arXiv subjects

Richard de Grijs

Publications and source records attributed to Richard de Grijs.

At least 73 records · Page 4Linked to original sources

arXiv2021

European Longitude Prizes. III. The Unsolved Mystery of an Alleged Venetian Longitude Prize

Despite frequent references in modern reviews to a seventeenth-century Venetian longitude prize, only a single, circumstantial reference to the alleged prize is known from contemporary sources. Edward Harrison's scathing assessment of the conditions governing the award of an alleged Venetian longitude prize simultaneously disparages the rewards offered by the Dutch States General. However, the latter had long run its course by 1696, the year of the citation, thus rendering Harrison's reference unreliable. Whereas other longitude awards offered by the leading European maritime nations attracted applicants from far and wide, often accompanied by extensive, self-published pamphlets, the alleged Venetian prize does not seem to have been subject to similar hype. The alleged existence of seventeenth-century Venetian award is particularly curious, because the city's fortune was clearly in decline, and longitude determination on the open seas does not appear to have been a priority; the city's mariners already had access to excellent "portolan" charts. It is therefore recommended that authors refrain from referring to a potentially phantom Venetian longitude prize in the same context as the major sixteenth- to eighteenth-century European awards offered by the dominant sea-faring nations.

physics.hist-ph↗

arXiv2021

European Longitude Prizes. IV. Thomas Axe's Impossible Terms

Although governments across Europe had realised the need to incentivise the development of practically viable longitude solutions as early as the late-sixteenth century, the English government was late to the party. An sense of urgency among the scientific community and maritime navigators led to the establishment of a number of longitude awards by private donors. The first private British award was bequeathed in 1691 by Thomas Axe, parish clerk of Ottery St. Mary (Devon). Despite the absence of an expenses component and the onerous and costly nature of its terms and conditions, the Axe prize attracted a number of optimistic claimants. Although the award was never disbursed, it may have contributed to the instigation of the government-supported monetary reward associated with the British Longitude Act of 1714. It is likely that the conditions governing the British "Longitude Prize", specifically the required accuracy and the need for sea trials and of disclosure of a successful method's theoretical principles, can be traced back at least in part to the Axe Prize requirements.

physics.hist-ph↗

arXiv2021

The GALAH+ Survey: Third Data Release

The ensemble of chemical element abundance measurements for stars, along with precision distances and orbit properties, provides high-dimensional data to study the evolution of the Milky Way. With this third data release of the Galactic Archaeology with HERMES (GALAH) survey, we publish 678 423 spectra for 588 571 mostly nearby stars (81.2% of stars are within <2 kpc), observed with the HERMES spectrograph at the Anglo-Australian Telescope. This release (hereafter GALAH+ DR3) includes all observations from GALAH Phase 1 (bright, main, and faint survey, 70%), K2-HERMES (17%), TESS-HERMES (5%), and a subset of ancillary observations (8%) including the bulge and >75 stellar clusters. We derive stellar parameters $T_\text{eff}$, $\log g$, [Fe/H], $v_\text{mic}$, $v_\text{broad}$ & $v_\text{rad}$ using our modified version of the spectrum synthesis code Spectroscopy Made Easy (SME) and 1D MARCS model atmospheres. We break spectroscopic degeneracies in our spectrum analysis with astrometry from $Gaia$ DR2 and photometry from 2MASS. We report abundance ratios [X/Fe] for 30 different elements (11 of which are based on non-LTE computations) covering five nucleosynthetic pathways. We describe validations for accuracy and precision, flagging of peculiar stars/measurements and recommendations for using our results. Our catalogue comprises 65% dwarfs, 34% giants, and 1% other/unclassified stars. Based on unflagged chemical composition and age, we find 62% young low-$α$, 9% young high-$α$, 27% old high-$α$, and 2% stars with $\mathrm{[Fe/H]} \leq -1$. Based on kinematics, 4% are halo stars. Several Value-Added-Catalogues, including stellar ages and dynamics, updated after $Gaia$ eDR3, accompany this release and allow chrono-chemodynamic analyses, as we showcase.

astro-ph.GA↗

arXiv2021

Stellar substructures in the periphery of the Magellanic Clouds with the VISTA Hemisphere Survey from the red clump and other tracers

