| 1. |
- Poley, L., et al.
(författare)
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The ABC130 barrel module prototyping programme for the ATLAS strip tracker
- 2020
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Ingår i: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221. ; 15:9
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Tidskriftsartikel (refereegranskat)abstract
- For the Phase-II Upgrade of the ATLAS Detector [1], its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100% silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-250) [2, 3] and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.
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| 2. |
- Harper, G. M., et al.
(författare)
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SOFIA-EXES Mid-IR Observations of [Fe II] Emission from the Extended Atmosphere of Betelgeuse
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 836:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a NASA-DLR SOFIA-Echelon Cross Echelle Spectrograph (EXES) and NASA Infrared Telescope Facility-Texas Echelon Cross Echelle Spectrograph (TEXES) mid-IR R ≃ 50,000 spectral study of forbidden Fe II transitions in the early-type M supergiants, Betelgeuse (α Ori: M2 Iab) and Antares (α Sco: M1 Iab + B3 V). With EXES, we spectrally resolve the ground term [Fe II] 25.99 μm ( a 6DJ= 7/2-9/2: Eup = 540 K) emission from Betelgeuse. We find a small centroid blueshift of 1.9 ± 0.4 km s-1 that is a significant fraction (20%) of the current epoch wind speed, with a FWHM of 14.3 ± 0.1 km s-1. The TEXES observations of [Fe II] 17.94 μm (a 4FJ= - 7/2 9/2: Eup = 3400 K) show a broader FWHM of 19.1 ± 0.2 km s-1, consistent with previous observations, and a small redshift of 1.6 ± 0.6 km s-1 with respect to the adopted stellar center-ofmass velocity of VCoM = 20.9 ± 0.3 km s-1. To produce [Fe II] 25.99 μm blueshifts of 20% wind speed requires that the emission arises closer to the star than existing thermal models for α Ori's circumstellar envelope predict. This implies a more rapid wind cooling to below 500 K within 10R∗ (q∗ = 44 mas, dist = 200 pc) of the star, where the wind has also reached a significant fraction of the maximum wind speed. The line width is consistent with the turbulence in the outflow being close to the hydrogen sound speed. EXES observations of [Fe II] 22.90 μm ( a 4DJ= 5/2-7/2: Eup = 11,700 K) reveal no emission from either star. These findings confirm the dominance of cool plasma in the mixed region where hot chromospheric plasma emits copiously in the UV, and they also constrain the wind heating produced by the poorly understood mechanisms that drive stellar outflows from these low variability and weak-dust signature stars.
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| 3. |
- Indriolo, Nick, et al.
(författare)
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High Spectral Resolution Observations toward Orion BN at 6 μm: No Evidence for Hot Water
- 2018
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 865:2
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Tidskriftsartikel (refereegranskat)abstract
- The Becklin-Neugebauer (BN) object in Orion has a large proper motion and radial velocity with respect to the gas and other stars in the region where it is presumed to have formed. Multiple dynamical interaction scenarios have been proposed to explain this motion. In one case BN is thought to have interacted with stars in the Trapezium cluster, while in another it is thought to have interacted with source I while deeply embedded in molecular gas. If there is dense gas that has been retained in close proximity to BN, it may be evidence that the latter scenario is favored. We observed BN at high spectral resolution in three windows near 6 mu m using the Echelon-Cross-Echelle Spectrograph on board the Stratospheric Observatory for Infrared Astronomy targeting the nu(2) vibrational band of H2O. Absorption from only three transitions of H2O is detected, and through kinematic analysis is associated with cool, dense foreground gas, not BN itself. We find no evidence for H2O absorption or emission at the systemic velocity of BN.
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| 4. |
- Indriolo, Nick, et al.
