Active Galaxies NewsletterAn electronic publication dedicated to the observations and theory of active galaxies
Edited by Megan Argo
The Active Galaxies Newsletter is an electronic publication dedicated to the observation and theory of active galaxies. It is intended to be used to notify others in the field of recently accepted papers, conference proceedings and dissertations, and also contains announcements of jobs and conferences. It is produced monthly and sent to over 600 subscribers.
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|Active||An electronic publication dedicated to|
|Galaxies||the observation and theory of|
|No. 204 -- October 2014||Editor: Megan Argo (firstname.lastname@example.org)|
Jobs Adverts - Meetings Adverts - Special Announcements
Welcome to all the new subscribers, and thanks to everyone who contributed to this issue of the Active Galaxies Newsletter. This newsletter is intended to disseminate paper abstracts, meeting announcements, job adverts and other information which may be of interest to the active galaxies community. It is produced monthly and, whilst the deadline for contributions is the last day of the month, contributions may be submitted at any time.
The Latex macros for submitting abstracts and dissertation abstracts are appended to each issue of the newsletter and are also available on the web page. Please note that the editor may reject submissions which do not use the template. As always, any suggestions or feedback regarding the newsletter are welcome.
Many thanks for your continued subscription.
A Variable PV Broad Absorption Line and Quasar Outflow Energetics
D. M. Capellupo1,2, F. Hamann1, T. A. Barlow3
1. Department of Astronomy, University of Florida, Gainesville, FL 32611-2055
2. School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
3. Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125
Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that might exist in all quasars and could play a major role in feedback to galaxy evolution. The viability of BAL outflows as a feedback mechanism depends on their kinetic energies, as derived from the outflow velocities, column densities, and distances from the central quasar. We estimate these quantities for the quasar, Q1413+1143 (redshift ze = 2.56), aided by the first detection of PV λλ1118, 1128 BAL variability in a quasar. In particular, PV absorption at velocities where the CIV trough does not reach zero intensity implies that the CIV BAL is saturated and the absorber only partially covers the background continuum source (with characteristic size <0.01 pc). With the assumption of solar abundances, we estimate that the total column density in the BAL outflow is log NH ≥ 22.3 cm-2. Variability in the PV and saturated CIV BALs strongly disfavors changes in the ionization as the cause of the BAL variability, but supports models with high-column density BAL clouds moving across our lines of sight. The observed variability time of 1.6 yr in the quasar rest frame indicates crossing speeds >750 km s-1 and a radial distance from the central black hole of ≤3.5 pc, if the crossing speeds are Keplerian. The total outflow mass is ∼4100 M⊙, the kinetic energy ∼4 × 1054 erg, and the ratio of the outflow kinetic energy luminosity to the quasar bolometric luminosity is ∼0.02 (at the minimum column density and maximum distance), which might be sufficient for important feedback to the quasar's host galaxy.
Accepted by MNRAS
E-mail contact: email@example.com
Preprint available at http://arxiv.org/abs/1407.7532
A mid-infrared view of the inner parsecs of the Seyfert galaxy Mrk1066 using CanariCam/GTC
C. Ramos Almeida1,2, A. Alonso-Herrero3, P. Esquej4, O. González-Martín1,2, R. A. Riffel5, I. García-Bernete1,2, J. M. Rodríguez Espinosa1,2, C. Packham6, N. A. Levenson7, P. Roche8, T. Díaz-Santos9, I. Aretxaga10, C. Álvarez1,2
1. Instituto de Astrofísica de Canarias, Calle Vía Láctea, s/n, E-38205, La Laguna, Tenerife, Spain
2. Departamento de Astrofísica, Universidad de La Laguna, E-38206, La Laguna, Tenerife, Spain
3. Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, E-39005, Santander, Spain
