| 1. |
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| 2. |
- Akiba, K., et al.
(författare)
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The LHCb VELO Upgrade module construction
- 2024
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Ingår i: Journal of Instrumentation. - : Institute of Physics Publishing (IOPP). - 1748-0221. ; 19:6
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Tidskriftsartikel (refereegranskat)abstract
- The LHCb detector has undergone a major upgrade for LHC Run 3. This Upgrade I detector facilitates operation at higher luminosity and utilises full-detector information at the LHC collision rate, critically including the use of vertex information. A new vertex locator system, the VELO Upgrade, has been constructed. The core element of the new VELO are the double-sided pixelated hybrid silicon detector modules which operate in vacuum close to the LHC beam in a high radiation environment. The construction and quality assurance tests of these modules are described in this paper. The modules incorporate 200 mu m thick, n -on -p silicon sensors bump-bonded to 130 nm technology ASICs. These are attached with high precision to a silicon microchannel substrate that uses evaporative CO 2 cooling. The ASICs are controlled and read out with flexible printed circuits that are glued to the substrate and wire -bonded to the chips. The mechanical support of the module is given by a carbon fibre plate, two carbon fibre rods and an aluminium plate. The sensor attachment was achieved with an average precision of 21 mu m, more than 99.5% of all pixels are fully functional, and a thermal figure of merit of 3 Kcm 2 W - 1 was achieved. The production of the modules was successfully completed in 2021, with the final assembly and installation completed in time for data taking in 2022.
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| 3. |
- Penston, M. V., et al.
(författare)
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The extended narrow line region of NGC 4151. I. Emission line ratios and their implications
- 1990
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 236:1, s. 53-6262
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents the first results from long-slit spectra of the Seyfert galaxy NGC 4151 which give average diagnostic ratios of weak lines in the extended narrow line region (ENLR) of that galaxy and the first direct density measurement in an ENLR. These data confirm that the ENLR is kinematically undisturbed gas in the disc of the galaxy which is illuminated by an ionizing continuum stronger by a factor of 13 than a power law interpolated between observed ultraviolet and X-ray fluxes. Explanations of this apparent excess include a hot thermal continuum, time variations and an anisotropic radiation field. The authors give reasons for favouring anisotropy which might be caused by shadowing by a thick accretion disc or by relativistic beaming. Shadowing by a molecular torus is unlikely, given the absence of an infrared signal from the reradiated flux absorbed by any torus. Anisotropy would have important implications for the bolometric luminosity and nature of active galactic nuclei
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| 4. |
- Dietrich, M., et al.
(författare)
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Monitoring of active galactic nuclei. IV. The Seyfert 1 galaxy NGC 4593
- 1994
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 284:1, s. 33-4343
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Tidskriftsartikel (refereegranskat)abstract
- Results of a five-month campaign of optical monitoring the Seyfert 1 galaxy NGC 4593 are presented. High resolution Halpha and Hbeta spectra and direct images in the Johnson U, B, V, R and I bands were obtained between January and June 1990. The emission lines and the continuum showed strong variations on time scales of weeks to days. The Halpha line varied by more than 30% within only 5 days. Cross-correlating the light curves of the Balmer lines with that of the optical continuum gives a lag of around 4 days. Therefore, this low luminosity Seyfert galaxy may have one of the smallest broad line regions known so far
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| 5. |
- Stirpe, G. M., et al.
(författare)
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Monitoring of active galactic nuclei. V. The Seyfert 1 galaxy Markarian 279
- 1994
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 285:3, s. 857-867867
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Tidskriftsartikel (refereegranskat)abstract
- For pt. IV see ibid., vol.284, no.1, p.33-43 (1994). Reports on the Lovers of Active Galaxies' (LAG) monitoring of the Seyfert 1 galaxy Markarian 279 from January to June 1990. The source, which was in a very bright state, gradually weakened after the first month of monitoring: the Halpha and Hbeta flux decreased by 20% and 35% respectively, and the continuum under Halpha by 30%. The luminosity-weighted radius of the broad line region (BLR), as derived from the cross-correlation function, is of the order of 10 light days. This result is very uncertain because the features in the light curves are very shallow, but it is unlikely that the radius of the BLR is more than 1 light month. The profile variations of Halpha confirm that the prevailing motions are not radial. The data of the present campaign and those obtained in previous years, when the source was in a much weaker state, show that the red asymmetry of the Balmer lines correlates positively with the broad line flux. This new effect is briefly discussed
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| 6. |
- Wanders, I., et al.
