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Your search keyword '"Van Helshoecht V."' showing total 12 results
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12 results on '"Van Helshoecht V."'

1. Ensemble asteroseismology of pulsating B-type stars in NGC 6910

Author

Moździerski, D., Pigulski, A., Kołaczkowski, Z., Michalska, G., Kopacki, G., Carrier, F., Walczak, P., Narwid, A., Stęślicki, M., Fu, J. -N., Jiang, X. -J., Zhang, Ch., Jackiewicz, J., Telting, J., Morel, T., Saesen, S., Zahajkiewicz, E., Bruś, P., Śródka, P., Vučković, M., Verhoelst, T., Van Helshoecht, V., Lefever, K., Gielen, C., Decin, L., Vanautgaerden, J., and Aerts, C.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Asteroseismology offers the possibility of probing stellar interiors and testing evolutionary and seismic models. Precise photometry and spectroscopy obtained during multi-site campaigns on young open clusters allows discovering rich samples of pulsating stars and using them in a simultaneous seismic modelling called ensemble asteroseismology. The aim of this study is to obtain the age of the open cluster NGC 6910 by means of ensemble asteroseismology of the early-type pulsating members, to derive their stellar parameters, and to classify the excited modes. We used time-series analysis, performed photometric and spectroscopic mode identification, and calculated grids of evolutionary and seismic models to apply the procedure of ensemble asteroseismology for nine pulsating members of NGC 6910. With two iterations of the procedure of ensemble asteroseismology applied to nine pulsating stars we derived an age of 10.6$^{+0.9}_{-0.8}$ Myr for NGC 6910. Of the nine pulsating stars examined in the paper, eight are $\beta$ Cep stars, including three that are hybrid $\beta$ Cep and slowly pulsating B-type (SPB) pulsators, and one is an SPB star. Interestingly, the least massive $\beta$ Cep star, NGC 6910-38, has a mass of about 5.6 M$_\odot$. The present theory does not predict unstable $p$ modes in B-type stars with such a low mass. The $g$ modes with relatively high frequencies ($>3.5$ d$^{-1}$), observed in three members of the cluster, are also stable according to seismic modelling. Both findings pose a challenge for theoretical calculations and prompt a revision of the opacities. The procedure of ensemble asteroseismology was found to be successful for NGC 6910 and $\chi$ Per on the basis of pulsating B-type stars and can therefore be applied to other young open clusters that are rich in such stars., Comment: 22 pages, 24 figures. Caution: arXiv abstract is shorter than in the article

Published
2019
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2. Towards ensemble asteroseismology of the young open clusters Chi Persei and NGC 6910

Author

Saesen, S., Pigulski, A., Carrier, F., Michalska, G., Aerts, C., De Ridder, J., Briquet, M., Handler, G., Kolaczkowski, Z., Acke, B., Bauwens, E., Beck, P. G., Blom, Y., Blommaert, J., Broeders, E., Cherix, M., Davignon, G., Debosscher, J., Degroote, P., Decin, L., Dehaes, S., De Meester, W., Deroo, P., Desmet, M., Drummond, R., Eggen, J. R., Fu, J., Gazeas, K., Gelven, G. A., Gielen, C., Huygen, R., Jiang, X., Kalomeni, B., Kim, S. -L., Kim, D. H., Kopacki, G., Kwon, J. -H., Ladjal, D., Lee, C. -U., Lee, Y. -J., Lefever, K., Leitner, A., Lenz, P., Liakos, A., Lorenz, D., Narwid, A., Niarchos, P., Oestensen, R., Poretti, E., Prins, S., Provencal, J., Antolin, E. Puga, Puschnig, J., Raskin, G., Reed, M. D., Reyniers, M., Schmidt, E., Schmitzberger, L., Spano, M., Steininger, B., Steslicki, M., Uytterhoeven, K., Vanautgaerden, J., Vandenbussche, B., Van Helshoecht, V., Vanhollebeke, E., Van Winckel, H., Verhoelst, T., Vuckovic, M., Waelkens, C., Wolf, G. W., Yakut, K., Zhang, C., and Zima, W.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

