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Alert Notice 533: Coverage of V5668 Sgr (Nova Sgr 2015 No. 2) requested in support of HST spectroscopy

October 30, 2015: Dr. Peter Kuin (Mullard Space Science Laboratory, University College London) and colleagues in the Swift Nova group have requested AAVSO observers' assistance in multicolor monitoring of V5668 Sgr (Nova Sgr 2015 No. 2, see AAVSO Alert Notices 512, 519) in support of an upcoming spectroscopic observation with the Hubble Space Telescope Imaging Spectrograph (STIS).

The purpose of the requested monitoring is two-fold: to know the brightness of V5668 Sgr at the time of the STIS observation (B magnitude is most helpful), and to know the nova's optical behavior prior to the time of observation in order to provide the HST operators with a status report of its brightness 24 hours before the observation time so they can make a final decision about approving the observations. If the nova re-brightens by about a magnitude, it could well be too bright for STIS and the observations would be cancelled. Thus, your observations are crucial.

Dr. Kuin writes: "We hope that the [STIS] high resolution spectrum will help determine the abundances and velocities of the different atomic and ionic species in the nova ejecta, and learn that way something new about the dust formation...this one observation is of sufficiently high spectral resolution that it complements what we (the Swift nova group) already have very nicely."  

The STIS observation will be carried out on 2015 November 6 around 01 hour UT. Beginning immediately, observers are requested to observe V5668 Sgr in B, V, and SDSS g' bands. Because the spectra will be taken in the UV and far UV regions, the bluer the monitoring band, the better; B photometry will be particularly valuable. Visual observations are also welcome. Nightly observations are requested through November 13; time series observations are not necessary.

Coordinates: R.A. 18 36 56.84   Dec. -28 55 39.8  (2000.0)

Charts for V5668 Sgr with comparison star sequence may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations promptly to the AAVSO International Database using the name "V5668 SGR".

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

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