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LBN 292, BDN 080+2, Cygnus

LBN 292, BDN 080+2, Cygnus

530 mm f/5 14.7 hours, August 2013, Photograph

LBN 292 — Comerón et al. intestigated the possible existence of an extended halo of early-type stars around the Cygnus OB2 association, including the HII region LBN 292 shown in this photograph. Using low resolution infrared spectroscopy, Comerón found a field population consisting largely of early B giant and supergiant stars, including AS 419, BD +41°3731 and BD +41°3762. The age and extension of this population discards a direct relationship with Cygnus OB2 or any other known association. The existence of this populaton of evolved stars with massive precursors suggests a massive star formation history in Cygnus having started long before the formation of the currently observed OB associations in the region. From Comerón et al., The outskirts of Cygnus OB2, Astronomy & Astrophysics, 486:453-466, 2008.

WR 142b — Wolf-Rayet (WR) stars have been enigmatic objects ever since the discovery of the first three WR stars in 1867 by Wolf & Rayet. As a result of their strong stellar winds, their spectra show strong, Doppler-broadened emission lines, primarily from helium and either carbon or nitrogen of various ionization states. The nitrogen-rich variety, which are classified as WN stars, outnumber the carbon-rich WC stars in current surveys of Galactic WR stars. In 1991 Lamers et al. conclusively showed that WR stars are evolved, high-surface-temperature stars that have shed their envelopes via their stellar winds. As WR stars lose mass, they expose elements created via hydrogen fusion and, eventually, those from helium fusion as well. They often have masses between 10 and 25 Msolar and even as high as 80 Msolar in some cases. WR stars are descended from O-type stars, and spend ~10% of their ~5 Myr lifetimes as WR stars. WR stars are destined to end their lives as Type Ib/c core-collapse supernovae and possibly gamma-ray bursts.

WR stars are rare, and only about 500 are known in the Galacy. Because they are young stars close to the Galactic plane, WR stars are often obscured by dust. Most recent searchs have used infrared wavelengths to avoid dust extinction and find new members of the WR family.

In 2012 Littlefield et al. reported the serendipitous discovery of a WR star, WR 142b, by first detecting its photometric variability and then obtaining spectroscopy. Its spectrum shows emission lines of He I, He II, N IV, and C IV, with no detectable hydrogen and normal line widths. The spectrum and its line strengths are best matched by a WN6 ionization classification. The spectrum shows good evidence for a significant reddening due to dust, with an estimated reddening E(B - V) from 2.2 to 2.6. For a standard dust law the star is dimmed by 8 mag in the V band and would have a visual brightness of 6.6 mag with no extinction.

Based on near-IR photometry, the estimated distance to WR 142b is 1.4 +/- 0.3 kpc. The distance estimate combined with its Galactic longitude places it 70 pc above the Galactic plane in the "Orion Spur". The distance and coordinates of WR 142b are consistent with membership in Cygnus X, a heavily obscured, 200 pc diameter, 3x10^6 Msolar mass region of strong star formation.

From Littlefield et al., "Discovery of a Wolf-Rayet star through detection of its photometric variability", The Astronomical Journal, 143:136-141, 2012 June.

From Crowther, "Physical Properties of Wolf-Rayet Stars", Annual Review of Astronomy & Astrophysics, 45:177-219, 2007.

V502 Cyg — The short period, close binary eclipsing system V502 Cyg is a variable of the W Ursae Majoris type. The components are A5V and F8V stars that share a common envelope of material and are thus in contact with one another. The light curve of the system undergoes a constant ellipsoidal variation rather than discrete eclipses, due to the gravitational distortion and constantly changing projected area of the stars. Period 0.45 day, magnitude +13.6 to +14.5, estimated distance 1.2 kpc. From Zakirov et al., "Close Binary Systems in Star-Forming Regions: V502 Cyg in the T Association Cyg T2", Astronomy Letters, 23(3):399-408, 1997.

Coordinates: RA 20h 24.0m, Dec +42° 58’, PA -0° 26’
Field of view: 1° 56’ x 1° 28’
Image scale: 4.2” / pixel

Date: August 2013
Location: Santa Lucia Range, California
Exposure: 22 x 40 minutes (14.7 hours), binned 2 x 2 at -20° C

Zenith SQM: 21.4 mag / "²
Guiding error: 0.7" rms
Star FWHM: 4.1", histogram
Star eccentricity: 0.37
Camera noise: 15 e- rms
Background noise: 25 e- rms
Subframe location: 442 e-
Subframe scale: 150 e-

Telescope: Takahashi FSQ-106EDX 530 mm f/5
Camera: Quantum Scientific Imaging 683wsg
Filter: Astrodon H-alpha, 3 nm bandwidth
Focuser: Finger Lakes Instrumentation Atlas, Quality Thermistor DirecTemp DTU6024C, 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, IHRP Platform, ASCOM Platform
Processing: Pleiades Astrophoto PixInsight, MathWorks MATLAB, IHRP Platform