Island Observatory Research Articles

Seven-year monitoring of mercury in wet precipitation and atmosphere at the Amsterdam Island GMOS station

Mercury (Hg) fate and transport research requires more effort to obtain a deep knowledge of its biogeochemical cycle, particularly in the Southern Hemisphere and Tropics that are still missing of distributed monitoring sites.Continuous monitoring of atmospheric Hg concentrations and trend worldwide is relevant for the effectiveness evaluation of the Minamata Convention on Mercury (MCM) actions. In this context, Gaseous Elemental Mercury (GEM) and total mercury (THg) in precipitations were monitored from 2013 to 2019 at the Amsterdam Island Observatory (AMS - 37°48′S, 77°34′E) to provide insights into the Hg pathway in the remote southern Indian Ocean, also considering ancillary dataset of Rn-222, CO2, CO, and CH4. GEM average concentration was 1.06 ± 0.07 ng m−3, with a slight increase during the austral winter due to both higher wind speed over the surface ocean and contributions from southern Africa. In wet depositions, THg average concentration was 2.39 ± 1.17 ng L−1, whereas the annual flux averaged 2.04 ± 0.80 μg m−2 year−1. In general, both GEM and Volume-Weighted Mean Concentration (VWMC) of THg did not show an increasing/decreasing trend over the seven-year period, suggesting a substantial lack of evolution about emission of Hg reaching AMS.Air masses Cluster Analysis and Potential Source Contribution Function showed that oceanic evasion was the main Hg contributor at AMS, while further contributions were attributable to long-range transport events from southern Africa, particularly when the occurrence of El Niño increased the frequency of wildfires.

Black carbon aerosols over Indian Ocean have unique source fingerprint and optical characteristics during monsoon season

Effects of aerosols such as black carbon (BC) on climate and buildup of the monsoon over the Indian Ocean are insufficiently quantified. Uncertain contributions from various natural and anthropogenic sources impede our understanding. Here, we use observations over 5 y of BC and its isotopes at a remote island observatory in northern Indian Ocean to constrain loadings and sources during little-studied monsoon season. Carbon-14 data show a highly variable yet largely fossil (65 ± 15%) source mixture. Combining carbon-14 with carbon-13 reveals the impact of African savanna burning, which occasionally approach 50% (48 ± 9%) of the total BC loadings. The BC mass-absorption cross-section for this regime is 7.6 ± 2.6 m2/g, with higher values during savanna fire input. Taken together, the combustion sources, longevity, and optical properties of BC aerosols over summertime Indian Ocean are different than the more-studied winter aerosol, with implications for chemical transport and climate model simulations of the Indian monsoon.

A Multi‐Resolution Finite‐Element Approach for Global Electromagnetic Induction Modeling With Application to Southeast China Coastal Geomagnetic Observatory Studies

AbstractWe present a multi‐resolution finite‐element approach for three‐dimensional (3D) electromagnetic (EM) induction modeling in spherical Earth. First, the secondary electric field approach is employed so that both magnetospheric and ionospheric current sources are naturally considered. Second, the multi‐resolution tetrahedral grids are used to approximate the heterogeneous crust and mantle, so that the local ocean effects at coastal and island observatories can be accurately simulated. Furthermore, a parallel goal‐oriented hp‐adaptive finite‐element method with Nédélec vector elements is employed to guarantee the accuracy of solutions for arbitrary 3D conductivity distributions. Finally, two synthetic models are used to verify the accuracy and efficiency of our newly developed forward modeling solver. Results show that accurate solutions can be obtained for problems with several million to hundreds of millions of unknowns in a few minutes using 128 cores on a cluster. We apply this approach to correct the near‐surface ocean effects for several unused Chinese coastal observatories by performing multi‐resolution 3D modeling. The corrected data are inverted for the subsurface layered mantle conductivity structures. The conductivity model beneath southeast China is more resistive than that beneath northeast China by more than half an order of magnitude. By comparing the inverse models with the latest laboratory conductivity‐depth profiles, the estimated transition zone water content is less than 0.01 wt% beneath southeast China irrespective of which laboratory data is used. Considering the low‐velocity anomalies in this region, which suggest high‐temperature structures, less water is expected. We, therefore, infer that the mantle transition zone beneath southeast China is dry.

