Browsing by Author "Eracleous, Michael"

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    A Transient "Changing-look" Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data
    (2022) Zeltyn, Grisha; Trakhtenbrot, Benny; Eracleous, Michael; Runnoe, Jessie; Trump, Jonathan R.; Stern, Jonathan; Shen, Yue; Hernandez-Garcia, Lorena; Bauer, Franz E.; Yang, Qian; Dwelly, Tom; Ricci, Claudio; Green, Paul; Anderson, Scott F.; Assef, Roberto J.; Guolo, Muryel; MacLeod, Chelsea; Davis, Megan C.; Fries, Logan; Gezari, Suvi; Grogin, Norman A.; Homan, David; Koekemoer, Anton M.; Krumpe, Mirko; LaMassa, Stephanie; Liu, Xin; Merloni, Andrea; Martinez-Aldama, Mary Loli; Schneider, Donald P.; Temple, Matthew J.; Brownstein, Joel R.; Ibarra-Medel, Hector; Burke, Jamison; Pellegrino, Craig; Kollmeier, Juna A.
    We report the discovery of a new "changing-look" active galactic nucleus (CLAGN) event, in the quasar SDSS J162829.17+432948.5 at z = 0.2603, identified through repeat spectroscopy from the fifth Sloan Digital Sky Survey (SDSS-V). Optical photometry taken during 2020-2021 shows a dramatic dimming of Delta g approximate to 1 mag, followed by a rapid recovery on a timescale of several months, with the less than or similar to 2 month period of rebrightening captured in new SDSS-V and Las Cumbres Observatory spectroscopy. This is one of the fastest CLAGN transitions observed to date. Archival observations suggest that the object experienced a much more gradual dimming over the period of 2011-2013. Our spectroscopy shows that the photometric changes were accompanied by dramatic variations in the quasar-like continuum and broad-line emission. The excellent agreement between the pre- and postdip photometric and spectroscopic appearances of the source, as well as the fact that the dimmest spectra can be reproduced by applying a single extinction law to the brighter spectral states, favor a variable line-of-sight obscuration as the driver of the observed transitions. Such an interpretation faces several theoretical challenges, and thus an alternative accretion-driven scenario cannot be excluded. The recent events observed in this quasar highlight the importance of spectroscopic monitoring of large active galactic nucleus samples on weeks-to-months timescales, which the SDSS-V is designed to achieve.
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    Exploring Changing-look Active Galactic Nuclei with the Sloan Digital Sky Survey V: First Year Results
    (2024) Zeltyn, Grisha; Trakhtenbrot, Benny; Eracleous, Michael; Yang, Qian; Green, Paul; Anderson, Scott F.; LaMassa, Stephanie; Runnoe, Jessie; Assef, Roberto J.; Bauer, Franz E.; Brandt, W. N.; Davis, Megan C.; Frederick, Sara E.; Fries, Logan B.; Graham, Matthew J.; Grogin, Norman A.; Guolo, Muryel; Hernandez-Garcia, Lorena; Koekemoer, Anton M.; Krumpe, Mirko; Liu, Xin; Martinez-Aldama, Mary Loli; Ricci, Claudio; Schneider, Donald P.; Shen, Yue; Sniegowska, Marzena; Temple, Matthew J.; Trump, Jonathan R.; Xue, Yongquan; Brownstein, Joel R.; Dwelly, Tom; Morrison, Sean; Bizyaev, Dmitry; Pan, Kaike; Kollmeier, Juna A.
    "Changing-look" active galactic nuclei (CL-AGNs) challenge our basic ideas about the physics of accretion flows and circumnuclear gas around supermassive black holes. Using first-year Sloan Digital Sky Survey V (SDSS-V) repeated spectroscopy of nearly 29,000 previously known active galactic nuclei (AGNs), combined with dedicated follow-up spectroscopy, and publicly available optical light curves, we have identified 116 CL-AGNs where (at least) one broad emission line has essentially (dis-)appeared, as well as 88 other extremely variable systems. Our CL-AGN sample, with 107 newly identified cases, is the largest reported to date, and includes similar to 0.4% of the AGNs reobserved in first-year SDSS-V operations. Among our CL-AGNs, 67% exhibit dimming while 33% exhibit brightening. Our sample probes extreme AGN spectral variability on months to decades timescales, including some cases of recurring transitions on surprisingly short timescales (less than or similar to 2 months in the rest frame). We find that CL events are preferentially found in lower-Eddington-ratio (f Edd) systems: Our CL-AGNs have a f Edd distribution that significantly differs from that of a carefully constructed, redshift- and luminosity-matched control sample (Anderson-Darling test yielding p AD approximate to 6 x 10-5; median f Edd approximate to 0.025 versus 0.043). This preference for low f Edd strengthens previous findings of higher CL-AGN incidence at lower f Edd, found in smaller samples. Finally, we show that the broad Mg ii emission line in our CL-AGN sample tends to vary significantly less than the broad H beta emission line. Our large CL-AGN sample demonstrates the advantages and challenges in using multi-epoch spectroscopy from large surveys to study extreme AGN variability and physics.
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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.