritis, Psoriatic, Outcome Assessment, Health Care, Humans, Pain, Patient Reported Outcome Measures, Fatigue, Information Systems
Abstract

Objective The Phase 3 DISCOVER-1 study of guselkumab is the first randomized controlled trial to use Patient-Reported Outcomes Measurement Information System (PROMIS) measures to assess the effects of treatment on general health outcomes in patients with psoriatic arthritis (PsA). Methods Patients (N = 381) with active PsA were randomized 1:1:1 to guselkumab 100 mg every 4 weeks (Q4W); guselkumab 100 mg at Week 0, Week 4, then every 8 weeks (Q8W); or placebo with Week 24 crossover to guselkumab Q4W. The PROMIS-29 Profile contains four items for each of seven domains (anxiety, depression, fatigue, pain interference, physical function, sleep disturbance, and social participation) and one pain-intensity item. Raw domain scores are converted to standardized T-scores, with norms based on a US general population mean of 50 (1 standard deviation (SD) = 10). T-score changes of ≥ 5 are considered clinically meaningful. Least-squares mean PROMIS-29 T-score changes from baseline to Week 24 and Week 52 were summarized for the guselkumab and placebo groups; nominal p-values comparing results between guselkumab and placebo were calculated at Week 24 using a mixed model for repeated measures. The proportions of patients who achieved clinically meaningful improvement in PROMIS-29 T-scores were also summarized at Week 24 and Week 52; nominal p-values comparing results between guselkumab and placebo were calculated at Week 24 using the Cochran-Mantel-Haenszel test. Results In the DISCOVER-1 patient population, mean PROMIS-29 T-scores at baseline were ~ 1 SD worse for physical function and pain interference and were numerically worse for social participation, fatigue, and sleep disturbance compared with the US general population. At Week 24, mean PROMIS-29 T-scores improved in guselkumab-treated patients, approaching US population norms; T-scores continued to improve through Week 52. Significantly higher proportions of patients in both guselkumab treatment arms (31–52% across domains) had clinically meaningful improvements in pain interference, fatigue, physical function, sleep, and social participation at Week 24 versus placebo (all nominal p ≤ 0.05). Conclusion In patients with active PsA, guselkumab treatment provided clinically meaningful reductions in fatigue and pain and improvement in physical function and social participation, as measured by the PROMIS-29 Profile. These improvements were maintained through 1 year. ClinicalTrials.gov Registration number, NCT03162796; Submission date 19 May 2017.

Published
2022

2. Post-operative fever in children undergoing mastoidectomy due to complicated acute mastoiditis

Author

Ziv O, Sapir A, El-Saied S, Leibowitz E, Kaplan D, and Kordeluk S

Subjects
Acute mastoiditis, medicine.medical_specialty, business.industry, medicine.medical_treatment, medicine, Mastoidectomy, Post operative, business, Surgery
Abstract

Objectives: To determine the immediate post-operative course and outcome of pediatric patients with complicated acute mastoiditis (CAM) following surgical treatment. Study Design: A retrospective chart review of children diagnosed with CAM who underwent mastoid surgery during 2012-2019. Setting: Tertiary care university hospital. Participants: the study includes 33 patients, divided into two groups: 17 patients with subperiosteal abscess (SPA) alone - single complication group (SCG) and 16 patients with SPA and additional intracranial or intratemporal complications -multiple complications group (MCG). Main Outcome Measures: post-operative fever course and pattern (POF). Results :33 patients belong to the SCG 17(51%) and 16(49%) belonged to the MCG, respectively. 6/17(35.3%) SCG patients experienced POF vs. 12/16(75%) in the MCG (P=0.012). At post-operative day 2 (POD2), 10/13(77%) febrile patients belonged to MCG and 3/13(23%) to SCG (P=0.013). POF was recorded until POD6 in both groups. Seven patients, all from MCG with POF, underwent second imaging with no new findings. Conclusion: Following a cortical mastoidectomy for CAM, POF is not unusual in the first 6 days and seem to be benign condition. POF is more common, higher, and persistent for a longer duration in MCG compared with SCG. At POD 6, fever is expected to normalize in both groups, so if fever persists further evaluation should be considered.

Published
2021
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3. Whole Earth Telescope observations of the subdwarf B star KPD1930+2752 : a rich, short-period pulsator in a close binary

