Cluster Origin of Triple Star HD 188753 and its Planet

The recent discovery by M. Konacki of a ``hot Jupiter'' in the hierarchical triple star system HD 188753 challenges established theories of giant-planet formation. If the orbital geometry of the triple has not changed since the birth of the planet, then a disk around the planetary host star would probably have been too compact and too hot for a Jovian planet to form by the core-accretion model or gravitational collapse. This paradox is resolved if the star was initially either single or had a much more distant companion. It is suggested here that a close multi-star dynamical encounter transformed this initial state into the observed triple, an idea that follows naturally if HD 188753 formed in a moderately dense stellar system--perhaps an open cluster--that has since dissolved. Three distinct types of encounters are investigated. The most robust scenario involves an initially single planetary host star that changes places with the outlying member of a pre-existing hierarchical triple.Comment: Accepted by ApJL; minor changes from origina

Exploring the Nature of Weak Chandra Sources near the Galactic Centre

We present results from the first near-IR imaging of the weak X-ray sources discovered in the Chandra/ACIS-I survey (Wang et al. 2002) towards the Galactic Centre (GC). These ~800 discrete sources, which contribute significantly to the GC X-ray emission, represent an important and previously unknown population within the Galaxy. From our VLT observations we will identify likely IR counterparts to a sample of the hardest sources, which are most likely X-ray binaries. With these data we can place constraints on the nature of the discrete weak X-ray source population of the GC.Comment: In Proc. of ``Interacting Binaries: Accretion, Evolution, and Outcomes'', eds. L. A. Antonelli et al., AIP, Cefalu, Sicily, 200

An Overabundance of Transient X-ray Binaries within 1 pc of the Galactic Center

During five years of Chandra observations, we have identified seven X-ray transients located within 23 pc of Sgr A*. These sources each vary in luminosity by more than a factor of 10, and have peak X-ray luminosities greater than 5e33 erg/s, which strongly suggests that they are accreting black holes or neutron stars. The peak luminosities of the transients are intermediate between those typically considered outburst and quiescence for X-ray binaries. Remarkably four of these transients lie within only 1 pc of Sgr A*. This implies that, compared to the numbers of similar systems located between 1 and 23 pc, transients are over-abundant by a factor of 20 per unit stellar mass within 1 pc of Sgr A*. It is likely that the excess transient X-ray sources are low-mass X-ray binaries that were produced, as in the cores of globular clusters, by three-body interactions between binary star systems and either black holes or neutron stars that have been concentrated in the central parsec through dynamical friction. Alternatively, they could be high-mass X-ray binaries that formed among the young stars that are present in the central parsec.Comment: 4 pages, including 2 figures (one color). Submitted to ApJ Letter

A numerical process study on the rapid transport of stratospheric air down to the surface over western North America and the Tibetan Plateau

Upper-level fronts are often associated with the rapid transport of stratospheric air along tilted isentropes to the middle or lower troposphere, where this air leads to significantly enhanced ozone concentrations. These plumes of originally stratospheric air can only occasionally be observed at the surface because (i) stable boundary layers prevent an efficient vertical transport down to the surface, and (ii) even if boundary layer turbulence were strong enough to enable this transport, the originally stratospheric air mass can be diluted by mixing, such that only a weak stratospheric signal can be recorded at the surface. Most documented examples of stratospheric air reaching the surface occurred in mountainous regions. This study investigates two such events, using a passive stratospheric air mass tracer in a mesoscale model to explore the processes that enable the transport down to the surface. The events occurred in early May 2006 in the Rocky Mountains and in mid-June 2006 on the Tibetan Plateau. In both cases, a tropopause fold associated with an upper-level front enabled stratospheric air to enter the troposphere. In our model simulation of the North American case, the strong frontal zone reaches down to 700&thinsp;hPa and leads to a fairly direct vertical transport of the stratospheric tracer along the tilted isentropes to the surface. In the Tibetan Plateau case, however, no near-surface front exists and a reservoir of high stratospheric tracer concentrations initially forms at 300–400&thinsp;hPa, without further isentropic descent. However, entrainment at the top of the very deep boundary layer (reaching to 300&thinsp;hPa over the Tibetan Plateau) and turbulence within the boundary layer allows for downward transport of stratospheric air to the surface. Despite the strongly differing dynamical processes, stratospheric tracer concentrations at the surface reach peak values of 10&thinsp;%–20&thinsp;% of the imposed stratospheric value in both cases, corroborating the potential of deep stratosphere-to-troposphere transport events to significantly influence surface ozone concentrations in these regions.</p

