January 21, 2013: Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471) and AAVSO Special Notice #309 (http://www.aavso.org/aavso-special-notice-309), the next HST COS target is the dwarf nova LT Eri (SDSS J040714.78-064425.1). HST COS is scheduled to observe it:
LT Eri 2013 January 24 03:55:46 through 06:29:15 UT
LT Eri is an eclipsing dwarf nova with outbursts about every 18 days. It reaches V magnitude 18-19 at minimum and 15.0-15.1 V at maximum, according to observations in the AAVSO International Database. It does not appear to become brighter than magnitude 15 at maximum, but it needs to be closely watched to make sure that HST planners will be aware should it become brighter than 15.
Your observations are essential, as the HST planners will decide whether to observe LT Eri based on your observations. They will likely make this decision sometime early on January 23.
As instructed in AAVSO Alert Notice 471, for CCD observers, simultaneous photometry [shortly before, during, and after the HST observations] would be ideal. B filter would be best for a light curve, although for the magnitude estimates, a V measurement would be best. An uninterrupted light curve would be better than cycling between filters. At 18-19 V at minimum, LT Eri is too faint for positive visual observations at minimum. If positive visual observations are possible, however, they are welcome, as are visual fainter-than observations fainter than magnitude 14.0.
Coordinates for LT Eri (SDSS J040714.78-064425.1): R.A. 04 07 14.78 Dec. -06 44 25.0 (2000.0)
Charts may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp).
Please report observations as soon as possible to the AAVSO International Database as LT ERI. If an outburst is detected, please report observations immediately. Many thanks!
This AAVSO Special Notice was compiled by Elizabeth O. Waagen.
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