Author

Quint, A. C., Eggen, J. R., McDaniel, S., Harms, S. L., Reed, M. D., Poindexter, S., Zhou, A.-Y., Morris, M. A., Østensen, R. H., Solheim, J.-E., Kepler, S. O., Costa, A. F. M., Provencal, J. L., Winget, D. W., Mullally, F., Bolton, D., Terry, D., Binder, P.-M., Crowe, R., Stewart, S., Avila, R., Berkey, B., Bodnarik, J., Sekiguchi, K., Sullivan, D. J., Kim, S.-L., Chen, C.-W., Lin, H.-C., Chen, W.-P., Wu, H., Gou, J.-P., Jian, X.-J., Liu, Z., Leibowitz, E., Lipkin, Y., Akan, C., Cakirli, O., Janulis, R., Pretorius, R., Zsuffa, D., Paparo, M., Szabo, R., Csubry, Z., Silvotti, R., Marinoni, S., Bruni, I., Chevreton, M., Cameron, C., Matthews, J. M., Baran, A., Stachowski, G., Ogloza, W., Zoła, Stanisław, Vauclair, G., Dolez, N., Pablo, H., Kawaler, S. D., Riddle, R., Vuckovic, M., Kurtz, D. W., Moskalik, P., Ege Üniversitesi, Department of Physics, Astronomy, and Materials Science, Missouri State University, Mount Suhora Observatory, Cracow Pedagogical University, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy, Iowa State University, Centre for Astrophysics, University of Central Lancashire, Centrum Astronomiczne im. M. Kopernika, Warszawa (CAMK), Isaac Newton Group of Telescopes, University of Oslo (UiO), Instituto de Física, Universidade Federal do Rio Grande do Sul, Universidade do Estado de Santa Catarina, CAV, Mount Cuba Observatory, University of Delaware, Department of Astronomy, University of Texas, Department of Physics and Astronomy, University of Hawaii, Subaru Observatory, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, School of Chemical and Physical Sciences, Victoria University, Korea Astronomy Observatory, Graduate Institute of Astronomy, National Astronomical Observatoires-CAS, Tel Aviv University (TAU), Ege University Observatory, Institute of Theoretical Physics and Astronomy, Vilnius University, South African Astronomical Observatory (SAAO), Konkoly Observatory, Research Center for Astronomy and Earth Sciences, INAF-Osservatorio Astrofisico di Torino (INAF-OATo), Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO), INAF-Osservatorio Astronomico di Bologna (OABO), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and Department of Physics and Astronomy, University of British Columbia

Subjects
individual: KPD 1930+2752 [Oscillations], binaries: close, close [binaries], oscillations: individual: KPD 1930+2752, general [Stars], oscillations [Stars], Subdwarfs, FOS: Physical sciences, close [Bbinaries], Astrophysics - Solar and Stellar Astrophysics, subdwarfs, Anãs brancas, Pulsacoes estelares, Oscilacoes, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, stars: oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], stars: general, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

WOS: 000288378100032, KPD 1930+2752 is a short-period pulsating subdwarf B (sdB) star. It is also an ellipsoidal variable with a known binary period of 2.3 h. The companion is most likely a white dwarf and the total mass of the system is close to the Chandresekhar limit. In this paper, we report the results of Whole Earth Telescope (WET) photometric observations during 2003 and a smaller multisite campaign of 2002. From 355 h of WET data, we detect 68 pulsation frequencies and suggest an additional 13 frequencies within a crowded and complex temporal spectrum between 3065 and 6343 mu Hz (periods between 326 and 157 s). We examine pulsation properties including phase and amplitude stability in an attempt to understand the nature of the pulsation mechanism. We examine a stochastic mechanism by comparing amplitude variations with simulated stochastic data. We also use the binary nature of KPD 1930+2752 for identifying pulsation modes via multiplet structure and a tidally induced pulsation geometry. Our results indicate a complicated pulsation structure that includes short-period (approximate to 16 h) amplitude variability, rotationally split modes, tidally induced modes and some pulsations which are geometrically limited on the sdB star., National Science FoundationNational Science Foundation (NSF) [0307480]; NASA through the American Astronomical Society; Missouri State University; HELAS travel funding; NASANational Aeronautics & Space Administration (NASA), This material is based upon work supported by the National Science Foundation under grant no. 0307480. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This research was supported in part by NASA through the American Astronomical Society's Small Research Grant Program. MDR was partially funded by a Summer Faculty Fellowship provided by Missouri State University and would like to acknowledge HELAS travel funding and Dr. Conny Aerts for helpful discussions. MAM, SLH, SP, JRE and ACQ were supported by the Missouri Space Grant Consortium, funded by NASA. We would also like to thank several other observers who assisted with observing, including E. Brassfield, D. McLemore, J. Peacock, R. Knight, T. Kawasaki, E. Hart, N. Purves, A. Nishimura, M. Hyogo and E. Rau.

Published
2011
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4. The pulsations of PG 1351+489

Author

Claver, C. F., Chernyshev, A. V., Wood, M. A., Giovannini, O., Hansen, C. J., Leibowitz, E., Handler, G., Sullivan, D. J., Rosen, R., Nagel, T., Chen, W.-P., Kanaan, A., Buckley, D., Walter, B., Winiarski, M., Ibbetson, P., Zhang, X., Redaelli, M., Chandler, D., Baliyan, K. S., Ogloza, W., Marar, T. M. K., Fraga, L., Brewer, M. M., Andreev, M. V., Winget, D. E., Henrique, P., Strickland, W., Provencal, J. L., Silvotti, R., Chevreton, M., Nather, R. E., Pajdosz, G., Clemens, J. C., Pfeiffer, B., Fremy, J. R., Shih, C.-Y., Costa, J. E. S., Moskalik, P., Hemar, S., Sergeev, A. V., Janulis, R., Kepler, S. O., Kim, S.-L., O'Donoghue, D., Jiang, X., Bognár, Zs, Dolez, N., Vats, H. O., Vauclair, G., Meištas, E. G., Yang, M., Barstow, M. A., Shipman, H. L., Mullally, F., Baran, A., Castanheira, B. G., Childers, D., Brown, T. M., Dalessio, J., Creevey, O. L., Ashoka, B. N., Seetha, S., Oksala, M. E., Bischoff-Kim, A., Thompson, S. E., Kleinman, S. J., Solheim, J.-E., Zola, S., Kawaler, S. D., Montgomery, M. H., Fu, J. N., Reed, M. D., Nitta, A., Bruni, I., Watson, T. K., Sefako, R., and Siwak, M.

