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| 54. |
- Wallström, Sofia, 1988, et al.
(författare)
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ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA
- 2024
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 681
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Tidskriftsartikel (refereegranskat)abstract
- Context. The dusty winds of cool evolved stars are a major contributor of the newly synthesised material enriching the Galaxy and future generations of stars. However, the details of the physics and chemistry behind dust formation and wind launching have yet to be pinpointed. Recent spatially resolved observations show the importance of gaining a more comprehensive view of the circumstellar chemistry, but a comparative study of the intricate interplay between chemistry and physics is still difficult because observational details such as frequencies and angular resolutions are rarely comparable. Aims. Aiming to overcome these deficiencies, ATOMIUM is an ALMA Large Programme to study the physics and chemistry of the circumstellar envelopes of a diverse set of oxygen-rich evolved stars under homogeneous observing conditions at three angular resolutions between ∼0.02′1.4′. Here we summarize the molecular inventory of these sources, and the correlations between stellar parameters and molecular content. Methods. Seventeen oxygen-rich or S-Type asymptotic giant branch (AGB) and red supergiant (RSG) stars have been observed in several tunings with ALMA Band 6, targeting a range of molecules to probe the circumstellar envelope and especially the chemistry of dust formation close to the star. We systematically assigned the molecular carriers of the spectral lines and measured their spectroscopic parameters and the angular extent of the emission of each line from integrated intensity maps. Results. Across the ATOMIUM sample, we detect 291 transitions of 24 different molecules and their isotopologues. This includes several first detections in oxygen-rich AGB/RSG stars: PO v = 1, SO2 v1 = 1 and v2 = 2, and several high energy H2O transitions. We also find several first detections in S-Type AGB stars: vibrationally excited HCN v2 = 2,3 and SiS v = 4,5,6, as well as first detections of the molecules SiC, AlCl, and AlF in W Aql. Overall, we find strong correlations between the following molecular pairs: CS and SiS, CS and AlF, NaCl and KCl, AlO and SO, SO2 and SO, and SO2 and H2O; meaning both molecules tend to have more detected emission lines in the same sources. The measured isotopic ratios of Si and S are found to be consistent with previous measurements, except for an anomalously high 29Si/30Si ratio of 4 ± 1 in the RSG VX Sgr. Conclusions. This paper presents the overall molecular inventory and an initial analysis of the large ATOMIUM dataset, laying the groundwork for future work deriving molecular abundances and abundance profiles using radiative transfer modeling which will provide more rigorous tests for chemical models.
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| 56. |
- Albert, Damien, et al.
(författare)
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A Decade with VAMDC : Results and Ambitions
- 2020
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Ingår i: Atoms. - : MDPI. - 2218-2004. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of the VAMDC e-infrastructure. We analyse the past 10 years of VAMDC development and operation, and assess their impact both on the field of atomic and molecular (A&M) physics itself and on heterogeneous data management in international cooperation. The highly sophisticated VAMDC infrastructure and the related databases developed over this long term make them a perfect resource of sustainable data for future applications in many fields of research. However, we also discuss the current limitations that prevent VAMDC from becoming the main publishing platform and the main source of A&M data for user communities, and present possible solutions under investigation by the consortium. Several user application examples are presented, illustrating the benefits of VAMDC in current research applications, which often need the A&M data from more than one database. Finally, we present our vision for the future of VAMDC.
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| 57. |
- Ashelford, Kevin, et al.
(författare)
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Full genome re-sequencing reveals a novel circadian clock mutationin Arabidopsis
- 2011
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Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X. ; 12, s. R28-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Map based cloning in Arabidopsis thaliana can be a difficult and time-consuming process,specifically if the phenotype is subtle and scoring labour intensive. An alternative to map basedcloning would be to directly sequence the whole genome of a mutant to uncover the mutationresponsible for the phenotype. Results: Here, we have re-sequenced the 120 Mb genome of a novel Arabidopsis clock mutant earlybird (ebi-1), using massively parallel sequencing by ligation. This process was further complicated by the fact that ebi-1 is in Wassilewskija (Ws-2), not the reference accession ofArabidopsis. The approach reveals evidence of DNA strand bias in the ethyl methanesulfonate(EMS) mutation process. We have demonstrated the utility of sequencing a backcrossed line andusing gene expression data to limit the number of SNP considered. Using new SNP informationwe have excluded a previously identified clock gene, PRR7. Finally, we have identified a SNPin the gene AtNFXL-2 as the likely cause of the ebi-1 phenotype and validated this bycharacterising a further allele. Conclusion: In Arabidopsis, as in other organisms, the (EMS) mutation load can be high. Here wedescribe how sequencing a backcrossed line, using functional genomics and analysing new SNPinformation can be used to reduce the number EMS mutations for consideration. Moreover, theapproach we describe here does not require out-crossing and scoring F2 mapping populations, anapproach which can be compromised by background effects. The strategy has broad utility andwill be an extremely useful tool to identify causative SNP in other organisms.
