AAVSO Alert Notice 521
June 23, 2015

Very rare outburst of the symbiotic variable AG Peg

The symbiotic variable AG Peg is in outburst, the first one observed since its only known outburst, which occurred in
1860-1870. Currently at visual/V magnitude 7.2 (B=7.8), it is an excellent target for visual, PEP, CCD, and DSLR observers and spectroscopists. The current outburst began after 2015 May 27 UT (T. Markham, Leek, Staffordshire, England, from the BAAVSS online database) and was underway by June 13.90 (A. Kosa-Kiss, Salonta, Romania).

AG Peg has a very interesting history. Regarding the 1860-1870 outburst, data collected by E. Zinner (Merrill, 1959, S&T, 18, 9, 490) show AG Peg slowly brightening from visual magnitude ~9.2 in ~1821 to ~8.0 in ~1855, then at ~6.2 in ~1860 and brightening to 6.0 in ~1870, then in decline at ~6.8 by ~1903, and continuing to decline slowly (~6.9 in ~1907, ~8.0 in ~1920, ~8.3 in ~1940).  Observations in the AAVSO International Database since July 1941
show that the decline has continued without interruption from an average magnitude of 7.7 to an average magnitude of 8.8-9.0 by mid-January 2015. The AAVSO data since 1941 also show the periodic ~0.4-magnitude variations (~825 days) that have been present since the 1920s.

Thus, after taking about 10 years to brighten from its minimum magnitude of about 9 to its maximum magnitude of 6.0, and then fading gradually over 140-145 years, AG Peg is now in outburst again.

There are no observations of the 1860-1870 outburst that show the outburst's beginning. This time, however, in 2015, the opportunity is here to follow the outburst itself closely and learn just what this system does during outburst. Observations in all bands and visual observations are strongly encouraged. AG Peg is bright enough to be
a very good PEP target. For spectroscopists, AG Peg has an extremely complex spectrum that undergoes substantial changes and would make a very interesting target.

Observations reported to the AAVSO include:
- Visual and untransformed CCD:
2015 Jan 6.773 UT, 8.7 (PYG, G. Poyner, Birmingham, England);
9.78, 9.3 (PUJ, F. Pujol-Clapes, Madrid, Spain);
16.773, 8.8 (Poyner);
18.76, 8.60 (PGRA, P. Grocaut, Pallud, France);
Apr. 21.1132, 9.0 (KWO, W. Kriebel, Schierling/Walkenstetten, Germany);
Jun 13.90, 7.7 (KOS, A. Kosa-Kiss, Salonta, Romania);
14.29375, 7.9 (ONJ, J. O'Neill, Topsfield, MA);
15.219, 7.7 (SEDB, E. Sawyer, Chicoutimi, QC, Canada);
17.0979, 7.4 (GZN, A. Glez-Herrera, Ferrol, Spain);
21.8109, 7.24(01) V (untransformed) (OCN, S. O'Connor, St. George, Bermuda);
21.946528, 7.4 (SSW, S. Swierczynski, Dobczyce, Poland);
21.9514, 7.2 (KBA, B. Kubiak, Ostrow Wielkopolski, Poland);
22.00208, 7.5 (BADA, A. Bielawny, Walbrzych, Poland);
22.00764, 7.4 (SPK, P. Schmeer, Bischmisheim, Germmany);
22.0347, 7.3 (DXAA, X. Domingo Martinez, Lleida, Spain);
22.057, 7.4 (Poyner);
22.2, 7.3 (BRJ, J. Bortle, Stormville, NY);
22.7284, 7.27(02) V (O'Connor);
22.8921, 7.4  HEN, C. Henshaw, Bowdon, Cheshire, England, via baavss-alert);
23.2, 7.2 (Bortle);

- Transformed PEP (PGD, G. Persha, Lowell, MI):
Jun 22.2114, 7.264(010) V; 22.2245, 7.285(007) V;
22.2114, 7.855(023) B; 22.2245, 7.860(015) B;

- Transformed CCD (AAVSOnet BSM camera, reduced and submitted by
A. Henden, Center Harbor, NH):
V data:
2014 Dec 31.94540, 8.877(013);
2105 Jan 1.95077, 8.932(006);
2.95145, 8.911(007);
5.95246, 8.920(007);
Apr 12.38419, 8.551(0.009);
18.37638, 8.531(008);
May 14.33688, 8.463(005);
15.33729, 8.459(007);
21.32786, 8.431(006);
23.31938, 8.424(007);
24.32849, 8.434(007);
Jun 14.30844, 7.803(005);
B data:
2104 Dec 31.94540, 10.074(025);
2015Jan 1.95077, 10.015(013);
2.95145, 10.030(012);
5.95246, 9.976(011);
Apr 12.38419, 9.590(016);
18.37638, 9.580(017);
May 14.33688, 9.635(013);
15.33729, 9.602(017);
21.32786, 9.587(017);
23.31938, 9.646(030);
24.32849, 9.563(016);
Jun 14.30844, 8.581(009);

Visual observations in the BAA,VSS database by J. Toone (TOO, Shrewsbury, Shropshire, England) and T. Markham (MTON, Leek, Staffordshire, England) indicate AG Peg was not in outburst from late April through May 27.

Coordinates: 21 51 01.98 +12 37 32.1  (J2000.0)

Charts with comparison star sequence for AG Peg may be created using the AAVSO Variable Star Plotter (VSP, http::www.aavso.org/vsp). A photometry table containing multicolor magnitudes of comparison stars may also be obtained via VSP.

Please report observations to the AAVSO International Database using the name AG PEG. Be sure to include error values and comparison star information.


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