Constraints on Jupiters from observations of Galactic bulge microlensing events during 2000

We present observations of eight Galactic bulge microlensing events taken with the 1.0-m Jacobus Kapteyn Telescope (JKT) on La Palma during 2000 June and July. The JKT observing schedule was optimized using a prioritizing algorithm to automatically update the target list. For most of these events we have sampled the light curves at times where no information was available from the OGLE alert team. We assume a point-source point-lens (PSPL) model and perform a maximum likelihood fit to both our data and the OGLE data to constrain the event parameters of the fit. We then refit the data assuming a binary lens and proceed to calculate the probability of detecting planets with mass ratio   q = 10⁻³  . We have seen no clear signatures of planetary deviations on any of the eight events and we quantify constraints on the presence of planetary companions to the lensing stars. For two well-observed events, 2000BUL31 and 2000BUL33, our detection probabilities peak at ∼30 and ∼20 per cent respectively for   q = 10⁻³  and   a ∼ R _E  for a  Δχ²  threshold value of 60.     

Secular light curve of Comet 9P/Tempel 1

In support of the Deep Impact Mission, we have updated the secular light curve of 9P/Tempel 1 presented in Paper I [Ferrín, I., 2005. Icarus 178, 493-516], with new data sets. The secular light curves (SLC) of the comet are presented in the log and time plots (Figs. 1 and 2) and provide a clear profile of the overall shape of the envelope. We arrive at the following conclusions: (1) Improved values of 18 photometric parameters are derived including the turn on and turn off points, RON=−3.47±0.05 AU, ROFF=+4.20±0.05 AU, and TON=−410±25 d, TOFF=+555±25 d. (2) The improved SLC shows a most interesting and peculiar shape, with a linear power law of slope n=7.7±0.1 from RON=−3.47 AU to RBP=−2.08±0.05 AU, and then converts to a law with curvature. The break point of the power law at RBP=−2.08 AU, mV(1,R)=14.0±0.1 mag, is interpreted as a change in sublimating something more volatile than water ice (most probably CO₂), to water ice sublimation. In other words, the comet's sublimation is controlled by two different substances. (3) The photometric-age (defined in Paper I) and the time-age of the comet [Ferrín, I., 2006. Icarus. In press] are recomputed, and results in a value P-AGE=21±2 and T-AGE=11±2 comet years. Thus 9P is a young comet. (4) The comet is active almost up to aphelion since the turn off point has been determined at ROFF=+4.20±0.05 AU while aphelion takes place at Q=+4.74 AU. (5) The comet exhibits activity post-aphelion which is not understood. Two hypothesis are advanced to explain this behavior.     

Decoding the spectra of SDSS early-type galaxies: new indicators of age and recent star formation

We apply principal component analysis (PCA) to a sample of early-type galaxies from the Sloan Digital Sky Survey (SDSS) in order to infer differences in their star formation histories from their unresolved stellar populations. We select a   z < 0.1  volume-limited sample comprising ∼7000 early-type galaxies from SDSS/Data Release 4. Out of the first few principal components (PC), we study four which give information about stellar populations and velocity dispersion. We construct two parameters (η and ζ) as linear combinations of PC1 and PC2. The four components can be presented as 'optimal filters' to explore in detail the properties of the underlying stellar populations. By comparing various photospectroscopic observables – including near-ultraviolet (NUV) photometry from Galaxy Evolution Explorer (GALEX) – we find ζ to be most sensitive to recent episodes of star formation, and η to be strongly dependent on the average age of the stellar populations. Both η and ζ also depend on metallicity. We apply these optimal filters to composite spectra assembled by Bernardi et al. The distribution of the η component of the composites appear to be indistinguishable between high- and low-density regions, whereas the distribution of ζ parameters have a significant skew towards lower values for galaxies in low-density regions. This result suggests that galaxies in lower density environments are less likely to present weak episodes of recent star formation. In contrast, a significant number of galaxies from our high-density subsample – which includes clusters (both outer regions and centres) and groups – underwent small but detectable recent star formation at high metallicity, in agreement with recent estimates targeting elliptical galaxies in Hickson Compact Groups and in the field.     

Palaeoenvironmental turnover across the Palaeocene/Eocene boundary at the Stratotype section in Dababiya (Egypt) based on benthic foraminifera

The Global Stratotype Section and Point for the Palaeocene/Eocene (P/E) boundary was defined at Dababiya Quarry (Egypt) at the base of the carbon isotope excursion (CIE). We present the first detailed analysis of Palaeocene–Eocene benthic foraminifera from Dababiya, in order to infer the palaeoenvironmental turnover across the P/E boundary. At Dababiya, the CIE coincides with a major turnover in foraminiferal assemblages; the last occurrence of Angulogavelinella avnimelechi, at the base of the CIE, may be correlated to the main phase of extinction of deep-sea benthic foraminifera. Benthic foraminifera indicate that stressful conditions such as oxygen deficiency, carbonate dissolution, and changes in food supply, persisted at the sea floor over most of the CIE interval. The main phase of recovery of benthic foraminifera is recorded c. 250 cm above the P/E boundary, and it may be linked to increased productivity and oxygenation at the sea floor.     