4. Departamento de Astrofísica, Facultad de CC. Físicas, Universidad Complutense de Madrid, E-28040, Madrid, Spain
5. Departamento de Física, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
6. Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, USA
7. Gemini Observatory, Casilla 603, La Serena, Chile
8. Department of Physics, University of Oxford, Oxford OX1 3RH, UK
9. Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125, USA
10. Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), 72000 Puebla, México
We present mid-infrared (MIR) imaging and spectroscopic data of the Seyfert 2 galaxy Mrk1066 obtained with CanariCam (CC) on the 10.4 m Gran Telescopio CANARIAS (GTC). The galaxy was observed in imaging mode with an angular resolution of 0.24'' (54 pc) in the Si-2 filter (8.7 μm). The image reveals a series of star-forming knots within the central ∼400 pc, after subtracting the dominant active galactic nucleus (AGN) component. We also subtracted this AGN unresolved component from the 8-13 μm spectra of the knots and the nucleus, and measured equivalent widths (EWs) of the 11.3 μm Polycyclic Aromatic Hydrocarbon (PAH) feature which are typical of pure starburst galaxies. This EW is larger in the nucleus than in the knots, confirming that, at least in the case of Mrk1066, the AGN dilutes, rather than destroys, the molecules responsible for the 11.3 μm PAH emission. By comparing the nuclear GTC/CC spectrum with the Spitzer/IRS spectrum of the galaxy, we find that the AGN component that dominates the continuum emission at λ<15 μm on scales of ∼60 pc (90-100%) decreases to 35-50% when the emission of the central ∼830 pc is considered. On the other hand, the AGN contribution dominates the 15-25 μm emission (75%) on the scales probed by Spitzer/IRS. We reproduced the nuclear infrared emission of the galaxy with clumpy torus models, and derived a torus gas mass of 2×105 M⊙, contained in a clumpy structure of ∼2 pc radius and with a column density compatible with Mrk1066 being a Compton-thick candidate, in agreement with X-ray observations. We find a good match between the MIR morphology of Mrk1066 and the extended Paβ, Brγ and [O III]λ5007 emission. This coincidence implies that the 8.7 μm emission is probing star formation, dust in the narrow-line region, and the oval structure previously detected in the near-infrared. On the other hand, the Chandra soft X-ray morphology does not match any of the previous, contrary to what it is generally assumed for Seyfert galaxies. A thermal origin for the soft X-ray emission, rather than AGN photoionization, is suggested by the different data analyzed here.
Accepted by MNRAS
E-mail contact: firstname.lastname@example.org
Preprint available at http://arxiv.org/abs/1409.0674
A Census of Gas Outflows in Type 2 Active Galactic Nuclei
Hyun-Jin Bae1 and Jong-Hak Woo2,3
1. Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749, Republic of Korea
2. Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea
3. TJ Park Science Fellow
We perform a census of ionized gas outflows using a sample of ∼23,000 type 2 active galactic nuclei (AGNs) out to z∼0.1. By measuring the velocity offset of narrow emission lines, i.e., [OIII] λ5007 and Hα, with respect to the systemic velocity measured from the stellar absorption lines, we find that 47% of AGNs display an [OIII] line-of-sight velocity offset ≥ 20 km s-1. The fraction of the [OIII] velocity offset in type 2 AGNs is comparable to that in type 1 AGNs after considering the projection effect. AGNs with a large [OIII] velocity offset preferentially have a high Eddington ratio, implying that the detected velocity offsets are related to black hole activity. The distribution of the host galaxy inclination is clearly different between the AGNs with blueshifted [OIII] and the AGNs with redshifted [OIII], supporting the combined model of the biconical outflow and dust obscuration. In addition, for ∼3% of AGNs, [OIII] and Hα show comparable large velocity offsets, indicating a more complex gas kinematics than decelerating outflows in a stratified narrow-line region.
