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The NSVS 5897136 photometric data set was initially pointed out by Ivan Adamin as the red object worth to revise back in 2012.

Hoffmeister, in his "Mitteilungen uber neuentdeckte Veranderliche Sterne" (1967), referenced the object called S 10089 Cyg (J1855.0: RA = 21h 11.4m; DEC = +40° 58') as a long-period variable, but no precise type or period were declared. Though there was a finding chart published in the same paper, related to the "Field 20h58m+44°" (Epoch 1855.0) in Cygnus, which is quite close to the famous planetary nebula NGC 7027.

Hoffmeister's finding chart for S 10089 Cyg (right).
and the DSS chart for NSV 13636 (left)

Comparing Hoffmeister's chart with the DSS plate for the mentioned region one can unambiguously figure out that S 10089 Cyg, NSVS 5897136 and NSV 13636 is exactly the same object referenced by different names.

Periodogram for the NSV 13636 data.

A period search was performed on the NSVS data by Siarhey Hadon (VS-COMPAS project). Calculated periodogram has a strong peak around 168.5 days. This period has a good match with a contemporary data from the APASS survey, conducted by the AAVSO.

Moreover, APASS data was obtained around the maximum brightness, giving a good match with the NSVS photometry. The star is in highly populated area in Cygnus, means there are some close neighbors around contaminating the light for wide-angle optics.

NSV 13636 in Cygnus. Period is 168.5 days.
by Ivan Adamin, Siarhey Hadon (VS-COMPAS)

Particularly, the NSVS magnitudes of are contaminated by the following stars:

1) 2MASS J21165325+4133591 (J-K= 1.59, V= 17.1, sep. 9")
2) 2MASS J21165635+4134093 (J-K= 0.24, V= 16.6, sep. 27")
3) 2MASS J21165663+4133582 (J-K= 0.28, V= 17.5, sep. 28")
4) 2MASS J21165651+4134144 (J-K= 0.71, V= 17.5, sep. 32")

To get the real magnitude range, there was a deblending method applied to the light curve data. This is allowed to get a better estimate for the minima. The VSX record for NSV 13636 was updated with the new data, so NSV 13636 joined the ranks of known variable stars.

This is a good candidate to complement the list of 177 other NSV records listed in the "Confirmation of 177 objects in the New Suspected Variables Catalogue as red long period variables" (Greaves, 2006), though Greaves processed ASAS3 time series data. NSV 13636 was not covered by ASAS3 survey, unfortunately.

View Issue Contents (July-August 2013)

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