An official website of the United States government
We present photometric and spectroscopic data on three extragalactic luminous red novae (LRNe): AT 2018bwo , AT 2021afy , and AT 2021blu . AT 2018bwo was discovered in NGC 45 (at about 6.8 Mpc) a few weeks after the outburst onset. During the monitoring period, the transient reached a peak luminosity of 10 40 erg s −1 . AT 2021afy , hosted by UGC 10043 (∼49.2 Mpc), showed a double-peaked light curve, with the two peaks reaching a similar luminosity of 2.1(±0.6)×10 41 erg s −1 . Finally, for AT 2021blu in UGC 5829 (∼8.6 Mpc), the pre-outburst phase was well-monitored by several photometric surveys, and the object showed a slow luminosity rise before the outburst. The light curve of AT 2021blu was sampled with an unprecedented cadence until the object disappeared behind the Sun, and it was then recovered at late phases. The light curve of LRN AT 2021blu shows a double peak, with a prominent early maximum reaching a luminosity of 6.5 × 10 40 erg s −1 , which is half of that of AT 2021afy . The spectra of AT 2021afy and AT 2021blu display the expected evolution for LRNe: a blue continuum dominated by prominent Balmer lines in emission during the first peak, and a redder continuum consistent with that of a K-type star with narrow absorption metal lines during the second, broad maximum. The spectra of AT 2018bwo are markedly different, with a very red continuum dominated by broad molecular features in absorption. As these spectra closely resemble those of LRNe after the second peak, AT 2018bwo was probably discovered at the very late evolutionary stages. This would explain its fast evolution and the spectral properties compatible with that of an M-type star. From the analysis of deep frames of the LRN sites years before the outburst, and considerations of the light curves, the quiescent progenitor systems of the three LRNe were likely massive, with primaries ranging from about 13 M ⊙ for AT 2018bwo , to 14 −1 +4 M ⊙ for AT 2021blu , and over 40 M ⊙ for AT 2021afy .
more »
« less
Unmanned Aerial Imagery over Stordalen Mire, Northern Sweden, 2016
RGB composite mosaic from over 600 images captured with a Panasonic Lumix-GM1 flown at solar noon aboard a fixed wing Robota Triton unmanned aircraft at approximately 70m above ground. Spatial resolution is 3 cm.
more »
« less
- Award ID(s):
- 2022070
- PAR ID:
- 10591401
- Publisher / Repository:
- Harvard Dataverse
- Date Published:
- Subject(s) / Keyword(s):
- Earth and Environmental Sciences
- Format(s):
- Medium: X Size: 510224536 Other: image/tiff
- Size(s):
- 510224536
- Location:
- Sweden, Lapland,, Abisko,, Stordalen,; (East Bound Longitude:19.049; North Bound Latitude:68.358; South Bound Latitude:68.352; West Bound Longitude:19.044)
- Right(s):
- Custom terms specific to this dataset
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Novel near-infrared ratiometric molecules (probes A and B) produced by linking formyl-functionalized xanthene and methoxybenzene moieties, respectively, onto a xanthene-hemicyanine framework are detailed. Probe A exhibited a primary absorption peak at 780 nm and a shoulder peak at 730 nm and exhibited fluorescence at 740 nm↓ (signifies a downward shift in intensity upon acidification) in a pH 9.3 buffer and 780 nm↑ at pH 2.8 under excitation at 700 nm. Probe B featured absorptions at 618 and 668 nm at pH 3.2 and at 717 nm at pH 8.6, and fluorescence at 693 nm↑ at pH 3.2 and at 739 nm↓ at pH 8.6, in mostly the red to near-IR region. The ratiometric changes in the intensity of the fluorescent absorptions were reversed between A and B upon acidification as indicated by the arrows. Theoretical calculations confirmed that there were slight changes in conformation between probes and the protonated molecules, suggesting that the changes in emission spectra were due mostly to conjugation effects. Calculations at the APFD/6-311+g(d,p) level with a solvent described by the polarizable continuum model resulted in pKa values for A at 6.33 and B at 6.41, in good agreement with the experimentally determined value of 6.97 and an average of 6.40, respectively. The versatilities of the probes were demonstrated in various experimental contexts, including the effective detection of mitochondrial pH fluctuations. Live cell experiments involving exposure to different pH buffers in the presence of H+ ionophores, monitoring mitophagy processes during cell starvation, studying hypoxia induced by CoCl2 treatment, and investigating responses to various oxidative stresses are detailed. Our findings highlight the potential of attaching xanthene and methoxybenzaldehyde groups onto xanthene-hemicyanine structures as versatile tools for monitoring pH changes in a variety of cellular environments and processes.more » « less
-
