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Alert Notice 570: NR TrA (Nova TrA 2008) monitoring in support of XMM observations

March 7, 2017 : Dr. Fred Walter (Stony Brook University) has requested AAVSO observers' assistance in monitoring NR TrA (Nova TrA 2008) in support of upcoming XMM Newton observations. The XMM observations will take place 2017 March 13 06:21 through March 14 10:34 UT.

Dr. Walter writes: "NR TrA (Nova TrA 2008) is a compact eclipsing system with a 5.5 hour period. It was a normal Fe II nova that, upon reaching quiescence, took on the appearance of a super-soft source in the optical high state, which suggests an extremely high mass accretion rate. The optical spectrum is dominated by hot permitted lines of O VI, N V, C IV, and He II. Some nova-like variables have similar spectra, though generally without the hot emission lines.

"Primary eclipse is broad - nearly 40% of the orbit - and deeper at shorter wavelengths, which suggests the eclipse of a hot accretion disk. Primary eclipse depth is about 1 mag at V. There appears to be a shallow secondary eclipse.

"We have a day-long XMM observation of NR TrA scheduled starting at 0621 UT 13 March and running through 1034 UT 14 March. The primary aim is to detect and characterize the eclipse at X-ray and UV wavelengths. We will obtain low cadence BVRI/JHK observations with SMARTS/Andicam.

"We request AAVSO support to obtain continuous photometric time series simultaneous with the XMM observation. Any filters are acceptable, but standard Johnson B, V or Cousins R, I are preferred. Clear filters are acceptable. Differential photometry is acceptable, as the shape and depth of the eclipse is of paramount importance; we can calibrate after the fact. Time resolution better than 5 minutes and uncertainties (outside of eclipse) <0.02 mag are preferred.

"The current out-of-eclipse V magnitude is about 16.5. The B-V and V-I colors are both about 0.3. The best ephemeris I have is:

                                       minimum light at JD 55956.822 + 0.219109E

This is based on data from 2013-2015."

Dr. Walter adds that while obtaining exactly simultaneous observations would be ideal and so preferred, obtaining a good light curve within a few days of the XMM observations is crucial.

Beginning now, observers are requested to monitor NR TrA with nightly snapshots through March 9, then switch to the cadence given above and - paying particular attention to the XMM observation interval - continue time series through March 18, and then return to nightly snapshots through March 22.

Coordinates for NR TrA:   R.A. 16 18 48.21   Dec. -60 27 49.2  (2000.0)

Charts: Charts with a comparison star sequence for NR TrA may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the name NR TRA. IF YOU SUBMIT DIFFERENTIAL PHOTOMETRY, be sure that in your data file, the MTYPE field reads DIF.

This campaign is being monitored on the AAVSO Observing Campaigns webpage and is being followed on the Campaigns and Observation Reports Forum at https://www.aavso.org/content/nr-tra-observing-campaign.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

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