On the characterization of tidal ocean-dynamo signals in coastal magnetic observatories

Periodic tidal ocean currents induce electric currents and, therefore, magnetic field signals that are observable using spaceborne and ground-based observation techniques. In theory, the signals can be used to monitor oceanic temperature and salinity variations. Tidal magnetic field amplitudes and phases have been extracted from magnetometer measurements in the past. However, due to uncertainties caused by a plentitude of influencing factors, the shape and temporal variation of these signals are only known to a limited extent. This study uses past extraction methods to characterize seasonal variations and long-term trends in the ten year magnetometer time series of three coastal island observatories. First, we assess data processing procedures used to prepare ground-based magnetometer observations for tidal ocean dynamo signal extraction to demonstrate that existing approaches, i.e., subtraction of core field models or first-order differencing, are unable to reliably remove low-frequency contributions. We hence propose low-frequency filtering using smoothing splines and demonstrate the advantages over the existing approaches. Second, we determine signal and side peak magnitudes of the M2 tide induced magnetic field signal by spectral analysis of the processed data. We find evidence for seasonal magnetic field signal variations of up to 25% from the annual mean. Third, to characterize the long-term behavior of tidal ocean dynamo signal amplitudes and phases, we apply different signal extraction techniques to identify tidal ocean-dynamo signal amplitudes and phases in sub-series of the ten-year time series with incrementally increasing lengths. The analyses support three main findings: (1) trends cause signal amplitude changes of up to approx 1~nT and phase changes are in the order of {mathcal {O}}(10^{circ }) within the observation period; (2) at least four years of data are needed to obtain reliable amplitude and phase values with the extraction methods used and (3) signal phases are a less dependent on the chosen extraction method than signal amplitudes.Graphical

Velocity dispersion and dynamical masses for 388 galaxy clusters and groups

The second catalogue of Planck Sunyaev-Zeldovich (SZ) sources, hereafter PSZ2, represents the largest galaxy cluster sample selected by means of their SZ signature in a full-sky survey. Using telescopes at the Canary Island observatories, we conducted the long-term observational program 128- MULTIPLE-16/15B (hereafter LP15), a large and complete optical follow-up campaign of all the unidentified PSZ2 sources in the northern sky, with declinations above −15° and no correspondence in the first Planck catalogue PSZ1. This paper is the third and last in the series of LP15 results, after Streblyanska et al. (2019, A&A, 628, A13) and Aguado-Barahona et al. (2019, A&A, 631, A148), and presents all the spectroscopic observations of the full program. We complement these LP15 spectroscopic results with Sloan Digital Sky Survey archival data and other observations from a previous program (ITP13-08), and present a catalogue of 388 clusters and groups of galaxies including estimates of their velocity dispersion. The majority of them (356) are optical counterparts of PSZ2 sources. A subset of 297 of those clusters are used to construct the MSZ − Mdyn scaling relation based on the estimated SZ mass from Planck measurements and our dynamical mass estimates. We discuss and correct for different statistical and physical biases in the estimation of the masses, such as the Eddington bias when estimating MSZ and the aperture and the number of galaxies used to calculate Mdyn. The SZ-to-dynamical mass ratio for those 297 PSZ2 clusters is (1 − B) = 0.80 ± 0.04 (stat) ± 0.05 (sys), with only marginal evidence for a possible mass dependence for this factor. Our value is consistent with previous results in the literature, but is associated with a significantly smaller uncertainty due to the use of the largest sample size for this type of study.