We study the morphology of the stellar periphery of the Magellanic Clouds in search of substructure using near-infrared imaging data from the VISTA Hemisphere Survey (VHS). Based on the selection of different stellar populations using the ($J-K_\mathrm{s}$, $K_\mathrm{s}$) colour-magnitude diagram, we confirm the presence of substructures related to the interaction history of the Clouds and find new substructures on the easter side of the LMC disc which may be owing to the influence of the Milky Way, and on the northern side of the SMC, which is probably associated to the ellipsoidal structure of the galaxy. We also study the luminosity function of red clump stars in the SMC and confirm the presence of a bi-modal distance distribution, in the form of a foreground population. We find that this bi-modality is still detectable in the eastern regions of the galaxy out to a 10 deg distance from its centre. Additionally, a background structure is detected in the North between 7 and 10 deg from the centre which might belong to the Counter Bridge, and a foreground structure is detected in the South between 6 and 8 deg from the centre which might be linked to the Old Bridge.

astro-ph.GA↗

arXiv2021

Gaia EDR3 Parallax Zero-point Offset based on W Ursae Majoris-type Eclipsing Binaries

We independently determine the zero-point offset of the Gaia early Data Release-3 (EDR3) parallaxes based on $\sim 110,000$ W Ursae Majoris (EW)-type eclipsing binary systems. EWs cover almost the entire sky and are characterized by a relatively complete coverage in magnitude and color. They are an excellent proxy for Galactic main-sequence stars. We derive a $W1$-band Period-Luminosity relation with a distance accuracy of $7.4\%$, which we use to anchor the Gaia parallax zero-point. The final, global parallax offsets are $-28.6\pm0.6$ $μ$as and $-25.4\pm4.0$ $μ$as (before correction) and $4.2\pm0.5$ $μ$as and $4.6\pm3.7$ $μ$as (after correction) for the five- and six-parameter solutions, respectively. The total systematic uncertainty is $1.8$ $μ$as. The spatial distribution of the parallax offsets shows that the bias in the corrected Gaia EDR3 parallaxes is less than 10 $μ$as across $40\%$ of the sky. Only $15\%$ of the sky is characterized by a parallax offset greater than 30 $μ$as. Thus, we have provided independent evidence that the parallax zero-point correction provided by the Gaia team significantly reduces the prevailing bias. Combined with literature data, we find that the overall Gaia EDR3 parallax offsets for Galactic stars are $[-20, -30]$ $μ$as and 4-10 $μ$as, respectively, before and after correction. For specific regions, an additional deviation of about 10 $μ$as is found.

astro-ph.SR↗

arXiv2021

Searching for chemical abundance variations in young star clusters in the Magellanic Clouds: NGC 411, NGC 1718 and NGC 2213

The conventional picture of coeval, chemically homogeneous, populous star clusters -- known as `simple stellar populations' (SSPs) -- is a view of the past. Photometric and spectroscopic studies reveal that almost all ancient globular clusters in the Milky Way and our neighbouring galaxies exhibit star-to-star light-element abundance variations, typically known as 'multiple populations' (MPs). Here, we analyse photometric $\it Hubble$ $\it Space$ $\it Telescope$ observations of three young ($<$2 Gyr-old) Large and Small Magellanic Cloud clusters, NGC 411, NGC 1718 and NGC 2213. We measure the widths of their red-giant branches (RGBs). For NGC 411, we also use a pseudo-colour--magnitude diagram (pseudo-CMD) to assess its RGB for evidence of MPs. We compare the morphologies of the clusters' RGBs with artificially generated SSPs. We conclude that their RGBs do not show evidence of significant broadening beyond intrinsic photometric scatter, suggesting an absence of significant chemical abundance variations in our sample clusters. Specifically, for NGC 411, NGC 1718 and NGC 2213 we derive maximum helium-abundance variations of delta_Y=0.003$\pm$0.001 Y=0.300), 0.002$\pm$0.001 (Y=0.350) and 0.004$\pm$0.002 (Y=0.300), respectively. We determined an upper limit to the NGC 411 nitrogen-abundance variation of $Δ$[N/Fe] = 0.3 dex; the available data for our other clusters do not allow us to determine useful upper limits. It thus appears that the transition from SSPs to MPs occurs at an age of ~2 Gyr, implying that age might play an important role in this transition. This raises the question as to whether this is indeed a fundamental minimum-age limit for the formation of MPs.

