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Alert Notice 596: GW Lib time set for second HST observation

August 31, 2017: Further to AAVSO Alert Notices 591 and 595, Dr. Boris Gaensicke (Warwick University) informs us that the date and time for the second of three HST observations in his campaign on the pulsating white dwarf-containing cataclysmic variable GW Lib has been scheduled for

2017 Sep 6 22:36:04 to Sep 7 02:49:26 UT.

Request Comparison Stars for Variable Star Charts

[Note: If your variable star has an existing sequence, even if it is only one comparison star, please request assistance via CHET. This page is only for variables that have NO comparison stars. Thank you.]

H-R Diagram Education Materials

Our own Donna Young has created an educational activity about variable stars on the HR Diagram. The activity is designed for formal K-16 educators and includes a teacher's guide, background material, student activities and answer keys.

However, the activity is also a great learning tool for those new to variable stars. It will introduce many of the most important types of variable stars and describe how they are related to other types. The genius of HR Diagrams is how they place everything in context of the grand scheme of things.

Alert Notice 595: GW Lib time scheduled for first HST observation

August 24, 2017: Further to AAVSO Alert Notice 591, Dr. Boris Gaensicke (Warwick University) informs us that the first of three HST observations in his campaign on the pulsating white dwarf-containing cataclysmic variable GW Lib has been scheduled for

2017 Aug 31 20:52:02 to 2017 Sep 1 02:12:21 UTC.

Alert Notice 594: Correction to Alert Notice 593

August 17, 2017: In AAVSO Alert Notice 593 we announced a campaign on the very long period VV Cep M2Iabe+B0/2Ve binary. The amplitude of the eclipse was wrongly given as slightly under a magnitude in the V band when it is actually around 0.1 mag. This means that the VV Cep eclipse is largely undetectable visually,  and is not a good candidate for visual observations. CCD and DSLR photometry, however, are still encouraged.

Solar Bulletin - Volume 73, Number 07

The July Solar Bulletin is now available. Please visit the Solar Bulletin web page to download your copy: https://www.aavso.org/solar-bulletin

The July SID Data report is available here: https://www.aavso.org/sid-database

Alert Notice 592: V404 Cyg observations needed tonight for Chandra observations

August 11, 2017: Dr. Gregory Sivakoff (University of Alberta) and colleagues have requested AAVSO observers' assistance in observing the black hole X-ray transient LMXB V404 Cyg in support of Chandra observations taking place TONIGHT. The Chandra schedule is

2017 Aug 11 23:49:04.072  - 2017 Aug 12 13:42:14.730 UTC

Alert Notice 591: GW Lib observations requested in support of K2 and HST observations

August 7, 2017: Dr. Boris Gaensicke (Warwick University) has requested our help in monitoring the pulsating white dwarf-containing cataclysmic variable GW Lib in preparation for and support of K2 (Kepler's Second Light) and Hubble Space Telescope (HST) observations scheduled for August to November 2017 and August and September 2017, respectively.

K2 will be observing GW Lib non-stop 2017 Aug 23 20:00:00 to 2017 Nov 19 23:00:00 UTC.

Alert Notice 590: V1117 Her observations requested

August 7, 2017: AAVSO Young Stellar Object (YSO) Section leader Michael Poxon (Great Plumstead, Norfolk, UK) requests coverage of the YSO V1117 Her.

He writes: "The peculiar YSO V1117 Herculis has undergone a second, rapid fade and recovery only a few days after its recovery from another rapid fade. Observations, both visual and multiwavelength, are encouraged, since the behaviour of this star's historical fading episodes may indicate rapidly-changing evolution of the protoplanetary clumps in the circumstellar disc.

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