Polarization Characteristics of High-Latitude Pi3 Geomagnetic Pulsations

The results of a statistical study of the polarization characteristics of irregular geomagnetic Pi3 pulsations observed in polar regions of the magnetosphere and the effect of interplanetary conditions on them are presented. One-minute digital observations of the magnetic field of the Heiss Island (HIS, Φ' = 74.80°, Λ' = 144.46°) and Mirny (MIR, Φ' = –76.93°, Λ' = 122.92°) observatories are used. Pi3 pulsations are characterized by right-handed, left-handed, and mixed polarizations (R, L, and R&L types, respectively). Regardless of the polarization type, Pi3 pulsations have been observed mainly in the night sector of the magnetosphere at the final stage of the explosive phase of the substorm. The duration of the time delay between the substorm onset and the occurrence of Pi3 pulsations depends significantly on their polarization type. HIS and MIR show no dependence of the main characteristics (amplitude, frequency, ellipticity, and tilt of the main axis of the polarization ellipse) of Pi3 pulsations of R, L, and R&L types on local time. In HIS, R- and R&L-type Pi3 pulsations are observed mainly during slow solar-wind streams, and L-type pulsations are observed during high-speed streams from coronal holes. In MIR, Pi3 pulsations of the three polarization types are observed mainly during high-speed solar-wind streams. Small-scale closed structures of the magnetic field in the flow of slow and fast solar-wind currents determine the polarization type of Pi3 pulsations. It is revealed that the excitation of Pi3 pulsations of the R, L, and R&L types occurs at different levels of plasma turbulence in the magnetotail.

Exploring effects in tippers at island geomagnetic observatories due to realistic depth- and time-varying oceanic electrical conductivity

Vertical magnetic transfer functions (tippers) estimated at island observatories can constrain the one-dimensional (1-D) conductivity distribution of the oceanic lithosphere and upper mantle. This is feasible due to the bathymetry-dependent ocean induction effect (OIE), which originates from lateral conductivity contrasts between ocean and land and leads to non-zero tippers even for 1-D conductivity distributions below the ocean. Proper analysis of island tippers requires accurate three-dimensional (3-D) modeling of the OIE, for which so far was performed assuming constant sea water electric conductivity with depth. In this study, we explore—using rigorous 3-D electromagnetic modeling—to what extent realistic, depth-dependent, oceanic conductivity affects island tippers. The modeling is performed for 11 island observatories around the world in the period range 10^{-1} to 10^{4} s. We also investigate the effect of seasonal variations of the oceanic conductivity and to which extent this could explain the observed systematic seasonal variation of tippers. Our model studies suggest that for most of the considered island observatories the effect from depth-varying oceanic conductivity is tangible and exceeds the error floor of 0.025, which usually is assigned to tippers during their inversion. The effect varies significantly with location, depending on regional bathymetry. Contrarily, the effects from seasonally varying oceanic conductivity were found to be too small to be worth consideration.

A New Method for Accurate and Efficient Modeling of the Local Ocean Induction Effects. Application to Long‐Period Responses from Island Geomagnetic Observatories

AbstractThere is significant interest in constraining mantle conductivity beneath oceans. One data source to probe oceanic mantle conductivity is magnetic fields measured at island observatories. From these data local responses are estimated and then inverted in terms of conductivity. However, island responses may be strongly distorted by the ocean induction effect (OIE) originating from conductivity contrasts between ocean and land. Insufficiently accurate accounting for OIE may lead to wrong interpretation of the responses. OIE is generally modeled by global simulations using relatively coarse grids to represent bathymetry. We explore whether very local bathymetry influences island responses. To address this question we developed a methodology for efficient modeling of effects of bathymetry of any resolution. On an example of two island observatories we demonstrate that small‐scale bathymetry dramatically influences the responses. Using new methodology we obtain new conductivity models beneath considered islands and observe very good agreement between modeled and experimental responses.

Probing upper mantle electrical conductivity with daily magnetic variations using global-to-local transfer functions

Summary We present new transfer functions (TFs) that can handle external electromagnetic (EM) sources of complex geometry. These TFs relate global expansion coefficients describing the source with a locally measured EM field. In this study, the new TFs concept was applied to the daily magnetic variations measured at the ground. The parameterisation of the source in terms of spherical harmonics was adopted. We used nearly 20 years of data from 125 mid-latitude observatories and explored how the results are affected by (I) solar activity conditions, (II) the choice of the prior conductivity model used for the source coefficient estimation, and (III) the presence of ocean tidal magnetic signals. We found that choosing magnetically quiet periods is beneficial due to simpler source morphology, and the choice of prior conductivity model may significantly affect the source coefficients and TFs at short periods. We further observed significant contributions by ocean tidal magnetic signals at coastal and island observatories and corrected for them. Finally, the estimated TFs were inverted for the mantle conductivity at several locations representing different geological settings.