Accepted for publication in The Astrophysical Journal
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Preprint available at http://arxiv.org/abs/1409.1580
The Mass of the Central Black Hole in the Nearby Seyfert Galaxy NGC5273
Misty C. Bentz1, Daniel Horenstein1, Craig Bazhaw1, Emily R. Manne-Nicholas1, Benjamin J. Ou-Yang1, Matthew Anderson1, Jeremy Jones1, Ryan P. Norris1, J. Robert Parks1, Dicy Saylor1, Katherine G. Teems1, and Clay Turner1
1. Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA
We present the results of a reverberation-mapping program targeting NGC5273, a nearby early-type galaxy with a broad-lined active galactic nucleus. Over the course of the monitoring program, NGC5273 showed strong variability that allowed us to measure time delays in the responses of the broad optical recombination lines to changes in the continuum flux. A weighted average of these measurements results in a black hole mass determination of MBH = (4.7 ± 1.6) × 106M⊙. An estimate of the size of the black hole sphere of influence in NGC5273 puts it just at the limit of the resolution achievable with current ground-based large aperture telescopes. NGC5273 is therefore an important future target for a black hole mass determination from stellar dynamical modeling, especially because it is the only nearby early-type galaxy hosting an AGN with a reverberation-based mass, allowing the best comparison for the masses determined from these two techniques.
Accepted by Ap. J.
E-mail contact: firstname.lastname@example.org
Preprint available at http://arxiv.org/abs/1409.5794
Time-correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission
W. Max-Moerbeck1,2, T. Hovatta1,3, J. L. Richards4, O. G. King1, T. J. Pearson1, A. C. S. Readhead1, R. Reeves1,9, M. C. Shepherd1, M. A. Stevenson1, E. Angelakis5, L. Fuhrmann5, K. J. B. Grainge7, V. Pavlidou1,5,6, R. W. Romani8, J. A. Zensus5
1. Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
2. National Radio Astronomy Observatory (NRAO), P.O. Box 0, Socorro, NM 87801, USA
3. Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
4. Department of Physics, Purdue University, West Lafayette, IN 47907, USA
5. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
6. Department of Physics, University of Crete / Foundation for Research and Technology - Hellas, Heraklion 71003, Greece
7. Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, M13 9PL
8. W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA
9. Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
In order to determine the location of the gamma-ray emission site in blazars, we investigate the time-domain relationship between their radio and gamma-ray emission. Light-curves for the brightest detected blazars from the first 3 years of the mission of the Fermi Gamma-ray Space Telescope are cross-correlated with 4 years of 15GHz observations from the OVRO 40-m monitoring program. The large sample and long light-curve duration enable us to carry out a statistically robust analysis of the significance of the cross-correlations, which is investigated using Monte Carlo simulations including the uneven sampling and noise properties of the light-curves. Modeling the light-curves as red noise processes with power-law power spectral densities, we find that only one of 41 sources with high quality data in both bands shows correlations with significance larger than 3σ (AO0235+164), with only two more larger than even 2.25σ (PKS1502+106 and B22308+34). Additionally, we find correlated variability in Mrk421 when including a strong flare that occurred in July-September 2012. These results demonstrate very clearly the difficulty of measuring statistically robust multiwavelength correlations and the care needed when comparing light-curves even when many years of data are used. This should be a caution. In all four sources the radio variations lag the gamma-ray variations, suggesting that the gamma-ray emission originates upstream of the radio emission. Continuous simultaneous monitoring over a longer time period is required to obtain high significance levels in cross-correlations between gamma-ray and radio variability in most blazars.