astro-ph.GA↗

arXiv2021

The spatial distributions of blue main-sequence stars in Magellanic Cloud star clusters

The color-magnitude diagrams (CMDs) of young star clusters show that, particularly at ultraviolet wavelengths, their upper main sequences (MSs) bifurcate into a sequence comprising the bulk population and a blue periphery. The spatial distribution of stars is crucial to understand the reasons for these distinct stellar populations. This study uses high-resolution photometric data obtained with the Hubble Space Telescope to study the spatial distributions of the stellar populations in seven Magellanic Cloud star clusters. The cumulative radial number fractions of blue stars within four clusters are strongly anti-correlated with those of the high-mass-ratio binaries in the bifurcated region, with negative Pearson coefficients < -0.7. Those clusters generally are young or in an early dynamical evolutionary stage. In addition, a supporting N-body simulation suggests the increasing percentage of blue-MS stars from the cluster centers to their outskirts may be associated with the dissolution of soft binaries. This study provides a different perspective to explore the MS bimodalities in young clusters and adds extra puzzles. A more comprehensive study combined with detailed simulations is needed in the future.

astro-ph.SR↗

arXiv2021

Binary-driven stellar rotation evolution at the main-sequence turn-off in star clusters

The impact of stellar rotation on the morphology of star cluster colour-magnitude diagrams is widely acknowledged. However, the physics driving the distribution of the equatorial rotation velocities of main-sequence turn-off (MSTO) stars is as yet poorly understood. Using Gaia Data Release 2 photometry and new Southern African Large Telescope medium-resolution spectroscopy, we analyse the intermediate-age ($\sim1\,$Gyr-old) Galactic open clusters NGC 3960, NGC 6134 and IC 4756 and develop a novel method to derive their stellar rotation distributions based on SYCLIST stellar rotation models. Combined with literature data for the open clusters NGC 5822 and NGC 2818, we find a tight correlation between the number ratio of slow rotators and the clusters' binary fractions. The blue-main-sequence stars in at least two of our clusters are more centrally concentrated than their red-main-sequence counterparts. The origin of the equatorial stellar rotation distribution and its evolution remains as yet unidentified. However, the observed correlation in our open cluster sample suggests a binary-driven formation mechanism.

astro-ph.SR↗

arXiv2021

Eclipsing Binary Populations across the Northern Galactic Plane from the KISOGP survey

We present a catalog of eclipsing binaries in the northern Galactic Plane from the Kiso Wide-Field Camera Intensive Survey of the Galactic Plane (KISOGP). We visually identified 7055 eclipsing binaries spread across $\sim$330 square degrees, including 4197 W Ursa Majoris/EW-, 1458 $β$ Lyrae/EB-, and 1400 Algol/EA-type eclipsing binaries. For all systems, $I$-band light curves were used to obtain accurate system parameters. We derived the distances and extinction values for the EW-type objects from their period--luminosity relation. We also obtained the structure of the thin disk from the distribution of our sample of eclipsing binary systems, combined with those of high-mass star-forming regions and Cepheid tracers. We found that the thin disk is inhomogeneous in number density as a function of Galactic longitude. Using this new set of distance tracers, we constrain the detailed structure of the thin disk. Finally, we report a global parallax zero-point offset of $ Δπ=-42.1\pm1.9\mbox{(stat.)}\pm12.9\mbox{(syst.)}$ $μ$as between our carefully calibrated EW-type eclipsing binary positions and those provided by Gaia Early Data Release 3. Implementation of the officially recommended parallax zero-point correction results in a significantly reduced offset. Additionally, we provide a photometric characterization of our EW-type eclipsing binaries that can be applied to further analyses.