Optical validation and characterization of Planck PSZ2 sources at the Canary Islands observatories

Aims. The second catalogue of Planck Sunyaev–Zeldovich (SZ) sources, hereafter PSZ2, is the largest sample of galaxy clusters selected through their SZ signature in the full sky. At the time of publication, 21% of these objects had no known counterpart at other wavelengths. Using telescopes at the Canary Island observatories, we conducted the long-term observational programme 128-MULTIPLE-16/15B (hereafter LP15), a large and complete optical follow-up campaign of all the unidentified PSZ2 sources in the northern sky, with declinations above −15° and no correspondence in the first Planck catalogue PSZ1. The main aim of LP15 is to validate all those SZ cluster candidates, and to contribute to the characterization of the actual purity and completeness of full Planck SZ sample. In this paper, we describe the full programme and present the results of the first year of observations. Methods. The LP15 programme was awarded 44 observing nights, spread over two years in three telescopes at the Roque de los Muchachos Observatory. The full LP15 sample comprises 190 previously unidentified PSZ2 sources. For each target, we performed deep optical imaging and spectroscopy. Our validation procedure combined this optical information with SZ emission as traced by the publicly available Planck Compton y-maps. The final classification of the new galaxy clusters as optical counterparts of the SZ signal is established according to several quantitative criteria based on the redshift, velocity dispersion, and richness of the clusters. Results. This paper presents the detailed study of 106 objects out of the LP15 sample, corresponding to all the observations carried out during the first year of the programme. We confirmed the optical counterpart for 41 new PSZ2 sources, 31 of them being validated using also velocity dispersion based on our spectroscopic information. This is the largest dataset of newly confirmed PSZ2 sources without any previous optical information. All the confirmed counterparts are rich structures (i.e. they show high velocity dispersion), and are well aligned with the nominal Planck coordinates (i.e. ∼70% of them are located at less than 3′ distance). In total, 65 SZ sources are classified as unconfirmed, 57 of them being due to the absence of an optical over-density, and eight of them due to a weak association with the observed SZ decrement. Most of the sources with no optical counterpart are located at low galactic latitudes and present strong galactic cirrus in the optical images, the dust contamination being the most probable explanation for their inclusion in the PSZ2 catalogue.

Application of Himawari-8 Satellite Data in Daytime Sea Fog Monitoring in South China Coast

Based on the high temporal and spatial resolution of Japanese Himawari-8 geostationary meteorological satellite data and visibility observation data, the band and band combination was selected suitable for daytime sea fog identification in coastal areas of South China, including R0.64, NDVI, BT11.2-BT10.4, BT11.2-BT3.9, BT11.2 etc, and taken into account the influence of solar elevation angle on the reflectivity channel, and constructed a new coastal fog monitoring model (SFM) in the coastal area of South China for the identification of sea fog in the coastal areas of South China And applications. According to the fog judgment standard promulgated by the China Meteorological Administration, the sea fog monitoring model (SFM) was used to remotely monitor the coastal fog events in South China from January to April 2018, and further used the three provinces of South China (Guangxi, Guangdong, Hainan). Visibility data from coastal and island observatories are verified. The results show that the accuracy of sea fog recognition based on SFM model is about 68.6%, which has a good business application prospect.

A Study of the Magnetospheric Micropulsations Pc5 and Pc6 Using Magnetic Stations at Low Latitude Northern Region of Brazil and Ascension Island during Magnetic Stormed Magnetospheric Plasma

In general, micropulsation is generated by the free energy within the magnetosphere, which is mainly caused by the magnetosphere-solar wind interactions and/or magnetic field reconnections in the magnetospheric tail. In this article, we studied the types of low-frequency magnetospheric micropulsations Pc5 and Pc6 (1 - 6 mHz), during three magnetic storms, using ground magnetic observations. One of the main motivations of this study was to produce scientific knowledge on the subject in order to fill knowledge gaps in this region, collaborating with existing bibliographies. The data were recorded in a series of six Brazilian stations close to the Dip Equator (dip = 0), with using data from the Ascension Island observatory. Pulse trains were found to occur simultaneously with almost identical waveforms, with significant amplitude increase near magnetic local noon. Amplitude spectra showed a clear similarity in all equatorial seasons. The results obtained were compared with studies performed in regions with similar low latitudes. The possible mechanisms that induced these micropulsations and the peculiarities presented by these data were also discussed in this article.