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics
Abstract

PG 1351+489 is one of the 20 DBVs – pulsating helium-atmosphere white dwarf stars – known and has the simplest power spectrum for this class of star, making it a good candidate to study cooling rates. We report accurate period determinations for the main peak at 489.334 48 s and two other normal modes using data from the Whole Earth Telescope (WET) observations of 1995 and 2009. In 2009, we detected a new pulsation mode and the main pulsation mode exhibited substantial change in its amplitude compared to all previous observations. We were able to estimate the star's rotation period, of 8.9 h, and discuss a possible determination of the rate of period change of (2.0 ± 0.9) × 10−13 s s −1, the first such estimate for a DBV.

Published
2011
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5. The pulsations of PG 1351+489

Author

Redaelli, M., Kepler, S. O., Costa, José Eduardo, Winget, D. E., Handler, Gerald, Castanheira, B. G., Kanaan, A., Fraga, L., Henrique, P., Giovannini, O., Provençal, J. L., Shipman, H. L., Dalessio, J., Thompson, S. E., Mullally, Fergal, Brewer, M. M., Childers, D., Oksala, Mary E., Rosen, R., Wood, M. A., Reed, M. D., Walter, B., Strickland, W., Chandler, D., Watson, T. K., Nather, R. E., Montgomery, M. H., Bischoff-Kim, A., Hansen, Candice J., Nitta, A., Kleinman, S. J., Claver, C. F., Brown, Timothy M., Sullivan, D. J., Kim, S.-L., Chen, Wen-Ping, Yang, M., Shih, C.-Y., Zhang, X., Jiang, X., Fu, J.-N., Seetha, S., Ashoka, B. N., Marar, T. M. K., Baliyan, Kiran S., Vats, H. O., Chernyshev, A. V., Ibbetson, P., Leibowitz, E. M., Hemar, S., Sergeev, A. V., Andreev, M. V., Janulis, R., Meistas, E. G., Moskalik, P. A., Pajdosz, G., Baran, A., Winiarski, M., Zola, S., Ogloza, W., Siwak, M., Bognar, Zs., Solheim, J.-E., Sefako, R., Buckley, D., O'Donoghue, Darragh, Nagel, T., Silvotti, R., Bruni, I., Fremy, Jean-René, Vauclair, Gérard, Chevreton, Michel, Dolez, N., Pfeiffer, B., Barstow, Martin A., Creevey, Orlagh L., Kawaler, Steven D., Clemens, J. C., Instituto de Física, Universidade Federal do Rio Grande do Sul, Department of Astronomy and McDonald Observatory, University of Texas, Austin, Institut für Astronomie, Universität Wien (IfA), Departamento de Física, Universidade Federal de Santa Catarina, Southern Observatory for Astrophysical Research, Departamento de Física e Química, Universidade de Caxias do Sul, Department of Physics and Astronomy, University of Delaware, Delaware Asteroseismic Research Center, Mt Cuba Observatory, Greenville, SETI Institute, NASA Ames Research Center, Moffett Field, William Jewell College, Department of Math and Science, Delaware County Community College, Bartol Research Institute, University of Delaware, National Radio Astronomy Observatory, Green Bank (NRAO), Florida Institute of Technology, Department of Physics and Space Sciences, Melbourne, Baker Observatory, Missouri State University, Meyer Observatory and Central Texas Astronomical Society, Waco, Southwestern University, Department of Chemistry, Physics and Astronomy, Georgia College and State University, University of Colorado, Joint Institute for Laboratory Astrophysics (JILA), Gemini Observatory, Kitt Peak National Observatory, National Optical Astronomy Observatory, Tucson, Las Cumbres Observatory, Goleta, Victoria University of Wellington, Korea Astronomy and Space Science Institute (KASI), Lulin Observatory, National Astronomical Observatoires-CAS, Department of Astronomy, Beijing Normal University, Indian Space Research Organization, Physical Research Laboratory, Astronomy & Astrophysics Division, Astronomical Institute, Tel Aviv University (TAU), Main Astronomical Observatory, Academy of Sciences of Ukraine, Institute of Theoretical Physics and Astronomy, Vilnius University, Centrum Astronomiczne im. M. Kopernika, Warszawa (CAMK), Mount Suhora Observatory, Cracow Pedagogical University, Astronomical Observatory, Jagiellonia University, Konkoly Observatory, Research Center for Astronomy and Earth Sciences, University of Oslo (UiO), South African Astronomical Observatory (SAAO), Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, INAF-Osservatorio Astrofisico di Torino (INAF-OATo), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Ingénierie, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Astronomy Department, Leicester University, Instituto de Astrofísica de Canarias (IAC), Department of Physics and Astronomy, Iowa State University, and Department of Physics and Astronomy, University of North Carolina