null (Ed.)We present the results of our monitoring campaigns of the luminous red novae (LRNe) AT 2020hat in NGC 5068 and AT 2020kog in NGC 6106. The two objects were imaged (and detected) before their discovery by routine survey operations. They show a general trend of slow luminosity rise, lasting at least a few months. The subsequent major LRN outbursts were extensively followed in photometry and spectroscopy. The light curves present an initial short-duration peak, followed by a redder plateau phase. AT 2020kog is a moderately luminous event peaking at ∼7 × 10 40 erg s −1 , while AT 2020hat is almost one order of magnitude fainter than AT 2020kog, although it is still more luminous than V838 Mon. In analogy with other LRNe, the spectra of AT 2020kog change significantly with time. They resemble those of type IIn supernovae at early phases, then they become similar to those of K-type stars during the plateau, and to M-type stars at very late phases. In contrast, AT 2020hat already shows a redder continuum at early epochs, and its spectrum shows the late appearance of molecular bands. A moderate-resolution spectrum of AT 2020hat taken at +37 d after maximum shows a forest of narrow P Cygni lines of metals with velocities of 180 km s −1 , along with an H α emission with a full-width at half-maximum velocity of 250 km s −1 . For AT 2020hat, a robust constraint on its quiescent progenitor is provided by archival images of the Hubble Space Telescope. The progenitor is clearly detected as a mid-K type star, with an absolute magnitude of M F 606 W = −3.33 ± 0.09 mag and a colour of F 606 W − F 814 W = 1.14 ± 0.05 mag, which are inconsistent with the expectations from a massive star that could later produce a core-collapse supernova. Although quite peculiar, the two objects nicely match the progenitor versus light curve absolute magnitude correlations discussed in the literature.more » « less
-
Depth profiles of water temperature on 1m intervals from 0.1 to 9 m depth; dissolved oxygen at 5 and 9 m depth; pressure at 9 m depth; and temperature, dissolved oxygen, conductivity, specific conductance, chlorophyll a, phycocyanin, total dissolved solids, fluorescent dissolved organic matter, and pressure at ~1.6 m depth were collected with a suite of high-frequency sensors at Falling Creek Reservoir (Vinton, Virginia, USA) on the 10-minute scale in 2018-2022. Falling Creek Reservoir is owned and managed by the Western Virginia Water Authority as a primary drinking water source for Roanoke, Virginia. This data product consists of one dataset compiled from water temperature data measured at multiple depths by thermistors, two dissolved oxygen sensors at multiple depths, pressure measured at one depth, and a YSI EXO2 sonde that measures temperature, dissolved oxygen, pressure, conductivity, specific conductance, chlorophyll a, phycocyanin, total dissolved solids, and fluorescent dissolved organic matter, at one depth, all measured at the deepest site of the reservoir adjacent to the dam.more » « less
-
Abstract We present phase‐equilibria experiments of a K‐bearing, depleted peridotite (Mg# 92) fluxed with a mixed CO2‐H2O fluid (0.5 wt.% CO2and 0.94 wt.% H2O in the bulk) to gain insight into the stability of volatile‐bearing partial melts versus volatile‐bearing mineral phases in a depleted peridotite system. Experiments were performed at 850–1150 °C and 2–4 GPa using a piston‐cylinder and a multianvil apparatus. Olivine, orthopyroxene, clinopyroxene, and spinel/garnet are present at all experimental conditions. Textural confirmation of partial melt is made at temperatures as low as 1000 °C at 2 GPa, 950 °C at 3 GPa, and 1000 °C at 4 GPa marking the onset of melting at 900–1000 °C at 2 GPa, 850–950 °C at 3 GPa, and 950–1000 °C at 3 GPa. Phlogopite and magnesite breakdown at 900–1000 °C at 2 GPa, 950–1000 °C at 3 GPa, and 1000–1050 °C at 4 GPa. Comparison with previously published experiments in depleted peridotite system with identical CO2‐H2O content introduced via a silicic melt show that introduction of CO2‐H2O as fluid lowers the temperature of phlogopite breakdown by 150–200 °C at 2–4 GPa and stabilizes partial melts at lower temperatures. Our study thus, shows that the volatile‐bearing phase present in the cratonic mantle is controlled by bulk composition and is affected by the process of volatile addition during craton formation in a subduction zone. In addition, volatile introduction via melt versus aqueous fluid, leads to different proportion of anhydrous phases such as olivine and orthopyroxene. Considering the agent of metasomatism is thus critical to evaluate how the bulk composition of depleted peridotite is modified, leading to potential stability of volatile‐bearing phases as the cause of anomalously low shear wave velocity in mantle domains such as mid lithospheric discontinuities beneath continents.more » « less