Magnetic Signals at Easter Island During the 2010 and 2015 Chilean Tsunamis Compared with Numerical Models

Tsunami flow across the geomagnetic field induces electric currents in both the ocean and the ionosphere. These currents generate secondary magnetic fields, observable at the seafloor and on land. Magnetic field disturbances during two Chilean tsunamis (2010 and 2015) were recorded at Easter Island Observatory. These tsunamis were produced after the earthquakes in Chile on February 27, 2010, at 06:34 UTC, and September 16, 2015, at 22:55 UTC, respectively. Differences between existing studies regarding the origin of the tsunamigenic disturbances, and the lack of studies using a numerical model for both the water velocity and the induced magnetic field, motivated us to compare magnetic records with computed magnetic fields for the two events. Modeled disturbances were calculated by applying the Biot–Savart law to tsunami simulations. Our model can calculate tsunami-induced perturbations in the vertical component of the geomagnetic field, obtaining a good agreement with the observations. We hypothesize that the magnetic measurements may be produced by a combination of oceanic and ionospheric electric currents. Our analysis further reveals that even a relatively small tsunami, such as the one produced by the 2015 $$M_\text {w}$$ 8.2 earthquake, induces an observable magnetic perturbation due to the water movement. Future improvements to our model may allow us to identify situations in which magnetic variations precede the tsunami arrival, thereby allowing early tsunami detection.

Characterization of a subsample of the Planck SZ source cluster catalogues using optical SDSS DR12 data

Aims. The Planck catalogues of Sunyaev –Zeldovich (SZ) sources, PSZ1 and PSZ2, are the largest catalogues of galaxy clusters selected through their SZ signature in the full sky. In 2013, we started a long-term observational programme at Canary Island observatories with the aim of validating ∼500 unconfirmed SZ sources. In this work we present results of the initial pre-screening of possible cluster counterparts using photometric and spectroscopic data of the Sloan Digital Sky Survey DR12. Our main aim is to identify previously unconfirmed PSZ2 cluster candidates and to contribute in the determination of the actual purity and completeness of Planck SZ source sample. Methods. Using the latest version of the PSZ2 catalogue, we selected all sources overlapping with the SDSS DR12 footprint and without redshift information. We validated these cluster fields following optical criteria (mainly distance with respect to the Planck pointing, magnitude of the brightest cluster galaxy, and cluster richness), and combined these criteria with the profiles of the Planck Compton y-maps. This combined procedure allows for a more robust identification of optical counterparts compared to simply cross-matching with existing SDSS cluster catalogues that have been constructed from earlier SDSS data releases. Results. The sample contains new redshifts for 37 Planck galaxy clusters that were not included in the original release of PSZ2 Planck catalogue. We detect three cases as possible multiple counterparts. We show that a combination of all available information (optical images and profile of SZ signal) can provide correct associations between the observed Planck SZ source and the optically identified cluster. We also show that Planck SZ detection is very sensitive even to high-z (z > 0.5) clusters. In addition, we also present updated spectroscopic information for 34 Planck PSZ1 sources (33 previously photometrically confirmed and 1 new identification).

Stochastic Inversion of Geomagnetic Observatory Data Including Rigorous Treatment of the Ocean Induction Effect With Implications for Transition Zone Water Content and Thermal Structure

AbstractIn this paper we estimate and invert local electromagnetic (EM) sounding data for 1‐D conductivity profiles in the presence of nonuniform oceans and continents to most rigorously account for the ocean induction effect that is known to strongly influence coastal observatories. We consider a new set of high‐quality time series of geomagnetic observatory data, including hitherto unused data from island observatories installed over the last decade. The EM sounding data are inverted in the period range 3–85 days using stochastic optimization and model exploration techniques to provide estimates of model range and uncertainty. The inverted conductivity profiles are best constrained in the depth range 400–1,400 km and reveal significant lateral variations between 400 km and 1,000 km depth. To interpret the inverted conductivity anomalies in terms of water content and temperature, we combine laboratory‐measured electrical conductivity of mantle minerals with phase equilibrium computations. Based on this procedure, relatively low temperatures (1200–1350°C) are observed in the transition zone (TZ) underneath stations located in Southern Australia, Southern Europe, Northern Africa, and North America. In contrast, higher temperatures (1400–1500°C) are inferred beneath observatories on islands, Northeast Asia, and central Australia. TZ water content beneath European and African stations is ∼0.05–0.1 wt %, whereas higher water contents (∼0.5–1 wt %) are inferred underneath North America, Asia, and Southern Australia. Comparison of the inverted water contents with laboratory‐constrained water storage capacities suggests the presence of melt in or around the TZ underneath four geomagnetic observatories in North America and Northeast Asia.