Subjects
oscillations [stars], [SDU]Sciences of the Universe [physics], evolution [stars], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], individual: PG 1351+489 [stars], white dwarfs
Abstract

International audience; PG 1351+489 is one of the 20 DBVs - pulsating helium-atmosphere white dwarf stars - known and has the simplest power spectrum for this class of star, making it a good candidate to study cooling rates. We report accurate period determinations for the main peak at 489.334 48 s and two other normal modes using data from the Whole Earth Telescope (WET) observations of 1995 and 2009. In 2009, we detected a new pulsation mode and the main pulsation mode exhibited substantial change in its amplitude compared to all previous observations. We were able to estimate the star's rotation period, of 8.9 h, and discuss a possible determination of the rate of period change of (2.0 ± 0.9) × 10-13 s s -1, the first such estimate for a DBV.

Published
2011
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6. Coordinated X-ray and optical observations of Scorpius X-1

Author

Augusteijn, T., Konstantinos Karatasos, Papadakis, M., Paterakis, G., Kikuchi, S., Brosch, N., Leibowitz, E., Hertz, P., Mitsuda, K., Dotani, T., Lewin, Whg, Vanderklis, M., and Vanparadijs, J.

Abstract

著者人数：13名, Accepted: 1992-02-23, 資料番号: SA1001425000

Published
1992

7. Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC20058-5234

Author

WET Collaboration, Sullivan, D. J., Metcalfe, T. S., O'Donoghue, D., Winget, D. E., Kilkenny, D., van Wyk, F., Kanaan, A., Kepler, S. O., Nitta, A., Kawaler, S. D., Montgomery, M. H., Nather, R. E., O'Brien, M. S., Bischoff-Kim, A., Wood, M., Jiang, X. J., Leibowitz, E. M., Ibbetson, P., Zola, S., Krzesinski, J., Pajdosz, G., Vauclair, G., Dolez, N., Chevreton, M., Brain imaging (LIAMA), Laboratoire Franco-Chinois d'Informatique, d'Automatique et de Mathématiques Appliquées (LIAMA), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Chinese Academy of Sciences [Changchun Branch] (CAS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institute of Automation - Chinese Academy of Sciences-Centre National de la Recherche Scientifique (CNRS)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Chinese Academy of Sciences [Changchun Branch] (CAS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institute of Automation - Chinese Academy of Sciences-Centre National de la Recherche Scientifique (CNRS), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées

Subjects
oscillations [stars], Stellar mass, FOS: Physical sciences, Astrophysics, Compact star, stars: interiors, 01 natural sciences, law.invention, Photometry (optics), Telescope, photometric [techniques], [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Análise asterosismológica, techniques: photometric, Observatory, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, white dwarfs, Physics, interiors [stars], 010308 nuclear & particles physics, Estrelas ZZ Ceti, Astrophysics (astro-ph), White dwarf, Astronomy and Astrophysics, Effective temperature, stars: individual: EC 20058-5234, individual: EC 20058-5234 [stars], Fotometria astronômica, Anãs brancas, Pulsacoes estelares, 13. Climate action, Space and Planetary Science, stars: oscillations, Instability strip
Abstract

We present the analysis of a total of 177h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058-5234. The bulk of the observations (135h) were obtained during a WET campaign (XCOV15) in July 1997 that featured coordinated observing from 4 southern observatory sites over an 8-day period. The remaining data (42h) were obtained in June 2004 at Mt John Observatory in NZ over a one-week observing period. This work significantly extends the discovery observations of this low-amplitude (few percent) pulsator by increasing the number of detected frequencies from 8 to 18, and employs a simulation procedure to confirm the reality of these frequencies to a high level of significance (1 in 1000). The nature of the observed pulsation spectrum precludes identification of unique pulsation mode properties using any clearly discernable trends. However, we have used a global modelling procedure employing genetic algorithm techniques to identify the n, l values of 8 pulsation modes, and thereby obtain asteroseismic measurements of several model parameters, including the stellar mass (0.55 M_sun) and T_eff (~28200 K). These values are consistent with those derived from published spectral fitting: T_eff ~ 28400 K and log g ~ 7.86. We also present persuasive evidence from apparent rotational mode splitting for two of the modes that indicates this compact object is a relatively rapid rotator with a period of 2h. In direct analogy with the corresponding properties of the hydrogen (DAV) atmosphere pulsators, the stable low-amplitude pulsation behaviour of EC 20058 is entirely consistent with its inferred effective temperature, which indicates it is close to the blue edge of the DBV instability strip. (abridged), 19 pages, 8 figures, 5 tables, MNRAS accepted

Published
2008
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8. Abell 43 and PG 0122+200: a Look at the Beginning and at the End of the PG 1159 Instability Strip