As a result of the variability survey in Chi Persei and NGC6910, the number of Beta Cep stars that are members of these two open clusters is increased to twenty stars, nine in NGC6910 and eleven in Chi Persei. We compare pulsational properties, in particular the frequency spectra, of Beta Cep stars in both clusters and explain the differences in terms of the global parameters of the clusters. We also indicate that the more complicated pattern of the variability among B type stars in Chi Persei is very likely caused by higher rotational velocities of stars in this cluster. We conclude that the sample of pulsating stars in the two open clusters constitutes a very good starting point for the ensemble asteroseismology of Beta Cep-type stars and maybe also for other B-type pulsators., Comment: 4 pages, Astronomische Nachrichten, HELAS IV Conference, Arecife, Lanzarote, Feb 2010, submitted

Published
2010
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3. Photometric multi-site campaign on the open cluster NGC 884 I. Detection of the variable stars

Author

Saesen, S., Carrier, F., Pigulski, A., Aerts, C., Handler, G., Narwid, A., Fu, J. N., Zhang, C., Jiang, X. J., Vanautgaerden, J., Kopacki, G., Stȩślicki, M., Acke, B., Poretti, E., Uytterhoeven, K., Gielen, C., Østensen, R., De Meester, W., Reed, M. D., Kołaczkowski, Z., Michalska, G., Schmidt, E., Yakut, K., Leitner, A., Kalomeni, B., Cherix, M., Spano, M., Prins, S., Van Helshoecht, V., Zima, W., Huygen, R., Vandenbussche, B., Lenz, P., Ladjal, D., Antolín, E. Puga, Verhoelst, T., De Ridder, J., Niarchos, P., Liakos, A., Lorenz, D., Dehaes, S., Reyniers, M., Davignon, G., Kim, S. -L., Kim, D. H., Lee, Y. -J., Lee, C. -U., Kwon, J. -H., Broeders, E., Van Winckel, H., Vanhollebeke, E., Waelkens, C., Raskin, G., Blom, Y., Eggen, J. R., Degroote, P., Beck, P., Puschnig, J., Schmitzberger, L., Gelven, G. A., Steininger, B., Blommaert, J., Drummond, R., Briquet, M., and Debosscher, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

CONTEXT: Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. AIMS: To improve our comprehension of the beta Cep stars, we studied the young open cluster NGC 884 to discover new B-type pulsators, besides the two known beta Cep stars, and other variable stars. METHODS: An extensive multi-site campaign was set up to gather accurate CCD photometry time series in four filters (U, B, V, I) of a field of NGC884. Fifteen different instruments collected almost 77500 CCD images in 1286 hours. The images were calibrated and reduced to transform the CCD frames into interpretable differential light curves. Various variability indicators and frequency analyses were applied to detect variable stars in the field. Absolute photometry was taken to deduce some general cluster and stellar properties. RESULTS: We achieved an accuracy for the brightest stars of 5.7 mmag in V, 6.9 mmag in B, 5.0 mmag in I and 5.3 mmag in U. The noise level in the amplitude spectra is 50 micromag in the V band. Our campaign confirms the previously known pulsators, and we report more than one hundred new multi- and mono-periodic B-, A- and F-type stars. Their interpretation in terms of classical instability domains is not straightforward, pointing to imperfections in theoretical instability computations. In addition, we have discovered six new eclipsing binaries and four candidates as well as other irregular variable stars in the observed field., Comment: Accepted for publication in Astronomy and Astrophysics, 21 pages, 14 figures, 4 tables. The full appendix is available at http://www.ster.kuleuven.be/~sophies/Appendix.pdf (74 MB, 169 pages, 343 figures, 1 table)

Published
2010
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4. Ensemble asteroseismology of pulsating B-type stars in NGC 6910

Author

Moździerski, D., primary, Pigulski, A., additional, Kołaczkowski, Z., additional, Michalska, G., additional, Kopacki, G., additional, Carrier, F., additional, Walczak, P., additional, Narwid, A., additional, Stęślicki, M., additional, Fu, J.-N., additional, Jiang, X.-J., additional, Zhang, Ch., additional, Jackiewicz, J., additional, Telting, J., additional, Morel, T., additional, Saesen, S., additional, Zahajkiewicz, E., additional, Bruś, P., additional, Śródka, P., additional, Vučković, M., additional, Verhoelst, T., additional, Van Helshoecht, V., additional, Lefever, K., additional, Gielen, C., additional, Decin, L., additional, Vanautgaerden, J., additional, and Aerts, C., additional