Three‐dimensional simulation of the electromagnetic fields induced by the 2011 Tohoku tsunami

AbstractThe motion of seawater induces electromotive force of significant intensity due to Faraday's law, and the resulting electromagnetic (EM) field can be recorded by instruments installed on land or on the ocean bottom. However, few studies have successfully made a quantitative interpretation to obtain geophysical information from observations of tsunami‐induced EM signals by an exact and accurate application of Maxwell equations. We built a scheme for three‐dimensional numerical simulation to calculate EM fields due to ocean tidal flow and tested the system's accuracy by using the source currents in the ocean as expected from a Tohoku tsunami simulation. Here we show examples of a comparison of data from one land observatory in the Tohoku district, one island observatory in the Izu‐Bonin arc, and one seafloor station in the northwest Pacific Ocean. The water motion that generates source current in the sea consists of both the primary poloidal and toroidal magnetic modes. Our numerical simulation shows that the field of the primary toroidal magnetic mode can be effective for seafloor observations but only when the seafloor is highly conductive. We examined how the conductivity of the shallower part of the seabed, composed of sediments, can be constrained by the tsunami‐induced EM field observations, which is difficult in case of using ordinary seafloor magnetotelluric signals. We also defined the motional impedance just as the case of ordinary magnetotellurics and showed that both modeled and observed impedances approximately indicate the phase velocity of the long wave as predicted by a simple theory.

Tippers at island observatories: Can we use them to probe electrical conductivity of the Earth's crust and upper mantle?

For decades, time series of hourly‐mean values of the geomagnetic field measured on a global network of observatories have been routinely used to recover the electrical conductivity distribution in midmantle depths. Nowadays, most observatories provide data in the form of minute‐means. This allows for analysis of short‐period geomagnetic variations, which, in principle, contain information about geoelectric structures in the crust and upper mantle. However, so far these data have been ignored for induction studies of the Earth due to a theoretical preconception. In this paper, we demonstrate that short‐period responses (tippers) at island observatories, being large owing to the ocean effect, are also sensitive to 1‐D structures and thus can be used for probing the Earth. This means that a huge amount of data that was not exploited hitherto for induction studies should be reconsidered as a useful source of information about geoelectric structures in oceanic regions where our knowledge is still very limited.

Trial of Multidisciplinary Observation at an Expandable Sub-Marine Cabled Station “Off-Hatsushima Island Observatory” in Sagami Bay, Japan

Sagami Bay is an active tectonic area in Japan. In 1993, a real-time deep sea floor observatory was deployed at 1,175 m depth about 7 km off Hatsushima Island, Sagami Bay to monitor seismic activities and other geophysical phenomena. Video cameras monitored biological activities associated with tectonic activities. The observation system was renovated completely in 2000. An ocean bottom electromagnetic meter (OBEM), an ocean bottom differential pressure gauge (DPG) system, and an ocean bottom gravity meter (OBG) were installed January 2005; operations began in February of that year. An earthquake (M5.4) in April 2006, generated a submarine landslide that reached the Hatsushima Observatory, moving some sensors. The video camera took movies of mudflows; OBEM and other sensors detected distinctive changes occurring with the mudflow. Although the DPG and OBG were recovered in January 2008, the OBEM continues to obtain data.

