Limb-darkening measurements for a cool red giant in microlensing event OGLE 2004-BLG-482

Aims: We present a detailed analysis of OGLE 2004-BLG-482, a relatively high-magnification single-lens microlensing event which exhibits clear extended-source effects. These events are relatively rare, but they potentially contain unique information on the stellar atmosphere properties of their source star, as shown in this study. Methods: Our dense photometric coverage of the overall light curve and a proper microlensing modelling allow us to derive measurements of the OGLE 2004-BLG-482 source star's linear limb-darkening coefficients in three bands, including standard Johnson-Cousins I and R, as well as in a broad clear filter. In particular, we discuss in detail the problems of multi-band and multi-site modelling on the expected precision of our results. We also obtained high-resolution UVES spectra as part of a ToO programme at ESO VLT from which we derive the source star's precise fundamental parameters. Results: From the high-resolution UVES spectra, we find that OGLE 2004-BLG-482's source star is a red giant of MK type a bit later than M3, with Teff = 3667 +/- 150 K, log g = 2.1 +/- 1.0 and an assumed solar metallicity. This is confirmed by an OGLE calibrated colour-magnitude diagram. We then obtain from a detailed microlensing modelling of the light curve linear limb-darkening coefficients that we compare to model-atmosphere predictions available in the literature, and find a very good agreement for the I and R bands. In addition, we perform a similar analysis using an alternative description of limb darkening based on a principal component analysis of ATLAS limb-darkening profiles, and also find a very good agreement between measurements and model predictions.Comment: Accepted in A&

Recent QCD results from the Tevatron

Recent QCD related results from the CDF and the D0 experiments are presented based on proton anti-proton collision data at sqrt(s)=1.96 TeV, taken in Run II of the Fermilab Tevatron Collider. Measured observables include inclusive photon and diphoton production, vector boson plus jets production, event shape variables, and inclusive multijet production. The measurement results are compared to QCD theory calculations in different approximations. A determination of the strong coupling constant from jet data is presented.Comment: 12 pages with 14 figures, to appear in the proceedings of the "Ringberg Workshop: New Trends in HERA Physics 2011", Ringberg Castle, Germany, 25-28 September, 201

Measurement of exclusive production of scalar χc0\chi_{c0} meson in proton-(anti)proton collisions via χc0→π+π−\chi_{c0} \to \pi^{+}\pi^{-} decay

We consider a measurement of exclusive production of scalar $\chi_{c}(0^{++})$ meson in the proton-proton collisions at LHC and RHIC and in the proton-antiproton collisions at the Tevatron via $\chi_{c0} \to \pi^{+}\pi^{-}$ decay. The corresponding amplitude for exclusive double-diffractive $\chi_{c0}$ meson production was obtained within the $k_{t}$-factorization approach including virtualities of active gluons and the corresponding cross section is calculated with unintegrated gluon distribution functions (UGDFs) known from the literature. The four-body $p p \to p p \pi^+ \pi^-$ reaction constitutes an irreducible background to the exclusive $\chi_{c0}$ meson production. We calculate several differential distributions for $pp(\bar{p}) \to pp(\bar{p})\chi_{c0}$ process including absorptive corrections. The influence of kinematical cuts on the signal-to-background ratio is investigated. Corresponding experimental consequences are discussed.Comment: 16 pages, 10 figures, 2 table

Exclusive Double Diffractive Events: Menu for LHC

Exclusive double diffractive events (EDDE) are considered in the framework of the Regge-eikonal approach and perturbative calculations for "hard" subprocesses. Total and differential cross-sections for processes $p+p\to p+X+p$ are calculated.Comment: 18 pages, Latex 2.09, 6 postscript figures, references are adde

Limits on Stellar and Planetary Companions in Microlensing Event OGLE-1998-BUL-14

