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- Dorn, R. J., et al.
(författare)
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CRIRES+ on sky at the ESO Very Large Telescope : Observing the Universe at infrared wavelengths and high spectral resolution
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 671
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Tidskriftsartikel (refereegranskat)abstract
- The CRyogenic InfraRed Echelle Spectrograph (CRIRES) Upgrade project CRIRES+ extended the capabilities of CRIRES. It transformed this VLT instrument into a cross-dispersed spectrograph to increase the wavelength range that is covered simultaneously by up to a factor of ten. In addition, a new detector focal plane array of three Hawaii 2RG detectors with a 5.3 mu m cutoff wavelength replaced the existing detectors. Amongst many other improvements, a new spectropolarimetric unit was added and the calibration system has been enhanced. The instrument was installed at the VLT on Unit Telescope 3 at the beginning of 2020 and successfully commissioned and verified for science operations during 2021, partly remotely from Europe due to the COVID-19 pandemic. The instrument was subsequently offered to the community from October 2021 onwards. This article describes the performance and capabilities of the upgraded instrument and presents on sky results.
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- Kamann, S., et al.
(författare)
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The effects of stellar rotation along the main sequence of the 100-Myr-old massive cluster NGC 1850
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 518:1, s. 1505-1521
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Tidskriftsartikel (refereegranskat)abstract
- Young star clusters enable us to study the effects of stellar rotation on an ensemble of stars of the same age and across a wide range in stellar mass and are therefore ideal targets for understanding the consequences of rotation on stellar evolution. We combine MUSE spectroscopy with HST photometry to measure the projected rotational velocities (Vsin i) of 2184 stars along the split main sequence and on the main sequence turn-off (MSTO) of the 100 Myr-old massive (10(5) M-circle dot) star cluster NGC 1850 in the Large Magellanic Cloud. At fixed magnitude, we observe a clear correlation between Vsin i and colour, in the sense that fast rotators appear redder. The average Vsin i values for stars on the blue and red branches of the split main sequence are similar to 100 km s(-1) and similar to 200 km s(-1), respectively. The values correspond to about 25 - 30 per cent and 50 - 60 per cent of the critical rotation velocity and imply that rotation rates comparable to those observed in field stars of similar masses can explain the split main sequence. Our spectroscopic sample contains a rich population of similar to 200 fast rotating Be stars. The presence of shell features suggests that 23 per cent of them are observed through their decretion discs, corresponding to a disc opening angle of 15 degrees. These shell stars can significantly alter the shape of the MSTO, hence care should be taken when interpreting this photometric feature. Overall, our findings impact our understanding of the evolution of young massive clusters and provide new observational constraints for testing stellar evolutionary models.
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| 4. |
- Nagao, T., et al.
(författare)
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Evidence for multiple origins of fast declining Type II supernovae from spectropolarimetry of SN 2013ej and SN 2017ahn
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 505:3, s. 3664-3680
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Tidskriftsartikel (refereegranskat)abstract
- The origin of the diverse light-curve shapes of Type II supernovae (SNe), and whether they come from similar or distinct progenitors, has been actively discussed for decades. Here, we report spectropolarimetry of two fast declining Type II (Type IIL) SNe: SN 2013ej and SN 2017ahn. SN 2013ej exhibited high continuum polarization from very soon after the explosion to the radioactive tail phase with time-variable polarization angles. The origin of this polarimetric behaviour can be interpreted as the combination of two different aspherical structures, namely an aspherical interaction of the SN ejecta with circumstellar matter (CSM) and an inherently aspherical explosion. Aspherical explosions are a common feature of slowly declining Type II (Type IIP) SNe. By contrast, SN 2017ahn showed low polarization not only in the photospheric phase but also in the radioactive tail phase. This low polarization in the tail phase, which has never before been observed in other Type IIP/L SNe, suggests that the explosion of SN 2017ahn was nearly spherical. These observations imply that Type IIL SNe have, at least, two different origins: they result from stars that have different explosion properties and/or different mass-loss processes. This fact might indicate that 13ej-like Type IIL SNe originate from a similar progenitor to those of Type IIP SNe accompanied by an aspherical CSM interaction, while 17ahn-like Type IIL SNe come from a more massive progenitor with less hydrogen in its envelope.
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| 5. |
- Weiss, W. W., et al.
(författare)
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New BRITE-Constellation observations of the roAp star α Cir⋆
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 642
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Tidskriftsartikel (refereegranskat)abstract
- Context. Chemically peculiar (CP) stars with a measurable magnetic field comprise the group of mCP stars. The pulsating members define the subgroup of rapidly oscillating Ap (roAp) stars, of which alpha Cir is the brightest member. Hence, alpha Cir allows the application of challenging techniques, such as interferometry, very high temporal and spectral resolution photometry, and spectroscopy in a wide wavelength range, that have the potential to provide unique information about the structure and evolution of a star.Aims. Based on new photometry from BRITE-Constellation, obtained with blue and red filters, and on photometry from WIRE, SMEI, and TESS we attempt to determine the surface spot structure of alpha Cir and investigate pulsation frequencies.Methods. We used photometric surface imaging and frequency analyses and Bayesian techniques in order to quantitatively compare the probability of different models.Results. BRITE-Constellation photometry obtained from 2014 to 2016 is put in the context of space photometry obtained by WIRE, SMEI, and TESS. This provides improvements in the determination of the rotation period and surface features (three spots detected and a fourth one indicated). The main pulsation frequencies indicate two consecutive radial modes and one intermediate dipolar mode. Advantages and problems of the applied Bayesian technique are discussed.
