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Sh 2-132 complex, Cepheus/Lacerta

Sh 2-132 complex, Cepheus/Lacerta

530 mm f/5 20 hours, September 2013, Photograph

Sh 2-132 — The star forming and ionized hydrogen region Sh 2-132 presents two bright regions named Shell A and Shell B, which are surrounded by diffuse emission regions. The HII region is excited by the massive O-type star BD+55°2722 and the Wolf-Rayet star WR153ab (HD 211853), which are located close to the center of the nebula and linked to Shell B. The filament along the southeast section of Shell B indicates the position of an ionization front related to the WR star. Its velocity and rms electron density are -50 +/- 9 km/s and 290 +/- 100 cm⁻³, respectively. A similar filament along the northeast section of Shell A indicates the position of an ionization front related to the B0V star LS+55°39. Adopting a mean velocity of -48 km/s for the HII region, and taking into account the presense of non-circular motions in this section of the Galaxy, a kinematical distance of 3.5 +/- 1 kpc is predicted, in close argreement with the distances derived optically for the WR star. The estimated rms electron density and ionized mass of the HII region are ~20 cm⁻³ and 1500 Msolar. The gas disributions can be explained in a senario where the massive stars in the region photodissociated, ionized and swept-up the dense molecular material from the parental cloud through their strong stellar winds and intense UV photon flux. From Vasquez et al., "Ionized gas, molecules, and dust in Sh2-132", Monthly Notices of the Royal Astronomical Association, 405:3(1976-1986), 2010 July.

WR 152 — The strong mass flow and high UV photon flux of Wolf-Rayet stars originate the so called ring nebulae, which can be identified as ring-like optical features in the environs of the stars. The ring nebula around the Wolf-Rayet star WR 152 (HD 211564) consists of two concentric ring structures having about 19' and 32' in diameter, detected in Hα + [NII], [OIII] and [SII] lines. The rings are denoted "Ring 1" and "Ring 2" on the map. Cappa et al. detected radio and infrared counterparts of the ring nebula around WR 152, and suggest that the optical nebula and its neutral counterparts originated from the stellar winds from the WR star and its massive progenitor, and are evolving in the envelope of a slowly expanding bubble. The rms electron density and ionized mass of the ring nebula are 10-16 cm⁻³ and 450-700 Msolar, respectively. Interstellar bubble expansion velocity 9 km/s, kinetic energy 4.8 x 10⁴⁸ ergs, dynamical age 1 Myr. The WR star generates sufficient number of UV photons to maintain the ionization of the rings and sufficient energy to blow the bubble. WR 152 is considered a probable member of the Cep OB1 association located in the Perseus sprial arm at distance of 3.5 +/- 1 kpc. From Cappa et al., "The radio and IR counterparts of the ring nebula around HD 211564", Monthly Notices of the Royal Astronomical Association, 403:1(387-397), 2009 March.

WR153ab — The Wolf-Rayet star WR153ab (HD 211853) is a binary system. The spectral types of the two WR components are WN6 and WCE+O6. The velocity of its stellar wind is as high as 1500 - 1800 km/s, leading to a mass loss rate of 10⁻⁴˙⁵ Msolar/yr. A ring-nebula associated with WR153ab is identified in radio emission, in polycyclic aromatic hydrocarbon (PAH) emission, and in molecular emission. The molecular ring consists of well-separated cores, which have a volume density of ~10³ cm⁻³ and a kinematic temperature of ~20 K. Most of the cores are under gravatational collapse due to external pressure from the surrounding ionized gas. One of the cores in Filament B harbors a very young star cluster. The presense of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the triggered star formation indicates that the "collect and collapse" star formation process functions in this region. The star-forming activities in the Filament B core seem to be affected by the "radiation-driven implosion" star formation process. From Liu et al., "Triggered star formation surrounding Wolf-Rayet Star HD 211853", The Astrophysical Journal, 751:68, 2012 May.

Be 94 — The open cluster Be 84 is located at a large Galactocentric distance well beyond the solar radius in the direction of the Perseus spiral arm. It appears to be connected with a clusters concentration in the Perseus arm, whose most conspicuous object is the HII region Sh 2-132. The cluster shows a distribution of the massive components with a high degree of struture and is at the same time centrally concentrated. This distribution could be explained by an early dynamical evolution under a supervirial regime, and followed by a warm collapse in its late evolution. Cluster distance 3 +/- 1 kpc, color excess E(B-V) 0.62 +/- 0.05, age 32 +/- 5 Myr, mass ~1600 Msolar. From Delgado et al., "Berkeley 94 and Berkeley 96: Two Young Clusters with Different Dynamical Evolution", accepted for publication in Monthly Notices of the Royal Astronomical Society.

RW Cep — RW Cep is a semi-regular variable red hypergiant of spectral type K2Ia0 and variable type SRd. One of the largest stars known, RW Cep is estimated at 1260 - 1610 solar radii, as large as the semi-major axis of Jupiter's orbit. RW Cep is assumed to be a member of the Cep OB1 association. Over the past 50 to 70 years it has varied from spectral classes G8 to M2 with no discernable pattern. Magnitude range 6.0 - 7.3 V, period several hundred days, distance 3.5 kpc, mass 50 Msolar, luminosity 770k Lsolar, temperature 4400 K, age unknown. From AAVSO, The International Variable Star Index, www.aavso.org/vsx/index.php?view=detail.top&oid=8367 and Wikipedia, en.wikipedia.org/wiki/RW_Cephei.

Coordinates: RA 22h 18.3m, Dec +55° 52’, PA -0° 34’
Field of view: 1° 56’ x 1° 28’
Image scale: 4.2” / pixel

Date: September 2013
Location: Santa Lucia Range, California
Exposure: 30 x 40 minutes (20 hours), binned 2 x 2 at -20° C

Zenith SQM: 21.4 mag / "²
Guiding error: 0.6" rms
Star FWHM: 4.2", histogram
Star eccentricity: 0.39
Camera noise: 15 e- rms
Background noise: 26 e- rms
Subframe location: 314 e-
Subframe scale: 108 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