Accepted for publication in MNRAS
E-mail contact: email@example.com
Preprint available at http://arxiv.org/abs/1408.6264
The host-galaxy of the gamma-ray Narrow-line Seyfert 1 galaxy 1H 0323+342
J. León-Tavares1,2, J. Kotilainen2 V. Chavushyan1, C. Añorve3, I. Puerari1, I. Cruz-González4, V. Patiño-Alvarez1, S. Antón5,6, A. Carramiñana1, L. Carrasco1, J. Guichard1, K. Karhunen7, A. Olguín-Iglesias1, J. Sanghvi7 and J. R. Valdes1
1. Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE), Apartado Postal 51 y 216, 72000 Puebla, México
2. Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, FI-21500 Piikkiö, Finland
3. Facultad de Ciencias de la Tierra y del Espacio (FACITE) de la Universidad Autónoma de Sinaloa, Blvd. de la Americas y Av. Universitarios S/N, Ciudad Universitaria, C.P. 80010, Culiacán Sinaloa, México
4. Instituto de Astronomía, Universidad Nacional Autónoma de México, Ap. 70-264, 04510 DF, México
5. Instituto de Astrofísica de Andalucía - CSIC, 18008 Granada, Spain
6. Instituto de Astrof??sica e Ciências do Espaço, Universidade de Lisboa, Faculdade de Ciencias, Campo Grande, PT1749-016 Lisboa, Portugal
7. Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 20100 Turku, Finland
We present optical and near infrared (NIR) imaging data of the radio-loud Narrow-line Seyfert 1 galaxy 1H 0323+342, which shows intense and variable gamma-ray activity discovered by the Fermi satellite with the Large Area Telescope. NIR and optical images are used to investigate the structural properties of the host galaxy of 1H 0323+342; this together with optical spectroscopy allowed us to examine its black hole mass. Based on the 2D multiwavelength surface brightness modeling, we find that, statistically, the best model fit is a combination of a nuclear component and a Sérsic profile (n ∼ 2.8). However, the presence of a disc component (with a small bulge n ∼ 1.2) remains also a possibility and cannot be ruled out with the present data. Although at first glance a spiral-arm like structure is revealed in our images, a 2D Fourier analysis of the imagery suggests that such structure corresponds to an asymmetric ring, likely associated to a recent violent dynamical interaction. We discuss our results on the context of relativistic jets production and galaxy evolution.
Accepted by ApJ
E-mail contact: firstname.lastname@example.org
Preprint available at http://arxiv.org/abs/1409.2518
AKARI IRC 2.5-5 μm Spectroscopy of Infrared Galaxies Over a Wide Luminosity Range
K. Ichikawa1, M. Imanishi2, Y. Ueda1, T. Nakagawa3, M. Shirahata4, H. Kaneda5, S. Oyabu5
1. Department of Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake cho, Kyoto 606-8502, Japan
2. Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720, USA
3. Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
4. National Institutes of Natural Science, National Astronomical Observatory of Japan (NAOJ) 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
5. Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
We present the result of a systematic infrared 2.5-5 μm spectroscopic study of 22 nearby infrared galaxies over a wide infrared luminosity range (1010 L⊙ < LIR < 1013 L⊙) obtained from AKARI Infrared Camera (IRC). The unique band of the AKARI IRC spectroscopy enables us to access both the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission feature from star forming activity and the continuum of torus-dust emission heated by an active galactic nucleus (AGN). Applying our AGN diagnostics to the AKARI spectra, we discover 14 buried AGNs. The large fraction of buried AGNs suggests that AGN activity behind the dust is almost ubiquitous in ultra-/luminous infrared galaxies (U/LIRGs). We also find that both the fraction and energy contribution of buried AGNs increase with infrared luminosity from 1010 L⊙ to 1013 L⊙, including normal infrared galaxies with LIR < 1011 L⊙. The energy contribution from AGNs in the total infrared luminosity is only ∼ 7% in LIRGs and ∼ 20% in ULIRGs, suggesting that the majority of the infrared luminosity originates from starburst activity. We investigate the luminosity relation between star formation and AGN. We find that these infrared galaxies exhibit higher star formation rates than optically selected Seyfert galaxies with the same AGN luminosities, implying that infrared galaxies could be an early evolutionary phase of AGN.
Accepted by ApJ
E-mail contact: email@example.com
Preprint available at http://arxiv.org/abs/1408.5975
Suzaku observation of IRAS00521-7054, a peculiar type-II AGN with a very broad feature at 6keV
