20 research outputs found
Tension Between the Cartagena Protocol and the WTO: The Significance of Recent WTO Developments in an Ongoing Debate
Disputes recently decided and pending before the WTO will significantly affect prior analyses of the conflict between treaties. A recent WTO Appellate Body decision against Japan concerning import restrictions on apples ( Apples ) sheds light on how the SPS Agreement interacts with trade restrictions based on environmental concerns. Also, a pending panel dispute addressing trade restrictions on LMOs ( Biotech Products ) will provide significant guidance as to how the WTO will resolve the conflict between the two treaties. This Development does not examine all potential conflicts between the treaties, but instead focuses on what these two WTO disputes mean for those conflicts. Part I of this Development provides background on the Protocol, the SPS Agreement, and their potential for conflict. Part II analyzes the Apples decision and its significance for the conflict between the two treaties. Part III examines the pending dispute before the WTO concerning a European Community ( EC ) trade moratorium on LMOs and the implications of the dispute for the Cartagena Protocol. Finally, Part IV considers the significance of these disputes in understanding the relationship between the two treaties
Supernova 2014J at M82 – II. Direct analysis of a middle-class Type Ia supernova
We analyze a time series of optical spectra of SN 2014J from almost two weeks prior to maximum to nearly four months after maximum. We perform our analysis using the SYNOW code, which is well suited to track the distribution of the ions with velocity in the ejecta. We show that almost all of the spectral features during the entire epoch can be identified with permitted transitions of the common ions found in normal SNe Ia in agreement with previous studies. We show that 2014J is a relatively normal SN Ia. At early times the spectral features are dominated by Si II, S II, Mg II, and Ca II. These ions persist to maximum light with the appearance of Na I and Mg I. At later times iron-group elements also appear, as expected in the stratified abundance model of the formation of normal type Ia SNe. We do not find significant spectroscopic evidence for oxygen, until 100 days after maximum light. The +100 day identification of oxygen is tentative, and would imply significant mixing of unburned or only slight processed elements down to a velocity of 6,000 km~s−1. Our results are in relatively good agreement with other analyses in the IR. We briefly compare SN 2011fe to SN 2014J and conclude that the differences could be due to different central densities at ignition or differences in the C/O ratio of the progenitors
Revealing AGNs Through TESS Variability
We used Transiting Exoplanet Survey Satellite (TESS) data to identify 29
candidate active galactic nuclei (AGNs) through their optical variability. The
high-cadence, high-precision TESS light curves present a unique opportunity for
the identification of AGNs, including those not selected through other methods.
Of the candidates, we found that 18 have either previously been identified as
AGNs in the literature or could have been selected based on emission-line
diagnostics, mid-IR colors, or X-ray luminosity. AGNs in low-mass galaxies
offer a window into supermassive black hole (SMBH) and galaxy co-evolution and
8 of the 29 candidates have estimated black hole masses . The low-mass galaxies NGC 4395 and NGC 4449 are two of our
five "high-confidence" candidates. By applying our methodology to the entire
TESS main and extended mission datasets, we expect to identify 45 more
AGN candidates, of which 26 will be new and 8 will be in low-mass
galaxies.Comment: 21 pages, 17 figures, 6 tables. Will be submitted to AAS journals.
Comments welcom
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
Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko
ASASSN-14ko is a nuclear transient at the center of the AGN ESO 253-G003 that
undergoes periodic flares. Optical flares were first observed in 2014 by the
All-Sky Automated Survey for Supernovae (ASAS-SN) and their peak times are
well-modeled with a period of days and period derivative
of . Here we present ASAS-SN, Chandra, HST/STIS, NICER,
Swift, and TESS data for the flares that occurred in December 2020, April 2021,
July 2021, and November 2021. The HST/STIS UV spectra evolve from blue shifted
broad absorption features to red shifted broad emission features over 10
days. The Swift UV/optical light curves peaked as predicted by the timing
model, but the peak UV luminosities varied between flares and the UV flux in
July 2021 was roughly half the brightness of all other peaks. The X-ray
luminosities consistently decreased and the spectra became harder during the
UV/optical rise but apparently without changes in absorption. Finally, two
high-cadence TESS light curves from December 2020 and November 2018 showed that
the slopes during the rising and declining phases changed over time, which
indicates some stochasticity in the flare's driving mechanism. ASASSN-14ko
remains observationally consistent with a repeating partial tidal disruption
event, but, these rich multi-wavelength data are in need of a detailed
theoretical model.Comment: 25 pages, 14 figures, 4 tables; Submitted to ApJ, comments welcom
TESS Shines Light on the Origin of the Ambiguous Nuclear Transient ASASSN-18el
We analyze high-cadence data from the Transiting Exoplanet Survey Satellite
(TESS) of the ambiguous nuclear transient (ANT) ASASSN-18el. The optical
changing-look phenomenon in ASASSN-18el has been argued to be due to either a
drastic change in the accretion rate of the existing active galactic nucleus
(AGN) or the result of a tidal disruption event (TDE). Throughout the TESS
observations, short-timescale stochastic variability is seen, consistent with
an AGN. We are able to fit the TESS light curve with a damped-random-walk (DRW)
model and recover a rest-frame variability amplitude of mJy and a rest-frame timescale of days.
We find that the estimated for ASASSN-18el is broadly consistent
with an apparent relationship between the DRW timescale and central
supermassive black hole mass. The large-amplitude stochastic variability of
ASASSN-18el, particularly during late stages of the flare, suggests that the
origin of this ANT is likely due to extreme AGN activity rather than a TDE.Comment: 13 pages, 8 figures. Will be submitted to AAS journals. Comments
welcom
Examining the Properties of Low-Luminosity Hosts of Type Ia Supernovae from ASAS-SN
We present a spectroscopic analysis of 44 low-luminosity host galaxies of
Type Ia supernovae (SNe Ia) detected by the All-Sky Automated Survey for
Supernovae (ASAS-SN), using the emission lines to measure metallicities and
star formation rates. We find that although the star formation activity of our
sample is representative of general galaxies, there is some evidence that the
lowest-mass SN Ia host galaxies (log()) in our sample have
high metallicities compared to general galaxies of similar masses. We also
identify a subset of 5 galaxies with particularly high metallicities. This
highlights the need for spectroscopic analysis of more low-luminosity, low-mass
SN Ia host galaxies to test the robustness of these conclusions and their
potential impact on our understanding of SN Ia progenitors.Comment: 13 pages, 7 figures, 2 tables. Submitted to ApJ. Full versions of the
tables in the paper are available in machine-readable format as ancillary
file
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