Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg0}\end{figure}$ Figure 1: Evolution tracks of low mass stars in the $\log \rho_{\rm c} - \log T_{\rm c}$ plane. Bold lines indicate the locations of the ZAMS ( left) and TAMS ( right). Dotted lines are evolution tracks, labelled with the ZAMS mass. The solid lines marked with $\blacksquare$ , $\bullet$ are lines of constant entropy across different stellar models, the dashed lines marked with $\ensuremath{ \settowidth{\timeswidth}{$\times$ } \settowidth{\pluswidth}{$+$ } \addtolength{\timeswidth}{\pluswidth} +\hspace{-.5\timeswidth}\times } , \times$ are isochrones. The shaded region indicates the region where the central entropy is lower than that of a $0.75~M_\odot$ star at 3100 Myr.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=7.8cm,clip]{9931fg1}\end{figure}$ Figure 2: Diagram showing the distribution of material from the parent stars within three of the collision products: t=2800, q = 0.8, M=1.7(corresponding to case M, see text) and t=2800, q = 0.4, M=1.8(case S) and t=3700, q=0.4, M=1.8 (case P) for the bottom row. The dark shading indicates the fraction of material from the primary while the lighter region shows the fraction of material from the secondary. Overplotted are the abundances by mass fraction of hydrogen (solid) and helium (dotted).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg2}\end{figure}$ Figure 3: Illustration of the different cases for the composition profiles in the collision products and the grid parameters for which they occur.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg3.eps}\end{figure}$ Figure 4: Kippenhahn diagrams showing the mixing regions during the contraction phase for the same collision products as shown in Fig. 2.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg4}\end{figure}$ Figure 5: Evolution track of the t=2800, q=0.8, M=1.9 remnant with a mass of $1.75~M_\odot$ ( top solid line) compared with the evolution track of a normal star of the same mass ( bottom solid line). The shape of the evolution tracks after the contraction of the merger remnant is very similar, but the merger track is offset to higher luminosity and is slightly cooler at the end of the main sequence. The dashed line is a shifted version of the main sequence track according to Eqs. (13) and (19), see Sect. 6.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg5}\end{figure}$ Figure 6: Observed colour-magnitude diagram of the open cluster M 67, with blue stragglers highlighted and the positions of the stars in our collision grid at the age of M 67 overplotted. Different symbols correspond to different times of collision, as indicated.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg6}\end{figure}$ Figure 7: As Fig. 6 for NGC 188.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg7} \end{figure}$ Figure 8: Effective core mass fraction for main sequence stars against ZAMS mass, for Z=0.02 ( $\odot$ ). The fitting formula (8) in the mass range 0.4-4.0 $M_\odot$ is shown as a dashed line.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg8}\end{figure}$ Figure 9: The predicted apparent age according to (12), for $\alpha =1.67$ (solid line). The detailed models are indicated by $\odot$ . The dashed line is the prescription from Hurley et al. (2000).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg2}\end{figure}$	Figure 3: Illustration of the different cases for the composition profiles in the collision products and the grid parameters for which they occur.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg3.eps}\end{figure}$	Figure 4: Kippenhahn diagrams showing the mixing regions during the contraction phase for the same collision products as shown in Fig. 2.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg5}\end{figure}$	Figure 6: Observed colour-magnitude diagram of the open cluster M 67, with blue stragglers highlighted and the positions of the stars in our collision grid at the age of M 67 overplotted. Different symbols correspond to different times of collision, as indicated.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg6}\end{figure}$	Figure 7: As Fig. 6 for NGC 188.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg7} \end{figure}$	Figure 8: Effective core mass fraction for main sequence stars against ZAMS mass, for Z=0.02 ( $\odot$ ). The fitting formula (8) in the mass range 0.4-4.0 $M_\odot$ is shown as a dashed line.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{9931fg8}\end{figure}$	Figure 9: The predicted apparent age according to (12), for $\alpha =1.67$ (solid line). The detailed models are indicated by $\odot$ . The dashed line is the prescription from Hurley et al. (2000).
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