Next Article in Journal
Cartesian Material Space with Active-Passive Densities of Complex Charges and Yin-Yang Compensation of Energy Integrals
Previous Article in Journal
Planets, Planetary Nebulae, and Intermediate Luminosity Optical Transients (ILOTs)
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Addendum

Addendum: Cohen, M.H. OJ 287 as a Rotating Helix. Galaxies 2017, 5, 12

Department of Astronomy, California Institute of Technology, Pasadena, 91125 CA, USA
Galaxies 2018, 6(2), 59; https://doi.org/10.3390/galaxies6020059
Submission received: 27 April 2018 / Revised: 22 May 2018 / Accepted: 22 May 2018 / Published: 28 May 2018

Abstract

:
In an earlier paper it was erroneously stated that the inner jet of OJ 287 has a right-hand helical structure. In this addendum we show that the observations underlying this statement are ambiguous, and that they cannot determine the rotation sense.

In Cohen [1] it was stated that the helical structure in the inner jet of OJ 287 has a right-hand twist. This conclusion was based on the evolution of the ridgelines of the object, but we now recognize that the observations are ambiguous. The penultimate sentence of the second paragraph of Section 3 (“The jet rotation … Figures 2 and 3.”) should be deleted. In addition, the third paragraph of Section 3 (“In Figures 2 and 3 … right-hand helix.”) should be deleted, and replaced by the following paragraph.
In Figures 2 and 3, the inner portions of the ridgelines rotate CW and in Figure 4 they lie in the sky plane, first north of the axis and then, from about 2000 to 2010, south of the axis. We assume that these motions are projections of rotations on a cone around the axis, of the long curves that represent the jet in Figure 4. These projections all appear to start in the x (west) direction, and Figure 4 shows the jet successively in black, red, and green at φ = 0 , 90 and −180 . This corresponds to a CW rotation on the cone, as seen by the observer. However, the deprojection could have been made the opposite way, with CCW rotation, with φ = 0 , + 90 and 180 , because the cone has a small intrinsic opening angle, α o . The apparent opening angle, α a p p , is measured in Figure 2 as the angle between the axis and the peak of the curves around 1997, and is about 22 . The relation connecting these angles is tan α o = tan α a p p sin θ o ; and, since α a p p is clearly less than 45 , α o < θ o and the entire cone is projected to the west. Both rotation senses are allowed by the observations.

References

  1. Cohen, M.H. OJ 287 as a Rotating Helix. Galaxies 2017, 5, 12. [Google Scholar] [CrossRef]

Share and Cite

MDPI and ACS Style

Cohen, M.H. Addendum: Cohen, M.H. OJ 287 as a Rotating Helix. Galaxies 2017, 5, 12. Galaxies 2018, 6, 59. https://doi.org/10.3390/galaxies6020059

AMA Style

Cohen MH. Addendum: Cohen, M.H. OJ 287 as a Rotating Helix. Galaxies 2017, 5, 12. Galaxies. 2018; 6(2):59. https://doi.org/10.3390/galaxies6020059

Chicago/Turabian Style

Cohen, Marshall H. 2018. "Addendum: Cohen, M.H. OJ 287 as a Rotating Helix. Galaxies 2017, 5, 12" Galaxies 6, no. 2: 59. https://doi.org/10.3390/galaxies6020059

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop