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M Berton - One of the best experts on this subject based on the ideXlab platform.

  • the flat spectrum radio quasar 3c 345 from the high to the low emission state
    Astronomy and Astrophysics, 2018
    Co-Authors: M Berton, N H Liao, G La Mura, E Jarvela, E Congiu, L Foschini, M Frezzato, V Ramakrishnan
    Abstract:

    We report simultaneous observations at different energy bands in radio, optical, UV, X-rays and γ rays of the flat-spectrum radio-quasar 3C 345. We built the light curve of the source at different frequencies from 2008, the beginning of the Fermi all-sky survey, to 2016, using new data and Public Archives. In particular we obtained several optical spectra, to study the behavior of emission lines and the continuum in different activity states and to derive the black hole mass. 3C 345 showed two flaring episodes in 2009, which occurred simultaneously in γ ray, optical/UV and X-rays, and were later followed in radio. The source shows an inverse Compton dominated spectral energy distribution, which moved from higher to lower frequencies from the high to the low state. The reverberation of emission lines during one outburst event allowed us to constrain the location of production of γ rays very close to the broad-line region, and possibly in the jet-base. We report the observation of an increased accretion after the outburst, possibly induced by the decrease of magnetic field intensity with respect to the low state.

  • the flat spectrum radio quasar 3c 345 from the high to the low emission state
    arXiv: High Energy Astrophysical Phenomena, 2017
    Co-Authors: M Berton, N H Liao, G La Mura, E Jarvela, E Congiu, L Foschini, M Frezzato, V Ramakrishnan
    Abstract:

    We report simultaneous observations at different energy bands in radio, optical, UV, X-rays and $\gamma$ rays of the flat-spectrum radio-quasar 3C 345. We built the light curve of the source at different frequencies from 2008, the beginning of the \textit{Fermi} all-sky survey, to 2016, using new data and Public Archives. In particular we obtained several optical spectra, to study the behavior of emission lines and the continuum in different activity states and to derive the black hole mass. 3C 345 showed two flaring episodes in 2009, which occurred simultaneously in $\gamma$ ray, optical/UV and X-rays, and were later followed in radio. The source shows an inverse Compton dominated spectral energy distribution, which moved from higher to lower frequencies from the high to the low state. The reverberation of emission lines during one outburst event allowed us to constrain the location of production of $\gamma$ rays very close to the broad-line region, and possibly in the jet-base. We report the observation of an increased accretion after the outburst, possibly induced by the decrease of magnetic field intensity with respect to the low state.

V Ramakrishnan - One of the best experts on this subject based on the ideXlab platform.

  • the flat spectrum radio quasar 3c 345 from the high to the low emission state
    Astronomy and Astrophysics, 2018
    Co-Authors: M Berton, N H Liao, G La Mura, E Jarvela, E Congiu, L Foschini, M Frezzato, V Ramakrishnan
    Abstract:

    We report simultaneous observations at different energy bands in radio, optical, UV, X-rays and γ rays of the flat-spectrum radio-quasar 3C 345. We built the light curve of the source at different frequencies from 2008, the beginning of the Fermi all-sky survey, to 2016, using new data and Public Archives. In particular we obtained several optical spectra, to study the behavior of emission lines and the continuum in different activity states and to derive the black hole mass. 3C 345 showed two flaring episodes in 2009, which occurred simultaneously in γ ray, optical/UV and X-rays, and were later followed in radio. The source shows an inverse Compton dominated spectral energy distribution, which moved from higher to lower frequencies from the high to the low state. The reverberation of emission lines during one outburst event allowed us to constrain the location of production of γ rays very close to the broad-line region, and possibly in the jet-base. We report the observation of an increased accretion after the outburst, possibly induced by the decrease of magnetic field intensity with respect to the low state.