astro-ph.SR↗

arXiv2021

Sydney's Scientific Beginnings: William Dawes' Observatories in Context

The voyage of the "First Fleet" from Britain to the new colony of New South Wales was not only a military enterprise, it also had a distinct scientific purpose. Britain's fifth Astronomer Royal, Nevil Maskelyne, had selected William Dawes, a promising young Marine with a propensity for astronomical observations, as his protégé. Maskelyne convinced the British Board of Longitude to supply Dawes with a suite of state-of-the-art instruments and allow the young Marine to establish an observatory in the new settlement. The Astronomer Royal may have had a dual motivation, one driven by strategic national interests combined with a personal investment linked to the suggested re-appearance of a comet in the southern sky. With the unexpected assistance of the French Lapérouse expedition, between 1788 and 1791 Dawes established not one but two observatories within a kilometre of Sydney's present-day city centre. Motivated by persisting confusion in the literature, we explore the historical record to narrow down the precise location of Dawes' observatory. We conclude that the memorial plaque attached to Sydney Harbour Bridge indicates an incorrect location. Overwhelming contemporary evidence -- maps, charts and pictorial representations -- implies that Dawes' observatory was located on the northeastern tip of the promontory presently known as The Rocks (formerly Dawes' Point), with any remains having vanished during the construction of the Harbour Bridge.

physics.hist-ph↗

arXiv2021

William Dawes: Practical Astronomy on the "First Fleet" from England to Australia

On 13 May 1787, a convict fleet of 11 ships left Portsmouth, England, on a 24,000 km, 8-month-long voyage to New South Wales. The voyage would take the "First Fleet" under Captain Arthur Phillip via Tenerife (Canary Islands), the port of Rio de Janeiro (Brazil), Table Bay at the southern extremity of the African continent and the southernmost cape of present-day Tasmania to their destination of Botany Bay. Given the navigation tools available at the time and the small size of the convoy's ships, their safe arrival within a few days of each other was a phenomenal achievement. This was particularly so, because they had not lost a single ship and only a relatively small number of crew and convicts. Phillip and his crew had only been able to ensure their success because of the presence of crew members who were highly proficient in practical astronomy, most notably Lieutenant William Dawes. We explore in detail his educational background and the events leading up to Dawes' appointment by the Board of Longitude as the convoy's dedicated astronomer-cum-Marine. In addition to Dawes, John Hunter, second captain of the convoy's flagship H.M.S. Sirius, Lieutenant William Bradley and Lieutenant Philip Gidley King were also experts in navigation and longitude determination, using both chronometers and "lunar distance" measurements. The historical record of the First Fleet's voyage is remarkably accurate, even by today's standards.

physics.hist-ph↗

arXiv2021

RR Lyrae variables in Messier 53: Near-infrared Period--Luminosity relations and the calibration using Gaia Early Data Release 3

We present new near-infrared, $JHK_s$, Period--Luminosity relations (PLRs) for RR Lyrae variables in the Messier 53 (M53 or NGC 5024) globular cluster. Multi-epoch $JHK_s$ observations, obtained with the WIRCam instrument on the 3.6-m Canada France Hawaii Telescope, are used for the first time to estimate precise mean-magnitudes for 63 RR Lyrae stars in M53 including 29 fundamental-mode (RRab) and 34 first-overtone modes (RRc) variables. The $JHK_s$-band PLRs for RR Lyrae stars are best constrained for RRab types with a minimal scatter of 22, 23, and 19 mmag, respectively. The combined sample of RR Lyrae is used to derive the $K_s$-band PLR, $K_s = -2.303 (0.063) \log P + 15.212 (0.016)$ exhibiting a $1σ$ dispersion of only $0.027$ mag. Theoretical Period--Luminosity--Metallicity (PLZ) relations are used to predict parallaxes for 400 Galactic RR Lyrae resulting in a median parallax zero-point offset of $-7\pm3~μ$as in {\it Gaia} Early Data Release 3 (EDR3), which increases to $22\pm2~μ$as if the parallax corrections are applied. We also estimate a robust distance modulus, $μ_\textrm{M53} = 16.403 \pm 0.024$ (statistical) $\pm 0.033$ (systematic) mag, to M53 based on theoretical calibrations. Homogeneous and precise mean-magnitudes for RR Lyrae in M53 together with similar literature data for M3, M4, M5, and $ω$ Cen are used to empirically calibrate a new RR Lyrae PLZ$_{K_s}$ relation, $K_s = -0.848 (0.007) -2.320 (0.006) \log P + 0.166 (0.011) {\rm[Fe/H]}$, anchored with {\it Gaia} EDR3 distances and theoretically predicted relations, and simultaneously estimate precise RR Lyrae based distances to these globular clusters.

