Suchergebnisse

The spatial decentralisation of urban firms has been the primary focus of urbanists seeking to understand how Black employment is impacted by the changing nature of business in the US. Very little attention has been given to the impact of market concentration on Black employment in the urban environment. Using the most recent data available from the Equal Employment Opportunity Commission, the paper finds that Black male and female employment is positively associated with greater market concentration, not greater market competition as predicted by some neo-classical economists. There is little support for the contention that economic forces at work in competitive markets tend to minimise discrimination, either in the urban environment, or in the nation as a whole. The central city continues to be an important factor in Black employment because central-city firms are in industries with higher market concentration, which tend to employ more Black workers. However, increased market concentration is a crucial element in Black employment, regardless of industry location or worker occupation.

SUMMARY Three problems with areal data collection units are identified, namely aggregation levels, areal boundaries and the size and shape of areal units. Examples are drawn from Malawi.RESUME Les Techniques de Planification : les Unités chargées de la Collecte des Données Zonales, et la migration au MalawiTrois problèmes sont précisés, relatifs à des unités chargées de la collecte des données zonales, en particulier des niveaux d'aggrégatton, de la délimitation zonale ainsi que des taille et forme des zones. Les exemples fournis proviennent du Malawi.RESUMEN Técnicas de Planificación : Unidades de Recolección de Datos por Areas y Migración en MalawiSe identifican tres problemas en relación con las unidades de recolección de datos por áreas, a saber, niveles de agregación, delimitación de las áreas y tamaño y forma de las unidades de área. Se usan ejemplos de Malawi.

This project is supported by the Great Barrier Reef Marine Park Authority through funding from the Australian Government Reef Program, the Reef 2050 Integrated Monitoring, and Reporting Program and AIMS.

Small low-mass stars are favourable targets for the detection of rocky habitable planets. In particular, planetary systems in the solar neighbourhood are interesting and suitable for precise characterization. The RedDots campaigns seek to discover rocky planets orbiting nearby low-mass stars. The 2018 campaign targeted GJ 1061, which is the 20th nearest star to the Sun. For three consecutive months we obtained nightly, high-precision radial velocity measurements with the HARPS spectrograph. We analysed these data together with archival HARPS data. We report the detection of three planet candidates with periods of 3.204 +/- 0.001, 6.689 +/- 0.005, and 13.03 +/- 0.03 d, which are close to 1:2:4 period commensurability. After several considerations related to the properties of the noise and sampling, we conclude that a fourth signal is most likely explained by stellar rotation, although it may be due to a planet. The proposed three-planet system (and the potential four-planet solution) is long-term dynamically stable. Planet-planet gravitational interactions are below our current detection threshold. The minimum masses of the three planets range from 1.4 +/- 0.2 to 1.8 +/- 0.3 M-circle plus. Planet d, with msin i = 1.64 +/- 0.24 M-circle plus, receives a similar amount of energy as Earth receives from the Sun. Consequently it lies within the liquid-water habitable zone of the star and has a similar equilibrium temperature to Earth. GJ 1061 has very similar properties to Proxima Centauri but activity indices point to lower levels of stellar activity. ; German Research Foundation (DFG) FOR2544 DR 281/32-1 JE 701/3-1 DFG priority program SPP 1992 'Ex-ploring the Diversity of Extrasolar Planets' RE 1664/18 Spanish Agencia Estatal de Investigacion AYA201679425-C3-3-P ESP2017-87676-C5-2-R ESP2017-87143-R Centre of Excellence 'Severo Ochoa' Instituto de Astrof'rasolar Planets' SEV-2017-0709 Science & Technology Facilities Council (STFC) ST/P000584/1 3180405 Spanish Ministry for Science, Innovation and Universities (MCIU) European Union (EU) ESP2016-80435-C2-1-R ESP2016-80435-C2-2-R Generalitat de Catalunya/CERCA programme STFC Consolidated Grant ST/P000592/1 Alfried Krupp von Bohlen und Halbach Foundation Mc Donald Observatory of the University of Texas at Austin National Research Foundation - South Africa 072.C-0488 183.C-0437 0101.C-0516(A) 198.C-0838(A)

