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Title: A discovery of young stellar objects in older clusters of the Large Magellanic Cloud
Author: Bi-Qing For, Kenji Bekki

Recent studies have shown that an extended main-sequence turn-off is a common feature among intermediate-age clusters (1--3 Gyr) in the Magellanic Clouds. Multiple-generation star formation and stellar rotation or interacting binaries have been proposed to explain the feature. However, it remains controversial in the field of stellar populations. Here we present the main results of an ongoing star formation among older star clusters in the Large Magellanic Cloud. Cross-matching the positions of star clusters and young stellar objects has yielded 15 matches with 7 located in the cluster center. We demonstrate that this is not by chance by estimating local number densities of young stellar objects for each star cluster. This method is not based on isochrone fitting, which leads to some uncertainties in age estimation and methods of background subtraction. We also find no direct correlation between atomic hydrogen and the clusters. This suggests that gas accretion for fuelling the star formation must be happening in situ. These findings support for the multiple-generations scenario as a plausible explanation for the extended main-sequence turn-off.

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Hubble Watches Stars' Clockwork Motion in Nearby Galaxy

Using the sharp-eyed NASA Hubble Space Telescope, astronomers have for the first time precisely measured the rotation rate of a galaxy based on the clock-like movement of its stars.
According to their analysis, the central part of the neighboring galaxy, called the Large Magellanic Cloud (LMC), completes a rotation every 250 million years. Coincidentally, it takes our Sun the same amount of time to complete a rotation around the center of our Milky Way galaxy.

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Title: Emission-line stars in the LMC: the Armagh survey, and a metacatalogue
Authors: Ian D. Howarth

[Aims] Accurate astrometry is required to reliably cross-match 20th-century photographic catalogues against 21st-century digital surveys. The present work provides modern-era identifications and astrometry for the 801 emission-line objects "of stellar appearance" in the Armagh survey (the largest of its nature to date).
[Methods] Targets have been individually identified in digital images using the Armagh Atlas and, in most cases, unambiguously matched to entries in the UCAC astrometric catalogues.
[Results] Astrometry with sub-arcsecond precision is now available for all the major photographic spectroscopic surveys of the LMC. The results are used to compile an annotated metacatalogue of 1675 individual, spectroscopically identified candidate H-alpha-emission stars, including detailed cross-matching between catalogues, and resolving many (though not all) identification ambiguities in individual primary sources.

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Title: An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
Authors: G. Pietrzyski, D. Graczyk, W. Gieren, I.B. Thompson, B. Pilecki, A. Udalski, I. Soszyski, S. Kozowski, P. Konorski, K. Suchomska, G. Bono, P. G. Prada Moroni, S. Villanova, N. Nardetto, F. Bresolin, R.P. Kudritzki, J. Storm, A. Gallenne, R. Smolec, D. Minniti, M. Kubiak, M. Szymaski, R. Poleski, . Wyrzykowski, K. Ulaczyk, P. Pietrukowicz, M. Górski, P. Karczmarek

In the era of precision cosmology it is essential to determine the Hubble Constant with an accuracy of 3% or better. Currently, its uncertainty is dominated by the uncertainty in the distance to the Large Magellanic Cloud (LMC) which as the second nearest galaxy serves as the best anchor point of the cosmic distance scale. Observations of eclipsing binaries offer a unique opportunity to precisely and accurately measure stellar parameters and distances. The eclipsing binary method was previously applied to the LMC but the accuracy of the distance results was hampered by the need to model the bright, early-type systems used in these studies. Here, we present distance determinations to eight long-period, late- type eclipsing systems in the LMC composed of cool giant stars. For such systems we can accurately measure both the linear and angular sizes of their components and avoid the most important problems related to the hot early-type systems. Our LMC distance derived from these systems is demonstrably accurate to 2.2 % (49.97 ± 0.19 (statistical) ± 1.11 (systematic) kpc) providing a firm base for a 3 % determination of the Hubble Constant, with prospects for improvement to 2 % in the future.

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Key galaxy distance re-measured

Astronomers have updated one of their most important numbers.
It is the distance to the Large Magellanic Cloud, a close-by galaxy to our own Milky Way.
By studying a clutch of rare double stars in the LMC, the scientists were able to determine the separation to be 163,000 light-years.
 