Published
2019
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5. Towards ensemble asteroseismology of the young open clusters χ Persei and NGC 6910

Author

Saesen, S. Pigulski, A. Carrier, F. Michalska, G. Aerts, C. De Ridder, J. Briquet, M. Handler, G. Kołaczkowski, Z. Acke, B. Bauwens, E. Beck Blom, Y. Blommaert, J. Broeders, E. Cherix, M. Davignon, G. Debosscher, J. Degroote, P. Decin, L. Dehaes, S. De Meester, W. Deroo, P. Desmet, M. Drummond, R. Eggen, J.R. Fu, J. Gazeas, K. Gelven, G.A. Gielen, C. Huygen, R. Jiang, X. Kalomeni, B. Kim, S.-L. Kim, D.H. Kopacki, G. Kwon, J.-H. Ladjal, D. Lee, C.-U. Lee, Y.-J. Lefever, K. Leitner, A. Lenz, P. Liakos, A. Lorenz, D. Narwid, A. Niarchos, P. Østensen, R. Poretti, E. Prins, S. Provencal, J. Puga Antolin, E. Puschnig, J. Raskin, G. Reed, M.D. Reyniers, M. Schmidt, E. Schmitzberger, L. Spano, M. Steininger, B. SteeLicki, M. Uytterhoeven, K. Vanautgaerden, J. Vandenbussche, B. Van Helshoecht, V. Vanhollebeke, E. Van Winckel, H. Verhoelst, T. Vućković, M. Waelkens, C. Wolf, G. Yakut, K. Zhang, C. Zima, W.

Abstract

As a result of the variability survey in χ Persei and NGC 6910, the number of β Cep stars that are members of these two open clusters is increased to twenty stars, nine in NGC 6910 and eleven in χ Persei. We compare pulsational properties, in particular the frequency spectra, of β Cep stars in both clusters and explain the differences in terms of the global parameters of the clusters. We also indicate that the more complicated pattern of the variability among B-type stars in χ Persei is very likely caused by higher rotational velocities of stars in this cluster. We conclude that the sample of pulsating stars in the two open clusters constitutes a very good starting point for the ensemble asteroseismology of β Cep-type stars and maybe also for other B-type pulsators. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Published
2010

6. Photometric multi-site campaign on the open cluster NGC 884 I. Detection of the variable stars

Author

Saesen, S. Carrier, F. Pigulski, A. Aerts, C. Handler, G. Narwid, A. Fu, J. N. Zhang, C. Jiang, X. J. and Vanautgaerden, J. Kopacki, G. Steslicki, M. Acke, B. and Poretti, E. Uytterhoeven, K. Gielen, C. Ostensen, R. De Meester, W. Reed, M. D. Kolaczkowski, Z. Michalska, G. and Schmidt, E. Yakut, K. Leitner, A. Kalomeni, B. Cherix, M. Spano, M. Prins, S. Van Helshoecht, V. Zima, W. and Huygen, R. Vandenbussche, B. Lenz, P. Ladjal, D. and Antolin, E. Puga Verhoelst, T. De Ridder, J. Niarchos, P. and Liakos, A. Lorenz, D. Dehaes, S. Reyniers, M. and Davignon, G. Kim, S. -L. Kim, D. H. Lee, Y. -J. Lee, C. -U. Kwon, J. -H. Broeders, E. Van Winckel, H. and Vanhollebeke, E. Waelkens, C. Raskin, G. Blom, Y. Eggen, J. R. Degroote, P. Beck, P. Puschnig, J. Schmitzberger, L. Gelven, G. A. Steininger, B. Blommaert, J. Drummond, R. Briquet, M. Debosscher, J.

