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Alert Notice 681: Photometry of more symbiotic candidates requested

September 18, 2019

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
 - Campaigns and Observing Reports
: https://www.aavso.org/symbiotic-candidates-campaign

Further to AAVSO Alert Notices 632 and 650, Mx. Adrian Lucy and Dr. Jeno Sokoloski (Columbia University) are requesting more AAVSO photometry in support of a continuing search for new symbiotic stars (see Lucy et al. 2019, https://iopscience.iop.org/article/10.3847/2515-5172/aaf71c). They provide the information and observing parameters below.

"Here we add 7 new candidates that emerged as high-priority emission line objects from a June spectroscopy run at the SAAO 1.9m or from previous observing runs, and which exhibit tentative evidence of minutes-timescale variability in SkyMapper u band survey photometry.

"In the AAVSO observations, we are looking for flickering above 0.1 mag on timescales of minutes to hours in candidate symbiotic stars, a signature of mass transfer sometimes obscured by the large luminosity of the companion red giant.

Photometry specifications:

-Cadence of 10-20 minutes or faster, for at least a few hours.

-SNR >= 100 preferred; >= 30 is still useful. Prioritize SNR over extra cadence speed.

-B band slightly preferred; V band is still very useful. Very experienced observers may try U band.

-Coordination between observers to observe simultaneously from multiple locations is strongly encouraged. If observers in widely separated locations both observe the same light curve at the same time, that can help rule out many of the systematic effects that make it difficult to prove the presence of low-level flickering. You can post in the forum [URL above] to coordinate with other observers.

-We are aiming for two or three 3+ hour light curves per object, so check the LCG to see if your target has already been observed. However, if you believe you can achieve higher SNR or smaller systematic effects than previous observers of a target, new observations are always welcome."

Target list:

Name RA (2000.0) Dec (2000.0) Range Const.
ASAS J152058-4519.7 15:20:58.29 -45:19:44.4 12.3-13.6 V LUP
Gaia DR2 6043925532812301184 16:27:49.76 -29:16:45.5 14.2-15.3 V SCO
Gaia DR2 5917238398632196736 17:07:10.56 -56:53:17.5 14.3-15.9 V ARA
KU Aps 17:21:50.99 -81:00:36.6 11.9-14.9 V APS
ASAS J185604-2327.2 18:56:04.01 -23:27:14.0 12.7-13.6 V SGR
IRAS F19019-1733 19:04:51.81 -17:28:39.9 13.0-<17.7 V SGR
GSC 05140-03255 19:05:48.04 -06:05:49.5 13.5-15.3 V AQL

AAVSO finder charts for these stars with comparison stars may be generated using the AAVSO Variable Star Plotter (VSP). Be sure to include spaces in names as shown in the "name" column above.

Please submit photometric observations to the AAVSO International Database using the names given in the table. Again, be sure to include spaces in names as shown above.

 This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using information supplied by Mx. Lucy and Dr. Sokoloski.
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