astro-ph.SR↗

arXiv2021

European Longitude Prizes. II. Astronomy, Religion and Engineering Solutions in the Dutch Republic

The late-sixteenth century witnessed a major expansion of Dutch shipping activity from northern European waters to the Indian Ocean and beyond. At a time when the Renaissance had just arrived on the North Sea's shores, scientist-scholars, navigators and merchants alike realised the urgent need for and potential profitability of developing a practical means of longitude determination at sea. Under pressure of early adopters, including Petrus Plancius and Simon Stevin, on 1 April 1600 the national government of the Dutch Republic announced a generous longitude prize, which would see gradual increases in value over the next two centuries. In addition to leading thinkers like Galileo and Christiaan Huygens, the Low Countries spawned major talent in pursuit of a longitude solution. Their solutions reached well beyond applications of the ephemerides of Jupiter's moons or the development of a stable marine timepiece. Studies of the Earth's magnetic field, lunar distances, astronomical observations combined with simple trigonometry and the design of a "golden compass" all pushed the nation's maritime capabilities to a higher level. Dutch efforts to "find East and West" were unparalleled and at least as insightful as those pursued elsewhere on the continent.

physics.hist-ph↗

arXiv2020

Multiple stellar populations at less evolved stages: detection of chemical variations among main-sequence dwarfs in NGC 1978

Multiple stellar populations (MPs) with different chemical compositions are not exclusive features of old GCs (older than 10 Gyr). Indeed, recent studies reveal that younger clusters ($\sim$2--6 Gyr-old) in the Magellanic Clouds also exhibit star-to-star chemical variations among evolved stars. However, whether MPs are present among less evolved dwarfs of these intermediate-age clusters is still unclear. In this work, we search for chemical variations among GK-type dwarfs in the $\sim$2 Gyr-old cluster NGC 1978, which is the youngest cluster with MPs. We exploit deep ultraviolet and visual observations from the Hubble Space Telescope to constrain the nitrogen (N) and oxygen (O) variations among MS stars. To do this, we compare appropriate photometric diagrams that are sensitive to N and O with synthetic diagrams of simple stellar populations and MPs. We conclude that the G- and K-type MS stars in NGC\,1978 host MPs. Our statistical analysis shows that the fraction of N-rich stars ranges from $\sim$40\% to $\sim$80\%, depending on the detailed distributions of nitrogen and oxygen.

astro-ph.SR↗

arXiv2020

Gaia view of a stellar sub-structure in front of the Small Magellanic Cloud

Recent observational studies identified a foreground stellar sub-structure traced by red clump (RC) stars (~ 12 kpc in front of the main body) in the eastern regions of the Small Magellanic Cloud (SMC) and suggested that it formed during the formation of the Magellanic Bridge (MB), due to the tidal interaction of the Magellanic Clouds. Previous studies investigated this feature only up to 4.0 deg from the centre of the SMC due to the limited spatial coverage of the data and hence could not find a physical connection with the MB. To determine the spatial extent and properties of this foreground population, we analysed data from the Gaia data release 2 (DR2) of a ~ 314 sq. deg region centred on the SMC, which cover the entire SMC and a significant portion of the MB. We find that the foreground population is present only between 2.5 deg to ~ 5-6 deg from the centre of the SMC in the eastern regions, towards the MB and hence does not fully overlap with the MB in the plane of the sky. The foreground stellar population is found to be kinematically distinct from the stellar population of the main body with ~ 35 km/s slower tangential velocity and moving to the North-West relative to the main body. Though the observed properties are not fully consistent with the simulations, a comparison indicates that the foreground stellar structure is most likely a tidally stripped counterpart of the gaseous MB and might have formed from the inner disc (dominated by stars) of the SMC. A chemical and 3D kinematic study of the RC stars along with improved simulations, including both tidal and hydro-dynamical effects, are required to understand the offset between the foreground structure and MB.