C. Ricci1, F. Tazaki1,2, Y. Ueda1, S. Paltani3, R. Boissay3, Y. Terashima4
1. Department of Astronomy, Kyoto University, Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
2. Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
3. Department of Astronomy, University of Geneva, ch. d'Ecogia 16, 1290 Versoix, Switzerland
4. Department of Physics, Ehime University, Matsuyama, 790-8577, Japan.
IRAS00521-7054 is the first Seyfert2 in which the presence of an extremely large FeKα line has been claimed. We report here on the analysis of a 100ks Suzaku observation of the source. We confirm the existence of a very strong excess over the power-law X-ray continuum at E ∼ 6keV (EW ≃ 800 eV), extending down to ∼4.5 keV, and found that the X-ray spectrum of the source can be explained by two different models. i) An absorption scenario, in which the X-ray source is obscured by two fully-covering ionized absorbers, with a strong reflection component from neutral material (R ∼ 1.7), a black body component and four narrow Gaussian lines (corresponding to Fe Kα, Fe Kβ, FeXXV and Fe XXVI). ii) A reflection scenario, in which the X-ray spectrum is dominated by an obscured (log NH ∼ 22.9) blurred reflection produced in an ionized disk around a rotating supermassive black hole with a spin of a ≥ 0.73, and affected by light-bending (R ∼ 2.7), plus two narrow Gaussian lines (corresponding to Fe Kα and Fe Kβ). The narrow Fe Kα and Kβ lines are consistent with being produced by ionized iron, and in particular by FeXIV-FeXVI and FeXII-FeXVI for the absorption and reflection scenario, respectively. While the X-ray continuum varies significantly during the observation, the intensity of the broad feature appears to be constant, in agreement with both the absorption and reflection scenarios. For both scenarios we obtained a steep power-law emission (Γ ∼ 2.2-2.3), and we speculate that the source might be an obscured narrow-line Seyfert 1.
Accepted by ApJ
E-mail contact: firstname.lastname@example.org
Preprint available at http://arxiv.org/abs/1408.6095
CIV and CIII] reverberation mapping of the luminous quasar PG 1247+267
D. Trevese1, M. Perna2, F. Vagnetti3, F.G. Saturni1,4, and M. Dadina5
1. Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro, 5, 00185 Roma, Italy
2. Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
3. Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy
4. European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
5. INAF-IASF Bologna, Via Gobetti 101, 40129 Bologna, Italy
So far the masses of about 50 active galactic nuclei have been measured through the reverberation mapping technique (RM). Most measurements have been performed for objects of moderate luminosity and redshift, based on Hβ, which is also used to calibrate the scaling relation which allows single-epoch (SE) mass determination based on AGN luminosity and the width of different emission lines. The SE mass obtained from CIV (1549 Å) line shows a large spread around mean values, due to complex structure and gas dynamics of the relevant emission region. Direct RM measures of CIV exist for only 6 AGNs of low luminosity and redshift, and only one luminous quasar (Kaspi et al. 2007). We have collected since 2003 photometric and spectroscopic observations of PG1247+267, the most luminous quasar ever analyzed for RM. We provide light curves for the continuum and for CIV (1549 Å) and CIII] (1909 Å), and measures of the reverberation time lags based on the SPEAR method (Zu et al. 2011). The sizes of the line emission regions are in a ratio RCIII]/RCIV ∼ 2, similar to the case of Seyfert galaxies, indicating for the first time a similar ionization stratification in a luminous quasar and low luminosity nuclei. Due to relatively small broad line region size and relatively narrow line widths, we estimate a small mass and an anomalously high Eddington ratio. We discuss the possibility that either the shape of the emission region or an amplification of the luminosity caused by gravitational lensing may be in part responsible of the result.
Accepted for publication in ApJ
E-mail contact: email@example.com
Preprint available at http://arxiv.org/abd/1409.5448
AGN Type-casting: Mrk590 No Longer Fits the Role
K. D. Denney1,5, G. De Rosa1,2, K. Croxall1, A. Gupta1,3, M. C. Bentz4, M. M. Fausnaugh1, C. J. Grier1, P. Martini1,2, S. Mathur1,2, B. M. Peterson1,2, R. W. Pogge1,2, and B. J. Shappee1
1. Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
2. Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA
3. Department of Biological and Physical Sciences, Columbus State Community College, Columbus, OH 43215, USA
4. Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303, USA
5. NSF Astronomy & Astrophysics Postdoctoral Fellow
We present multi-wavelength observations that trace more than 40 years in the life of the active galactic nucleus (AGN) in Mrk590, traditionally known as a classic Seyfert 1 galaxy. From spectra recently obtained from HST, Chandra, and the Large Binocular Telescope, we find that the activity in the nucleus of Mrk590 has diminished so significantly that the continuum luminosity is a factor of 100 lower than the peak luminosity probed by our long baseline observations. Furthermore, the broad emission lines, once prominent in the UV/optical spectrum, have all but disappeared. Since AGN type is defined by the presence of broad emission lines in the optical spectrum, our observations demonstrate that Mrk590 has now become a "changing look" AGN. If classified by recent optical spectra, Mrk590 would be a Seyfert ∼1.9-2, where the only broad emission line still visible in the optical spectrum is a weak component of HHα. As an additional consequence of this change, we have definitively detected UV narrow-line components in a Type 1 AGN, allowing an analysis of these emission-line components with high-resolution COS spectra. These observations challenge the historical paradigm that AGN type is only a consequence of the line of sight viewing angle toward the nucleus in the presence of a geometrically-flattened, obscuring medium (i.e., the torus). Our data instead suggest that the current state of Mrk 590 is a consequence of the change in luminosity, which implies the black hole accretion rate has significantly decreased.
