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Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
| Do the Infrared Emission Features Need Ultraviolet Excitation? The Polycyclic Aromatic Hydrocarbon Model in UV-poor Reflection Nebulae
One of the major challenges to identification of the 3.3, 6.2, 7.7, 8.6,and 11.3 μm interstellar infrared (IR) emission bands with polycyclicaromatic hydrocarbon (PAH) molecules has been the recent detection ofthese bands in regions with little ultraviolet (UV) illumination, sincesmall, neutral PAH molecules have little or no absorption at visiblewavelengths and therefore require UV photons for excitation. We showhere that our ``astronomical'' PAH model, incorporating the experimentalresult that the visual absorption edge shifts to longer wavelength uponionization and/or as the PAH size increases, can closely reproduce theobserved IR emission bands of vdB 133, a UV-poor reflection nebula. Wealso show that single-photon heating of ``astronomical'' PAHs inreflection nebulae near stars as cool as Teff=3000K canresult in observable emission at 6.2, 7.7, 8.6, and 11.3 μm.Illustrative mid-IR emission spectra are calculated for reflectionnebulae illuminated by cool stars with Teff=3500, 4500, and5000 K. These will allow comparison with future Space Infrared TelescopeFacility observations of vdB 135 (Teff=3600K), vdB 47(Teff=4500K), and vdB 101 (Teff=5000K). Thedependence on the effective temperature of the exciting star of theobserved 12 μm IRAS emission (relative to the total far-IR emission)is consistent with the PAH model for3000K<=Teff<=30,000K.
| Observational constraints on the ERE interpretation
Empirical relationships on the properties of the Extended Red Emission(ERE) are presented. They are based on published observational data andon new results obtained on reflection nebulae illuminated by cold stars.The plot of the width versus the central wavelength of the ERE band isin agreement with laboratory properties of the materials commonlyproposed as the ERE carriers. But this is not the case for the plot ofthe ERE band width versus the effective temperature of the nebulailluminating star. Partly based on observations made at Observatoire deHaute Provence du CNRS and at European Southern Observatory (ESO), LaSilla (Chile)}
| A Survey of Near-Infrared Emission in Visual Reflection Nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..102..369S&db_key=AST
| A search for hot post-AGB stars in the IRAS Point Source Catalog.
In this paper a first step is made to search for hot post-AGB stars inthe IRAS Point Source Catalog. In order to find objects that evolved offthe AGB a longer time ago than post-AGB objects discussed in theliterature, objects that were not detected at 12 μm by IRAS wereselected, The selection yielded 15 objects, of which 12 have spectraltype B, and would appear to be efficient in finding hot objects.However, this result does not necessarily mean that these are oldevolved objects. Some stars are associated with dense galactic cirrusand are probably normal massive supergiants, and a number of stars aregood post-AGB candidates because of their galactic latitudes and theircool, extended infrared emission. The possibility remains that theseobjects are normal supergiants heating the local interstellar medium.Finally, three remaining objects appear to be genuine post-AGB(candidate) stars, as is attested by their spectral and photometricproperties. The main conclusion derived from modelling their spectralenergy distributions is that the objects evolved off the AGB about 1000years ago, significantly longer than what is found for other post-AGBstars. Emission lines have appeared in the spectrum of one of theseobjects, SAO 243756, over the last 20 years. SAO 243756 bears closeresemblance to other objects that have been proposed to have entered thePlanetary Nebula phase recently. Several aspects of the problem ofselecting post-AGB stars in general are discussed.
| Large and kinematically unbiased samples of G- and K-type stars. V - Evolved stars in the selected areas at + 15-deg declination
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990PASP..102..242E&db_key=AST
| The excitation of 12 micron emission from very small particles
The results of IRAS observations of visual reflection nebulaeilluminated by stars with effective temperatures between 3000 and 33,000K are presented. The ratio of the energy radiated in the IRAS 12-micronsband to the total energy radiated at far-infrared wavelengths (60 and100 microns) is about 0.2, with little or no dependence on thetemperature of the illuminating star for stellar temperatures betweenabout 5000 and 33,000 K. This is interpreted as requiring that visualphotons as well as ultraviolet photons are capable of exciting12-microns emission from very small particles.