Author

Vauclair, Gérard, Solheim, J.-E., Fu, J.-N., Chevreton, Michel, Dolez, N., O'Brien, M. S., Mukadam, Anjum S., Kim, S.-L., Park, B.-G., Handler, Gerald, Medupe, R., Wood, M., González Perez, J., Hashimoto, O., Kinugasa, K., Taguchi, H., Kambe, Eiji, Dobrovolskas, V., Provençal, J. L., Dreizler, Stefan, Schuh, S., Leibowitz, E. M., Lipkin, Y., Zhang, X.-B., Paparó, M., Szeidl, B., Viraghalmy, G., Zsuffa, D., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris

Subjects
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience

Published
2006

9. The Hottest Known DBV White Dwarf

Author

Sullivan, D. J., Travis Metcalfe, O Donoghue, D., Winget, D. E., Kilkenny, D., Wyk, F., Kanaan, A., Kepler, S. O., Nitta, A., Kawaler, S. D., Montgomery, M. H., Nather, R. E., Steeghs, D., Koester, D., Bergeron, P., O Brien, M. S., Wood, M., Jiang, X. J., Leibowitz, E. M., Ibbetson, P., Zola, S., Krzesinski, J., Pajdosz, G., Vauclair, G., Dolez, N., Chevreton, M., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris

Subjects
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience

Published
2006

10. Asteroseismology of RXJ 2117+3412, the hottest pulsating PG 1159 star

Author

Nather, R. E., Hansen, C. J., Barstow, M., Jiang, S. Y., Chernyshev, A. V., Chevreton, M., Pfeiffer, B., Clemens, J. C., Serre, B., Bruvold, A., Yanagida, K., Wood, M. A., Dolez, N., Winget, D. E., Provencal, J., Nitta Kleinman, A., Meistas, E. G., Hemar, S., Sansom, A. E., Kawaler, S. D., Watson, T. K., Krzesinski, J., Dixson, J. S., Klumpe, E. W., Pajdosz, G., Belmonte, J. A., Marar, T. M.K., Vauclair, G., Solheim, J. E., Grauer, A. D., Bradley, P. A., Zola, S., Moskalik, P., Kanaan, A., Kleinman, S. J., Giovannini, O., Kepler, S. O., Fu, J. N., Mazeh, T., Leibowitz, E., Ashoka, B. N., O'Brien, M. S., Achilleos, N., and Montgomery, M.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The pulsating PG 1159 planetary nebula central star RXJ 2117+3412 has been observed over three successive seasons of a multisite photometric campaign. The asteroseismological analysis of the data, based on the 37 identified

Published
2002
Full Text
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11. STEPS TOWARD DETERMINATION OF THE SIZE AND STRUCTURE OF THE BROAD-LINE REGION IN ACTIVE GALACTIC NUCLEI .1. AN 8 MONTH CAMPAIGN OF MONITORING NGC-5548 WITH IUE

Author

CLAVEL J, REICHERT GA, ALLOIN D, CRENSHAW DM, KRISS G, KROLIK JH, MALKAN MA, NETZER H, PETERSON BM, WAMSTEKER W, ALTAMORE, Aldo, BARIBAUD T, BARR P, BECK S, BINETTE L, BROMAGE GE, BROSCH N, DIAZ AI, FILIPPENKO AV, FRICKE K, GASKELL CM, GIOMMI P, GLASS IS, GONDHALEKAR P, HACKNEY RL, HALPERN JP, HUTTER DJ, JORSATER S, KINNEY AL, KOLLATSCHNY W, KORATKAR A, KORISTA KT, LAOR A, LASOTA JP, LEIBOWITZ E, MAOZ D, MARTIN PG, MAZEH T, MEURS EJA, NAIR AD, OBRIEN P, PELAT D, PEREZ E, PEROLA GC, PTAK RL, RODRIGUEZPASCUAL P, ROSENBLATT EI, SADUN AC, SANTOSLLEO M, SHAW RA, SMITH PS, STIRPE GM, STONER R, SUN WH, ULRICH MH, VANGRONINGEN E, ZHENG W., Clavel, J, Reichert, Ga, Alloin, D, Crenshaw, Dm, Kriss, G, Krolik, Jh, Malkan, Ma, Netzer, H, Peterson, Bm, Wamsteker, W, Altamore, Aldo, Baribaud, T, Barr, P, Beck, S, Binette, L, Bromage, Ge, Brosch, N, Diaz, Ai, Filippenko, Av, Fricke, K, Gaskell, Cm, Giommi, P, Glass, I, Gondhalekar, P, Hackney, Rl, Halpern, Jp, Hutter, Dj, Jorsater, S, Kinney, Al, Kollatschny, W, Koratkar, A, Korista, Kt, Laor, A, Lasota, Jp, Leibowitz, E, Maoz, D, Martin, Pg, Mazeh, T, Meurs, Eja, Nair, Ad, Obrien, P, Pelat, D, Perez, E, Perola, Gc, Ptak, Rl, Rodriguezpascual, P, Rosenblatt, Ei, Sadun, Ac, Santoslleo, M, Shaw, Ra, Smith, P, Stirpe, Gm, Stoner, R, Sun, Wh, Ulrich, Mh, Vangroningen, E, and Zheng, W.