Accepted by ApJ
E-mail contact: firstname.lastname@example.org
Preprint available at http://arxiv.org/abs/1404.4879
Brightest Fermi-LAT Flares of PKS 1222+216: Implications on Emission and Acceleration Processes
Pankaj Kushwaha1, K. P. Singh1 and S. Sahayanathan2
1. Department of Astronomy & Astrophysics, Tata Institute of Fundamental Research, Mumbai, India
2. Astrophysical Sciences Division, Bhabha Atomic Research Centre, Mumbai, India
We present a high time resolution study of the two brightest γ-ray outbursts from a blazar PKS 1222+216 observed by the Fermi Large Area Telescope (LAT) in 2010. The γ-ray light-curves obtained in four different energy bands: 0.1-3, 0.1-0.3, 0.3-1 and 1-3 GeV, with time bin of 6 hr, show asymmetric profiles with a similar rise time in all the bands but a rapid decline during the April flare and a gradual one during the June. The light-curves during the April flare show ∼ 2 days long plateau in 0.1-0.3 GeV emission, erratic variations in 0.3-1 GeV emission, and a daily recurring feature in 1-3 GeV emission until the rapid rise and decline within a day. The June flare shows a monotonic rise until the peak, followed by a gradual decline powered mainly by the multi-peak 0.1-0.3 GeV emission. The peak fluxes during both the flares are similar except in the 1-3 GeV band in April which is twice the corresponding flux during the June flare. Hardness ratios during the April flare indicate spectral hardening in the rising phase followed by softening during the decay. We attribute this behavior to the development of a shock associated with an increase in acceleration efficiency followed by its decay leading to spectral softening. The June flare suggests hardening during the rise followed by a complicated energy dependent behavior during the decay. Observed features during the June flare favor multiple emission regions while the overall flaring episode can be related to jet dynamics.
Accepted by ApJ
E-mail contact: email@example.com
Preprint available at http://arxiv.org/abs/1409.8201
Deadline: 1st November 2014
Further Information: http://www.astro.ethz.ch/schawinski
The Institute for Astronomy of the ETH Zurich invites applications for a postdoctoral position in the new research group of Prof. Schawinski to work on active galaxies, galaxy-black hole co-evolution and the origin of black holes.
The successful candidate will be involved in the planning, execution and analysis of observational projects. Experience with survey data, optical/NIR spectroscopy and radio/sub-mm data would be a particular asset. There are also opportunities to get involved in Zooniverse citizen science projects and in the mentoring of students.
The position is initially for two years, but can be extended to a third year subject to funding. The salary scale is attractive and there is substantial support for travel (observing, conference, collaboration), computing and publication charges. Switzerland is a full member of ESO and ESA. Zurich is regularly rated one of the top 10 cities of the world in terms of quality of life.
Applicants should have a PhD in astronomy or related field and should send a CV, publication list and a brief (3 pages max.) summary of past research and future research interests as a single PDF to firstname.lastname@example.org and arrange three letters of reference to be sent to the same address, by 1 November 2014. For further information, please contact Prof. Schawinski (email@example.com).
Included Benefits: Standard Swiss Social Security, Accident Insurance and Pension contributions.