757 research outputs found
Optimal control problems with maximum functional
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76172/1/AIAA-20777-321.pd
Discovery and Early Evolution of ASASSN-19bt, the First TDE Detected by TESS
We present the discovery and early evolution of ASASSN-19bt, a tidal
disruption event (TDE) discovered by the All-Sky Automated Survey for
Supernovae (ASAS-SN) at a distance of Mpc and the first TDE to be
detected by TESS. As the TDE is located in the TESS Continuous Viewing Zone,
our dataset includes 30-minute cadence observations starting on 2018 July 25,
and we precisely measure that the TDE begins to brighten days before
its discovery. Our dataset also includes 18 epochs of Swift UVOT and XRT
observations, 2 epochs of XMM-Newton observations, 13 spectroscopic
observations, and ground data from the Las Cumbres Observatory telescope
network, spanning from 32 days before peak through 37 days after peak.
ASASSN-19bt thus has the most detailed pre-peak dataset for any TDE. The TESS
light curve indicates that the transient began to brighten on 2019 January 21.6
and that for the first 15 days its rise was consistent with a flux power-law model. The optical/UV emission is well-fit by a blackbody SED,
and ASASSN-19bt exhibits an early spike in its luminosity and temperature
roughly 32 rest-frame days before peak and spanning up to 14 days that has not
been seen in other TDEs, possibly because UV observations were not triggered
early enough to detect it. It peaked on 2019 March 04.9 at a luminosity of
ergs s and radiated
ergs during the 41-day rise to peak. X-ray observations after peak indicate a
softening of the hard X-ray emission prior to peak, reminiscent of the
hard/soft states in X-ray binaries.Comment: 23 pages, 14 figures, 5 tables. A machine-readable table containing
the host-subtracted photometry presented in this manuscript is included as an
ancillary fil
An Amusing Look at the Host of the Periodic Nuclear Transient ASASSN-14ko Reveals a Second AGN
We present Multi-Unit Spectroscopic Explorer (MUSE) integral-field
spectroscopy of ESO 253G003, which hosts a known Active Galactic Nucleus
(AGN) and the periodic nuclear transient ASASSN-14ko, observed as part of the
All-weather MUse Supernova Integral-field of Nearby Galaxies (AMUSING) survey.
The MUSE observations reveal that the inner region hosts two AGN separated by
(\approx 1.\!\!^{\prime\prime}7). The brighter nucleus
has asymmetric broad, permitted emission-line profiles and is associated with
the archival AGN designation. The fainter nucleus does not have a broad
emission-line component but exhibits other AGN characteristics, including
forbidden line emission,
, and high excitation potential
emission lines such as [FeVII] and HeII. The
host galaxy exhibits a disturbed morphology with large kpc-scale tidal
features, potential outflows from both nuclei, and a likely superbubble. A
circular relativistic disk model cannot reproduce the asymmetric broad
emission-line profiles in the brighter nucleus, but two non-axisymmetric disk
models provide good fits to the broad emission-line profiles: an elliptical
disk model and a circular disk + spiral arm model. Implications for the
periodic nuclear transient ASASSN-14ko are discussed.Comment: 20 pages, 16 figures, and 2 tables. Accepted by MNRA
Once is an Instance, Twice is a Hobby: Multiple Optical and Near-Infrared Changing-Look Events in NGC 5273
NGC 5273 is a known optical and X-ray variable AGN. We analyze new and
archival IR, optical, UV, and X-ray data in order to characterize its long-term
variability from 2000 to 2022. At least one changing-look event occurred
between 2011 and 2014, when the AGN changed from a Type 1.8/1.9 Seyfert to a
Type 1. It then faded considerably at all wavelengths, followed by a dramatic
but slow increase in UV/optical brightness between 2021 and 2022. We propose
that NGC 5273 underwent multiple changing-look events between 2000 and 2022 --
starting as a Type 1.8/1.9, NGC 5273 changes-look to a Type 1 only temporarily
in 2002 and again in 2014, reverting back to a Type 1.8/1.9 by 2005 and 2017,
respectively. In 2022, it is again a Type 1 Seyfert with optical and NIR broad
emission lines. We characterize the changing-look events and their connection
to the dynamic accretion and radiative processes in NGC 5273.Comment: 18 pages, 13 figures, 4 tables, submitting to MNRA
ASASSN-14ko is a Periodic Nuclear Transient in ESO 253-G003
We present the discovery that ASASSN-14ko is a periodically flaring AGN at
the center of the galaxy ESO 253-G003. At the time of its discovery by the
All-Sky Automated Survey for Supernovae (ASAS-SN), it was classified as a
supernova close to the nucleus. The subsequent six years of V- and g-band
ASAS-SN observations reveal that ASASSN-14ko has nuclear flares occurring at
regular intervals. The seventeen observed outbursts show evidence of a
decreasing period over time, with a mean period of days
and a period derivative of . The most recent
outburst in May 2020, which took place as predicted, exhibited spectroscopic
changes during the rise and a had a UV bright, blackbody spectral energy
distribution similar to tidal disruption events (TDEs). The X-ray flux
decreased by a factor of 4 at the beginning of the outburst and then returned
to its quiescent flux after ~8 days. TESS observed an outburst during Sectors
4-6, revealing a rise time of days in the optical and a decline
that is best fit with an exponential model. We discuss several possible
scenarios to explain ASASSN-14ko's periodic outbursts, but currently favor a
repeated partial TDE. The next outbursts should peak in the optical on UT
2020-09-7.41.1 and UT 2020-12-26.51.4.Comment: 26 pages, 15 figures, 7 tables. Will be submitted to ApJ. The latest
flare is currently ongoing, as we predicte
What Qualities Are Most Important to Making a Point of Care Test Desirable for Clinicians and Others Offering Sexually Transmitted Infection Testing?