No evidence of a hot Jupiter around HD 188753 A

The discovery of a short-period giant planet (a hot Jupiter) around the primary component of the triple star system HD 188753 has often been considered as an important observational evidence and as a serious challenge to planet-formation theories. Following this discovery, we monitored HD 188753 during one year to better characterize the planetary orbit and the feasibility of planet searches in close binaries and multiple star systems. We obtained Doppler measurements of HD 188753 with the ELODIE spectrograph at the Observatoire de Haute-Provence. We then extracted radial velocities for the two brightest components of the system using our multi-order, two-dimensional correlation algorithm, TODCOR. Our observations and analysis do not confirm the existence of the short-period giant planet previously reported around HD 188753 A. Monte Carlo simulations show that we had both the precision and the temporal sampling required to detect a planetary signal like the one quoted. From our failure to detect the presumed planet around HD 188753 A and from the available data on HD 188753, we conclude that there is currently no convincing evidence of a close-in giant planet around HD 188753 A.Comment: 8 pages, 3 figures, accepted for publication in A&A. Corrected typos and minor mistake

Models of Ultraluminous X-Ray Sources with Intermediate-Mass Black Holes

We have computed models for ultraluminous X-ray sources ("ULXs") consisting of a black-hole accretor of intermediate mass ("IMBH"; e.g., ~1000 Msun) and a captured donor star. For each of four different sets of initial donor masses and orbital separations, we computed 30,000 binary evolution models using a full Henyey stellar evolution code. To our knowledge this is the first time that a population of X-ray binaries this large has been carried out with other than approximation methods, and it serves to demonstrate the feasibility of this approach to large-scale population studies of mass-transfer binaries. In the present study, we find that in order to have a plausible efficiency for producing active ULX systems with IMBHs having luminosities > 10^{40} ergs/sec, there are two basic requirements for the capture of companion/donor stars. First, the donor stars should be massive, i.e., > 8 Msun. Second, the initial orbital separations, after circularization, should be close, i.e., < 6-30 times the radius of the donor star when on the main sequence. Even under these optimistic conditions, we show that the production rate of IMBH-ULX systems may fall short of the observed values by factors of 10-100.Comment: 5 pages, 2 figures, submitted to Ap

The PHASES Differential Astrometry Data Archive. III. Limits to Tertiary Companions

The Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) monitored 51 subarcsecond binary systems to evaluate whether tertiary companions as small as Jovian planets orbited either the primary or secondary stars, perturbing their otherwise smooth Keplerian motions. Twenty-one of those systems were observed 10 or more times and show no evidence of additional companions. A new algorithm is presented for identifying astrometric companions and establishing the (companion mass)-(orbital period) combinations that can be excluded from existence with high confidence based on the PHASES observations, and the regions of mass-period phase space being excluded are presented for 21 PHASES binaries.Comment: 16 pages, Accepted to A

Industry-academia collaborations in software engineering: An empirical analysis of challenges, patterns and anti-patterns in research projects

Research collaboration between industry and academia supports improvement and innovation in industry and helps to ensure industrial relevance in academic research. However, many researchers and practitioners believe that the level of joint industry-academia collaboration (IAC) in software engineering (SE) research is still relatively low, compared to the amount of activity in each of the two communities. The goal of the empirical study reported in this paper is to exploratory characterize the state of IAC with respect to a set of challenges, patterns and anti-patterns identified by a recent Systematic Literature Review study. To address the above goal, we gathered the opinions of researchers and practitioners w.r.t. their experiences in IAC projects. Our dataset includes 47 opinion data points related to a large set of projects conducted in 10 different countries. We aim to contribute to the body of evidence in the area of IAC, for the benefit of researchers and practitioners in conducting future successful IAC projects in SE. As an output, the study presents a set of empirical findings and evidence-based recommendations to increase the success of IAC projects.Supported by the National Research Fund, Luxembourg FNR/P10/03. Supported by FCT (Fundação para a Ciˆencia e Tecnologia) within the Project Scope UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio

A multi-dimensional energy-based analysis of neighbourhood sustainability assessment tools: are institutional indicators really missing?

Neighbourhood Sustainability Assessment Tools (NSATs) have become the modern day template for urban planners to achieve sustainable development in their communities, districts and cities. The popularity of the pioneering NSATs led to the creation of other tools in different regions. Also, with the popularity and replication of these tools came the replication of their limitations. The most notable limitation and motivation for this study is the inadequate recognition of the complexities of institutional dimensions (i.e. policies, laws and regulation) that contribute to mainstreaming and operationalising sustainable neighbourhood development. Studies that have investigated NSATs generally argue lack of coverage of the institutional dimension. However, there has been little consistent and explicit mention of the precise indicators and criteria sought out to make this claim. Also, there is a clear confusion as to what institutional indicators actually are, what characteristics they possess and how best they can be identified. This study, via the lens of energy-based indicators, expands on the role of the institutional indicator and its associated dimensions. This study also utilises a multi-dimensional approach to indicator analysis and draws out current trend or characteristics of institutional indicators in 15 currently existing NSATs. The results show a limited view on the classification of institutional indicators. The study also demonstrates that there are more institutional indicators than previously reported in prior studies. Additionally, this study confirms that an institutional indicator cannot be a single entity or identity but rather it must operate under the linkage of the other dimensions (environment, social and economic). Finally, this study, based on the analysis of 15 NSATs provides a definition of what can be considered an institutional indicator. In conclusion, it is recommended that future development of NSATs should ensure a constant institutional link to indicators, as this could provide an enhanced alternative to the development of NSATs, particularly for regions that are looking into developing their own assessment tools