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William Herschel Telescope Identifies the Companion Star to Type Ia Tycho Brahe´s 1572 Supernova

Centre of Tycho's supernova remnant (Tycho SNR). The star marked as 'g' is the one identified as the companion star of Tycho Brahe´s 1572 supernova as published in Nature on 28 October, 2004 (P. Ruiz-Lapuente, F. Comeron, J. Méndez, R. Canal, S. Smartt, A. Filippenko, R. L. Kurucz, R. Chornock, R. J. Foley, V. Stanishev & R. Ibata, 2004, "The binary progenitor of Tycho Brahe's 1572 supernova", Nature, 431, 1069). Since the supernova explosion in 1572 Tycho G has moved 2.6 arcseconds south on the sky and it is still within a radius of 40 arcseconds centred on Chandra´s measured centre of the X-ray remnant (40 arcseconds is 15% of the innermost radius of Tycho SNR and taken by the authors as the error in the determination of the remnant centre). Tycho G is a star of type G0-G2IV located at the distance of Tycho SNR and it moves in space at 136 km/s, which is a factor of over 3 larger than the mean velocity of the surrounding stars (Tycho G´s metallicity in Fe and Ni are similar to solar values and therefore it can´t be a halo star). Its low surface gravity can also be interpreted as a consequence of mass strip by the impact of the supernova explosion. William Herschel Telescope´s instruments UES, ISIS and Aux Port Camera have played a key role on this research.

Spectra of candidates and Tycho G
Model fits to observed spectra. The stars shown here are the candidate star for the companion of SN 1572 (Tycho G), the red giant (Tycho A) and main-sequence star (Tycho B) nearest to the distance of SN 1572 and to the SNR X-ray centre. Identifications of the most significant metal lines are given. Spectra were obtained at the WHT with UES and ISIS. The upper panel shows the observed spectrum near Hα. This line is blueshifted, implying a peculiar radial velocity exceeding about 3 times the velocity dispersion for its stellar type. More information can be found at Pilar Ruiz-Lapuente et al., 2004, Nature, 431, 1069.



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Last modified: 22 December 2010