8 research outputs found
Discovery and physical characterization as the first response to a potential asteroid collision: The case of 2023 DZ2
Near-Earth asteroids (NEAs) that may evolve into impactors deserve detailed
threat assessment studies. Early physical characterization of a would-be
impactor may help in optimizing impact mitigation plans. We first detected NEA
2023~DZ on 27--February--2023. After that, it was found to have a Minimum
Orbit Intersection Distance (MOID) with Earth of 0.00005~au as well as an
unusually high initial probability of becoming a near-term (in 2026) impactor.
We aim to perform a rapid but consistent dynamical and physical
characterization of 2023~DZ as an example of a key response to mitigate
the consequences of a potential impact. We use a multi-pronged approach,
drawing from various methods (observational/computational) and techniques
(spectroscopy/photometry from multiple instruments), and bringing the data
together to perform a rapid and robust threat assessment.} The visible
reflectance spectrum of 2023~DZ is consistent with that of an X-type
asteroid. Light curves of this object obtained on two different nights give a
rotation period =6.27430.0005 min with an amplitude
=0.570.14~mag. We confirm that although its MOID is among the smallest
known, 2023~DZ will not impact Earth in the foreseeable future as a
result of secular near-resonant behaviour. Our investigation shows that
coordinated observation and interpretation of disparate data provides a robust
approach from discovery to threat assessment when a virtual impactor is
identified. We prove that critical information can be obtained within a few
days after the announcement of the potential impactor.Comment: Accepted for publication in Astronomy and Astrophysics, 15 page
Early Spectroscopy and Dense Circumstellar Medium Interaction in SN~2023ixf
We present the optical spectroscopic evolution of SN~2023ixf seen in
sub-night cadence spectra from 1.18 to 14 days after explosion. We identify
high-ionization emission features, signatures of interaction with material
surrounding the progenitor star, that fade over the first 7 days, with rapid
evolution between spectra observed within the same night. We compare the
emission lines present and their relative strength to those of other supernovae
with early interaction, finding a close match to SN~2020pni and SN~2017ahn in
the first spectrum and SN~2014G at later epochs. To physically interpret our
observations we compare them to CMFGEN models with confined, dense
circumstellar material around a red supergiant progenitor from the literature.
We find that very few models reproduce the blended \NC{} emission lines
observed in the first few spectra and their rapid disappearance thereafter,
making this a unique diagnostic. From the best models, we find a mass-loss rate
of \mlunit{}, which far exceeds the mass-loss rate for any
steady wind, especially for a red supergiant in the initial mass range of the
detected progenitor. These mass-loss rates are, however, similar to rates
inferred for other supernovae with early circumstellar interaction. Using the
phase when the narrow emission features disappear, we calculate an outer dense
radius of circumstellar material and a mean circumstellar material density
of . This is consistent with the
lower limit on the outer radius of the circumstellar material we calculate from
the peak \Halpha{} emission flux, .Comment: Submitted to ApJ
A scanning electron microscope characterisation of biofilm on failed craniofacial osteosynthesis miniplates
Introduction: between 3-18% of craniofacial osteosynthesis plates are removed due to chronic infection. Removal of the plate is necessary to manage the chronic infective state i.e. miniplate removal results in resolution of the infection. These observations are suggestive of a biofilm-related infection. The aim of this retrospective study was to characterise the presence of biofilm on the removed miniplates from oral and maxillofacial surgery.Materials and methods: a total of 12 plates and associated screws were recovered from eleven patients suffering from persistent, trauma site infection. The recovered plates plus 1 control plate were imaged using scanning electron microscopy (SEM). One recovered plate was also imaged using confocal microscopy (CM) for comparative purposes.Results: of the 12 plates, 3 (25%) demonstrated highly localised polymicrobial biofilms, five (42%) demonstrated coccal biofilms, one possessed a filamentous biofilm and one showed attached yeast. Overall, 75% of the plates and 82% of the patients exhibited evidence of biofilm to varying degrees. All of the infections resolved following removal of the plates and antibiotic treatment.Conclusion: microbial biofilms can explain the clinical course of chronic infections associated with miniplates
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Early Spectroscopy and Dense Circumstellar Medium Interaction in SN 2023ixf
We present the optical spectroscopic evolution of SN 2023ixf seen in subnight cadence spectra from 1.18 to 15 days after explosion. We identify high-ionization emission features, signatures of interaction with material surrounding the progenitor star, that fade over the first 7 days, with rapid evolution between spectra observed within the same night. We compare the emission lines present and their relative strength to those of other supernovae with early interaction, finding a close match to SN 2020pni and SN 2017ahn in the first spectrum and SN 2014G at later epochs. To physically interpret our observations, we compare them to CMFGEN models with confined, dense circumstellar material around a red supergiant (RSG) progenitor from the literature. We find that very few models reproduce the blended N iii (λλ4634.0,4640.6)/C iii (λλ4647.5,4650.0) emission lines observed in the first few spectra and their rapid disappearance thereafter, making this a unique diagnostic. From the best models, we find a mass-loss rate of 10−3-10−2 M ⊙ yr−1, which far exceeds the mass-loss rate for any steady wind, especially for an RSG in the initial mass range of the detected progenitor. These mass-loss rates are, however, similar to rates inferred for other supernovae with early circumstellar interaction. Using the phase when the narrow emission features disappear, we calculate an outer dense radius of circumstellar material R CSM,out ≈ 5 × 1014 cm, and a mean circumstellar material density of ρ = 5.6 × 10−14 g cm−3. This is consistent with the lower limit on the outer radius of the circumstellar material we calculate from the peak Hα emission flux, R CSM,out ≳ 9 × 1013 cm. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Early Spectroscopy and Dense Circumstellar Medium Interaction in SN 2023ixf
We present the optical spectroscopic evolution of SN 2023ixf seen in subnight cadence spectra from 1.18 to 15 days after explosion. We identify high-ionization emission features, signatures of interaction with material surrounding the progenitor star, that fade over the first 7 days, with rapid evolution between spectra observed within the same night. We compare the emission lines present and their relative strength to those of other supernovae with early interaction, finding a close match to SN 2020pni and SN 2017ahn in the first spectrum and SN 2014G at later epochs. To physically interpret our observations, we compare them to CMFGEN models with confined, dense circumstellar material around a red supergiant (RSG) progenitor from the literature. We find that very few models reproduce the blended N iii ( λλ 4634.0,4640.6)/C iii ( λλ 4647.5,4650.0) emission lines observed in the first few spectra and their rapid disappearance thereafter, making this a unique diagnostic. From the best models, we find a mass-loss rate of 10 ^−3 –10 ^−2 M _⊙ yr ^−1 , which far exceeds the mass-loss rate for any steady wind, especially for an RSG in the initial mass range of the detected progenitor. These mass-loss rates are, however, similar to rates inferred for other supernovae with early circumstellar interaction. Using the phase when the narrow emission features disappear, we calculate an outer dense radius of circumstellar material R _CSM,out ≈ 5 × 10 ^14 cm, and a mean circumstellar material density of ρ = 5.6 × 10 ^−14 g cm ^−3 . This is consistent with the lower limit on the outer radius of the circumstellar material we calculate from the peak H α emission flux, R _CSM,out ≳ 9 × 10 ^13 cm