Browsing by Author "Kochanek, C. S."

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    COSMOGRAIL XVIII. time delays of the quadruply lensed quasar WFI2033-4723
    (2019) Bonvin, V.; Millon, M.; Chan, J. H. -H.; Courbin, F.; Rusu, C. E.; Sluse, D.; Suyu, S. H.; Wong, K. C.; Fassnacht, C. D.; Marshall, P. J.; Treu, T.; Buckley-Geer, E.; Frieman, J.; Hempel, A.; Kim, S.; Lachaume, R.; Rabus, M.; Chao, D. C. -Y.; Chijani, M.; Gilman, D.; Gilmore, K.; Rojas, K.; Williams, P.; Anguita, T.; Kochanek, C. S.; Morgan, C.; Motta, V.; Tewes, M.; Meylan, G.
    We present new measurements of the time delays of WFI2033-4723. The data sets used in this work include 14 years of data taken at the 1.2 m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3 m telescope at Las Campanas Observatory and a single year of high-cadence and high-precision monitoring at the MPIA 2.2 m telescope. The time delays measured from these different data sets, all taken in the R-band, are in good agreement with each other and with previous measurements from the literature. Combining all the time-delay estimates from our data sets results in Delta t(AB) = 36.2(-0.8)(+0.7) days (2.1% precision), Delta t(AC) = 23.3(-1.4)(+1.2) days (5.6%) and Delta t(BC) = 59.4(-1.3)(+1.3) days (2.2%). In addition, the close image pair A1-A2 of the lensed quasars can be resolved in the MPIA 2.2 m data. We measure a time delay consistent with zero in this pair of images. We also explore the prior distributions of microlensing time-delay potentially affecting the cosmological time-delay measurements of WFI2033-4723. Our time-delay measurements are not precise enough to conclude that microlensing time delay is present or absent from the data. This work is part of a H0LiCOW series focusing on measuring the Hubble constant from WFI2033-4723.
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    REVERBERATION MAPPING OF THE SEYFERT 1 GALAXY NGC7469
    (2014) Peterson, B. M.; Grier, C. J.; Horne, Keith; Pogge, R. W.; Bentz, M. C.; De Rosa, G.; Denney, K. D.; Martini, Paul; Sergeev, S. G.; Kaspi, S.; Minezaki, T.; Zu, Y.; Kochanek, C. S.; Siverd, R. J.; Shappee, B.; Salvo, C. Araya; Beatty, T. G.; Bird, J. C.; Bord, D. J.; Borman, G. A.; Che, X.; Chen, C. -T.; Cohen, S. A.; Dietrich, M.; Doroshenko, V. T.; Drake, T.; Efimov, Yu. S.; Free, N.; Ginsburg, I.; Henderson, C. B.; King, A. L.; Koshida, S.; Mogren, K.; Molina, M.; Mosquera, A. M.; Motohara, K.; Nazarov, S. V.; Okhmat, D. N.; Pejcha, O.; Rafter, S.; Shields, J. C.; Skowron, D. M.; Skowron, J.; Valluri, M.; van Saders, J. L.; Yoshii, Y.
    A large reverberation-mapping study of the Seyfert 1 galaxy NGC7469 has yielded emission-line lags for H beta lambda 4861 and He He II lambda 4686 and a central black hole mass measurement M-BH approximate to 1 x 10(7)M(circle dot) , consistent with previous measurements. A very low level of variability during the monitoring campaign precluded meeting our original goal of recovering velocity-delay maps from the data, but with the new H beta measurement, NGC7469 is no longer an outlier in the relationship between the size of the H beta-emitting broad-line region and the luminosity of the active galactic nucleus. It was necessary to detrend the continuum and H beta and He He II lambda 4686 line light curves and those from archival UV data for different time-series analysis methods to yield consistent results.
