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Alert Notice 650 - REVISED: Photometry and spectroscopy of more symbiotic candidates requested

This replaces the text of AAVSO Alert Notice 650 issued earlier on Spetember 14, 2018. - E. O. Waagen, AAVSO

September 14, 2018: Further to AAVSO Alert Notice 632, Mx. Adrian Lucy and Dr. Jeno Sokoloski (Columbia University) write: "We are requesting more AAVSO observations in support of a continuing search for new symbiotic stars — an AAVSO campaign which has already yielded at least one confirmed new symbiotic. We have added new targets, and revised observational specifications following feedback from observers.

"In photometry, 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. In spectroscopy, we are looking for optical emission lines and cool giant absorption bands.

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 preferred; V band is still 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 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.

Spectroscopy specifications:

-Coverage at best possible resolution of any of the following possible features: Balmer emission (e.g., H-alpha at 6563A), [O III] emission at 5007A, Raman O VI emission at 6830A and 7088A, broad coverage of TiO absorption bands (especially around 6800A) and the optical continuum as a whole, and Mg b absorption bands around 5000A.

-Multiple epochs of spectroscopy are not a priority, although they could be useful if emission lines are detected.

Target list:

Check the forum (https://www.aavso.org/symbiotic-candidates-campaign) for posts containing "#UPDATES" for up-to-date information on which targets still need observations, and new targets.

Name RA (2000.0) Dec (2000.0) V mag* Const.
GAIA DR2 4131587500273361280 16 39 59.65 -18 44 38.1 13.9 OPH
ASASSN-V J164007.54-382216.1 16 40 07.54 -38 22 16.1 13.86-14.74 SCO
GAIA DR2 6019720819446985984 16 45 31.78 -36 22 31.6 12.9 SCO
V2096 OPH 16 56 05.46 -24 06 37.0 12.9-14.0 OPH
ER OPH 17 00 42.14 -26 10 12.4 11.8-<14.8 OPH
ASASSN-V J170231.98-275954.2 17 02 31.98 -27 59 54.4 13.98-14.94 OPH
GAIA DR2 4334886650491663104 17 06 08.44 -10 58 33.0 14.3 OPH
SS 295 17 07 38.16 -07 44 48.6 13.1 OPH
V2525 OPH 17 15 05.27 -09 23 50.1 11.9-<15.1 OPH
GAIA DR2 4115021291723497088 17 17 45.67 -21 31 16.9 13.7 OPH
GAIA DR2 4168021909706732672 17 25 26.34 -07 48 27.5 14.3 OPH
GAIA DR2 4111779763989583232 17 26 18.27 -22 12 46.4 14.1 OPH
GAIA DR2 4120809606303456896 17 27 08.69 -21 39 04.5 13.1 OPH
GAIA DR2 5919388180059095296 17 30 58.39 -56 29 53.4 12.6 ARA
ASASSN-V J173832.43-492840.2 17 38 32.42 -49 28 40.1 13.96-14.55 ARA
FASTT 1100 17 53 45.30 -01 07 46.8 14.04-14.30 OPH
GAIA DR2 4150446010182968192 17 56 04.34 -13 10 03.4 13.1 SER
GAIA DR2 4150099732733146112 17 59 43.87 -13 58 32.0 13.9 SER
SY CRA 18 03 21.54 -42 37 56.8 13.0-16.5p CRA
GAIA DR2 6345873798283774848 18 14 18.07 -85 59 06.5 11.7 OCT
GAIA DR2 4048168377818693632 18 28 31.28 -28 45 02.9 11.9 SGR
ASASSN-V J185421.70-274827.4 18 54 21.70 -27 48 27.8 12.89-13.63 SGR
EN SGR 19 22 42.08 -13 59 56.5 11.95-14.61 SGR
ASASSN-V J192916.53-224040.3 19 29 16.53 -22 40 40.3 12.52-13.02 SGR
GAIA DR2 4636654969717900032 01 50 49.53 -76 49 42.6 12.9 HYI

*Where a single magnitude is given, it is not necessarily a max or min value.

"Charts with comparison star sequences for these stars may be created using the AAVSO Variable Star Plotter (VSP). Be sure to include spaces in names as shown in the table.

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

"Please email spectra to Adrian (lucy@astro.columbia.edu) and the ARAS database (francoismathieu.teyssier@bbox.fr)."

Special thanks are extended to the AAVSO Sequence Team for their excellent and efficient work in creating all of these sequences.

This campaign is being followed on the AAVSO Campaigns and Observing Reports online forum at https://www.aavso.org/symbiotic-candidates-campaign

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