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19 results on '"Ignace, R"'

2. X-Shooting ULLYSES: Massive stars at low metallicity. I. Project description

Author

Vink, Jorick S., primary, Mehner, A., additional, Crowther, P. A., additional, Fullerton, A., additional, Garcia, M., additional, Martins, F., additional, Morrell, N., additional, Oskinova, L. M., additional, St-Louis, N., additional, ud-Doula, A., additional, Sander, A. A. C., additional, Sana, H., additional, Bouret, J.-C., additional, Kubátová, B., additional, Marchant, P., additional, Martins, L. P., additional, Wofford, A., additional, van Loon, J. Th., additional, Grace Telford, O., additional, Götberg, Y., additional, Bowman, D. M., additional, Erba, C., additional, Kalari, V. M., additional, Abdul-Masih, M., additional, Alkousa, T., additional, Backs, F., additional, Barbosa, C. L., additional, Berlanas, S. R., additional, Bernini-Peron, M., additional, Bestenlehner, J. M., additional, Blomme, R., additional, Bodensteiner, J., additional, Brands, S. A., additional, Evans, C. J., additional, David-Uraz, A., additional, Driessen, F. A., additional, Dsilva, K., additional, Geen, S., additional, Gómez-González, V. M. A., additional, Grassitelli, L., additional, Hamann, W.-R., additional, Hawcroft, C., additional, Herrero, A., additional, Higgins, E. R., additional, John Hillier, D., additional, Ignace, R., additional, Istrate, A. G., additional, Kaper, L., additional, Kee, N. D., additional, Kehrig, C., additional, Keszthelyi, Z., additional, Klencki, J., additional, de Koter, A., additional, Kuiper, R., additional, Laplace, E., additional, Larkin, C. J. K., additional, Lefever, R. R., additional, Leitherer, C., additional, Lennon, D. J., additional, Mahy, L., additional, Maíz Apellániz, J., additional, Maravelias, G., additional, Marcolino, W., additional, McLeod, A. F., additional, de Mink, S. E., additional, Najarro, F., additional, Oey, M. S., additional, Parsons, T. N., additional, Pauli, D., additional, Pedersen, M. G., additional, Prinja, R. K., additional, Ramachandran, V., additional, Ramírez-Tannus, M. C., additional, Sabhahit, G. N., additional, Schootemeijer, A., additional, Reyero Serantes, S., additional, Shenar, T., additional, Stringfellow, G. S., additional, Sudnik, N., additional, Tramper, F., additional, and Wang, L., additional

Published
2023
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3. X-Shooting ULLYSES: Massive stars at low metallicity. III. Terminal wind speeds of ULLYSES massive stars

Author

Hawcroft, C., Sana, H., Mahy, L., Sundqvist, J. O., de Koter, A., Crowther, P. A., Bestenlehner, J. M., Brands, S. A., David-Uraz, A., Decin, L., Erba, C., Garcia, M., Hamann, W. -R., Herrero, A., Ignace, R., Kee, N. D., Kubátová, B., Lefever, R., Moffat, A., Najarro, F., Oskinova, L., Pauli, D., Prinja, R., Puls, J., Sander, A. A. C., Shenar, T., St-Louis, N., ud-Doula, A., and Vink, J. S.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

The winds of massive stars have an impact on stellar evolution and on the surrounding medium. The maximum speed reached by these outflows, the terminal wind speed, is a global wind parameter and an essential input for models of stellar atmospheres and feedback. With the arrival of the ULLYSES programme, a legacy UV spectroscopic survey with HST, we have the opportunity to quantify the wind speeds of massive stars at sub-solar metallicity (in the Large and Small Magellanic Clouds, 0.5Z and 0.2Z) at an unprecedented scale. We empirically quantify the wind speeds of a large sample of OB stars, including supergiants, giants, and dwarfs at sub-solar metallicity. Using these measurements, we investigate trends of terminal wind speed with a number of fundamental stellar parameters, namely effective temperature, metallicity, and surface escape velocity. We empirically determined the terminal wind speed for a sample of 149 OB stars in the Magellanic Clouds either by directly measuring the maximum velocity shift of the absorption component of the Civ 1548-1550 line profile, or by fitting synthetic spectra produced using the Sobolev with exact integration method. Stellar parameters were either collected from the literature, obtained using spectral-type calibrations, or predicted from evolutionary models. We find strong trends of terminal wind speed with effective temperature and surface escape speed when the wind is strong enough to cause a saturated P Cygni profile in Civ 1548-1550. We find evidence for a metallicity dependence on the terminal wind speed proportional to Z^0.22+-0.03 when we compared our results to previous Galactic studies. Our results suggest that effective temperature rather than surface escape speed should be used as a straightforward empirical prediction of terminal wind speed and that the observed metallicity dependence is steeper than suggested by earlier works., Comment: 21 pages, 16 figures, 8 tables. Accepted in A&A