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    Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548
    (IOP PUBLISHING LTD, 2017) Pei, L.; Fausnaugh, M. M.; Barth, A. J.; Peterson, B. M.; Bentz, M. C.; De Rosa, G.; Denney, K. D.; Goad, M. R.; Kochanek, C. S.; Korista, K. T.; Kriss, G. A.; Pogge, R. W.; Bennert, V. N.; Brotherton, M.; Clubb, K. I.; Dalla Bonta, E.; Filippenko, A. V.; Greene, J. E.; Grier, C. J.; Vestergaard, M.; Zheng, W.; Adams, Scott M.; Beatty, Thomas G.; Bigley, A.; Brown, Jacob E.; Brown, Jonathan S.; Canalizo, G.; Comerford, J. M.; Coker, Carl T.; Corsini, E. M.; Croft, S.; Croxall, K. V.; Deason, A. J.; Eracleous, Michael; Fox, O. D.; Gates, E. L.; Henderson, C. B.; Holmbeck, E.; Holoien, T. W. S.; Jensen, J. J.; Johnson, C. A.; Kelly, P. L.; Kim, S.; King, A.; Lau, M. W.; Li, Miao; Lochhaas, Cassandra; Ma, Zhiyuan; Manne Nicholas, E. R.; Mauerhan, J. C.; Malkan, M. A.; McGurk, R.; Morelli, L.; Mosquera, Ana; Mudd, Dale; Sanchez, F. Muller; Nguyen, M. L.; Ochner, P.; Ou Yang, B.; Pancoast, A.; Penny, Matthew T.; Pizzella, A.; Poleski, Radoslaw; Runnoe, Jessie; Scott, B.; Schimoia, Jaderson S.; Shappee, B. J.; Shivvers, I.; Simonian, Gregory V.; Siviero, A.; Somers, Garrett; Stevens, Daniel J.; Strauss, M. A.; Tayar, Jamie; Tejos, N.; Treu, T.; Van Saders, J.; Vican, L.; Villanueva, S., Jr.; Yuk, H.; Zakamska, N. L.; Zhu, W.; Anderson, M. D.; Arevalo, P.; Bazhaw, C.; Bisogni, S.; Borman, G. A.; Bottorff, M. C.; Brandt, W. N.; Breeveld, A. A.; Cackett, E. M.; Carini, M. T.; Crenshaw, D. M.; De Lorenzo Caceres, A.; Dietrich, M.; Edelson, R.; Efimova, N. V.; Ely, J.; Evans, P. A.; Ferland, G. J.; Flatland, K.; Gehrels, N.; Geier, S.; Gelbord, J. M.; Grupe, D.; Gupta, A.; Hall, P. B.; Hicks, S.; Horenstein, D.; Horne, Keith; Hutchison, T.; Im, M.; Joner, M. D.; Jones, J.; Kaastra, J.; Kaspi, S.; Kelly, B. C.; Kennea, J. A.; Kim, M.; Kim, S. C.; Klimanov, S. A.; Lee, J. C.; Leonard, D. C.; Lira, P.; MacInnis, F.; Mathur, S.; McHardy, I. M.; Montouri, C.; Musso, R.; Nazarov, S. V.; Netzer, H.; Norris, R. P.; Nousek, J. A.; Okhmat, D. N.; Papadakis, I.; Parks, J. R.; Pott, J. U.; Rafter, S. E.; Rix, H. W.; Saylor, D. A.; Schnuelle, K.; Sergeev, S. G.; Siegel, M.; Skielboe, A.; Spencer, M.; Starkey, D.; Sung, H. I.; Teems, K. G.; Turner, C. S.; Uttley, P.; Villforth, C.; Weiss, Y.; Woo, J. H.; Yan, H.; Young, S.; Zu, Y.
    We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The H beta and He II lambda 4686 broad emission-line light curves lag that of the 5100 angstrom optical continuum by 4.17(-0.36)(+0.36) days and 0.79(-0.34)(+0.35) days, respectively. The H beta lag relative to the 1158 angstrom ultraviolet continuum light curve measured by the Hubble Space Telescope is similar to 50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is similar to 50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for H beta and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broadline region dominated by Keplerian motion. The responses of both the H beta and He II emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C IV, Lya, He II (+ O III]), and Si IV(+ O IV]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured H beta lag is a factor of five shorter than the expected value implied by the R-BLR-L-AGN relation based on the past behavior of NGC 5548.
