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Are both DY Cyg and its companion variable?

Sebastian Otero
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Joined: 2010-09-19

DY Cyg certainly deserves to be included in the Double-Trouble campaign list.

It turns out that it has a ~13.6 Vmag. companion only 3" to its SW.

While DY Cyg is a mira and its variations can be easily seen in the NSVS light curve (where the red component dominates):
http://skydot.lanl.gov/nsvs/star.php?num=8359533&mask=18708, the GCVS has an interesting remark: "Slow oscillations are superimposed by rapid ones with A = 0.3m [A.A.Wachmann, Bergd Abh V1, N4, 1966.]. According to [H.Gessner, VSS 7, H.2, 65, 1966.] type EB? Min = 2436659.531 + 0.6990d(:)*E (JD2436600 - 37000)"

The reported superimposed variations could arise from the companion and be apparent in B magnitudes (and when the mira is at minimum).
 

This looks like an interesting case to investigate.

We have only 4 observations in the AID and they were contaminated by the companion. It would be interesting if observers could perform dense coverage of the companion when the mira is around minimum. It goes fainter than 16.7 so its contribution would be small at those phases:

http://www.aavso.org/vsx/index.php?view=detail.top&oid=11067

Unfortunately as I write this, the mira is exactly around maximum (October 14) but it would be a good chance to observe it (low cadence now, it's better to wait to observe the companion) and then compare the results with those obtained 4 or 5 months from now.

The observations in the VSX plot were corrected for the light contamination of the 13.6 mag. companion.

Is anyone willing to take up the challenge?

Cheers,
Sebastian
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Sebastian Otero
VSX Team
American Association of Variable Star Observers

Thanks for LANL Skydot
WBY
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Joined: 2010-07-24

the LANL Skydot online database was a new one for me. Thanks for the reference. It is a great resource. 

Brad Walter

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484