Subjects
Astronomy, Astrophysics
Published
1991

12. Gravitational Microlensing Evidence for a Planet Orbiting a Binary Star System

Author

Bennett, D. P., Rhie, S. H., Becker, A. C., Butler, N., Dann, J., Kaspi, S., Leibowitz, E. M., Lipkin, Y., Maoz, D., Mendelson, H., Peterson, B. A., Quinn, J., Shemmer, O., Thomson, S., and Turner, S. E.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The study of extra-solar planetary systems has emerged as a new discipline of observational astronomy in the past few years with the discovery of a number of extra-solar planets. The properties of most of these extra-solar planets were not anticipated by theoretical work on the formation of planetary systems. Here we report observations and light curve modeling of gravitational microlensing event MACHO-97-BLG-41, which indicates that the lens system consists of a planet orbiting a binary star system. According to this model, the mass ratio of the binary star system is 3.8:1 and the stars are most likely to be a late K dwarf and an M dwarf with a separation of about 1.8 AU. A planet of about 3 Jupiter masses orbits this system at a distance of about 7 AU. If our interpretation of this light curve is correct, it represents the first discovery of a planet orbiting a binary star system and the first detection of a Jovian planet via the gravitational microlensing technique. It suggests that giant planets may be common in short period binary star systems., 11 pages, with 1 color and 2 b/w Figures included (published version)

Published
1999

13. The effect of magnetic fields on gamma-ray bursts inferred from multi-wavelength observations of the burst of 23 January 1999

Author

Galama, TJ, Briggs, MS, Wijers, RAMJ, Rol, E, Band, D, van Paradijs, J, Kouveliotou, C, Preece, RD, Smith, IA, Tilanus, RPJ, de Bruyn, AG, Strom, RG, Pooley, G, Castro-Tirado, AJ, Tanvir, N, Robinson, C, Hurley, K, Heise, J, Telting, J, Rutten, RGM, Packham, C, Swaters, R, Fassia, A, Green, SF, Foster, MJ, Sagar, R, Pandey, AK, Nilakshi, [No Value], Yadav, RKS, Ofek, EO, Leibowitz, E, Ibbetson, P, Rhoads, J, Falco, E, Petry, C, Impey, C, Geballe, TR, Bhattacharya, D, and Kapteyn Astronomical Institute

Subjects
RADIO TELESCOPE, AFTERGLOW, Astrophysics::High Energy Astrophysical Phenomena, BATSE OBSERVATIONS, PHOTOMETRY, SPECTRA, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Gamma-ray bursts (GRBs) are thought to arise when an extremely relativistic outflow of particles from a massive explosion (the nature of which is still unclear) Interacts with material surrounding the site of the explosion. observations of the evolving changes in emission at many wavelengths allow us to Investigate the origin of the photons, and so potentially determine the nature of the explosion. Here we report the results of gamma-ray, optical, Infrared, submillimetre, millimetre and radio observations of the burst GRB990123 and Its afterglow. Our Interpretation of the data Indicates that the initial and afterglow emissions are associated with three distinct regions In the fireball. The peak flux of the afterglow, one day after the burst, has a lower frequency than observed for other bursts; this explains tbe short-lived radio emission. We suggest that the differences between bursts reflect variations In the magnetic-field strength in the afterglow-emitting regions.

Published
1999

14. Novae Crossing the Thermal Stability Line

Author

Retter, A., Naylor, T., and Leibowitz, E. M.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics
Abstract

A method, based on the disc instability model, for testing the thermal stability of Cataclysmic Variables (CVs), is presented. It is shown that the border line between thermal stability and instability is crossed during some nova outbursts and decays, however it is not clear whether this is the general behaviour. We suggest two new evolutionary scenarios for short orbital period CVs. One of them is the analogy for the 'modified hibernation scenario' and the other is an extension of the ideas of Mukai and Naylor (1993) for long orbital period CVs. We conclude that the observations have not favoured one of the two models. Finally, we speculate the existence of a new type of nova - an AM CVn like nova., Comment: 6 pages, Latex, 3 style files, to be published in the proceedings of ''Disk Instabilities in Close Binary Systems'', Kyoto, 27-30/11/98, eds. Mineshige S., Wheeker C., Universal Academy Press

Published
1998
Full Text
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15. Understanding the Cool DA White Dwarf, G29-38

Author

Kleinman, S. J., Nather, R. E., Winget, D. E., Clemens, J. C., Bradley, P. A., Kanaan, A., Provencal, J. L., Claver, C. F., Watson, T. K., Yanagida, K., Nitta, A., Dixson, J. S., Wood, M. A., Grauer, A. D., Hine, B. P., Fontaine, G., Liebert, James, Sullivan, D. J., Wickramasinghe, D. T., Marar, N. Achilleos. T. M. K., Seetha, S., Ashoka, B. N., Meistas, E., Leibowitz, E. M., Moskalik, P., Krzesinski, J., Solheim, J. -E., Bruvold, A., Kurtz, D. W., Warner, B., Martinez, Peter, Vauclair, G., Dolez, N., Chevreton, M., Barstow, M. A., Kepler, S. O., Giovannini, O., Augusteijn, T., Hansen, C. J., and Kawaler, S. D.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post main sequence evolution, along with their cooling rates, allowing us to calibrate their ages directly. The most important set of white dwarf variables to measure are the oldest of the pulsators, the cool DAVs, which have not previously been explored through asteroseismology due to their complexity and instability. Through a time-series photometry data set spanning ten years, we explore the pulsation spectrum of the cool DAV, G29-38 and find an underlying structure of 19 (not including multiplet components) normal-mode, probably l=1 pulsations amidst an abundance of time variability and linear combination modes. Modelling results are incomplete, but we suggest possible starting directions and discuss probable values for the stellar mass and hydrogen layer size. For the first time, we have made sense out of the complicated power spectra of a large-amplitude DA pulsator. We have shown its seemingly erratic set of observed frequencies can be understood in terms of a recurring set of normal-mode pulsations and their linear combinations. With this result, we have opened the interior secrets of the DAVs to future asteroseismological modelling, thereby joining the rest of the known white dwarf pulsators., 29 pages including 5 figures To appear in ApJ 1 Mar 98