  • the flat spectrum radio quasar 3c 345 from the high to the low emission state
    arXiv: High Energy Astrophysical Phenomena, 2017
    Co-Authors: M Berton, N H Liao, G La Mura, E Jarvela, E Congiu, L Foschini, M Frezzato, V Ramakrishnan
    Abstract:

    We report simultaneous observations at different energy bands in radio, optical, UV, X-rays and $\gamma$ rays of the flat-spectrum radio-quasar 3C 345. We built the light curve of the source at different frequencies from 2008, the beginning of the \textit{Fermi} all-sky survey, to 2016, using new data and Public Archives. In particular we obtained several optical spectra, to study the behavior of emission lines and the continuum in different activity states and to derive the black hole mass. 3C 345 showed two flaring episodes in 2009, which occurred simultaneously in $\gamma$ ray, optical/UV and X-rays, and were later followed in radio. The source shows an inverse Compton dominated spectral energy distribution, which moved from higher to lower frequencies from the high to the low state. The reverberation of emission lines during one outburst event allowed us to constrain the location of production of $\gamma$ rays very close to the broad-line region, and possibly in the jet-base. We report the observation of an increased accretion after the outburst, possibly induced by the decrease of magnetic field intensity with respect to the low state.

E Congiu - One of the best experts on this subject based on the ideXlab platform.

  • the flat spectrum radio quasar 3c 345 from the high to the low emission state
    Astronomy and Astrophysics, 2018
    Co-Authors: M Berton, N H Liao, G La Mura, E Jarvela, E Congiu, L Foschini, M Frezzato, V Ramakrishnan
    Abstract:

    We report simultaneous observations at different energy bands in radio, optical, UV, X-rays and γ rays of the flat-spectrum radio-quasar 3C 345. We built the light curve of the source at different frequencies from 2008, the beginning of the Fermi all-sky survey, to 2016, using new data and Public Archives. In particular we obtained several optical spectra, to study the behavior of emission lines and the continuum in different activity states and to derive the black hole mass. 3C 345 showed two flaring episodes in 2009, which occurred simultaneously in γ ray, optical/UV and X-rays, and were later followed in radio. The source shows an inverse Compton dominated spectral energy distribution, which moved from higher to lower frequencies from the high to the low state. The reverberation of emission lines during one outburst event allowed us to constrain the location of production of γ rays very close to the broad-line region, and possibly in the jet-base. We report the observation of an increased accretion after the outburst, possibly induced by the decrease of magnetic field intensity with respect to the low state.

  • the flat spectrum radio quasar 3c 345 from the high to the low emission state
    arXiv: High Energy Astrophysical Phenomena, 2017
    Co-Authors: M Berton, N H Liao, G La Mura, E Jarvela, E Congiu, L Foschini, M Frezzato, V Ramakrishnan
    Abstract:

    We report simultaneous observations at different energy bands in radio, optical, UV, X-rays and $\gamma$ rays of the flat-spectrum radio-quasar 3C 345. We built the light curve of the source at different frequencies from 2008, the beginning of the \textit{Fermi} all-sky survey, to 2016, using new data and Public Archives. In particular we obtained several optical spectra, to study the behavior of emission lines and the continuum in different activity states and to derive the black hole mass. 3C 345 showed two flaring episodes in 2009, which occurred simultaneously in $\gamma$ ray, optical/UV and X-rays, and were later followed in radio. The source shows an inverse Compton dominated spectral energy distribution, which moved from higher to lower frequencies from the high to the low state. The reverberation of emission lines during one outburst event allowed us to constrain the location of production of $\gamma$ rays very close to the broad-line region, and possibly in the jet-base. We report the observation of an increased accretion after the outburst, possibly induced by the decrease of magnetic field intensity with respect to the low state.

Peter B Stetson - One of the best experts on this subject based on the ideXlab platform.

  • homogeneous photometry v the globular cluster ngc 4147
    Publications of the Astronomical Society of the Pacific, 2005
    Co-Authors: Peter B Stetson, M Catelan, H A Smith
    Abstract:

    New BVRI broadband photometry and astrometry are presented for the globular cluster NGC 4147, based upon measurements derived from 524 ground-based CCD images mostly either donated by colleagues or retrieved from Public Archives. We have also reanalyzed five exposures of the cluster obtained with WFPC2 on the Hubble Space Telescope in the F439W and F555W (B and V) filters. We present calibrated color-magnitude and color-color diagrams. Analysis of the color-magnitude diagram reveals morphological properties generally consistent with published metal-abundance estimates for the cluster, and an age typical of other Galactic globular clusters of similar metallicity. We have also redetermined the periods and mean magnitudes for the RR Lyrae variables, including a new c-type variable reported here for the first time. Our data do not show clear evidence for photometric variability in candidate V18, recently reported by Arellano Ferro et al. (2004, Rev. Mex. A&A, 40, 209). These observations also support the nonvariable status of candidates V5, V9, and V15. The union of our light-curve data with those of Newburn (1957, AJ, 62, 197), Mannino (1957, Mem. Soc. Astron. Italiana, 28, 285), and Arellano Ferro et al. (op. cit.) permits the derivation of significantly improved periods. The mean periods and the Bailey period-amplitude diagrams support the classification of the cluster as Oosterhoff I, despite its predominantly blue horizontal branch. The number ratio of c- to ab-type RR Lyrae stars, on the other hand, is unusually high for an Oosterhoff I cluster. The calibrated results have been made available through the first author's Web site.

  • homogeneous photometry v the globular cluster ngc 4147
    arXiv: Astrophysics, 2005
    Co-Authors: Peter B Stetson, M Catelan, H A Smith
    Abstract:

    New BVRI broad-band photometry and astrometry are presented for the globular cluster NGC 4147, based upon measurements derived from 524 ground-based CCD images mostly either donated by colleagues or retrieved from Public Archives. We have also reanalysed five exposures of the cluster obtained with WFPC2 on the Hubble Space Telescope in the F439W and F555W (B and V) filters. We present calibrated color-magnitude and color-color diagrams. Analysis of the color-magnitude diagram reveals morphogical properties generally consistent with published metal-abundance estimates for the cluster, and an age typical of other Galactic globular clusters of similar metallicity. We have also redetermined the periods and mean magnitudes for the RR Lyrae variables, including a new c-type variable reported here for the first time. Our data do not show clear evidence for photometric variability in candidate V18, recently reported by Arellano Ferro et al. (2004). These observations also support the non-variable status of candidates V5, V9, and V15. The union of our light-curve data with those of Newburn (1957), Mannino (1957) and Arellano Ferro et al. (op. cit.) permits the derivation of significantly improved periods. The mean periods and the Bailey period-amplitude diagrams support the classification of the cluster as Oosterhoff I despite its predominantly blue horizontal branch. The number ratio of c- to ab-type RR Lyrae stars, on the other hand, is unusually high for an Oosterhoff I cluster. The calibrated results have been made available through the first author's web site.

  • homogeneous photometry iv on the standard sequence in the globular cluster ngc 2419
    Publications of the Astronomical Society of the Pacific, 2005
    Co-Authors: Peter B Stetson
    Abstract:

    I present a new analysis of CCD-based BVRI broadband photometry for the globular cluster NGC 2419, based on 340 CCD images either donated by colleagues or retrieved from Public Archives. The calibrated results have been made available through my Web site. I compare the results of my analysis with those of an independent analysis of a subset of these data by Saha et al. (2005, PASP, 117, 37), who have found a color-dependent discrepancy of up to 0.05 mag between their I-band photometry and mine for stars in this cluster. I conclude that a major part of the discrepancy appears to be associated with small shutter timing errors (a few hundredths of a second) in the Mini-Mosaic (MIMO) camera on the WIYN 3.5 m telescope. Smaller contributions to the anomaly likely come from (1) a color-scale error with a maximum amplitude of ~±0.02 mag in my secondary standard list as of 2004 September, and (2) statistical effects arising from the previous study's use of a relatively small number of standard-star observations to determine a comparatively large number of fitting parameters in the photometric transformations.

  • homogeneous photometry iv on the standard sequence in the globular cluster ngc2419
    arXiv: Astrophysics, 2005
    Co-Authors: Peter B Stetson
    Abstract:

    A new analysis of CCD-based BVRI broad-band photometry for the globular cluster NGC2419 is presented, based on 340 CCD images either donated by colleagues or retrieved from Public Archives. The calibrated results have been made available through my Web site. I compare the results of my analysis with those of an independent analysis of a subset of these data by Saha et al. (2005, PASP, 117, 37), who have found a color-dependent discrepancy of up to 0.05 mag between their I-band photometry and mine for stars in this cluster. I conclude that a major part of the discrepancy appears to be associated with small (a few hundredths of a second) shutter-timing errors in the MiniMos camera on the WIYN 3.5-m telescope. Smaller contributions to the anomaly likely come from (a) a color-scale error with a maximum amplitude of ~ +/-0.02 mag in my secondary standard list as of September 2004; and (b) statistical effects arising from the previous study's use of a relatively small number of standard-star observations to determine a comparatively large number of fitting parameters in the photometric transformations.

Pavel Bolotov - One of the best experts on this subject based on the ideXlab platform.

  • large scale sequencing of human influenza reveals the dynamic nature of viral genome evolution
    Nature, 2005
    Co-Authors: Elodie Ghedin, Naomi Sengamalay, Martin Shumway, Jennifer Zaborsky, Tamara Feldblyum, Vik Subbu, David J Spiro, Jeff Sitz, Hean Koo, Pavel Bolotov
    Abstract:

    Influenza viruses are remarkably adept at surviving in the human population over a long timescale. The human influenza A virus continues to thrive even among populations with widespread access to vaccines, and continues to be a major cause of morbidity and mortality. The virus mutates from year to year, making the existing vaccines ineffective on a regular basis, and requiring that new strains be chosen for a new vaccine. Less-frequent major changes, known as antigenic shift, create new strains against which the human population has little protective immunity, thereby causing worldwide pandemics. The most recent pandemics include the 1918 'Spanish' flu, one of the most deadly outbreaks in recorded history, which killed 30-50 million people worldwide, the 1957 'Asian' flu, and the 1968 'Hong Kong' flu. Motivated by the need for a better understanding of influenza evolution, we have developed flexible protocols that make it possible to apply large-scale sequencing techniques to the highly variable influenza genome. Here we report the results of sequencing 209 complete genomes of the human influenza A virus, encompassing a total of 2,821,103 nucleotides. In addition to increasing markedly the number of Publicly available, complete influenza virus genomes, we have discovered several anomalies in these first 209 genomes that demonstrate the dynamic nature of influenza transmission and evolution. This new, large-scale sequencing effort promises to provide a more comprehensive picture of the evolution of influenza viruses and of their pattern of transmission through human and animal populations. All data from this project are being deposited, without delay, in Public Archives.

  • large scale sequencing of human influenza reveals the dynamic nature of viral genome evolution
    Nature, 2005
    Co-Authors: Elodie Ghedin, Naomi Sengamalay, Martin Shumway, Jennifer Zaborsky, Tamara Feldblyum, Vik Subbu, David J Spiro, Jeff Sitz, Hean Koo, Pavel Bolotov
    Abstract:

    Published on 5 October online, the in-print version of the survey of more than 200 influenza virus sequences by The Institute for Genomic Research appears this week. Influenza viruses are remarkably adept at surviving in the human population over a long timescale. The human influenza A virus continues to thrive even among populations with widespread access to vaccines, and continues to be a major cause of morbidity and mortality1,2. The virus mutates from year to year, making the existing vaccines ineffective on a regular basis, and requiring that new strains be chosen for a new vaccine. Less-frequent major changes, known as antigenic shift, create new strains against which the human population has little protective immunity, thereby causing worldwide pandemics. The most recent pandemics include the 1918 ‘Spanish’ flu, one of the most deadly outbreaks in recorded history, which killed 30–50 million people worldwide, the 1957 ‘Asian’ flu, and the 1968 ‘Hong Kong’ flu3. Motivated by the need for a better understanding of influenza evolution, we have developed flexible protocols that make it possible to apply large-scale sequencing techniques to the highly variable influenza genome. Here we report the results of sequencing 209 complete genomes of the human influenza A virus, encompassing a total of 2,821,103 nucleotides. In addition to increasing markedly the number of Publicly available, complete influenza virus genomes, we have discovered several anomalies in these first 209 genomes that demonstrate the dynamic nature of influenza transmission and evolution. This new, large-scale sequencing effort promises to provide a more comprehensive picture of the evolution of influenza viruses and of their pattern of transmission through human and animal populations. All data from this project are being deposited, without delay, in Public Archives.