The Close AGN Reference Survey (CARS)

McElroy, Rebecca; Husemann, B.; Croom, S. M.; Davis, Timothy A.; Bennert, Vardha N.; Busch, G.; Combes, F.; Eckart, A.; Pérez-Torres, M. Á.; Powell, Meredith C.; Scharwächter, J.; Tremblay, G. R.; Urrutia, T.

doi:10.1051/0004-6361/201629102

Cited by 133 publications

(157 citation statements)

References 31 publications

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“…This blue asymmetry was not present during the bright Type 1 AGN phase, and has likely appeared now because the red wing of Hα disappeared amid the dimming phase, as discussed in McElroy et al (2016). More importantly, we confirm that the prominent red wing asymmetry in Lyα and C iv is not present in Hα line only one month before the HST observations were taken.…”

Section: Broad Emission-line Variationssupporting

confidence: 79%

“…Bennert et al (2011) found log (M BH /M ) = 8.15. The current L bol /L edd is around 0.03 (McElroy et al 2016). We note that because the broad-line region (BLR) of Mrk 1018 is currently not in an equilibrium or the virial factor has changed, recent M BH estimates are significantly different (e.g., current faint phase: log (M BH /M ) = 7.4; McElroy et al 2016).…”

Section: Introductionmentioning

confidence: 85%

“…These values are guided by a best-fit model of the deep coadded SDSS Stripe 82 model that we used previously to generate the long-term light curve in McElroy et al (2016). The resulting U-band light curve of the AGN component is shown in Fig.…”

Section: Reaching a Minimum In October 2016mentioning

confidence: 99%

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The Close AGN Reference Survey (CARS)

Krumpe

Tremblay

Urrutia

et al. 2017

A&A

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After changing optical AGN type from 1.9 to 1 in 1984, the AGN Mrk 1018 recently reverted back to its type 1.9 state. Our ongoing monitoring now reveals that the AGN has halted its dramatic dimming, reaching a minimum around October 2016. The minimum was followed by an outburst rising with ∼0.25 U-band mag/month. The rebrightening lasted at least until February 2017, as confirmed by joint Chandra and Hubble observations. Monitoring was resumed in July 2017 after the source emerged from sunblock, at which point the AGN was found only ∼0.4 mag brighter than its minimum. The intermittent outburst was accompanied by the appearance of a red wing asymmetry in broad-line shape, indicative of an inhomogeneous broad-line region. The current flickering brightness of Mrk 1018 following its rapid fading either suggests that the source has reignited, remains variable at a low level, or may continue dimming over the next few years. Distinguishing between these possibilities requires continuous multiwavelength monitoring.

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Section: Broad Emission-line Variationssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 85%

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The Close AGN Reference Survey (CARS)

Krumpe

Tremblay

Urrutia

et al. 2017

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“…Based on follow-up X-ray observations we rule out an obscuring-cloud event as the cause of the change of type again after 30 yr, as discovered in McElroy et al (2016). All observations, in particular the optical-UV SED, are consistent with a declining accretion rate of a geometrically thin, optically thick accretion disc.…”

Section: Discussionmentioning

confidence: 61%

The Close AGN Reference Survey (CARS)

Husemann

Urrutia

Tremblay

et al. 2016

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We recently discovered that the active galactic nucleus (AGN) of Mrk 1018 has changed optical type again after 30 yr as a type 1 AGN. Here we combine Chandra, NuStar, Swift, Hubble Space Telescope and ground-based observations to explore the cause of this change. The 2-10 keV flux declines by a factor of ∼8 between 2010 and 2016. We show with our X-ray observation that this is not caused by varying neutral hydrogen absorption along the line-of-sight up to the Compton-thick level. The optical-UV spectral energy distributions are well fit with a standard geometrically thin optically thick accretion disc model that seems to obey the expected L ∼ T 4 relation. It confirms that a decline in accretion disc luminosity is the primary origin for the type change. We detect a new narrow-line absorber in Lyα blue-shifted by ∼700 km s −1 with respect to the systemic velocity of the galaxy. This new Lyα absorber could be evidence for the onset of an outflow or a companion black hole with associated gas that could be related to the accretion rate change. However, the low column density of the absorber means that it is not the direct cause for Mrk 1018's changing-look nature.

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“…These could be related to AGNs that change their BLR type and/or missing them (e.g. Tran 2001;Bianchi et al 2005;Zhang & Wang 2006;Kaastra et al 2014), which can occur even on short timescales (Storchi-Bergmann, Baldwin & Wilson 1993;Aretxaga 1999;Shappee et al 2014;Oknyansky et al 2016;McElroy et al 2016). Some peculiar types of AGNs could play a similar role, e.g.…”

Section: Subluminous Agn Flaring Scenariomentioning

confidence: 99%

Spectral features of tidal disruption candidates and alternative origins for such transient flares

Saxton

Perets

Baskin

2017

Monthly Notices of the Royal Astronomical Society

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UV and optically selected candidates for stellar tidal disruption events (TDE) often exhibit broad spectral features (He ii emission, Hα emission, or absorption lines) on a blackbody-like continuum (10 4 K T 10 5 K). The lines presumably emit from TDE debris or circumnuclear clouds photoionized by the flare. Line velocities however are much lower than expected from a stellar disruption by supermassive black hole (SMBH), and are somewhat faster than expected for the broad line region (BLR) clouds of a persistently active galactic nucleus (AGN). The distinctive spectral states are not strongly related to observed luminosity and velocity, nor to SMBH mass estimates. We use exhaustive photoionization modelling to map the domain of fluxes and cloud properties that yield (e.g.) a He-overbright state where a large He II(4686Å )/Hα line-ratio creates an illusion of helium enrichment. Although observed line ratios occur in a plausible minority of cases, AGN-like illumination can not reproduce the observed equivalent widths. We therefore propose to explain these properties by a light-echo photoionization model: the initial flash of a hot blackbody (detonation) excites BLR clouds, which are then seen superimposed on continuum from a later, expanded, cooled stage of the luminous source. The implied cloud mass is substellar, which may be inconsistent with a TDE. Given these and other inconsistencies with TDE models (e.g. host-galaxies distribution) we suggest to also consider alternative origins for these nuclear flares, which we briefly discuss (e.g. nuclear supernovae and starved/subluminous AGNs).

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The Close AGN Reference Survey (CARS)

Cited by 133 publications

References 31 publications

The Close AGN Reference Survey (CARS)

The Close AGN Reference Survey (CARS)

The Close AGN Reference Survey (CARS)

Spectral features of tidal disruption candidates and alternative origins for such transient flares

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