Published
1997

16. Understanding the Cool DA White Dwarf Pulsator, G29–38

Author

Solheim, Jan Erik, Kleinman, S. J., Bruvold, A., Nather, R. E., Winget, D. E., Clemens, J. C., Bradley, A., Kanaan, A., Claver, C. F., Watson, T. K., Yanagida, K., Nitta, A., Dixson, J. S., Grauer, A. D., Hine, B. P., Fontaine, G., Liebert, James, Sullivan, D. J., Wickramasinghe, D. T., Achilleos, N., Mara, T. M. K., Seetha, S., Ashoka, B. N., Leibowitz, E. M., Moskalik, P., Krzesi´nski, J., O’Donoghue, D., Kurtz, D. W., Warner, B., Martinez, Peter, Dolez, N., Chevreton, M., Barstow, M. A., Kepler, S. O., Giovannini, O., Hansen, C. J., and Augusteijn, T.

Subjects
VDP::Mathematics and natural science: 400::Physics: 430::Astrophysics, astronomy: 438, stars: pulsations, stars: white dwarfs, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Galaxy Astrophysics, stars:individual(G29–38)
Abstract

This is the authors' accepted version of the article. The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and compositions, critical to understanding post main sequence evolution, along with their cooling rates, allowing us to calibrate their ages directly. The most important set of white dwarf variables to measure are the oldest of the pulsators, the cool DAVs, which have not previously been explored through asteroseismology due to their complexity and instability. Through a time-series photometry data set spanning ten years, we explore the pulsation spectrum of the cool DAV, G29–38 and find an underlying structure of 19 (not including multiplet components) normal-mode, probably ℓ = 1 pulsations amidst an abundance of time variability and linear combination modes. Modelling results are incomplete, but we suggest possible starting directions and discuss probable values for the stellar mass and hydrogen layer size. For the first time, we have made sense out of the complicated power spectra of a large-amplitude DA pulsator. We have shown its seemingly erratic set of observed frequencies can be understood in terms of a recurring set of normal-mode pulsations and their linear combinations. With this result, we have opened the interior secrets of the DAVs to future asteroseismological modelling, thereby joining the rest of the known white dwarf pulsators.

Published
1997

17. The Presence of Accretion Disks in Novae Shortly After their Outbursts

Author

Retter, A. and Leibowitz, E. M.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics
Abstract

It was believed, with little theoretical basis, that the accretion disk (AD) is destroyed in nova outbursts, and recovers only a few decades later. In my thesis I tried to find observational signature for the presence of ADs in young novae. I will discuss two cases: 1. Nova V1974 Cyg 1992 - we found permanent superhumps about 2.5 years after the nova eruption. This is a very strong evidence for the presence of the AD according to the disk - instability model. 2. Nova V1425 Aql 1995 - photometric features which characterize the Intermediate Polars systems were detected about 15 months after its discovery. It is most likely that the accretion is maintained through an AD., 2 pages, Latex, Proc. of the 13th North-American Workshop on CVs, ed. Howell S., Kuulkers E. and Woodward C. in press

Published
1997

18. Permanent Superhumps in V1974 Cyg

Author

Retter, A., Leibowitz, E. M., and Ofek, E. O.

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics
Abstract

We present results of 32 nights of CCD photometry of V1974 Cygni, from the years 1994 and 1995. We verify the presence of two distinct periodicities in the light curve: 0.0812585 day~1.95 hours and 0.0849767 d~2.04 hr. We establish that the shorter periodicity is the orbital period of the underlying binary system. The longer period oscillates with an average value of |dot(P)| ~ 3x10^(7)--typical to permanent superhumps. The two periods obey the linear relation between the orbital and superhump periods that holds among members of the SU Ursae Majoris class of dwarf novae. A third periodicity of 0.083204 d~2.00 hr appeared in 1994 but not in 1995. It may be related to the recently discovered anti-superhump phenomenon. These results suggest a linkage between the classical nova V1974 Cyg and the SU UMa stars, and indicate the existence of an accretion disk and permanent superhumps in the system no later than 30 months after the nova outburst. From the precessing disk model of the superhump phenomenon we estimate that the mass ratio in the binary system is between 2.2 and 3.6. Combined with previous results this implies a white dwarf mass of 0.75-1.07 M sun., 11 pages, 10 eps. figures, Latex, accepted for publication in MNRAS

