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Special Notice #340: HST/COS observations 2013 March 8 and March 9

March 6, 2013: Further to AAVSO Alert Notice 471 ( and AAVSO Special Notice #339 (, HST/COS is scheduled to observe two of the dwarf novae in the CV campaign back-to-back:

on 2013 March 8:
SDSS J103533.03+055158.4  2013 March 8 07:42:37 through 15:04:27 UT
(V=18.8 at minimum, has eclipses)

on 2013 March 9:
SDSS J143544.02+233638.7  2013 March 9 08:35:01 through 13:40:17 UT
(V=18.2 at minimum)

Observations are crucial beginning now and continuing through one night after the HST observations. About 24-36 hours before the planned observations the HST/COS scheduling team will make the final decision whether to observe each system.

As instructed in AAVSO Alert Notice 471, for CCD observers, simultaneous photometry [shortly before, during, and after the HST observations] would be ideal. For the magnitude estimates, a nightly V measurement from now through the HST observations and a day beyond would be best. If positive visual observations are possible, they are welcome, as are visual fainter-than observations fainter than magnitude 15.0.

The next HST/COS target is scheduled to be V485 Cen:
    V485 Cen  2013 March 16 03:02:56 through 09:44:57 UT

V485 Cen, a dwarf nova, is V=18.2 at minimum and V=14 at maximum.

Coordinates (2000.0)
SDSS J103533.03+055158.4  R.A. 10 35 33.03  Dec. +05 51 58.6
SDSS J143544.02+233638.7  R.A. 14 35 44.02  Dec. +23 36 38.7
V485 Cen                  R.A. 12 57 23.18  Dec. -33 12 05.7

Charts may be created using the AAVSO Variable Star Plotter (

Please report observations as soon as possible to the AAVSO International Database using the names SDSS J103533.03+055158.4, SDSS J143544.02+233638.7, and V485 CEN, respectively. 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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