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Context. Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. Aims. To improve our comprehension of the beta Cep stars, we studied the young open cluster NGC 884 to discover new B- type pulsators, besides the two known beta Cep stars, and other variable stars. Methods. An extensive multi-site campaign was set up to gather accurate CCD photometry time series in four filters (U, B, V, I) of a field of NGC 884. Fifteen different instruments collected almost 77 500 CCD images in 1286 h. The images were calibrated and reduced to transform the CCD frames into interpretable differential light curves. Various variability indicators and frequency analyses were applied to detect variable stars in the field. Absolute photometry was taken to deduce some general cluster and stellar properties. Results. We achieved an accuracy for the brightest stars of 5.7 mmag in V, 6.9 mmag in B, 5.0 mmag in I and 5.3 mmag in U. The noise level in the amplitude spectra is 50 mu mag in the V band. Our campaign confirms the previously known pulsators, and we report more than one hundred new multi- and mono- periodic B-, A- and F-type stars. Their interpretation in terms of classical instability domains is not straightforward, pointing to imperfections in theoretical instability computations. In addition, we have discovered six new eclipsing binaries and four candidates as well as other irregular variable stars in the observed field.

Published
2010

7. Asteroseismology of massive stars in the young open cluster NGC 884: a status report

Author

Saesen, S., Carrier, F., Pigulski, A., Aerts, C., Handler, G., Narwid, A., Fu, J. N., Zhang, C., Jiang, X. J., Kopacki, G., Vanautgaerden, J., Steślicki, M., Acke, B., Poretti, E., Uytterhoeven, K., De Meester, W., Reed, M. D., Kołaczkowski, Z., Michalska, G., Schmidt, E., xd6stensen, R., Gielen, C., Yakut, K., Leitner, A., Kalomeni, B., Prins, S., van Helshoecht, V., Zima, W., Huygen, R., Vandenbussche, B., Lenz, P., Ladjal, E., Puga Antolxedn, E., Verhoelst, T., De Ridder, J., Niarchos, P., Liakos, A., Lorenz, Saesen, Carrier, Pigulski, Aerts, Handler, Narwid, J. N., Zhang, Jiang, X. J., Kopacki, Vanautgaerden, Steślicki, Acke, Poretti, Uytterhoeven, De Meester, Reed, M. D., Kołaczkowski, Michalska, Schmidt, xd6stensen, Gielen, Yakut, Leitner, Kalomeni, Prins, van Helshoecht, Zima, Huygen, Vandenbussche, Lenz, Ladjal, Puga Antolxedn, Verhoelst, De Ridder, Niarchos, and Liakos

Published
2009

8. Photometric multi-site campaign on massive B stars in the open cluster chi Persei (NGC 884)

Author

Saesen, S. Pigulski, A. Carrier, F. De Ridder, J. Aerts, C. Handler, G. Narwid, A. Fu, J. N. Zhang, C. Jiang, X. J. Kopacki, G. Vanautgaerden, J. Steslicki, M. Acke, B. Poretti, E. Uytterhoeven, K. De Meester, W. Reed, M. D. Kolaczkowski, Z. Michalska, G. Schmidt, E. Ostensen, R. Gielen, C. Yakut, K. Leitner, A. Kalomeni, B. and Prins, S. Van Helshoecht, V. Zima, W. Huygen, R. and Vandenbussche, B. Lenz, P. Ladjal, D. Antolin, E. Puga and Verhoelst, T. Niarchos, P. Liakos, A. Lorenz, D. Dehaes, S. Reyniers, M. Davignon, G. Kim, S-L Kim, D. H. and Lee, Y-J Lee, C-U Kwon, J-H Broeders, E. Van Winckel, H. and Vanhollebeke, E. Raskin, G. Blom, Y. Eggen, J. R. and Beck, P. Puschnig, J. Schmitt, L. Gelven, G. A. and Steiniger, B. Drummond, R.

Abstract

In 2005 a photometric observation campaign started on the open cluster chi Persei, involving 13 telescopes spread over the whole northern hemisphere. After two years we gathered almost 1200 hours of data. We present here preliminary results on the variability search, especially from the 60-cm telescope in Bialkow (Poland), which show seven confirmed beta Cephei stars, four candidate B-type pulsators and other interesting variable stars.