Published
1996

19. Observational limits on companions to g29-38

Author

Kleinman, S. J., Nather, R. E., Winget, D. E., Clemens, J. C., Bradley, P. A., Kanaan, A., Provencal, J. L., Claver, C. F., Watson, T. K., Yanagida, K., Dixson, J. S., Wood, M. A., Sullivan, D. J., Meištas, E., Leibowitz, E. M., Moskalik, P., Zola, S., Pajdosz, G., Krzesinski, J., Solheim, J. -E, Bruvold, A., O Donoghue, D., Katz, M., Vauclair, G., Dolez, N., Chevreton, M., Barstow, M. A., Kepler, S. O., Giovannini, O., Hansen, C. J., and Steven Kawaler

Subjects
low-mass, brown dwarfs [Stars], general [Binaries], Anãs brancas, oscillations [Stars], White dwarfs, Fotometria estelar, individual (G29-38) [Stars], Estrelas binarias, Estrelas variaveis
Abstract

Recent interest in the variable (DAV) white dwarf G29-38 has been stirred by a tentative report of a radial velocity variation that may be due to an unseen companion. Earlier evidence for a brown dwarf in the system has come from an observed infrared excess in the star's spectrum. For asteroseismological reasons, we have accumulated more than five seasons of high-speed photometric data on the star. By measuring the phase of an isolated, stable frequency in the power spectrum, we show the measured variation is not due (at least in its entirety) to an orbital companion. Because any orbital radial velocity variation must result in a systematic phase variation, the data we present can be used to place stringent limits on the types of companions the system may contain.

Published
1994

20. Spectral Energy Distributions and Light Curves of GRB 990123 and its Afterglow

Author

Galama, T. J., Briggs, M. S., Ralph Wijers, Vreeswijk, P. M., Rol, E., Band, D., Paradijs, J., Kouveliotou, C., Preece, R. D., Bremer, M., Smith, I. A., Tilanus, R. P. J., Bruyn, A. G., Strom, R. G., Pooley, G., Castro-Tirado, A. J., Tanvir, N., Robinson, C., Hurley, K., Heise, J., Telting, J., Rutten, R. G. M., Packham, C., Swaters, R., Davies, J. K., Fassia, A., Green, S. F., Foster, M. J., Sagar, R., Pandey, A. K., Nilakshi, Yadav, R. K. S., Ofek, E. O., Leibowitz, E., Ibbetson, P., Rhoads, J., Falco, E., Petry, C., Impey, C., Geballe, T. R., and Bhattacharya, D.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics
Abstract

Gamma-ray bursts (GRBs) are thought to result from the interaction of an extremely relativistic outflow interacting with a small amount of material surrounding the site of the explosion. Multi-wavelength observations covering the gamma-ray to radio wavebands allow investigations of this `fireball' model. On 23 January 1999 optical emission was detected while the gamma-ray burst was still underway. Here we report the results of gamma-ray, optical/infra-red, sub-mm, mm and radio observations of this burst and its afterglow, which indicate that the prompt and afterglow emissions from GRB 990123 are associated with three distinct regions in the fireball. The afterglow one day after the burst has a much lower peak frequency than those of previous bursts; this explains the short-lived nature of the radio emission, which is not expected to reappear. We suggest that such differences reflect variations in the magnetic-field strengths in the afterglow emitting regions., Comment: Accepted for publication in Nature. Under press embargo

21. Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. I. An 8 month campaign of monitoring NGC 5548 with IUE

Author

Clavel, J., Reichert, G. A., Alloin, D., Crenshaw, D. M., Kriss, G., Krolik, J. H., Malkan, M. A., Netzer, H., Peterson, B. M., Wamsteker, W., Altamore, A., Baribaud, T., Barr, P., Beck, S., Luc Binette, Bromage, G. E., Brosch, N., Diaz, A. I., Filippenko, A. V., Fricke, K., Gaskell, C. M., Giommi, P., Glass, I. S., Gondhalekar, P., Hackney, R. L., Halpern, J. P., Hutter, D. J., Jörsäter, S., Kinney, A. L., Kollatschny, W., Koratkar, A., Korista, K. T., Laor, A., Lasota, J. P., Leibowitz, E., Maoz, D., Martin, P. G., Mazeh, T., Meurs, E. J. A., Nair, A. D., O Brien, P., Pelat, D., Perez, E., Perola, G. C., Ptak, R. L., Rodriguez-Pascual, P., Rosenblatt, E. I., Sadun, A. C., Santos-Lleo, M., Shaw, R. A., Smith, P. S., Stirpe, G. M., Stoner, R., Sun, W. H., Ulrich, M. -H, Groningen, E., and Zheng, W.

Subjects
Galaxies: individual (NGC 5548), Seyfert [Galaxies], Galaxies: Seyfert, spectra [Ultraviolet], individual (NGC 5548) [Galaxies], nuclei [Galaxies], Física, Ultraviolet: spectra, Galaxies: nuclei
Abstract

This is an electronic version of an article published in The Astrophysical Journal. Clavel, J. et al. Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. I. An 8 month campaign of monitoring NGC 5548 with IUE. The Astrophysical Journal 366 (1991): 64-81

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