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    Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy
    (IOP PUBLISHING LTD, 2017) Mathur, S.; Gupta, A.; Page, K.; Pogge, R. W.; Krongold, Y.; Goad, M. R.; Adams, S. M.; Anderson, M. D.; Arevalo, P.; Barth, A. J.; Bazhaw, C.; Beatty, T. G.; Bentz, M. C.; Bigley, A.; Bisogni, S.; Borman, G. A.; Boroson, T. A.; Bottorff, M. C.; Brandt, W. N.; Breeveld, A. A.; Brown, J. E.; Brown, J. S.; Cackett, E. M.; Canalizo, G.; Carini, M. T.; Clubb, K. I.; Comerford, J. M.; Coker, C. T.; Corsini, E. M.; Crenshaw, D. M.; Croft, S.; Croxall, K. V.; Dalla Bonta, E.; Deason, A. J.; Denney, K. D.; De Lorenzo Caceres, A.; De Rosa, G.; Dietrich, M.; Edelson, R.; Ely, J.; Eracleous, M.; Evans, P. A.; Fausnaugh, M. M.; Ferland, G. J.; Filippenko, A. V.; Flatland, K.; Fox, O. D.; Gates, E. L.; Gehrels, N.; Geier, S.; Gelbord, J. M.; Gorjian, V.; Greene, J. E.; Grier, C. J.; Grupe, D.; Hall, P. B.; Henderson, C. B.; Hicks, S.; Holmbeck, E.; Holoien, T. W. S.; Horenstein, D.; Horne, Keith; Hutchison, T.; Im, M.; Jensen, J. J.; Johnson, C. A.; Joner, M. D.; Jones, J.; Kaastra, J.; Kaspi, S.; Kelly, B. C.; Kelly, P. L.; Kennea, J. A.; Kim, M.; Kim, S.; Kim, S. C.; King, A.; Klimanov, S. A.; Kochanek, C. S.; Korista, K. T.; Kriss, G. A.; Lau, M. W.; Lee, J. C.; Leonard, D. C.; Li, M.; Lira, P.; Ma, Z.; MacInnis, F.; Manne Nicholas, E. R.; Malkan, M. A.; Mauerhan, J. C.; McGurk, R.; McHardy, I. M.; Montouri, C.; Morelli, L.; Mosquera, A.; Mudd, D.; Muller Sanchez, F.; Musso, R.; Nazarov, S. V.; Netzer, H.; Nguyen, M. L.; Norris, R. P.; Nousek, J. A.; Ochner, P.; Okhmat, D. N.; Ou Yang, B.; Pancoast, A.; Papadakis, I.; Parks, J. R.; Pei, L.; Peterson, B. M.; Pizzella, A.; Poleski, R.; Pott, J. U.; Rafter, S. E.; Rix, H. W.; Runnoe, J.; Saylor, D. A.; Schimoia, J. S.; Schnuelle, K.; Sergeev, S. G.; Shappee, B. J.; Shivvers, I.; Siegel, M.; Simonian, G. V.; Siviero, A.; Skielboe, A.; Somers, G.; Spencer, M.; Starkey, D.; Stevens, D. J.; Sung, H. I.; Tayar, J.; Tejos, N.; Turner, C. S.; Uttley, P.; Van Saders, J.; Vestergaard, M.; Vican, L.; Villanueva, S., Jr.; Villforth, C.; Weiss, Y.; Woo, J. H.; Yan, H.; Young, S.; Yuk, H.; Zheng, W.; Zhu, W.; Zu, Y.
    During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on-and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.
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    Supernova progenitors, their variability and the Type IIP Supernova ASASSN-16fq in M66
    (OXFORD UNIV PRESS, 2017) Kochanek, C. S.; Fraser, M.; Adams, S. M.; Sukhbold, T.; Prieto, J. L.; Mueller, T.; Bock, G.; Brown, J. S.; Dong, Subo; Holoien, T. W. S.; Khan, R.; Shappee, B. J.; Stanek, K. Z.
    We identify a pre-explosion counterpart to the nearby Type IIP supernova ASASSN-16fq (SN 2016cok) in archival Hubble Space Telescope data. The source appears to be a blend of several stars that prevents obtaining accurate photometry. However, with reasonable assumptions about the stellar temperature and extinction, the progenitor almost certainly had an initial mass M-* less than or similar to 17M(circle dot), and was most likely in the mass range of M-* = 8-12M(circle dot). Observations once ASASSN-16fq has faded will have no difficulty accurately determining the properties of the progenitor. In 8 yr of Large Binocular Telescope (LBT) data, no significant progenitor variability is detected to rms limits of roughly 0.03 mag. Of the six nearby supernova (SN) with constraints on the low-level variability, SN 1987A, SN 1993J, SN 2008cn, SN 2011dh, SN 2013ej and ASASSN-16fq, only the slowly fading progenitor of SN 2011dh showed clear evidence of variability. Excluding SN 1987A, the 90 per cent confidence limit implied by these sources on the number of outbursts over the last decade before the SN that last longer than 0.1 yr (full width at half-maximum) and are brighter than M-R < -8 mag is approximately N-out less than or similar to 3. Our continuing LBT monitoring programme will steadily improve constraints on pre-SN progenitor variability at amplitudes far lower than achievable by SN surveys.