Published
2008

9. Towards ensemble asteroseismology of the young open clusters χ Persei and NGC 6910

Author

Saesen, S., primary, Pigulski, A., additional, Carrier, F., additional, Michalska, G., additional, Aerts, C., additional, De Ridder, J., additional, Briquet, M., additional, Handler, G., additional, Kołaczkowski, Z., additional, Acke, B., additional, Bauwens, E., additional, Beck, P.G., additional, Blom, Y., additional, Blommaert, J., additional, Broeders, E., additional, Cherix, M., additional, Davignon, G., additional, Debosscher, J., additional, Degroote, P., additional, Decin, L., additional, Dehaes, S., additional, De Meester, W., additional, Deroo, P., additional, Desmet, M., additional, Drummond, R., additional, Eggen, J.R., additional, Fu, J., additional, Gazeas, K., additional, Gelven, G.A., additional, Gielen, C., additional, Huygen, R., additional, Jiang, X., additional, Kalomeni, B., additional, Kim, S.‐L., additional, Kim, D.H., additional, Kopacki, G., additional, Kwon, J.‐H., additional, Ladjal, D., additional, Lee, C.‐U., additional, Lee, Y.‐J., additional, Lefever, K., additional, Leitner, A., additional, Lenz, P., additional, Liakos, A., additional, Lorenz, D., additional, Narwid, A., additional, Niarchos, P., additional, Østensen, R., additional, Poretti, E., additional, Prins, S., additional, Provencal, J., additional, Puga Antolin, E., additional, Puschnig, J., additional, Raskin, G., additional, Reed, M.D., additional, Reyniers, M., additional, Schmidt, E., additional, Schmitzberger, L., additional, Spano, M., additional, Steininger, B., additional, Stęślicki, M., additional, Uytterhoeven, K., additional, Vanautgaerden, J., additional, Vandenbussche, B., additional, Van Helshoecht, V., additional, Vanhollebeke, E., additional, Van Winckel, H., additional, Verhoelst, T., additional, Vučković, M., additional, Waelkens, C., additional, Wolf, G.W., additional, Yakut, K., additional, Zhang, C., additional, and Zima, W., additional

Published
2010
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10. Photometric multi-site campaign on the open cluster NGC 884

Author

Saesen, S., primary, Carrier, F., additional, Pigulski, A., additional, Aerts, C., additional, Handler, G., additional, Narwid, A., additional, Fu, J. N., additional, Zhang, C., additional, Jiang, X. J., additional, Vanautgaerden, J., additional, Kopacki, G., additional, Stęślicki, M., additional, Acke, B., additional, Poretti, E., additional, Uytterhoeven, K., additional, Gielen, C., additional, Østensen, R., additional, De Meester, W., additional, Reed, M. D., additional, Kołaczkowski, Z., additional, Michalska, G., additional, Schmidt, E., additional, Yakut, K., additional, Leitner, A., additional, Kalomeni, B., additional, Cherix, M., additional, Spano, M., additional, Prins, S., additional, Van Helshoecht, V., additional, Zima, W., additional, Huygen, R., additional, Vandenbussche, B., additional, Lenz, P., additional, Ladjal, D., additional, Puga Antolín, E., additional, Verhoelst, T., additional, De Ridder, J., additional, Niarchos, P., additional, Liakos, A., additional, Lorenz, D., additional, Dehaes, S., additional, Reyniers, M., additional, Davignon, G., additional, Kim, S.-L., additional, Kim, D. H., additional, Lee, Y.-J., additional, Lee, C.-U., additional, Kwon, J.-H., additional, Broeders, E., additional, Van Winckel, H., additional, Vanhollebeke, E., additional, Waelkens, C., additional, Raskin, G., additional, Blom, Y., additional, Eggen, J. R., additional, Degroote, P., additional, Beck, P., additional, Puschnig, J., additional, Schmitzberger, L., additional, Gelven, G. A., additional, Steininger, B., additional, Blommaert, J., additional, Drummond, R., additional, Briquet, M., additional, and Debosscher, J., additional

Published
2010
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12. K-band magnitude of the red clump as a distance indicator*

Author

Van Helshoecht, V., Groenewegen, M. A. T., Van Helshoecht, V., and Groenewegen, M. A. T.

Abstract

We have investigated how the K-band magnitude of the red clump $[M_K(RC)]$depends on age and metallicity, using 2MASS infrared data for a sample of 24 open clusters with known distances. We show that a constant value of $M_K(RC)=-1.57 \pm 0.05$is a reasonable assumption to use in distance determinations for clusters with metallicity between -0.5 and +0.4 dex and age between 108.5and 109.9years.

Published
2007
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