Published
2023
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4. Revealing the structure of the outer disks of Be stars (Corrigendum)

Author

Klement, R., primary, Carciofi, A. C., additional, Rivinius, Th., additional, Matthews, L. D., additional, Vieira, R. G., additional, Ignace, R., additional, Bjorkman, J. E., additional, Mota, B. C., additional, Faes, D. M., additional, Bratcher, A. D., additional, Curé, M., additional, and Štefl, S., additional

Published
2020
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6. Revealing the structure of the outer disks of Be stars

Author

Klement, R., primary, Carciofi, A. C., additional, Rivinius, T., additional, Matthews, L. D., additional, Vieira, R. G., additional, Ignace, R., additional, Bjorkman, J. E., additional, Mota, B. C., additional, Faes, D. M., additional, Bratcher, A. D., additional, Curé, M., additional, and Štefl, S., additional

Published
2017
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8. XMM-Newton observations of the nitrogen-rich Wolf-Rayet star WR 1

Author

Ignace, R., Oskinova, L.M., and Brown, J.C.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics
Abstract

We present XMM-Newton results for the X-ray spectrum from the N-richWolf-Rayet (WR) star WR1. The EPIC instrument was used to obtain a medium-resolution spectrum. The following features characterize this spectrum: ( a) significant emission "bumps" appear that are coincident with the wavelengths of typical strong lines, such as MgXI, SiXIII, and SXV; (b) little emission is detected above 4 keV, in contrast to recent reports of a hard component in the stars WR 6 and WR 110 which are of similar subtype; and ( c) evidence for sulfur K-edge absorption at about 2.6 keV, which could only arise from absorption of X- rays by the ambient stellar wind. The lack of hard emission in our dataset is suggestive that WR 1 may truly be a single star, thus representing the first detailed X-ray spectrum that isolates the WR wind alone ( in contrast to colliding wind zones). Although the properties of the S-edge are not well- constrained by our data, it does appear to be real, and its detection indicates that at least some of the hot gas in WR 1 must reside interior to the radius of optical depth unity for the total absorptive opacity at the energy of the edge.

Published
2003

9. Microlensing of circumstellar envelopes: II. emission lines from radial and azimuthal flow during fold caustic crossings

Author

Bryce, H.M., Ignace, R., and Hendry, M.A.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

This paper examines the line profile evolution due to bulk motion in circumstellar envelopes during microlensing fold caustic crossing events. These events have recently been shown to be a sensitive probe of stellar surface brightness profiles, thus providing a means - through both photometric and spectroscopic observations - to constrain and test stellar atmosphere models. Here it is demonstrated, through the examination of simplified line profiles, that spectroscopic studies of fold caustic crossings could also prove to be a powerful diagnostic of bulk motion in circumstellar envelopes.

Published
2003

15. On X-ray pulsations in β Cephei-type variables.

Author

Oskinova, L. M., Todt, H., Huenemoerder, D. P., Hubrig, S., Ignace, R., Hamann, W.-R., and Balona, L.

Subjects
CEPHEIDS, STELLAR oscillations, X-ray astronomy, SUPERGIANT stars, STELLAR spectra
Abstract

Context. β Cep-type variables are early B-type stars that are characterized by oscillations observable in their optical light curves. At least one β Cep-variable also shows periodic variability in X-rays. Aims. Here we study the X-ray light curves in a sample of β Cep-variables to investigate how common X-ray pulsations are for this type of stars. Methods. We searched the Chandra and XMM-Newton X-ray archives and selected stars that were observed by these telescopes for at least three optical pulsational periods. We retrieved and analyzed the X-ray data for κ Sco, β Cru, and αVir. The X-ray light curves of these objects were studied to test for their variability and periodicity. Results. While there is a weak indication for X-ray variability in βCru, we find no statistically significant evidence of X-ray pulsations in any of our sample stars. This might be due either to the insufficient data quality or to the physical lack of modulations. New, more sensitive observations should settle this question. [ABSTRACT FROM AUTHOR]

Published
2015
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