Happy birthday Hubble

Posted on April 17, 2012 | Leave a comment

Several million stars are vying for attention in this NASA/ESA Hubble Space Telescope image of a raucous stellar breeding ground in 30 Doradus, located in the heart of the Tarantula nebula.

30 Doradus is the brightest star-forming region in our galactic neighbourhood and home to the most massive stars ever seen. The nebula resides 170 000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way. No known star-forming region in our galaxy is as large or as prolific as 30 Doradus.

The image comprises one of the largest mosaics ever assembled from Hubble photos and consists of observations taken by Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, combined with observations from the European Southern Observatory’s MPG/ESO 2.2-metre telescope that trace the location of glowing hydrogen and oxygen.

The image is being released to celebrate Hubble’s 22nd anniversary.

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Hunting for runaway stars

Posted on December 29, 2011 | Leave a comment

In this astrometric program we use the unique capabilities of the Hubble Space Telescope to measure the proper motions of stars in the 30 Doradus region in the Large Magellanic Cloud. Here we present the first epoch of observations, a 16’x13’ mosaic of the data.

Selma E. de Mink, Elena Sabbi, Jay Anderson, Daniel J. Lennon, (PI), Sangmo Tony Sohn, Roeland P. van der Marel, Nolan R. Walborn, Nate Bastian, Luigi R. Bedin, Eli Bressert, Paul A. Crowther, Chris J. Evans, Artemio Herrero, Norbert Langer, Imants Platais, Alex de Koter, & Hugues Sana.

Poster design: Erik Buunk.  Presented at the poster exposition at the AAS meeting in Austin, January 2012.

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Paper accepted: Trumpler 20: multiple populations, stellar rotation or differential reddening?

Posted on December 29, 2011 | Leave a comment

The effects of differential reddening and stellar rotation  on the appearance of multiple populations in star clusters: the case of Trumpler 20.

I. Platais, C. Melo, S. N. Quinn, J. L. Clem, S. E. de Mink, A. Dotter, V. Kozhurina-Platais, D. W. Latham, A. Bellini.

Accepted by ApJ Letters, Dec 2011

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Popular science podscast scienceupdate.com discusses Fastest Spinning Star

Posted on December 21, 2011 | Leave a comment

Bob Hirshon from the AAAS science society discusses the discovery of the fastest spinning star in the popular science podcast: scienceupdate.comhttp://www.scienceupdate.com/2011/12/star/

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Press Release: Fastest Rotating Star Found in Neighboring Galaxy

Posted on December 5, 2011 | Leave a comment

An international team of astronomers using the European Southern Observatory’s Very Large Telescope have found the fastest spinning star ever discovered. VFTS 102 rotates at a dizzying 1 million miles per hour and is very close to the point at which it would be torn apart due to centrifugal forces. The star lies in a neighboring dwarf galaxy, the Large Magellanic Cloud, about 160,000 light-years from Earth. Astronomers think that it may have had a violent past and has been ejected from a double star system by its exploding companion. The team will use NASA’s Hubble Space Telescope to make precise measurements of the star’s proper motion across space.  Press release HubbleSIte NewsCenter

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Pers bericht: Snelst draaiende ster ontdekt

Posted on December 2, 2011 | Leave a comment

VFTS 102 Credit: Morgan Fraser/Philip Dufton/Paul Dunstall/Hubble Legacy ArchiveEen internationaal team van astronomen, onder wie Alex de Koter en Hugues Sana (Universiteit van Amsterdam) en Selma de Mink (Space Telescope Science Institute, Baltimore, VS), heeft in de Grote Magelhaense Wolk een supersnel draaiende ster ontdekt. De equatoriale rotatiesnelheid van VFTS 102 wordt geschat op meer dan twee miljoen kilometer per uur, waarmee het de snelst draaiende ster is die astronomen ooit hebben waargenomen. Het onderzoeksresultaat is gepubliceerd in Astrophysical Journal Letters.
Persbericht NOVA (Nederlandse Onderzoeksschool voor astronomie)

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Paper accepted: Fastest rotating O-type star

Posted on November 1, 2011 | Leave a comment

The VLT-FLAMES Tarantula Survey: The fastest rotating O-type star and shortest period LMC pulsar – remnants of a supernova disrupted binary?

P. L. Dufton, P. R. Dunstall, C. J. Evans, I. Brott, M. Cantiello, A. de Koter, S.E. de Mink, M. Fraser, V. Hénault-Brunet, I. D. Howarth, N. Langer, D. J. Lennon, N. Markova, H. Sana, W. D. Taylor

We present a spectroscopic analysis of an extremely rapidly rotating late O-type star, VFTS102, observed during a spectroscopic survey of 30 Doradus. VFTS102 has a projected rotational velocity larger than 500kms and probably as large as 600kms; as such it would appear to be the most rapidly rotating massive star currently identified. Its radial velocity differs by 40kms from the mean for 30 Doradus, suggesting that it is a runaway. VFTS102 lies 12 pcs from the X-ray pulsar PSR J0537-6910 in the tail of its X-ray diffuse emission. We suggest that these objects originated from a binary system with the rotational and radial velocities of VFTS102 resulting from mass transfer from the progenitor of PSR J0537-691 and the supernova explosion respectively.