The closet exoplanets to the Sun provide opportunities for detailed characterization of planets outside the Solar System. We report the discovery, using radial velocity measurements, of a compact multiplanet system of super-Earth exoplanets orbiting the nearby red dwarf star GJ 887. The two planets have orbital periods of 9.3 and 21.8 days. Assuming an Earth-like albedo, the equilibrium temperature of the 21.8-day planet is similar to 350 kelvin. The planets are interior to, but close to the inner edge of, the liquid-water habitable zone. We also detect an unconfirmed signal with a period of similar to 50 days, which could correspond to a third super-Earth in a more temperate orbit. Our observations show that GJ 887 has photometric variability below 500 parts per million, which is unusually quiet for a red dwarf. ; German Research Foundation (DFG) FOR2544 JE 701/3-1 German Research Foundation (DFG) SPP 1992 JE 701/5-1 Science & Technology Facilities Council (STFC) ST/P000584/1 ST/T000295/1 ST/P000592/1 Spanish Agencia Estatal de Investigacion AYA2017-89637R AYA2016-79425-C3-3-S ESP2017-87676-C5-2-R ESP2017-87143R PGC2018-098153-B-C31 ESP2016-80435-C2-2-R Centre of Excellence "Severo Ochoa" Instituto de Astrofisica de Andalucia SEV-2017-0709 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3180405 Swiss National Science Foundation (SNSF) CONICYT/PFCHA-Doctorado Nacional, Chile 21140646 Spanish Government ESP2016-80435-C2-1-R PGC2018-098153-B-C33 European Union (EU) ESP2016-80435-C2-1-R PGC2018-098153-B-C33 Generalitat de Catalunya/CERCA program Science & Technology Facilities Council (STFC) ST/M001008/1 Australian Research Council DP0774000 DP130102695 DP170103491 NASA through Hubble Fellowship - Space Telescope Science Institute HST-HF2-51399.001 Ministerio de Ciencia, Innovacion y Universidades Ramon y Cajal fellowship RYC-2017-22489 Science & Technology Facilities Council (STFC) ST/P000592/1 National Aeronautics & Space Administration (NASA) NAS5-26555

Context. The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. Aims. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. Methods. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. Results. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is i(min) = 0.9 deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of i(max) = 87.43 deg. Conclusions. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters. ; German Research Foundation (DFG) FOR2544 RE 2694/4-1 German Max-Planck-Gesellschaft (MPG) Consejo Superior de Investigaciones Cientificas (CSIC) European Union through FEDER/ERF FICTS -2011 -02 Spanish Ministry of Economy German Science Foundation through the Major Research Instrumentation Programme Klaus Tschira Stiftung state of Baden-Wurttemberg state of Niedersachsen Junta de Andalucia High Performance and Cloud Computing Group at the Zentrum fur Datenverarbeitung of the University of Tubingen state of Baden-Wurttemberg through bwHPC German Research Foundation (DFG) INST 37/935 -1 FUGG European FEDER/ERF funds AYA2015-69350-C3-2-P AYA2016-79425-C3-1/2/3-P ESP2017-87676-C5-2-R ESP2017-87143-R Centre of Excellence "Severo Ochoa" award SEV-2015-0548 Centre of Excellence "Maria de Maeztu" award SEV-2015-0548 Instituto de Astrofisica de Andalucia SEV-2017-0709 Centro de Astrobiologia MDM-2017-0737 Generalitat de Catalunya/CERCA programme Science & Technology Facilities Council (STFC) ST/M001008/1 ST/P000584/1 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1161218 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) PB06 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 3180405 Hong Kong RGC grant HKU 17305618 European Research Council under the Horizon 2020 Framework Program via the ERC 83 24 28 Max-Planck-Institut fur Astronomie Instituto de Astrofisica de Andalucia Landessternwarte Konigstuhl Institut de Ciencies de l'Espai Insitut fur Astrophysik Gottingen Universidad Complutense de Madrid Thuringer Landessternwarte Tautenburg Instituto de Astrofisica de Canarias Hamburger Sternwarte Centro de Astrobiologia Centro Astronomico Hispano -Aleman Agencia Estatal de Investigacion of the Ministerio de Ciencia, Innovacion y Universidades AYA2015-69350-C3-2-P AYA2016-79425-C3-1/2/3-P ESP2017-87676-C5-2-R ESP2017-87143-R