A Brave New World of Knowledge: Shakespeare's 'The Tempest' and Early Modern Epistemology by B. J. Sokol (review)

MLR, 100.3, 2005 773 A Brave New World of Knowledge: Shakespeare's 'The Tempest' and Early Modern Epistemology. By B. J. Sokol. Madison, NJ: Fairleigh Dickinson University Press; London: Associated University Presses. 2003. 274 pp. ?4?- ISBN o8386 -3925-9. At the heart of B. J.Sokol's latest contribution to Shakespeare studies is a presentation of 'scientific matters that have hardly ever before been discussed as significant to The Tempest' (p. 101), the most novel of which are some glass figurines recently recovered by archaeologists working at the site ofthe Jamestown colony. The discoverers ofthese curios believe they were used as weights in prototypicalthermometers; and thus Sokol adduces them as evidence that among the settlers at Jamestown there 'may possibly have been a gentleman scientist' (p. 115). This possibility, what might have been, provides the basis for further speculations about the money loaned to George Percy, one ofthe colonists, by his elder brother, the Earl of Northumberland: 'could some of this [money]', Sokol asks his readers, 'have been fora scientific instrument?' (p. 116). If so, might Shakespeare have known about the atmospheric experiments potentially taking place in Virginia? Personally, I appreciate Sokol's tentative and exploratory approach to these matters and find the admission, on this matter particularly, that crucial information may have been irretrievably lost from the historical record to be a welcome departure from more positivist, but less convincing, attempts to understand the play through its historical contexts. A Brave New World of Knowledge is indeed intrepid in its early chapters, each of which invites us to rethink the old canard that Shakespeare was indifferent, if not inimical, to the scientific revolution burgeoning around him in the seventeenth century. In Sokol's analysis Shakespeare writes within, and with full working knowledge of, the same hydraulically driven clockwork universe that gives rise to Kepler's laws of planetary motion, Cornelis Drebbel's artificial egg hatcheries, and Thomas Harriot's 'computations of potential population growth over time' (p. 52). It comes as a disappointment, therefore, when the final chapter inexplicably exchanges the 'early modern epistemology' of the book's subtitle for a half-hearted Freudian reading of anger, guilt, work, and (not once, but thrice) the 'menstrual theme of The Tempest' (p. 180). Although Sokol's firstsix chapters stress the values of 'incremental' analysis and warn against the dangers of a 'master-discourse' that would seek to account forevery detail of the play, his last chapter nevertheless admits that its 'depth psychological approach to The Tempest is hardly new' except for its 'linking' of other (presumably more incremental) discussions of the same material (p. 189). This shift to psychoanalysis also causes Sokol to overlook a possibility that is, in this reviewer's opinion, every bit as tantalizing as the one about a gentleman scientist at Jamestown. In the final pages Sokol asks, 'what can the play's log-carrying represent that has such necessity that it justifies the retention of Caliban [...]?' His answer: the logs are indices of the male characters' 'painfully carried' erections (pp. 179-80). Here, Sokol could have made better use of one of his own notes about Johannes Kepler's 'elderly mother [. . .] accused of witchcraft' (p. 209 n. 15). Kepler's Somnium, which describes his magic-practising mother and his 'half-savage' upbringing, provocatively parallels the untold story of Caliban and Sycorax even as it makes explicit reference to the island observatory of Tycho Brahe. Sokol's complete omission of Tycho, the alchemist-cum-astronomer, is puzzling. King James, Shakespeare's patron at the time he was writing The Tempest,had some twenty years in the past visited Tycho's island as part of his prenuptial trip to Denmark. Like Prospero, Tycho also surrendered his ancestral estate to a younger brother before relocating, with his renowned library, to Hven. But Tycho did more than read on the island. He published his own books. 774 Reviews So, upon his return to Scotland, King James helped to subsidize the construction of a paper mill on Tycho's island. Given the presence of hunting dogs on Prospero's island, a reminder of the two British mastiffs James left as gifts for Tycho, is it possible that Prospero...

Properties of the EXPORT sample: Spectral type determination

In this paper we present the results of the spectral classification of stars included in the EXPORT (EXoPlanetary Observational Research Team) sample and observed during the 1998–1999 International Time campaigns in the Canary Island observatories. Intermediate resolution spectra obtained with the Isaac Newton Telescope (INT) were used in this work. In addition to the confirmation of some spectral types and changes to previous classifications, we report new results for stars whose spectral type had not been accurately assigned before.