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    The 2014-2017 outburst of the young star ASASSN-13db A time-resolved picture of a very-low-mass star between EXors and FUors
    (2017) Sicilia Aguilar, A.; Oprandi, A.; Froebrich, D.; Fang, M.; Prieto, J. L.; Stanek, K.; Scholz, A.; Kochanek, C. S.; Henning, Th.; Rabus, Markus
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    The ASAS-SN bright supernova catalogue - I. 2013-2014
    (OXFORD UNIV PRESS, 2017) Holoien, T. W. S.; Stanek, K. Z.; Kochanek, C. S.; Shappee, B. J.; Prieto, J. L.; Brimacombe, J.; Bersier, D.; Bishop, D. W.; Dong, Subo; Brown, J. S.; Danilet, A. B.; Simonian, G. V.; Basu, U.; Beacom, J. F.; Falco, E.; Pojmanski, G.; Skowron, D. M.; Wozniak, P. R.; Avila, C. G.; Conseil, E.; Contreras, C.; Cruz, I.; Fernandez, J. M.; Koff, R. A.; Guo, Zhen; Herczeg, G. J.; Hissong, J.; Hsiao, E. Y.; Jose, J.; Kiyota, S.; Long, Feng; Monard, L. A. G.; Nicholls, B.; Nicolas, J.; Wiethoff, W. S.
    We present basic statistics for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) during its first year-and-a-half of operations, spanning 2013 and 2014. We also present the same information for all other bright (mV <= 17), spectroscopically confirmed supernovae discovered from 2014 May 1 through the end of 2014, providing a comparison to the ASAS-SN sample starting from the point where ASAS-SN became operational in both hemispheres. In addition, we present collected redshifts and near-UV through IR magnitudes, where available, for all host galaxies of the bright supernovae in both samples. This work represents a comprehensive catalogue of bright supernovae and their hosts from multiple professional and amateur sources, allowing for population studies that were not previously possible because the all-sky emphasis of ASAS-SN redresses many previously existing biases. In particular, ASAS-SN systematically finds bright supernovae closer to the centres of host galaxies than either other professional surveys or amateurs, a remarkable result given ASAS-SN's poorer angular resolution. This is the first of a series of yearly papers on bright supernovae and their hosts that will be released by the ASAS-SN team.
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    The ASAS-SN bright supernova catalogue - V. 2018-2020
    (2023) Neumann, K. D.; Holoien, T. W-S; Kochanek, C. S.; Stanek, K. Z.; Vallely, P. J.; Shappee, B. J.; Prieto, J. L.; Pessi, T.; Jayasinghe, T.; Brimacombe, J.; Bersier, D.; Aydi, E.; Basinger, C.; Beacom, J. F.; Bose, S.; Brown, J. S.; Chen, P.; Clocchiatti, A.; Desai, D. D.; Dong, Subo; Falco, E.; Holmbo, S.; Morrell, N.; Shields, J. V.; Sokolovsky, K. V.; Strader, J.; Stritzinger, M. D.; Swihart, S.; Thompson, T. A.; Way, Z.; Aslan, L.; Bishop, D. W.; Bock, G.; Bradshaw, J.; Cacella, P.; Castro-Morales, N.; Conseil, E.; Cornect, R.; Cruz, I.; Farfan, R. G.; Fernandez, J. M.; Gabuya, A.; Gonzalez-Carballo, J-L; Kendurkar, M. R.; Kiyota, S.; Koff, R. A.; Krannich, G.; Marples, P.; Masi, G.; Monard, L. A. G.; Munoz, J. A.; Nicholls, B.; Post, R. S.; Pujic, Z.; Stone, G.; Tomasella, L.; Trappett, D. L.; Wiethoff, W. S.
    We catalogue the 443 bright supernovae (SNe) discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) in 2018-2020 along with the 519 SNe recovered by ASAS-SN and 516 additional m(peak) <= 18 mag SNe missed by ASAS-SN. Our statistical analysis focuses primarily on the 984 SNe discovered or recovered in ASAS-SN g-band observations. The complete sample of 2427 ASAS-SN SNe includes earlier V-band samples and unrecovered SNe. For each SN, we identify the host galaxy, its UV to mid-IR photometry, and the SN's offset from the centre of the host. Updated peak magnitudes, redshifts, spectral classifications, and host galaxy identifications supersede earlier results. With the increase of the limiting magnitude to g <= 18 mag, the ASAS-SN sample is nearly complete up to m(peak) = 16.7 mag and is 90 per cent complete for m(peak) <= 17.0 mag. This is an increase from the V-band sample, where it was roughly complete up to m(peak) = 16.2 mag and 70 per cent complete for m(peak) <= 17.0 mag.