On the CN (0, 0) spectrum of Comet Mrkos 1957d

We have carried out an analysis of the (0, 0) vibrational band of the CN molecule in Comet Mrkos 1957d, including the effect of collisions. We found that the sum of the squares of the residuals can be reduced by a factor of ten, if collisions account for 46±3% of the population of the lower level. A rotational temperature can be assigned to the cometary gas. The best value found was 410±40 K. The best fit for the constantR ₁ was (1.07±0.10)×10^–4. The velocity of the comet was left as a free parameter. We found for it a value of 34.38±0.10 km s^–1. This result is in disagreement with the nuclear orbital velocity of 34.74 km s^–1. The discrepancy can be explained, if the CN molecules are ejected from the cometary nucleus preferentially in the sunward direction, with a mean velocity that corresponds to the above temperature.     

Saturn's rings. I. Optical thickness of rings A,B, D and structure of ring B

A photometric study of high-resolution (～0″.3) plates of Saturn taken at the Lowell Observatory in 1943 and 1945 is presented. N-S scans were taken over both the planet and rings. The excess brightness due to the planet seen through the rings is found by taking the difference between the central meridian (CM) scans and scans displaced by 5″.7. Adopting a value for the albedo of the planet, it is possible to obtain the optical thickness, τ_CM(r). In particular, for the regions of maximum brightness in rings A and B, we find τ_CM(I_{A max}) = 0.38 ± 0.11 and τ_CM(I_{B max}) = 0.61 ± 0.11. Observations by Barnard made in 1890 show evidence of ring D, recently discovered by Guerin (1969). The value for the optical thickness of this ring is τ_D(I_{D max}) = 0.03 ± 0.01. Ring B exhibits a pronounced (7–10%) decrease in brightness from the extremity of the major axis to the CM. After considering several possible explanations, we conclude that the ring particles are nonspherical and are in synchronous rotation around the planet with their long axis toward it. The mean value for the ratio of major to minor axis for the particles at 15″ is $\text{(a/b)}\text{? 1.08}$. Because of the shape and orientation of the particles, the optical thickness at the extremity of the major axis and at the CM are different for any saturnicentric latitude B ≠ 90°. Under these circumstances, only a minimum value for τ at the extremity can be derived.     

Chemical and isotopic assessment in volcanic thermal waters: Cases of Ischia (Italy) and São Miguel (Azores,Portugal)

Isotopic fractionation of ¹⁰B/¹¹B provides a sound tool for identifying hydrogeochemical processes in complex areas, owing to its ability to discriminate between various scenarios. In addition, the occurrence of boron as a minor element in areas of active volcanism allows its use in comparison with concentrations of other conservative or non‐conservative ions. This allows the detection of water mixtures of diverse origin and temperature, deep or shallow, including fresh water, seawater and even brines. This tool was applied in studies of the volcanic islands of Ischia and São Miguel, across widely differing geographical and climatic contexts. Five groups of waters have been identified in Ischia Island: marine, transition, hot carbonated, cold carbonated and fresh waters. For São Miguel Island the identified groups are cold carbonic, hot carbonic, boiling and acidic boiling waters. Copyright © 2008 John Wiley & Sons, Ltd.     

Evaluating Duero's basin (Spain) response to the NAO phases: spatial and seasonal variability

In this study, we analysed the influence of the North Atlantic Oscillation (NAO) on the hydrological response of the Duero River (central Spain) and its tributaries. We identified the positive and negative phases of the winter NAO for the period 1961–2006 and related precipitation and river discharge anomalies. Significant differences in precipitation and river discharge were found between the positive and negative NAO phases with negative anomalies (dry conditions) during positive NAO periods, and positive anomalies (wet conditions) during negative NAO periods. Marked differences were also found in the precipitation and river discharge response times to the NAO episodes, with an immediate response for precipitation but a lag and more sustained response for river discharges. Differing patterns were also identified in the response of river discharge to the NAO throughout the Duero basin. The physical characteristics of watersheds (including area, altitude and permeability explained most of the differences in the timing and magnitude of anomalies in the river discharge in response to the NAO. The findings highlight the great variability in the hydrological response of rivers to the NAO episodes. Copyright © 2010 John Wiley & Sons, Ltd.     

Star formation and nuclear activity in close pairs of early-type galaxies

We extract from the Sloan Digital Sky Survey a sample of 347 systems involving early-type galaxies separated by less than 30 kpc, in projection, and 500 km s⁻¹ in radial velocity. These close pairs are likely progenitors of dry mergers. The (optical) spectra are used to determine how the interaction affects the star formation history and nuclear activity of the galaxies. The emission lines (or lack thereof) are used to classify the sample into AGN, star forming or quiescent. Increased AGN activity and reduced star formation in early-type pairs that already appear to be interacting indicate that the merging process changes the nature of nebular activity, a finding that is also supported by an increase in AGN luminosity with decreasing pair separation. Recent star formation is studied on the absorption-line spectra, both through the principal component analysis and via a comparison of the spectra with composite stellar population models. We find that the level of recent star formation in close pairs is raised relative to a control sample of early-type galaxies. This excess of residual star formation is found throughout the sample of close pairs and does not correlate with pair separation or with visual signs of interaction. Our findings are consistent with a scenario whereby the first stage of the encounter (involving the outer parts of the haloes) triggers residual star formation, followed by a more efficient inflow towards the centre – switching to an AGN phase – after which the systems are quiescent.