A Family Tree of Optical Transients from Narrow-Line Seyfert 1 Galaxies

Frederick, Sara; Gezari, Suvi; Graham, Matthew J.; Sollerman, Jesper; van Velzen, Sjoert; Perley, Daniel A.; Stern, Daniel; Ward, Charlotte; Hammerstein, Erica; Hung, Tiara; Yan, Lin; Andreoni, Igor; Bellm, Eric C.; Duev, Dmitry A.; Kowalski, Marek; Mahabal, Ashish A.; Masci, Frank J.; Medford, Michael; Rusholme, Ben; Walters, Richard

doi:10.48550/arxiv.2010.08554

Cited by 9 publications

(20 citation statements)

References 31 publications

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“…About 15% of these are spectroscopically confirmed SN. The photometric selection recovers all ZTF TDEs and all large-amplitude flares from Seyfert galaxies that have been reported in earlier work (12,23,42).…”

Section: A Flare Selection and Photometrysupporting

confidence: 66%

“…Due to photon trapping, this high accretion rate makes the scale height of the accretion disk significantly larger compared to the common geometrically thin disk that is reached at Eddington ratios of ≈ 10% (21). This state change is supported by observations: the X-ray spectra of typical AGN are hard and non-thermal, while TDE and extreme AGN flares have thermal and soft X-ray spectra (22,23).…”

supporting

confidence: 56%

“…Of these, eight are classified as accretion flares with potential dust echoes. In addition, spectroscopic follow-up observations of ZTF transients have yielded nine more type I AGN, six of these have been published (23,52) and three are presented for the first time in this work: AT2019meh (ZTF19abclykm), AT2020afab (ZTF19abkdlkl), and AT2020iq (ZTF20aabcemq). We also obtained a new post-peak spectrum of AT2019aalc (Fig.…”

Section: B Optical Spectroscopy and Black Hole Mass Estimatesmentioning

confidence: 99%

“…8). The references listed behind the black hole mass estimates give the origin of the optical spectrum that was used: T13 (95), L19 (32), F19 (52), F20 (23), N20 (57), C21 (58), V21b (this work).…”

Section: H Neutrino Arrival Delaymentioning

confidence: 99%

“…Figure 7: Optical spectra of the three accretion flares coincident with a high-energy neutrino.The observed time relative to the peak of the optical emission is indicated. Including data from(10,11,23).…”

mentioning

confidence: 99%

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Establishing accretion flares from massive black holes as a major source of high-energy neutrinos

Velzen¹,

Stein²,

Gilfanov³

et al. 2021

Preprint

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High-energy neutrinos have thus far been observed in coincidence with timevariable emission from three different accreting black holes: a gamma-ray flare from a blazar (TXS 0506+056), an optical transient following a stellar tidal disruption (AT2019dsg), and an optical outburst from an active galactic nucleus (AT2019fdr). Here we present a unified explanation for the latter two of these sources: accretion flares that reach the Eddington limit. A signature of these events is a luminous infrared reverberation signal from circumnuclear dust that is heated by the flare. Using this property we construct a sample of similar sources, revealing a third event coincident with a PeV-scale neutrino. This sample of three accretion flares is correlated with high-energy neutrinos at a significance of 3.7σ. Super-Eddington accretion could explain the high particle acceleration efficiency of this new population.Accreting black holes have long been suggested as potential sources of high-energy particles (1, 2) and this expectation was supported by the detection of a high-energy neutrino coincident (at the 3σ-level) with gamma-ray flaring from the blazar TXS 0506+056 (3). However, blazars alone cannot account for the observed high-energy neutrino flux (4, 5); similar to the electromagnetic sky, we can expect that the observed cosmic neutrino flux (6) arises from multiple source populations (7).In the last two years, optical follow-up observations of neutrino alerts (8) using the Zwicky Transient Facility (ZTF, ( 9)) have identified two optical flares from the centers of galaxies coincident with PeV-scale neutrinos: AT2019dsg (10) and AT2019fdr (11). The former belongs to the class of spectroscopically-classified tidal disruption events (TDEs) from quiescent black holes, while the latter originated from a type 1 (i.e., unobscured) active galactic nucleus (AGN).However, the distinctive shared properties we present below suggest these flares share a common origin.