Table B.1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/636/A119. ; Context. The nearby ultra-compact multiplanetary system YZ Ceti consists of at least three planets, and a fourth tentative signal. The orbital period of each planet is the subject of discussion in the literature due to strong aliasing in the radial velocity data. The stellar activity of this M dwarf also hampers significantly the derivation of the planetary parameters. Aims. With an additional 229 radial velocity measurements obtained since the discovery publication, we reanalyze the YZ Ceti system and resolve the alias issues. Methods. We use model comparison in the framework of Bayesian statistics and periodogram simulations based on a method by Dawson and Fabrycky to resolve the aliases. We discuss additional signals in the RV data, and derive the planetary parameters by simultaneously modeling the stellar activity with a Gaussian process regression model. To constrain the planetary parameters further we apply a stability analysis on our ensemble of Keplerian fits. Results. We find no evidence for a fourth possible companion. We resolve the aliases: the three planets orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also investigate an effect of the stellar rotational signal on the derivation of the planetary parameters, in particular the eccentricity of the innermost planet. Using photometry we determine the stellar rotational period to be close to 68 d and we also detect this signal in the residuals of a three-planet fit to the RV data and the spectral activity indicators. From our stability analysis we derive a lower limit on the inclination of the system with the assumption of coplanar orbits which is imin = 0.9 deg. From the absence of a transit event with TESS, we derive an upper limit of the inclination of imax = 87.43 deg. Conclusions. YZ Ceti is a prime example of a system where strong aliasing hindered the determination of the orbital periods of exoplanets. Additionally, stellar activity influences the derivation of planetary parameters and modeling them correctly is important for the reliable estimation of the orbital parameters in this specific compact system. Stability considerations then allow additional constraints to be placed on the planetary parameters. © 2020 ESO. ; This work was supported by the DFG Research Unit FOR2544 "Blue Planets around Red Stars", project no. RE 2694/4-1. CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS -2011 -02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Insitut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia and Centro Astronomico Hispano -Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucia. The authors acknowledge support by the High Performance and Cloud Computing Group at the Zentrum fur Datenverarbeitung of the University of Tubingen, the state of Baden-Wurttemberg through bwHPC and the German Research Foundation (DFG) through grant no. INST 37/935 -1 FUGG. We acknowledge financial support from the Agencia Estatal de Investigacion of the Ministerio de Ciencia, Innovacion y Universidades and the European FEDER/ERF funds through projects AYA2015-69350-C3-2-P, AYA2016-79425-C3-1/2/3-P, ESP2017-87676-C5-2-R, ESP2017-87143-R and the Centre of Excellence "Severo Ochoa" and "Maria de Maeztu" awards to the Instituto de Astrofisica de Canarias (SEV-2015-0548), Instituto de Astrofisica de Andalucia (SEV-2017-0709), and Centro de Astrobiologia (MDM-2017-0737), and the Generalitat de Catalunya/CERCA programme. This work is supported by the Science and Technology Facilities Council [ST/M001008/1 and ST/P000584/1]. J.S.J. acknowledges support by Fondecyt grant 1161218 and partial support by CATA-Basal (PB06, CONICYT). Z.M.B acknowledges funds from CONICYT-FONDECYT/Chile Postdoctorado 3180405. M.H.L. was supported in part by Hong Kong RGC grant HKU 17305618. T.H. acknowledges support from the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28. Data were partly collected with the robotic 40-cm telescope ASH2 at the SPACEOBS observatory (San Pedro de Atacama, Chile) and the 90-cm telescope at Sierra Nevada Observatory (Granada, Spain) both operated by the Instituto de Astrofifica de Andalucia (IAA). This work has made use of the Exo-Striker tool (Trifonov 2019).

Barnard's star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard's star is also among the least magnetically active red dwarfs known and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging, astrometry and direct imaging, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard's star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard's star, making it an excellent target for direct imaging and astrometric observations in the future. © 2018, Springer Nature Limited. ; The results are based on observations made with the CARMENES instrument at the 3.5-m telescope of the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain), funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union and the CARMENES Consortium members; the 90-cm telescope at the Sierra Nevada Observatory (Granada, Spain) and the 40-cm robotic telescope at the SPACEOBS observatory (San Pedro de Atacama, Chile), both operated by the Instituto de Astrofisica de Andalucia (IAA); and the 80-cm Joan Oro Telescope (TJO) of the Montsec Astronomical Observatory (OAdM), owned by the Generalitat de Catalunya and operated by the Institute of Space Studies of Catalonia (IEEC). This research was supported by the following institutions, grants and fellowships: Spanish MINECO ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, AYA2016-79425-C3-1-P, AYA2016-79245-C3-2-P, AYA2016-79425-C3-3-P, AYA2015-69350-C3-2-P, ESP2014-54362-P, AYA2014-56359-P, RYC-2013-14875; Generalitat de Catalunya/CERCA programme; Fondo Europeo de Desarrollo Regional (FEDER); German Science Foundation (DFG) Research Unit FOR2544, project JE 701/3-1; STFC Consolidated Grants ST/P000584/1, ST/P000592/1, ST/M001008/1; NSF AST-0307493; Queen Mary University of London Scholarship; Perren foundation grant; CONICYT-FONDECYT 1161218, 3180405; Swiss National Science Foundation (SNSF); Koshland Foundation and McDonald-Leapman grant; and NASA Hubble Fellowship grant HST-HF2-51399.001. J.T. is a Hubble Fellow.