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Special Notice #338: HM Leo HST/COS observations tomorrow; V406 Vir is next target

February 21, 2013: Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471) and AAVSO Special Notice #336 (http://www.aavso.org/aavso-special-notice-336), HST/COS is scheduled to observe HM Leo tomorrow:

    HM Leo  2013 February 22 07:17:20 through 14:22:37 UT
 
Please observe this dwarf nova (V=17.5 at minimum and V=13 at maximum) tonight through February 23 at least and report your observations to the AAVSO.

The next HST/COS target is the novalike variable V406 Vir (SDSS J123813.73-033932.9). It is scheduled to be observed on:

V406 Vir (SDSS J123813.73-033932.9) 2013 March 1 08:37:30 through 14:04:3 UT

V406 Vir is V=17.1-18.0 at minimum. Observations are crucial now through March 2, and especially so through February 28, when the HST/COS scheduling team will make the final decision whether to observe this 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.

Coordinates (2000.0)
HM Leo                               R.A. 09 38 36.99   Dec. +07 14 55.0
V406 Vir (SDSS J123813.73-033932.9)  R.A. 12 38 13.73   Dec. -03 39 32.8

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 using the names HM Leo and V406 Vir, 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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