(författare)
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Spectroscopic monitoring of active galactic nuclei. II. The Seyfert-1 galaxy NGC 3516
- 1993
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 269:1-2, s. 39-5353
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Tidskriftsartikel (refereegranskat)abstract
- The authors present the results of a five month spectroscopic monitoring campaign of the Seyfert-1 galaxy NGC 3516. Using a new calibration method and applying a correction for seeing differences during the various observations they can scale the spectra to each other with a much higher accuracy than hitherto achieved. NGC 3516 shows large amplitude variations on a time scale of several weeks. Asymmetric profile variations occur on the same time scale as the continuum variations. The authors show the presence of a varying dip on the blue wing of the Hbeta profile, which is not present on the Halpha profile, and which corresponds to the absorption features previously seen in the UV emission lines of NGC 3516. From cross-correlation analysis they find a time lag of 14plusmn2 days for the Halpha and 7plusmn3 days for the Hbeta emission-line response to continuum variations
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| 7. |
- Erkens, U., et al.
(författare)
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Monitoring of active galactic nuclei. VI. The quasar Mrk 876
- 1995
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 296:1, s. 90-9898
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Tidskriftsartikel (refereegranskat)abstract
- For pt. V see ibid., vol. 285, no. 3, p. 857-67 (1994). We present the results of a 6 month monitoring campaign of Mrk 876, a low luminosity quasar with M absap-24. High resolution spectroscopy and direct imaging in the Johnson filters B, V, R, I was carried out in the first half of 1990. Line and continuum light curves are presented. Mrk 876 showed a decrease of 17% in the continuum over the whole observing period whereas the line flux of Hbeta and Halpha stayed constant. This implies, that the radius of the broad line region is larger than 6 light months. Coadded spectra of Hbeta and Halpha are presented which confirm an extreme asymmetry of the line profiles to the red. With respect to much earlier spectra the line profiles changed considerably
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| 8. |
- Jackson, N., et al.
(författare)
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Monitoring of active galactic nuclei. I. The quasars 1302-102 and 1217+023
- 1992
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 262:1, s. 17-2525
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Tidskriftsartikel (refereegranskat)abstract
- Presents the results of a five-month spectroscopic monitoring campaign of two radio-loud quasars PKS 1217+023 and PKS 1302-102. There is a pronounced lack of variability in 1302-102 apart from a possible small change in the continuum level near the end of the monitoring period, but 1217+023 underwent a 20% continuum decrease in the middle of the campaign. No line variability at all was observed. The co-added data represent two of the best spectra yet obtained of any radio-loud quasar other than 3C 273, and the shape of the Hbeta line and the presence underneath it of other contaminating lines are well determined. The Hbeta broad line in 1302-102 is redshifted by 3 Aring with respect to the narrow line region and there is evidence for a separate broad Hbeta feature on top of the main Hbeta emission in both quasars. This feature is stronger in 1217+023 than in 1302-102
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| 9. |
- Salamanca, I., et al.
(författare)
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Spectroscopic monitoring of active galactic nuclei. III. Size of the broad line region in NGC 3227
- 1994
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 282:3, s. 742-752752
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Tidskriftsartikel (refereegranskat)abstract
- For pt.II see ibid., vol.269, no.1-2, p.39-53 (1993). The authors present the results of a five-month monitoring campaign of the active galactic nucleus in NGC 3227. The Hbeta and Halpha emission lines and the optical continuum have been analysed. The optical AGN continuum and the broad-line region (BLR) emission in NGC 3227 appear to vary by about 40% on a timescale of 1.5 month. The levels of the broad-line emission and the 675.0 nm continuum are well correlated, a fact consistent with the assumption that the BLR material is photoionised by the central continuum source. Cross-correlation analyses between the light curves of the 675.0 nm AGN continuum and the BLR H emission indicate that the lag of the BLR emission with respect to the continuum variations is 17plusmn7 days. This result suggests that the BLR clouds that are affected by the changes in the flux of the central ionising source lie about 17 light days away from it
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| 10. |
- Stirpe, G. M., et al.
(författare)
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Broad emission line variability in the Seyfert 1 galaxies NGC 5548 and NGC 3783
- 1988
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 200:1-2, s. 9-1616
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Tidskriftsartikel (refereegranskat)abstract
- High quality spectra are presented for the Seyfert 1 galaxies NGC 5548 and NGC 3783. Halpha and Hbeta were observed at different epochs, with time intervals between 4 and 13 months. The spectra have been scaled to each other by normalizing the flux of the narrow lines. The difference spectra show that the broad emission lines have varied not only in flux, but also in shape. The authors compare their data with those published by Peterson (1987) and Peterson et al. (1987) and conclude that the supermassive binary scenario proposed by the latter is not unique. The observed variations can be interpreted in an accretion disk scenario. The whole data-set also provides evidence against models based on outflowing motion. The He II lambda4686 line discussed together with N III lambda4640 Bowen emission. A limit to the results is given by the long time intervals separating the observations, which do not allow the authors to set as strong constraints on the BLR as high quality, frequent monitoring of Seyfert 1 spectra would
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