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| 58. |
- Cawood, Peter A., et al.
(författare)
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Neoproterozoic to early Paleozoic extensional and compressional history of East Laurentian margin sequences : The Moine Supergroup, Scottish Caledonides
- 2015
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Ingår i: Geological Society of America Bulletin. - 0016-7606 .- 1943-2674. ; 127:3-4, s. 349-371
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Tidskriftsartikel (refereegranskat)abstract
- Neoproterozoic siliciclastic-dominated sequences are widespread along the eastern margin of Laurentia and are related to rifting associated with the breakout of Laurentia from the supercontinent Rodinia. Detrital zircons from the Moine Supergroup, NW Scotland, yield Archean to early Neoproterozoic U-Pb ages, consistent with derivation from the Grenville-Sveconorwegian orogen and environs and accumulation post–1000 Ma. U-Pb zircon ages for felsic and associated mafic intrusions confirm a widespread pulse of extension-related magmatism at around 870 Ma. Pegmatites yielding U-Pb zircon ages between 830 Ma and 745 Ma constrain a series of deformation and metamorphic pulses related to Knoydartian orogenesis of the host Moine rocks. Additional U-Pb zircon and monazite data, and 40Ar/39Ar ages for pegmatites and host gneisses indicate high-grade metamorphic events at ca. 458–446 Ma and ca. 426 Ma during the Caledonian orogenic cycle.The presence of early Neoproterozoic siliciclastic sedimentation and deformation in the Moine and equivalent successions around the North Atlantic and their absence along strike in eastern North America reflect contrasting Laurentian paleogeography during the breakup of Rodinia. The North Atlantic realm occupied an external location on the margin of Laurentia, and this region acted as a locus for accumulation of detritus (Moine Supergroup and equivalents) derived from the Grenville-Sveconorwegian orogenic welt, which developed as a consequence of collisional assembly of Rodinia. Neoproterozoic orogenic activity corresponds with the inferred development of convergent plate-margin activity along the periphery of the supercontinent. In contrast in eastern North America, which lay within the internal parts of Rodinia, sedimentation did not commence until the mid-Neoproterozoic (ca. 760 Ma) during initial stages of supercontinent fragmentation. In the North Atlantic region, this time frame corresponds to a second pulse of extension represented by units such as the Dalradian Supergroup, which unconformably overlies the predeformed Moine succession.
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| 59. |
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| 60. |
- Danilovich, Taissa, 1987, et al.
(författare)
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Chemical tracers of a highly eccentric AGB–main-sequence star binary
- 2024
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Ingår i: Nature Astronomy. - 2397-3366. ; 8, s. 308-327
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Tidskriftsartikel (refereegranskat)abstract
- Binary interactions have been proposed to explain a variety of circumstellar structures seen around evolved stars, including asymptotic giant branch (AGB) stars and planetary nebulae. Studies resolving the circumstellar envelopes of AGB stars have revealed spirals, disks and bipolar outflows, with shaping attributed to interactions with a companion. Here we use a combined chemical and dynamical analysis to reveal a highly eccentric and long-period orbit for W Aquilae, a binary system containing an AGB star and a main-sequence companion. Our results are based on anisotropic SiN emission, the detections of irregular NS and SiC emission towards the S-type star, and density structures observed in the CO emission. These features are all interpreted as having formed during periastron interactions. Our astrochemistry-based method can yield stringent constraints on the orbital parameters of long-period binaries containing AGB stars, and will be applicable to other systems.
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