Universitat de - Departament d'Astronomia i Meteorologia ...

98 Chapter 3. LS 5039 as a runaway microquasar
∆α cos δ (mas)
200
0
−200
−400
−600
−800
1900 1920 1940 1960
Time (yr)
1980 2000 2020
∆δ (mas)
1400
1200
1000
800
600
400
200
0
−200
−400
1900 1920 1940 1960
Time (yr)
1980 2000 2020
Figure 3.1: Offsets in Right Ascension (left) and Declination (right), relatives to the
fitted ones for year 2000.0, versus time for all the positions listed in Table 3.1. Open
circles represent the optical positions, and filled circles the radio ones. The solid lines
represent the least squares fits to the whole data sets.
point because of the small error in position, while the proper motions are obtained
by the optical points due to the huge time span.
In Fig. 3.1 we have plotted the offsets in α cos δ and δ from the fitted values for
year 2000.0 versus time, for the data listed in Table 3.1, together with the respective
fits to the data. Notice that in both plots the UCAC1 and VLBA data are almost
superimposed.
3.2 Ejection from the galactic plane
If we assume a distance of 2.9 ± 0.3 kpc to LS 5039, as seen in Sect. 2.5.3, and a
systemic Vr = 4.6 ± 0.5 km s −1 (McSwain et al. 2001), the proper motions estimates
translate into (U = 40 ± 5, V = −82 ± 16, W = −118 ± 19) km s −1 in the Local
Standard of Rest (LSR) defined by (U⊙ = 9, V⊙ = 12, W⊙ = 7) km s −1 . This gives
a total systemic velocity of vsys = (U 2 + V 2 + W 2 ) 1/2 = 149 ± 18 km s −1 . Using a
value of 215 km s −1 for the galactic rotation at 5.8 kpc from the galactic center (Fich
et al. 1989) we can transform the galactic plane space velocities (U and V ) from the
LSR into the LS 5039 regional standard of rest (RSR). Applying this transformation
we find U = 51 ± 6 and V = −71 ± 16 km s −1 , and vsys = 147 ± 17 km s −1 . All
these results are summarized in Table 3.3.