| MK spectral classifications for 30 faint stars in Praesepe
Faint members of the Praesepe open cluster were observed with theGarrison prime-focus spectrograph on the C. F. H. Telescope. MK spectralclassifications are presented for 30 stars from F3 V to K7 V in acentral region of the cluster. The spectra look identical to those ofthe Hyades stars in this interval. Apart from two obvious binaries and abackground star, the H-R diagram shows an extremely narrow mainsequence. This yields a distance modulus, Praesepe minus Hyades, of 3.0mag.
| Metal abundance and microturbulence in F0-G2 stars and the calibration of the Stromgren m1 index
The strengths of two narrow groups of metal lines are measuredphotoelectrically by means of an echelle spectrometer for 16 F0-G2 giantfield stars and for 12 Hyades main-sequence stars. A model-atmosphereanalysis of these observations and similar observations of main-sequencefield stars observed earlier results in the determination of the metalabundance for 179 stars. In addition, the microturbulence parameter isdetermined for 73 of these stars. The internal accuracy of the resultsis estimated to be plus or minus 0.08 for the logarithmicmetal-to-hydrogen ratio and plus or minus 0.2 km/sec for themicroturbulence parameter. The metal abundances are found to agree verysatisfactorily with values of the logarithmic iron-to-hydrogen ratiodetermined from classical coude spectroscopy regarding both zero pointand scale. It is found that the microturbulence parameter is a functionof the effective temperature and the surface gravity. It increases from1.2 km/sec for solar type stars to approximately 3.0 km/sec for earlyF-type giants.
| The differential blanketing of the main-sequence and near-main-sequence M67 stars relative to the Hyades and Coma
The blanketing of main-sequence stars in the Hyades, Coma, and M67, andof F subgiants in M67 is compared on the basis of red photometry. Therequired reddening corrections are derived by several techniques thatare insensitive or probably insensitive to blanketing. The meanreddening values obtained are E(B-V) of approximately 0.016 for theHyades, 0.006 for Coma, and 0.053 for M67. These reddening values areshown to imply that there is measurable reddening well inside 100 pc,that Crawford's (1975) A- and F-star relations must be slightly revised,that significant numbers of relatively nearby field A stars are slightlyreddened, that the North Galactic Pole stars of Hilditch et al. (1976)are reddened by 0.01 to 0.03 in B-V, and that Hyades-field F-star b-ycomparisons must be revised. It is found from the reddening-correctedphotometry that: (1) the differential Hyades-M67 blocking is greater inabsolute value for early G late F stars; (2) effects of evolution on theF IV stars in M67 are clearly discernible in the UV and marginally so inB-V; and (3) the F stars on and very near the M67 main sequence haveapproximately the Coma blocking and considerably less than the Hyadesblocking, which indicates that the zero-age metallicity of M67 issolar-normal.
| Infrared observations of late-type stars in nebulae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87..421C&db_key=AST
| Photoelectric radial velocities. IV. 528 7 to 10 mag stars in the +15degree selected areas.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971MNRAS.155....1G&db_key=AST
| Stars in reflection nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..233R&db_key=AST
| A study of reflection nebulae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966AJ.....71..990V&db_key=AST
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Observation and Astrometry data
| Constellation: | Ωρίων |
| Right ascension: | 05h14m59.44s |
| Declination: | +13°00'50.8" |
| Apparent magnitude: | 8.641 |
| Proper motion RA: | 0.3 |
| Proper motion Dec: | -6.6 |
| B-T magnitude: | 10.032 |
| V-T magnitude: | 8.756 |
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