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Section: A Flare Selection and Photometrysupporting

confidence: 66%

supporting

confidence: 56%

Section: B Optical Spectroscopy and Black Hole Mass Estimatesmentioning

confidence: 99%

Section: H Neutrino Arrival Delaymentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Establishing accretion flares from massive black holes as a major source of high-energy neutrinos

Velzen¹,

Stein²,

Gilfanov³

et al. 2021

Preprint

View full text Add to dashboard Cite

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AT 2019avd: a novel addition to the diverse population of nuclear transients

Malyali

Rau

Merloni

et al. 2021

A&A

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We report on SRG/eROSITA, ZTF, ASAS-SN, Las Cumbres, neoWISE and Swift XRT/UVOT observations of the unique ongoing event AT 2019avd, located in the nucleus of a previously inactive galaxy at z = 0.029. eROSITA first observed AT 2019avd on 2020-04-28 during its first all sky survey, when it was detected as an ultrasoft X-ray source (kT ∼ 85 eV) that was 90 times brighter in the 0.2 − 2 keV band than a previous 3σ upper flux detection limit (with no archival X-ray detection at this position). The ZTF optical lightcurve in the ∼ 450 days preceding the eROSITA detection is double peaked, and the eROSITA detection coincides with the rise of the second peak. Follow-up optical spectroscopy shows the emergence of a Bowen fluorescence feature and high ionisation coronal lines ([Fe x] 6375 Å, [Fe xiv] 5303 Å), along with persistent broad Balmer emission lines (FWHM∼ 1400 km s −1). Whilst the X-ray properties make AT 2019avd a promising tidal disruption event (TDE) candidate, the optical properties are atypical for optically-selected TDEs. We discuss potential alternative origins that could explain the observed properties of AT 2019avd, such as a stellar binary TDE candidate, or a TDE involving a super massive black hole binary.

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Searching for Changing-state AGNs in Massive Data Sets. I. Applying Deep Learning and Anomaly-detection Techniques to Find AGNs with Anomalous Variability Behaviors

Sánchez-Sáez

Lira

Martí

et al. 2021

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The classic classification scheme for active galactic nuclei (AGNs) was recently challenged by the discovery of the so-called changing-state (changing-look) AGNs. The physical mechanism behind this phenomenon is still a matter of open debate and the samples are too small and of serendipitous nature to provide robust answers. In order to tackle this problem, we need to design methods that are able to detect AGNs right in the act of changing state. Here we present an anomaly-detection technique designed to identify AGN light curves with anomalous behaviors in massive data sets. The main aim of this technique is to identify CSAGN at different stages of the transition, but it can also be used for more general purposes, such as cleaning massive data sets for AGN variability analyses. We used light curves from the Zwicky Transient Facility data release 5 (ZTF DR5), containing a sample of 230,451 AGNs of different classes. The ZTF DR5 light curves were modeled with a Variational Recurrent Autoencoder (VRAE) architecture, that allowed us to obtain a set of attributes from the VRAE latent space that describes the general behavior of our sample. These attributes were then used as features for an Isolation Forest (IF) algorithm that is an anomaly detector for a "one class" kind of problem. We used the VRAE reconstruction errors and the IF anomaly score to select a sample of 8809 anomalies. These anomalies are dominated by bogus candidates, but we were able to identify 75 promising CSAGN candidates.

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A Family Tree of Optical Transients from Narrow-Line Seyfert 1 Galaxies

Cited by 9 publications

References 31 publications

Establishing accretion flares from massive black holes as a major source of high-energy neutrinos

Establishing accretion flares from massive black holes as a major source of high-energy neutrinos

AT 2019avd: a novel addition to the diverse population of nuclear transients

Searching for Changing-state AGNs in Massive Data Sets. I. Applying Deep Learning and Anomaly-detection Techniques to Find AGNs with Anomalous Variability Behaviors

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