Alert Notice 819: XX Oph and V5569 Sgr photometry needed in support of spectroscopic observations

Note: Text and forum links edited per request of Dr. Howell.  -  Elizabeth O. Waagen, April 21, 2023

April 13, 2023

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
 - Campaigns and Observing Reports:
 - Eclipsing Binaries:

Please subscribe to these threads if you are participating in the campaign so you may be updated by the astronomer and by HQ. Join in the discussion or ask questions there!

Dr. Steve B. Howell (NASA Ames Research Center) has requested AAVSO observers' assistance in obtaining photometry in support of spectroscopy observations of the eclipsing variables XX Oph and V5569 Sgr scheduled for 14-16 April 2023.

Dr. Howell writes: "I am likely to be getting the first high-resolution optical spectra ever taken of two of my old friends: AS 325 (now =V5569 Sgr) and XX Oph.

"I have noted from AAVSO data (LCG, really great tool) that AAVSO is still following these stars, mainly in visual. Is it possible to get some coverage in BVRI...over the next few nights? I also see that XX Oph has still not eclipsed again - making it a LONG period eclipsing binary > 28 years and V5569 Sgr (AS 325) looks to have some eclipses missing and other times two eclipses over the (likely incorrect) orbital period. Gotta love these stars - the Iron Stars."

BVRI photometry of XX Oph and V5569 Sgr is requested, beginning immediately and continuing through April 21, with a cadence of a few to several observations per night per filter. Visual observations are welcome. If either target is seen going into eclipse, please carry out time-series observations. Both targets are quite bright, so be careful about saturating images.

XX Oph has a range of 8.59-10.2 V; the most recent observations in the AAVSO International Database (AID) show it at 8.99 V +/-0.005 on 2023 Apr. 11.3626 UT, 9.92 B +/-0.004 on Apr. 11.36079, and 7.129 I +/-0.006 on Apr. 11.36388 (D. Means, Marana, AZ). V5569 Sgr has a range of 9.8-12.1 V; the most recent AID observations show it at visual magnitude 10.0 on 2023 Apr 9.54306 UT (B. Cudnik, Houston, TX).

The cadence and/or end date of coverage may be revised, so please be sure to subscribe to the AAVSO forum threads above to stay informed.

V5569 Sgr was the subject of an observing campaign requested by Dr. Howell and colleagues in 2005 (AAVSO Alert Notice 321).

Coordinates (J2000):
XX Oph   R.A. 17 43 56.50  Dec. -06 16 08.8   (from VSX entry for XX Oph)
V5569 Sgr (AS 325)   R.A. 18 50 03.57  Dec. -26 24 15.4  (from VSX entry for V5569 Sgr)

Charts with comparison stars for XX Oph and for V5569 Sgr may be created using the AAVSO Variable Star Plotter (VSP).

Please report observations to the AAVSO International Database using the names XX OPH and V5569 SGR, respectively.

This Alert Notice was compiled by Elizabeth O. Waagen using information provided by Dr. Howell.


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