To investigate the possible effects of different levels of attributes of a point-of-care test (POCT) on sexually transmitted infection (STI) professionals' decisions regarding an ideal POCT for STI(s).An online survey was designed based on a large-scale in-depth focus discussion study among STI experts and professionals. The last section of the survey "build your own POCT" was designed by employing the discrete choice experiment approach. Practicing clinicians from two venues, STI-related international conference attendees and U.S. STD clinic clinicians were invited to participate in the survey. Conditional logistical regression modeling was used for data analysis.Overall, 256 subjects took the online survey with 218 (85%) completing it. Most of the participants were STD clinic clinicians who already used some POCTs in their practice. "The time frame required" was identified as a major barrier that currently made it difficult to use STI POCTs. Chlamydia trachomatis was the organism chosen as the top priority for a new POCT, followed by a test that would diagnose early seroconversion for HIV, and a syphilis POCT. Without regard to organism type selected, sensitivity of 90-99% was always the most important attribute to be considered, followed by a cost of $20. However, when the test platform was prioritized for early HIV seroconversion or syphilis, sensitivity was still ranked as most important, but specificity was rated second most important.STI professionals preferred C. trachomatis as the top priority for a new POCT with sensitivity over 90%, low cost, and a very short completion time
The blue supergiant progenitor of the Supernova Imposter at 2019krl
Extensive archival Hubble Space Telescope, Spitzer Space Telescope, and Large Binocular Telescope imaging of the recent intermediate-luminosity transient, AT 2019krl in M74, reveal a bright optical and mid-infrared progenitor star. While the optical peak of the event was missed, a peak was detected in the infrared with an absolute magnitude of M 4.5 μm = -18.4 mag, leading us to infer a visual-wavelength peak absolute magnitude of -13.5 to -14.5. The pre-discovery light curve indicated no outbursts over the previous 16 yr. The colors, magnitudes, and inferred temperatures of the progenitor best match a 13-14 M o˙ yellow or blue supergiant (BSG) if only foreground extinction is taken into account, or a hotter and more massive star if any additional local extinction is included. A pre-eruption spectrum of the star reveals strong Hα and [N ii] emission with wings extending to 2000 km s-1. The post-eruption spectrum is fairly flat and featureless with only Hα, Na i D, [Ca ii], and the Ca ii triplet in emission. As in many previous intermediate-luminosity transients, AT 2019krl shows remarkable observational similarities to luminous blue variable (LBV) giant eruptions, SN 2008S-like events, and massive-star mergers. However, the information about the pre-eruption star favors either a relatively unobscured BSG or a more extinguished LBV with M > 20 Mo˙ likely viewed pole-on.Fil: Andrews, Jennifer E.. University of Arizona; Estados UnidosFil: Jencson, Jacob E.. University of Arizona; Estados UnidosFil: Van Dyk, Schuyler D.. Spitzer Science Center; Estados UnidosFil: Smith, Nathan. University of Arizona; Estados UnidosFil: Neustadt, Jack M. M.. Ohio State University; Estados UnidosFil: Sand, David J.. University of Arizona; Estados UnidosFil: Kreckel, K.. Astronomisches Rechen-institut Heidelberg; AlemaniaFil: Kochanek, C.S.. Ohio State University; Estados UnidosFil: Valenti, S.. University of California at Davis; Estados UnidosFil: Strader, Jay. Michigan State University; Estados UnidosFil: Bersten, Melina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Blanc, Guillermo A.. Universidad de Chile; ChileFil: Bostroem, K. Azalee. University of California at Davis; Estados UnidosFil: Brink, Thomas G.. University of California at Berkeley; Estados UnidosFil: Emsellem, Eric. European Southern Observatory; AlemaniaFil: Filippenko, Alexei V.. University of California at Berkeley; Estados UnidosFil: Folatelli, Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Kasliwal, Mansi. California Institute of Technology; Estados UnidosFil: Masci, Frank J.. Spitzer Science Center; Estados UnidosFil: McElroy, Rebecca. The University Of Sydney; AustraliaFil: Milisavljevic, Dan. Purdue University; Estados UnidosFil: Santoro, Francesco. Max Planck Institut für Astronomie; AlemaniaFil: Szalai, Tamás. University of Szeged; Hungrí
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