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Alert Notice 658: EC 21178-5417 being observed with Chandra

December 3, 2018: Further to AAVSO Alert Notice 652, Dr. Koji Mukai (NASA-Greenbelt Space Flight Center) informs us that EC 21178-5417, one of the novalike variables in his target list, will be observed with Chandra on 2018 December 5 20:18 UT - December 6 01:00 UT.

Knowing the status of the target is essential for interpreting the X-ray data. Dr. Mukai thanks observers for the observations they have already made of EC 21178-5417, and asks if more observations (a snapshot every one to two nights) could be made between now and December 15. V filter is optimal. Visual observations are welcome. The range of EC 21178-5417 is 13.4-15.2 CV.

As Dr. Mukai wrote in Alert Notice 652, "We think we know how dwarf novae behave in X-rays, through various campaigns (famously that one on SS Cyg in outburst that Janet Mattei [and AAVSO observers] was heavily involved in, with Pete Wheatley and Chris Mauche, 2003MNRAS.345...49W): they are X-ray bright in optical quiescence, and fainter and softer in X-rays during outburst. In the optical, we think of nova-likes as systems in permanent outburst — but in X-rays, they don’t quite resemble dwarf novae in outburst. In fact, we haven’t seen a clear pattern, when we made X-ray observations of nova-like systems at various optical magnitudes. This Chandra program is part of an effort to look for patterns and to understand their X-ray emission."

Observers are reminded that occasional snapshots (again, V is preferred) are also needed of the remaining targets on the list given in Alert Notice 652 (1SWASP J022916.91-395901.4, KQ Mon, LQ Peg, UU Aqr; V378 Peg has already been observed). Please see that Alert Notice for information on coordinates and magnitude ranges.

Coordinates (2000) of EC 21178-5417: RA 21 21 26.53  Dec. -54 04 34.6

Charts with comparison star sequences for EC 21178-5417 may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the name EC 21178-5417.

AAVSO Forums: This campaign is the topic of the AAVSO Campaigns and Observation Reports forum thread https://www.aavso.org/six-novalikes-2018-campaign
and the Cataclysmic Variables forum thread https://www.aavso.org/six-novalikes-2018-campaign-01

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

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