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Sh 2-108, NGC 6913, Cygnus

Sh 2-108, NGC 6913, Cygnus

530 mm f/5 18 hours, August 2012, Photograph

V444 Cyg — V444 Cygni is a close colliding wind binary system made up of an O6III-V star and a Wolf-Rayet WN5 star. It is a double eclipse system with a period of ~4.2 days. The O star wind probably dominates the WN star wind, with the hard X-ray emission arising close to the WN star. O/WN star mass 28/12 Msolar, radius 10/3 Rsolar, star separation 38 Rsolar, pre-shock wind velocity ~2,200/440 km/s, post-shock temperature ~9 keV (100 MK), magnitude range +7.92 to +8.22, distance 1.7 kpc. From Fauchez et al., "The X-ray emission of the colliding wind binary V444 Cyg", Bulletin de la Société Royale des Sciences de Liège, 80:673-677, 2011.

V455 Cyg — V455 Cyg is a close eclipsing binary system of the Beta Lyrae type. The semi detached system is in an interacting stage of mass exchange, with the hotter star having an geometrically and optically thick accretion disc, and the cooler star filling it Ronche-lobe and streaming gas to its companion. The change in shape of its light curves, including prominent variations in the depth of the eclipses, can be explained by the changes in the parameters of the accretion disc and the active regions of the disc, arising in turn from a variable rate of mass transfer. Magnitude range +9.30 to +9.77, period 8.75 days. From Djurašević, et al., A study of the interacting binary system V455 Cygni, Monthly Notices of the Royal Astronomical Society, 420(4):3081-3090, 2012 March.

NGC 6913 (M 29) — NGC 6913 is a young open cluster containing O-type member stars. Despite appearing in the Messier catalog as M 29, few papers deal with it, furthermore they show disagreement in the results, possibly due to varying foreground obscuration. In a recent study Boeche et al. obtained high resolution spectra of 16 stars in the field of the cluster to constrain its properties and study its kinematics. Luminous mass 700 Msolar, half mass radius 8', radial velocity -17 km/s, radial velocity dispersion 1.7 km/s, distance 1.6 kpc, age ~5 Myr. From Boeche et al., "Kinematics and binaries in young stellar aggregates - II. NGC 6913 ≡ M 29", Astronomy & Astrophysics, 415(1):145-154, 2004 February.

Be 86 — Be 86 is a young open cluster harboring O-type member stars, located in the Cygnus OB1 association, and obscured by a foreground dust cloud. The eclipsing binary system V444 Cygni is a member of Be 86. Bhavya et al. suggests that star formation in the cluster started about 5 Myr ago, continued at a relatively low level until 1 Myr ago, and has been vigorous in the last 1 Myr. Distance 1.7 kpc. From Bhavya et al., "Pre-main sequence stars, emission stars and recent star formation in the Cygnus region", The Bulletin of the Astronomical Society of India, 35:383-411, 2007.

Sh 2-108 — Relatively strong CO emission was detected from a molecular cloud complex in the projected area of Sh 2-108, but the emission could not be definitely associated with the HII region. Adopted distance 1.8 kpc. From Bliz et al., "Catalog of CO Radial Velocities Toward Galactic H II Regions", The Astrophysical Journal Supplement Series, 49:183-206, 1982 June.

Coordinates: RA 20h 22.7m, Dec +39° 1’, PA +0° 9’
Field of view: 1° 56’ x 1° 28’
Image scale: 4.2” / pixel

Date: August 2012
Location: Ochoco Range, Oregon
Exposure: 27 x 40 minutes (18 hours), binned 2 x 2 at -20° C

Guiding error: 0.6" rms
Star FWHM: 4.3", histogram
Star eccentricity: 0.36
Camera noise: 14 e- rms
Background noise: 22 e- rms
Subframe location: 389 e-
Subframe scale: 204 e-

Telescope: Takahashi FSQ-106EDX 530 mm f/5
Camera: Quantum Scientific Imaging 683wsg
Filter: Astrodon H-alpha, 3 nm bandwidth
Focuser: Spike-a Bahtinov Mask
Guider: Santa Barbara Instrument Group ST-i
Flats: Alnitak Astrosystems Flat-Man
USB: Icron Ranger 2122, Moxa UPort 404
Mount: Takahashi EM-400 Temma2M
Acquisition: Diffraction Limited MaxIm DL, CCDAstro Temma, ASCOM Platform
Processing: Pleiades Astrophoto PixInsight, MathWorks MATLAB, IHRP Platform