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Classification of MASTER OT J061451.70-272535.5 as an eclipsing Polar

ATel #7169; D. A.H. Buckley, J. Breytenbach, A. Kniazev, M. M. Kotze, M. Motsoaledi, S. Potter (SAAO), J. Thorstensen (Dartmouth College), E. Gorbovskoy, V. Lipunov (SAI), P. Woudt (UCT)
on 3 Mar 2015; 00:43 UT
Credential Certification: David Buckley (dibnob@saao.ac.za)

Subjects: Optical, Cataclysmic Variable

MASTER OT J061451.70-272535.5, which was discovered by MASTER SAAO on Feb.19.97 UT (ATel #7127) as an unfiltered 18.3 magnitude transient, was observed photometrically at the SAAO using the 1.9 m and 1.0 m telescopes using the SHOC high speed EM-CCD cameras. Observations were obtained as follows: Date; Time Start (UT); Observation Length; Exposure Time; Filter; Telescope 2015-02-24; 18:15:44; 206.1min; 15s; clear filter; 1.9m 2015-02-25; 18:19:10; 208.5 min; 10s; clear; 1.9 m 2015-02-26; 18:41:19; 231.8 min; 10s; clear; 1.9 m 2015-02-27; 18:14:37; 200.6 min; 10s; clear; 1.9 m 2015-02-28; 18:40:16; 240.0 min; 45s; B filter; 1.0 m 2015-02-28; 18:55:15; 225.1 min; 15s; V filter; 1.9 m 2015-03-01; 18:29:20; 93.4 min; 10s; clear; 1.9 m Light curves have revealed that the system shows eclipses, with a period of 2.08 hours, confirming it as a Cataclysmic Variable. In addition, the eclipse is structured with an initial sharp ingress, where the intensity drops to ~50% of the pre-eclipse level, before slowly increasing in brightness again. A second rapid ingress follows, where the system becomes totally eclipsed, followed by a sharp egress. We interpret this as evidence for initial obscuration of a bright component of the accretion stream, followed by an eclipse of the white dwarf and accretion spot(s), which is often seen in eclipsing Polar (AM Herculis) systems. A preliminary eclipse ephemeris for the sharp egress is: T = 2457080.4403(3) + 0.08660(2) E. The target was observed with SALT RSS on Feb. 28.88 UT using the PG900 lines/mm grating at an angle of 14.75 degrees. An 800 s exposure spectrum, covering 4060 - 7120 Angstroms at a resolution of 7.6 Angstroms with a 2.0 arcsec slit, was obtained in clear conditions. The spectrum shows all of the Balmer lines in emission, a strong HeII 4686Å line at a peak flux greater than H-beta, and weaker HeI lines. The parameters from Gaussian fits (all +/- 1 A) are as follows: Line; E.W. (A); FWHM (A) H-delta; 16.5; 9.7 H-gamma; 22.6; 14.2 HeII 4686A; 25.9; 15.1 H-beta; 27.3; 21.1 H-alpha; 19.8; 18.8 The lines appear asymmetric and double peaked, with wings extending to shorter wavelengths. This spectrum is typical of a magnetic Cataclysmic Variable, and therefore together with the photometric evidence, we identify the system to be a new eclipsing Polar.