371 research outputs found
The V471 Tauri System: A Multi-datatype Probe
V471 Tauri, a white dwarf--red dwarf eclipsing binary in the Hyades, is well
known for stimulating development of common envelope theory, whereby novae and
other cataclysmic variables form from much wider binaries by catastrophic orbit
shrinkage. Our evaluation of a recent imaging search that reported negative
results for a much postulated third body shows that the object could have
escaped detection or may have actually been seen. The balance of evidence
continues to favor a brown dwarf companion about 12 AU from the eclipsing
binary. A recently developed algorithm finds unified solutions from three
datatypes. New radial velocities (RVs) of the red dwarf and BV RCIC light
curves are solved simultaneously along with white dwarf and red dwarf RVs from
the literature, uvby data, the MOST mission light curve, and 40 years of
eclipse timings. Precision-based weighting is the key to proper information
balance among the various datasets. Timewise variation of modeled starspots
allows unified solution of multiple data eras. Light curve amplitudes strongly
suggest decreasing spottedness from 1976 to about 1980, followed by
approximately constant spot coverage from 1981 to 2005. An explanation is
proposed for lack of noticeable variation in 1981 light curves, in terms of
competition between spot and tidal variations. Photometric spectroscopic
distance is estimated. The red dwarf mass comes out larger than normal for a
K2V star, and even larger than adopted in several structure and evolution
papers. An identified cause for this result is that much improved red dwarf RVs
curves now exist
The impact of CoRoT on close binary research
The space experiment CoRoT will provide continuous monitoring and high
accuracy light curves of about sixty thousand stars. Selected binary systems
will be observed in the Additional Program frame as targets of long and
continuous pointed observations. Moreover, thousands of new binaries will
certainly be detected and hundreds of them will have extremely accurate light
curves. This will allow studies of fine effects on the light curves, monitoring
of stellar activity and, in combination with ground-based observations, will
provide exquisite determination of stellar parameters.
Among the new discoveries of interesting systems of special value will be
those of low mass binaries.Comment: 6 pages, 2 figures, contribution to "Colse binaries in the 21th
century", Syros (Greece), June 2005. To be published by Ap&S
An Eccentric Eclipsing Binary: CGAur
In this study, we present CG Aur's photometric observations obtained in the
observing seasons 2011 and 2012, the first available multi-colour light curves.
Their shape indicates that the system is an Algol binary. The light curve
analyses reveal that CG Aur is a detached binary system with an effective
temperature difference between the components, approximately 1000 K. The first
estimate of the absolute dimensions of the components indicated that the system
locates on the main sequence in the HR diagram. The primary component is
slightly evolved from the ZAMS.Comment: 18 pages, 6 figures, 3 table
METRO - The role and future perspectives of Cohesion Policy in the planning of Metropolitan Areas and Cities. Policy brief: The added value of the EU cohesion policy in the planning and implementation of metropolitan policies
This policy brief seeks to unpack the multiple added value of the European Union (EU) cohesion policy in metropolitan areas by exploring its priorities, funds and geographical distribution as well as the successful outcomes. Starting from the idea that the metropolitan scale is the most relevant to deal with those ‘functional’ issues that have a scope that exceeds the municipal boundaries (such as mobility, economic development, climate change etc.), this policy brief offers an overview of the added value of the EU cohesion policy on the planning and implementation of metropolitan policies in the 2014-20 programming period and elaborates a set of recommendations for policy and decision makers aiming at increasing this added value in the programming period 2021-27.
Based on the nine case studies explored in the ESPON METRO targeted analysis, which include the metropolitan areas of Barcelona, Brno, Brussels, Florence, Gdańsk-Gdynia-Sopot, Lisbon, Lyon, Riga and Turin, this policy brief aims to support planners and policy officers in making well-informed decisions at EU, national and local level, when it comes to maximise the added value that the EU cohesion policy can provide to metropolitan development and policies. It does so by presenting possible ways of dealing with the complexity of the multiple impacts of cohesion policy and its metropolitan dimension
METRO - The role and future perspectives of Cohesion Policy in the planning of Metropolitan Areas and Cities. Annex I: Conceptual framework and methodology
The scope of the ESPON METRO project is rather broad, as its research positions at the intersection of a number of fields, ranging from territorial governance and spatial planning, to public administration and policy analysis and European integration studies, up to regional development studies.
In order to explore the role that metropolitan areas play as catalysts and drivers of global development, as a consequence of complex processes of socioeconomic reorganisation and rescaling that have evolved through time, and with particular reference to the European Union (EU) cohesion policy, the METRO research team has framed its action and analysis within a composite and articulated conceptual and methodological framework. In particular, the latter has been shaped in order to allow the researchers engaged in the project to answer the three main policy questions animating the study:
PQ1 | What role do metropolitan areas play in the development, management and implementation of the cohesion policy?
PQ2 | What is the added value of the cohesion policy in the planning and implementation of metropolitan policies?
PQ3 | What role does the cohesion policy play in consolidating metropolitan governance and cooperation?
The conceptual and methodological framework for the project has been developed during the first months of the research, building on the materials already included in the project proposal, that were further detailed and consolidated through:
A thorough consideration of previous research works on similar matters as well as of the existing scientific literature in the field of metropolitan governance and European integration and Europeanisation.
The interaction with the project’s Steering Committee Members during the METRO kick-off meeting (October the 9th, 2020), the comments received in response to the Delivery n.1 and the outcomes
of the Steering Committee Meeting n. 2 (November the 16th, 2020) and 3 (February the 23rd, 2021).
This Annex to the Final Report presents said conceptual framework and methodology more in detail
Disentangling effective temperatures of individual eclipsing binary components by means of color-index constraining
Eclipsing binary stars are gratifying objects because of their unique
geometrical properties upon which all important physical parameters such as
masses, radii, temperatures, luminosities and distance may be obtained in
absolute scale. This poses strict demand on the model to be free of systematic
effects that would influence the results later used for calibrations, catalogs
and evolution theory. We present an objective scheme of obtaining individual
temperatures of both binary system components by means of color-index
constraining, with the only requirement that the observational data-set is
acquired in a standard photometric system. We show that for a modest case of
two similar main-sequence components the erroneous approach of assuming the
temperature of the primary star from the color index yields temperatures which
are systematically wrong by ~100K.Comment: 6 pages, 3 figures, 1 table; to appear in proceedings of the Close
Binaries in the 21st Century conference in Syros, Greec
The massive Wolf-Rayet Binary LSS1964 (=WR29), II: the V light curve
Context. WR 29 is a known WN7h+O double-lined binary system with a rather short period (3.164 days). Aims. We search for light variations to determine the inclination of the system and thus the absolute masses of both components. Methods. We observed photometrically the field of WR 29 between December, 2002, and February, 2006. Results. We find that the V light of WR 29 varies in phase with the spectroscopic period of 3.16412 days, presenting two minima corresponding to the conjunctions of the binary components. Numerical models fitted to the light curve indicate an orbital inclination of about 44â—¦, and masses of 53 M and 42 M for the O- and WN-type components, respectively.Fil: Gamen, Roberto Claudio. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto de AstrofÃsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas. Instituto de AstrofÃsica La Plata; ArgentinaFil: Fernandez Lajus, Eduardo Eusebio. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto de AstrofÃsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas. Instituto de AstrofÃsica La Plata; ArgentinaFil: Niemela, Virpi Sinikka. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas; ArgentinaFil: Barba, Rodolfo Hector. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentin
Revealing the Nature of Algol Disks through Optical and UV Spectroscopy, Synthetic Spectra, and Tomography of TT Hydrae
We have developed a systematic procedure to study the disks in Algol-type
binaries using spectroscopic analysis, synthetic spectra, and tomography. We
analyzed 119 H-alpha spectra of TT Hya, an Algol-type eclipsing interacting
binary, collected from 1985-2001. The new radial velocities enabled us to
derive reliable orbital elements, including a small non-zero eccentricity, and
to improve the accuracy of the absolute dimensions of the system. High
resolution IUE spectra were also analyzed to study the formation of the
ultraviolet lines and continuum. Synthetic spectra of the iron curtain using
our new shellspec program enabled us to derive a characteristic disk
temperature of 7000K. We have demonstrated that the UV emission lines seen
during total primary eclipse cannot originate from the accretion disk, but most
likely arise from a hotter disk-stream interaction region.
The synthetic spectra of the stars, disk, and stream allowed us to derive a
lower limit to the mass transfer rate of 2e-10 solar masses per year. Doppler
tomography of the observed H-alpha profiles revealed a distinct accretion disk.
The difference spectra produced by subtracting the synthetic spectra of the
stars resulted in an image of the disk, which virtually disappeared once the
composite synthetic spectra of the stars and disk were used to calculate the
difference spectra. An intensity enhancement of the resulting tomogram revealed
images of the gas stream and an emission arc. We successfully modeled the gas
stream using shellspec and associated the emission arc with an asymmetry in the
accretion disk.Comment: 46 pages, 15 figures, 6 tables, accepted by Ap
BD+36 3317: An algol type eclipsing binary in Delta Lyrae cluster
In this paper, we present standard Johnson UBV photometry of the eclipsing
binary BD+36 3317 which is known as a member of Delta Lyrae (Stephenson 1)
cluster. We determined colors and brightness of the system, calculated E(B - V)
color excess. We discovered that the system shows total eclipse in secondary
minimum. Using this advantage, we found that the primary component of the
system has B9 - A0 spectral type. Although there is no published orbital
solution, we tried to estimate the physical properties of the system from
simultaneous analysis of UBV light curves with 2003 version of Wilson-Devinney
code. Then we considered photometric solution results together with
evolutionary models and estimated the masses of the components as M1 = 2.5 Msun
and M2 = 1.6 Msun. Those estimations gave the distance of the system as 353 pc.
Considering the uncertainties in distance estimation, resulting distance is in
agreement with the distance of Delta Lyrae cluster.Comment: 18 pages, 4 figures, 5 table
Photometric and spectroscopic observations of the F3+M3 eclipsing binary T-Lyr0-08070
The multi-color photometric and spectroscopic observations of the newly
discovered eclipsing binary T-Lyr0-08070 were obtained. The resultant light and
radial velocities were analysed and the absolute parameters of the components
were determined. The system is composed of an F3 and an M3 main-sequence stars.
Masses and radii were estimated to be 1.370.23 M and
1.600.09 R for the primary and 0.320.04 M and
0.860.06R for the secondary star. The less massive secondary
component has a radius at least two times larger with respect to its mass.
Using the BVJHK magnitudes of the system we estimated an interstellar reddening
of 0.22 mag and a distance to the system as 47936 pc.Comment: Accepted. 21 pages, 7 figures; 2012, Sept.New.Ast. arXiv admin note:
text overlap with arXiv:0909.1921, arXiv:1007.513
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