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Table 4

Position angle (PA) determinations by various authors (see Fig. 11 for an illustration).

Author Refa Obs date PA (°) Wavelength Regionb

Lattanzi et al. (1997) [8] 1995 Dec. 17 143c 583 nm inner
Tuthill et al. (1999) [7] 1993 Jun. 94  ±  33 700 and 710 nm inner
Ireland et al. (2004a)  − 2001 Feb. 8/9  −d 680–940 nm inner
Monnier et al. (2004)  − 2000 Jan./Feb.  −d 2.25 μm (K-band) inner
this work [9] 2007–2009 11  ±  20 8–12 μm (N-band) inner
Reid & Menten (2007) [6] 2000 Oct./Nov. 83  ±  18 43 GHz (radio continuum) inner
[5] 2000 Oct./Nov. contours 43 GHz (SiO maser) inner
Imai et al. (2010) [10] 2009 Feb. spots 43 GHz (SiO maser) inner
Reid & Menten (1990) [4] 1990 Feb. contours 22 GHz (H2O maser) intermediate
Marengo et al. (2000)  −e 1999 Jun. N − S 18 μm (1.18′′ × 1.45′′FWHM) outer
Szymczak et al. (1998) [1] 1996 Jan. 15 N → S 1667 MHz (OH maser), velocity gradient outer
[2] 1996 Jan. 15  −20  ±  20f 1667 MHz (OH maser), magnetic field outer
Muller et al. (2008) [3] 2008 Apr. 13/15 NW → SE 266 GHz (thermal HCN), velocity gradient outer
Vlemmings et al. (2011)  −e 2008 Jul. 20 3  ±  10 215 GHz (SO 55 − 44) outer

Notes. 

(a)

Numbering used in Fig. 11;

(b)

probed regions: inner = 50–100 mas, outer  ≈  1000 mas;

(c)

the true major axis cannot be recovered since observations are at two perpendicular baselines;

(d)

no departures from symmetry could be detected within the measurement uncertainties;

(e)

not shown in Fig. 11 since the whole structure does not fit into the illustration;

(f)

the position angle of the major axis of the underlying OH maser distribution is 70°.

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