Comments: Accepted by ApJL, arXiv:1111.0157v1

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Paper accepted: Extragalactic young massive star clusters

Posted on July 1, 2011 | Leave a comment

Resolved photometry of extragalactic young massive star clusters

S. S. Larsen, S. E. de Mink, J. J. Eldridge, N. Langer, N. Bastian, A. Seth, L. J. Smith, J. Brodie, Y. N. Efremov

We present colour-magnitude diagrams (CMDs) for a sample of seven young massive clusters in the galaxies NGC 1313, NGC 1569, NGC 1705, NGC 5236 and NGC 7793. The clusters have ages in the range 5-50 million years and masses of 10^5 -10^6 Msun. Although crowding prevents us from obtaining photometry in the central regions of the clusters, we are still able to measure up to 30-100 supergiant stars in each of the richest clusters, along with the brighter main sequence stars. The resulting CMDs and luminosity functions are compared with photometry of artificially generated clusters, designed to reproduce the photometric errors and completeness as realistically as possible. In agreement with previous studies, our CMDs show no clear gap between the H-burning main sequence and the He-burning supergiant stars, contrary to predictions by common stellar isochrones. In general, the isochrones also fail to match the observed number ratios of red-to-blue supergiant stars, although the difficulty of separating blue supergiants from the main sequence complicates this comparison. In several cases we observe a large spread (1-2 mag) in the luminosities of the supergiant stars that cannot be accounted for by observational errors. This spread can be reproduced by including an age spread of 10-30 million years in the models. However, age spreads cannot fully account for the observed morphology of the CMDs and other processes, such as the evolution of interacting binary stars, may also play a role.

Comments: 15 pages, 12 figures, Accepted for publication in A&A, arXiv:1106.4560v1 [astro-ph.GA]

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Paper accepted: a massive binary system

Posted on May 1, 2011 | Leave a comment

The VLT-FLAMES Tarantula Survey II: R139 revealed as a massive binary system

W. D. Taylor, C. J. Evans, H. Sana, N. R. Walborn, S. E. de Mink, V. E. Stroud, A. Alvarez-Candal, R. H. Barbá, J. M. Bestenlehner, A. Z. Bonanos, I. Brott, P. A. Crowther, A. de Koter, K. Friedrich, G. Gräfener, V. Hénault-Brunet, A. Herrero, L. Kaper, N. Langer, D. J. Lennon, J. Maíz Apellániz, N. Markova, N. Morrell, L. Monaco, J. S. Vink

We report the discovery that R139 in 30 Doradus is a massive spectroscopic binary system. Multi-epoch optical spectroscopy of R139 was obtained as part of the VLT-FLAMES Tarantula Survey, revealing a double-lined system. The two components are of similar spectral types; the primary exhibits strong C III 4650 emission and is classified as an O6.5 Iafc supergiant, while the secondary is an O6 Iaf supergiant. The radial-velocity variations indicate a highly eccentric orbit with a period of 153.9 days. Photometry obtained with the Faulkes Telescope South shows no evidence for significant variability within an 18 month period. The orbital solution yields lower mass limits for the components of M1sin^3 i = 78 pm 8 Msun and M2sin^3 i = 66 pm 7 Msun. As R139 appears to be the most massive binary system known to contain two evolved Of supergiants, it will provide an excellent test for atmospheric and evolutionary models.

Comments: 5 pages, 5 figures. Letter accepted for publication in A&A, arXiv:1103.5387v1

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Paper accepted: The Tarantula survey of massive stars

Posted on May 1, 2011 | Leave a comment

The VLT-FLAMES Tarantula Survey I: Introduction and observational overview

C. J. Evans (UKATC), W. D. Taylor, V. Henault-Brunet, H. Sana, A. de Koter, S. Simon-Diaz, G. Carraro, T. Bagnoli, N. Bastian, J. M. Bestenlehner, A. Z. Bonanos, E. Bressert, I. Brott, M. A. Campbell, M. Cantiello, J. S. Clark, E. Costa, P. A. Crowther, S. E. de Mink, E. Doran, P. L. Dufton, P. R. Dunstall, K. Friedrich, M. Garcia, M. Gieles, G. Graefener, A. Herrero, I. D. Howarth, R. G. Izzard, N. Langer, D. J. Lennon, J. Maiz Apellaniz, N. Markova, F. Najarro, J. Puls, O. H. Ramirez, C. Sabin-Sanjulian, S. J. Smartt, V. E. Stroud, J. Th. van Loon, J. S. Vink, N. R. Walborn

The VLT-FLAMES Tarantula Survey (VFTS) is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). Here we introduce our scientific motivations and give an overview of the survey targets, including optical and near-infrared photometry and comprehensive details of the data reduction. One of the principal objectives was to detect massive binary systems via variations in their radial velocities, thus shaping the multi-epoch observing strategy. Spectral classifications are given for the massive emission-line stars observed by the survey, including the discovery of a new Wolf-Rayet star (VFTS 682, classified as WN5h), 2′ to the northeast of R136. To illustrate the diversity of objects encompassed by the survey, we investigate the spectral properties of sixteen targets identified by Gruendl & Chu from Spitzer photometry as candidate young stellar objects or stars with notable mid-infrared excesses. Detailed spectral classification and quantitative analysis of the O- and B-type stars in the VFTS sample, paying particular attention to the effects of rotational mixing and binarity, will be presented in a series of future articles to address fundamental questions in both stellar and cluster evolution.

Comments: Accepted by A&A, 52 pages, arXiv:1103.5386v3

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