4 research outputs found
Recommended from our members
A Transient âChanging-lookâ Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data
We report the discovery of a new âchanging-lookâ 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 Îg â 1 mag, followed by a rapid recovery on a timescale of several months, with the âČ2 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
A Transient "Changing-look'' Active Galactic Nucleus Resolved on Month Timescales from First-year Sloan Digital Sky Survey V Data
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
g1 mag, followed by a rapid recovery on a timescale of
several months, with the 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.Comment: Published in ApJ
The SDSS-V Black Hole Mapper Reverberation Mapping Project: Unusual Broad-Line Variability in a Luminous Quasar
We present a high-cadence multi-epoch analysis of dramatic variability of
three broad emission lines (MgII, H, and H) in the spectra of
the luminous quasar ((5100\r{A}) =
erg s) SDSS J141041.25+531849.0 at with 127 spectroscopic
epochs over 9 years of monitoring (2013-2022). We observe anti-correlations
between the broad emission-line widths and flux in all three emission lines,
indicating that all three broad emission lines "breathe" in response to
stochastic continuum variations. We also observe dramatic radial velocity
shifts in all three broad emission lines, ranging from 400 km
s to 800 km s, that vary over the course of the monitoring
period. Our preferred explanation for the broad-line variability is complex
kinematics in the broad-line region gas. We suggest a model for the broad-line
variability that includes a combination of gas inflow with a radial gradient,
an azimuthal asymmetry (e.g., a hot spot), superimposed on the stochastic
flux-driven changes to the optimal emission region ("line breathing"). Similar
instances of line-profile variability due to complex gas kinematics around
quasars are likely to represent an important source of false positives in
radial velocity searches for binary black holes, which typically lack the kind
of high-cadence data we analyze here. The long-duration, wide-field, and
many-epoch spectroscopic monitoring of SDSS-V BHM-RM provides an excellent
opportunity for identifying and characterizing broad emission-line variability,
and the inferred nature of the inner gas environment, of luminous quasars