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Glistening cloud acts as cosmic centimetre

Object: Large Magellanic Cloud
Distance: 162,983.82 light years

Glittering like a cobweb covered in dew, the Large Magellanic Cloud floats lazily across the southern sky, blissfully unaware that it is at the centre of a raging controversy. The cloud - really a small galaxy orbiting the Milky Way - is part of a cosmic yardstick, helping us measure how far apart objects are in the universe.
But no one could quite agree on exactly how far away the Large Magellanic Cloud is from Earth. Now the most accurate measurement yet of its distance is helping astronomers use the aloof beauty as the first centimetre in their cosmic ruler.
 
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LHA 120-N 11
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A hidden treasure in the Large Magellanic Cloud

heic1301a.jpg

Nearly 200 000 light-years from Earth, the Large Magellanic Cloud, a satellite galaxy of the Milky Way, floats in space, in a long and slow dance around our galaxy. Vast clouds of gas within it slowly collapse to form new stars. In turn, these light up the gas clouds in a riot of colours, visible in this image from the NASA/ESA Hubble Space Telescope.
The Large Magellanic Cloud (LMC) is ablaze with star-forming regions. From the Tarantula Nebula, the brightest stellar nursery in our cosmic neighbourhood, to LHA 120-N 11, part of which is featured in this Hubble image, the small and irregular galaxy is scattered with glowing nebulae, the most noticeable sign that new stars are being born.

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Title: A multi-wavelength investigation of newly discovered planetary nebulae in the Large Magellanic Cloud: Central stars
Authors: Warren A. Reid

Having completed my search for faint PNe in the LMC, including the outer 64 deg2 area not covered in the original UKST survey, I now have the most complete number of PNe within any galaxy with which to assess stellar parameters. I present preliminary estimates for planetary nebula central star temperatures for 688 LMC PNe using the excitation class parameter derived from emission lines in the nebula. These are then compared to a photoionisation model in order to evaluate the contribution of metallicity when determining stellar temperatures using only emission lines. I include measurements from my latest confirmatory spectroscopic observations which have yielded a further 110 new LMC PNe while confirming the 102 previously known PNe in the outer LMC. These observations, providing low and medium resolution spectra from 3650{\AA} to 6900{\AA}, have been added to my comparable data for PNe in the central 25deg2 of the LMC. The combined data were used to measure fluxes in preparation for a number of projects related to luminosity functions, chemical abundances, central star properties and LMC kinematics. Here I provide a preliminary look at the range of derived central star effective temperature estimates. I also show a correlation between the central star temperatures and the expansion velocity of the nebula.

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Title: Two new Wolf-Rayet stars in the LMC
Authors: Ian D. Howarth, Nolan R. Walborn

We report the discovery of two previously unknown WN3 stars in the Large Magellanic Cloud. Both are bright (15th magnitude), isolated, and located in regions covered in earlier surveys, although both are relatively weak-lined. We suggest that there may be O(10) remaining undiscovered WNE stars in the LMC.

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LMC Clusters
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Title: Age and Mass for 920 LMC Clusters Derived from 100 Million Monte Carlo Simulations
Authors: Bogdan Popescu, M. M. Hanson, Bruce G. Elmegreen

We present new age and mass estimates for 920 stellar clusters in the Large Magellanic Cloud (LMC) based on previously published broad-band photometry and the stellar cluster analysis package, MASSCLEANage. Expressed in the generic fitting formula, d˛N/dM dt ~ M^{\alpha} t^{\beta}, the distribution of observed clusters is described by \alpha = -1.5 to -1.6 and \beta = -2.1 to -2.2. For 288 of these clusters, ages have recently been determined based on stellar photometric colour-magnitude diagrams, allowing us to gauge the confidence of our ages. The results look very promising, opening up the possibility that this sample of 920 clusters, with reliable and consistent age, mass and photometric measures, might be used to constrain important characteristics about the stellar cluster population in the LMC. We also investigate a traditional age determination method that uses a chi˛ minimisation routine to fit observed cluster colours to standard infinite mass limit simple stellar population models. This reveals serious defects in the derived cluster age distribution using this method. The traditional chi˛ minimisation method, due to the variation of U,B,V,R colours, will always produce an overdensity of younger and older clusters, with an underdensity of clusters in the log(age/yr)=[7.0,7.5] range. Finally, we present a unique simulation aimed at illustrating and constraining the fading limit in observed cluster distributions that includes the complex effects of stochastic variations in the observed properties of stellar clusters.

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