We present the PLANET photometric data set for \ob14, a high magnification ($A_{\rm max}\sim 16$) event alerted by the OGLE collaboration toward the Galactic bulge in 1998. The PLANET data set consists a total of 461 I-band and 139 $V-$band points, the majority of which was taken over a three month period. The median sampling interval during this period is about 1 hour, and the $1\sigma$ scatter over the peak of the event is 1.5%. The excellent data quality and high maximum magnification of this event make it a prime candidate to search for the short duration, low amplitude perturbations that are signatures of a planetary companion orbiting the primary lens. The observed light curve for \ob14 is consistent with a single lens (no companion) within photometric uncertainties. We calculate the detection efficiency of the light curve to lensing companions as a function of the mass ratio and angular separation of the two components. We find that companions of mass ratio $\ge 0.01$ are ruled out at the 95% confidence level for projected separations between 0.4-2.4 \re, where \re is the Einstein ring radius of the primary lens. Assuming that the primary is a G-dwarf with \re\sim3 {\rm AU} our detection efficiency for this event is $\sim 60$ for a companion with the mass and separation of Jupiter and $\sim5$ for a companion with the mass and separation of Saturn. Our efficiencies for planets like those around Upsilon And and 14 Her are > 75%.Comment: Data available at http://www.astro.rug.nl/~planet/planetpapers.html 20 pages, 10 figures. Minor changes. ApJ, accepte

Blending in Gravitational Microlensing Experiments: Source Confusion And Related Systematics

Gravitational microlensing surveys target very dense stellar fields in the local group. As a consequence the microlensed source stars are often blended with nearby unresolved stars. The presence of `blending' is a cause of major uncertainty when determining the lensing properties of events towards the Galactic centre. After demonstrating empirical cases of blending we utilize Monte Carlo simulations to probe the effects of blending. We generate artificial microlensing events using an HST luminosity function convolved to typical ground-based seeing, adopting a range of values for the stellar density and seeing. We find that a significant fraction of bright events are blended, contrary to the oft-quoted assumption that bright events should be free from blending. We probe the effect that this erroneous assumption has on both the observed event timescale distribution and the optical depth, using realistic detection criteria relevent to the different surveys. Importantly, under this assumption the latter quantity appears to be reasonably unaffected across our adopted values for seeing and density. The timescale distribution is however biased towards smaller values, even for the least dense fields. The dominant source of blending is from lensing of faint source stars, rather than lensing of bright source stars blended with nearby fainter stars. We also explore other issues, such as the centroid motion of blended events and the phenomena of `negative' blending. Furthermore, we breifly note that blending can affect the determination of the centre of the red clump giant region from an observed luminosity function. This has implications for a variety of studies, e.g. mapping extinction towards the bulge and attempts to constrain the parameters of the Galactic bar through red clump giant number counts. (Abridged)Comment: 18 pages, 10 figures. MNRAS (in press

Reconstituting the Public-Private Divide under Global Conditions: the Case of Dutch and British Water Management

How is the line to be drawn in the public–private divide when those who would bridge it also assert that globalization restricts the state's ability to deliver public policy objectives? Critics of modernity have seen the distinction between two public–private discourses, state and market, the open and the hidden, as a modern flawed version of classic notions of the democratic citizen community. The projection of the divide on to a global stage appears to take us even further from that ideal. We report the results of a narrative analysis of the way practitioners in the Netherlands and England and Wales now deliver global public goods in the management of water as compared with their predecessors delivering public health and progress in the 19th century. In their adherence to the water systems concept we find them actively supporting a transparent public sphere beyond the state where multiple forms of agency assert global responsibilities

Optical Gravitational Lensing Experiment. OGLE-1999-BUL-19: The First Multi-Peak Parallax Event

We describe a highly unusual microlensing event, OGLE-1999-BUL-19, which exhibits multiple peaks in its light curve. The Einstein radius crossing time for this event is approximately one year, which is unusually long. We show that the motion of the Earth induces these multiple peaks in the light curve, since the relative transverse velocity of the lens projected into the observer plane is very small (v = 12.5 km/s). This is the lowest velocity so far published and we believe that this is the first multiple-peak parallax event ever observed. We also believe that this event may be exhibiting slight binary-source signatures in addition to these parallax-induced multiple peaks. With spectroscopic observations it is possible to test this `parallax plus binary-source' hypothesis and (if this hypothesis turns out to be correct) to simultaneously fit both models and obtain a measurement of the lens mass. Furthermore, spectroscopic observations could also supply information regarding the lens properties, possibly providing another avenue for determining the lens mass. We found that most of the I-band blending is probably caused by light from the lens or a binary companion to the source. However, in the V-band, there appears to be a second blended source 0.35" away from the lensed source. HST observations will be very useful for understanding the nature of the blends. We also suggest that a radial velocity survey of all parallax events will be very useful for further constraining the lensing kinematics and understanding the origins of these events and the excess of long events toward the bulge.Comment: 36 pages, 7 figures. Accepted for publication in MNRA