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| 6. |
- Claeson, Magdalena, 1976, et al.
(författare)
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Clinicopathological factors associated with death from thin (<= 1 center dot 00 mm) melanoma
- 2020
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Ingår i: British Journal of Dermatology. - : Oxford University Press (OUP). - 0007-0963 .- 1365-2133. ; 182:4, s. 927-931
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Tidskriftsartikel (refereegranskat)abstract
- Background Thin cutaneous melanomas (<= 1 center dot 00 mm) are increasing worldwide, causing around a quarter of all melanoma deaths in the U.S.A. and Australia. Identification of predictive factors for potentially fatal thin melanomas could allow better use of resources for follow-up. Objectives To identify the clinicopathological factors associated with fatal thin melanomas. Methods This large, nested case-case study extracted data from the population-based Queensland Cancer Registry, Australia. Our cohort consisted of Queensland residents aged 0-89 years who were diagnosed with a single, locally invasive thin melanoma (<= 1 center dot 00 mm) between 1995 and 2014. Fatal cases (eligible patients who died from melanoma) were individually matched to three nonfatal cases (eligible patients who were not known to have died from melanoma) according to sex, age, year of diagnosis and follow-up interval. Using conditional logistic regression, we calculated odds ratios (ORs) for melanoma-specific death, adjusting for all collected clinicopathological variables. Results In the cohort, 27 660 eligible patients were diagnosed with a single, thin melanoma. The final case-case series included 424 fatal cases and 1189 nonfatal cases. Fatal cases were sixfold as likely to arise on the scalp as on the back [OR 6 center dot 39, 95% confidence interval (CI) 2 center dot 57-15 center dot 92] and six times as likely to be of thickness 0 center dot 80-1 center dot 00 mm as of < 0 center dot 30 mm (OR 6 center dot 00, 95% CI 3 center dot 55-10 center dot 17). Conclusions Scalp location is a strong prognostic factor of death from thin melanoma. Further, this study provides support that melanomas with a thickness of 0 center dot 80-1 center dot 00 mm are the more hazardous thin lesions. Patients with these tumour characteristics require specific attention during follow-up. What's already known about this topic? Thin invasive melanomas (<= 1 center dot 00 mm) contribute a substantial proportion of melanoma fatalities, owing to the high volume of disease. There is a need to find prognostic factors that will better identify fatal thin melanomas at the time of diagnosis. What does this study add? In this large population-based study, fatal thin tumours were sixfold as likely to be located on the scalp as on the back. Thin melanomas of 0 center dot 80-1 center dot 00 mm thickness were six times as likely to be associated with death as tumours < 0 center dot 30 mm. Scalp location and increasing thickness are strong predictive factors of fatal thin melanomas, indicating that patients with these tumour characteristics require close follow-up.
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| 9. |
- Yang (杨轶), Yi, et al.
(författare)
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The interaction of supernova 2018evt with a substantial amount of circumstellar matter – An SN 1997cy-like event
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 519:2, s. 1618-1647
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Tidskriftsartikel (refereegranskat)abstract
- A rare class of supernovae (SNe) is characterized by strong interaction between the ejecta and several solar masses of circumstellar matter (CSM) as evidenced by strong Balmer-line emission. Within the first few weeks after the explosion, they may display spectral features similar to overluminous Type Ia SNe, while at later phase their observation properties exhibit remarkable similarities with some extreme case of Type IIn SNe that show strong Balmer lines years after the explosion. We present polarimetric observations of SN 2018evt obtained by the ESO Very Large Telescope from 172 to 219 d after the estimated time of peak luminosity to study the geometry of the CSM. The non-zero continuum polarization decreases over time, suggesting that the mass-loss of the progenitor star is aspherical. The prominent H α emission can be decomposed into a broad, time-evolving component and an intermediate-width, static component. The former shows polarized signals, and it is likely to arise from a cold dense shell (CDS) within the region between the forward and reverse shocks. The latter is significantly unpolarized, and it is likely to arise from shocked, fragmented gas clouds in the H-rich CSM. We infer that SN 2018evt exploded inside a massive and aspherical circumstellar cloud. The symmetry axes of the CSM and the SN appear to be similar. SN 2018evt shows observational properties common to events that display strong interaction between the ejecta and CSM, implying that they share similar circumstellar configurations. Our preliminary estimate also suggests that the circumstellar environment of SN 2018evt has been significantly enriched at a rate of ∼0.1 M⊙ yr−1 over a period of >100 yr.
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