(författare)
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SOFIA/EXES observations of water absorption in the protostar AFGL 2591 at high spectral resolution
- 2015
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Ingår i: Astrophysical Journal Letters. - 2041-8213. ; 802:2
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Tidskriftsartikel (refereegranskat)abstract
- We present high spectral resolution (similar to 3 km s(-1)) observations of the nu(2) ro-vibrational band of H2O in the 6.086-6.135 mu m range toward the massive protostar AFGL 2591 using the Echelon-Cross-Echelle Spectrograph (EXES) on the Stratospheric Observatory for Infrared Astronomy (SOFIA). Ten absorption features are detected in total, with seven caused by transitions in the nu(2) band of H2O, two by transitions in the first vibrationally excited nu(2) band of H2O, and one by a transition in the nu(2) band of (H2O)-O-18. Among the detected transitions is the nu(2) 1(1,1)-0(0,0) line that probes the lowest-lying rotational level of para-H2O. The stronger transitions appear to be optically thick, but reach maximum absorption at a depth of about 25%, suggesting that the background source is only partially covered by the absorbing gas or that the absorption arises within the 6 mu m emitting photosphere. Assuming a covering fraction of 25%, the H2O column density and rotational temperature that best fit the observed absorption lines are N(H2O) = (1.3 +/- 0.3) x 10(19) cm(-2) and T = 640 +/- 80 K.
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| 5. |
- Encrenaz, T., et al.
(författare)
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A map of D/H on Mars in the thermal infrared using EXES aboard SOFIA
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 586
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Tidskriftsartikel (refereegranskat)abstract
- On a planetary scale, the D/H ratio on Mars is a key diagnostic for understanding the past history of water on the planet; locally, it can help to constrain the sources and sinks of water vapor through the monitoring of condensation and sublimation processes. To obtain simultaneous measurements of H2O and HDO lines, we have used the Echelle Cross Echelle Spectrograph (EXES) instrument aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) facility to map the abundances of these two species over the Martian disk. High-resolution spectra (R = 6 × 104) were recorded in the 1383-1390 cm-1 range (7.2 μm) on April 08, 2014. Mars was very close to opposition and near northern summer solstice (Ls = 113°). Maps of the H2O and HDO mixing ratios were retrieved from the line depth ratios of weak H2O and HDO transitions divided by a weak CO2 line. As expected for this season, the H2O and HDO maps show a distinct enhancement toward polar regions, and their mixing ratios are consistent with previous measurements and with predictions by the global climate models, except at the north pole where the EXES values are weaker. We derive a disk-integrated D/H ratio of 6.8 (+1.6, -1.0) × 10-4. It is higher than the value in Earth's oceans by a factor 4.4 (+1.0, -0.6). The D/H map also shows an enhancement from southern to northern latitudes, with values ranging from about 3.5 times to 6.0 times the VSMOW (Vienna standard mean ocean water) value. The D/H distribution shows a depletion over the Tharsis mountains and is consistent with observed latitudinal variations. The variations in D/H with latitude and altitude agree with the models and with the isotope fractionation expected from condensation and sublimation processes.
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| 6. |
- Ryde, N., et al.
(författare)
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Evolved Stars with Complex Atmospheres - the High Spectral Resolution, mid-IR View
- 2015
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Ingår i: Why galaxies care about AGB stars III. - : ASTRONOMICAL SOC PACIFIC. - 9781583818794 - 9781583818787 ; , s. 67-71
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Konferensbidrag (refereegranskat)abstract
- The physical structures of the outer atmospheres of red giants are not known. They are certainly complex, and a range of recent observations are showing that we need to embrace non-classical model atmospheres to interpret these regions. This region's properties are of importance, not the least for an understanding of the mass-loss mechanism for these stars. Here we present observational constraints on the outer regions of red giants, based on mid-IR, high spectral resolution spectra. We also discuss possible non-LTE effects and highlight a new non-LTE code that will be used to analyse the spectra of these atmospheric layers. We conclude by mentioning our new SOFIA/EXES observations of red giants at 67 mu m, where the vibration-rotation lines of water vapour can be detected and spectrally resolved for the first time.
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