astro-ph.GA↗

arXiv2020

European Longitude Prizes. I. Longitude Determination in the Spanish Empire

Following Columbus' voyages to the Americas, Castilian (Spanish) and Portuguese rulers engaged in heated geopolitical competition, which was eventually reconciled through a number of treaties that divided the world into two unequal hemispheres. However, the early-sixteenth-century papal demarcation line was poorly defined. Expressed in degrees with respect to a vague reference location, determination of longitude at sea became crucial in the nations' quest for expanding spheres of influence. In Spain, King Philip II and his son, Philip III, announced generous rewards for those whose solutions to the longitude problem performed well in sea trials and which were suitable for practical implementation. The potential reward generated significant interest from scientist-scholars and opportunists alike. The solutions proposed and the subset taken to sea provided important physical insights that still resonate today. None of the numerous approaches based on compass readings ("magnetic declination") passed the exacting sea trials, but the brightest sixteenth-century minds already anticipated that lunar distances and the use of marine timepieces would eventually enable more precise navigation. With most emphasis in the English-language literature focused on longitude solutions developed in Britain, France and the Low Countries, the earlier yet groundbreaking Spanish efforts have, undeservedly, largely been forgotten. Yet, they provided a firm basis for the development of an enormous "cottage industry" that lasted until the end of the eighteenth century.

physics.hist-ph↗

arXiv2020

The intrinsic reddening of the Magellanic Clouds as traced by background galaxies -- II. The Small Magellanic Cloud

We present a map of the total intrinsic reddening across ~34 deg$^{2}$ of the Small Magellanic Cloud (SMC) derived using optical ($ugriz$) and near-infrared (IR; $YJK_{\mathrm{s}}$) spectral energy distributions (SEDs) of background galaxies. The reddening map is created using a subsample of 29,274 galaxies with low levels of intrinsic reddening based on the LePhare $χ^{2}$ minimisation SED-fitting routine. We find statistically significant enhanced levels of reddening associated with the main body of the SMC compared with regions in the outskirts [$ΔE(B-V)\simeq 0.3$ mag]. A comparison with literature reddening maps of the SMC shows that, after correcting for differences in the volume of the SMC sampled, there is good agreement between our results and maps created using young stars. In contrast, we find significant discrepancies between our results and maps created using old stars or based on longer wavelength far-IR dust emission that could stem from biased samples in the former and uncertainties in the far-IR emissivity and the optical properties of the dust grains in the latter. This study represents one of the first large-scale categorisations of extragalactic sources behind the SMC and as such we provide the LePhare outputs for our full sample of ~500,000 sources.

astro-ph.GA↗

arXiv2020

Near-infrared Census of RR Lyrae variables in the Messier 3 globular cluster and the Period--Luminosity Relations

We present new near-infrared ($JHK_s$) time-series observations of RR Lyrae variables in the Messier 3 (NGC 5272) globular cluster using the WIRCam instrument at the 3.6-m Canada France Hawaii Telescope. Our observations cover a sky area of $\sim 21'\times 21'$ around the cluster center and provide an average of twenty epochs of homogeneous $JHK_s$-band photometry. New homogeneous photometry is used to estimate robust mean magnitudes for 175 fundamental-mode (RRab), 47 overtone-mode (RRc), and 11 mixed-mode (RRd) variables. Our sample of 233 RR Lyrae variables is the largest thus far obtained in a single cluster with time-resolved, multi-band near-infrared photometry. Near-infrared to optical amplitude ratios for RR Lyrae in Messier 3 exhibit a systematic increase moving from RRc to short-period ($P < 0.6$~days) and long-period ($P \gtrsim 0.6$~days) RRab variables. We derive $JHK_s$-band Period--Luminosity relations for RRab, RRc, and the combined sample of variables. Absolute calibrations based on the theoretically predicted Period--Luminosity--Metallicity relations for RR Lyrae stars yield a distance modulus, $μ= 15.041 \pm 0.017~(\textrm{statistical}) \pm 0.036~(\textrm{systematic})$~mag, to Messier 3. When anchored to trigonometric parallaxes for nearby RR Lyrae stars from the {\it Hubble Space Telescope} and the {\it Gaia} mission, our distance estimates are consistent with those resulting from the theoretical calibrations, albeit with relatively larger systematic uncertainties.

astro-ph.SR↗