UBV and DDO photoelectric photometry in the field of the open cluster NGC 2323 is presented. The analysis yields 109 probable members; one of them being a red giant, and 3 possible members. The basic cluster parameters are derived. NGC 2323 appears not to be physically connected to the CMa OB1 association.
Photoelectric UBV values, derived from observations made at the Boyden and ESO observatories, are presented for 358 early-type stars in the Vela section of the southern Milky Way. Remarks, accurate positions and notes have been added in July 2016 at CDS (Francois Ochsenbein)
UBV photometry of OB associations in LMC superbubbles
Short Name:
J/ApJS/104/71
Date:
21 Oct 2021
Publisher:
CDS
Description:
This work presents UBV photometry of the stellar populations associated with seven superbubble nebulae and five classical H II regions in the Large Magellanic Cloud. Although the nebular morphology of the superbubbles appears to be substantially evolved compared to the classical nebulae, the color-magnitude diagrams do not reveal any noticeable correlation between the resident stellar population and nebular morphology. The photometry presented here will be used in a forthcoming paper to examine further the stellar content and dynamics of these superbubbles.
An analysis of photometric observations of the Be star OT Gem (HD 58050, HR 2817, 2000 position: 07 24 27.64 +15 31 02.0) is presented. A positive correlation between the light and colour variations and the emission strength was found.
We describe photometric and spectroscopic observations of the major outburst that AG Dra underwent between 2006 and 2008. The outburst peaked at U=8.4, B=9.0, V=8.7 around 2006 September 6, making it the brightest U-band event since the 1994 outburst. It was of the cold type, according to the classification of AG Dra outbursts introduced by Gonzalez-Riestra et al. (2006JAVSO..35..172G ). A second, fainter maximum (this time of the hot type) followed 400 days after the primary one, peaking at U=9.1, B=9.7, V=9.0 on 2007 October 7. The outburst phase ended about 600 days after the primary maximum. High resolution spectra obtained during early decline from primary maximum showed emission lines of Mg II, Si II, Ti II, and Fe II in addition to the usual lines of H, He I, and He II.
A detailed analysis of a very rich collection of spectroscopic and photometric observations of the bright Be star {phi} Per (HR 496, or HD 10516, 2000 position: 01 43 39.4 +50 41 20) is presented. Earlier reports that {phi} Per is a double-lined spectroscopic binary consisting of two emission-line objects are confirmed.
This catalogue groups broad-band CCD photometry made in 8 regions of the Magellanic Clouds which were used for the study of stellar populations in the Magellanic Clouds. The photometry yielded 293693 BV entries with 136155 having additional U information, published or to be published in 4 different papers.
Spectra, position, magnitudes and colors are presented for 485 faint (B_J_<20.5) emission line objects selected with the ultraviolet-excess (UVX) criterion on a area of 24.6 sq. deg. in the South Galactic Pole. The objects were selected from the analysis of pixel-to-pixel stacking of COSMOS scans of UKST U_J_ and R plates. The candidates were observed with the Meudon-ESO Fiber Optics System (MEFOS) at the ESO 3.6m telescope. 429 type 1 AGNs have been identified (373 in the redshift range 0.3<z<=2.2). This sample has allowed the measure of a difference on the QSO clustering evolution in comparison with that found for galaxies (La Franca et al., 1998ApJ...497..529L). The region is part of the ESO Imaging Survey (EIS) and of the 2dF QSO redshift survey.
The detailed spiral structure of the outer Galactic disk remains poorly constrained, and for several line of sights in the Galaxy we depend on model extrapolations. One of these regions is the fourth Galactic quadrant, between Vela and Carina (270{deg}<=l<=300{deg}), where, apart from the conspicuous Carina branch of the Carina Sagittarius arm, no spiral arms have been detected so far in the optical beyond l~270{deg}. By means of deep UBVI photometry, we search for spiral features in known low absorption windows. Although observationally demanding, U photometry constitutes a powerful tool for detecting and characterizing distant aggregates of young stars, and allows firmer distance estimates to be derived. We study a direction close to the tangent (l~290{deg}) of the Carina arm, in an attempt to detect optical spiral tracers far beyond the Carina branch, where radio observations and model predictions appear to indicate the presence of an extension of the Perseus and Norma-Cygnus spiral arms in the fourth quadrant. Along this line of sight, we detect three distinct groups of young stars. Two of them, at distances of ~2.5 and ~6.0kpc, belong to the Carina spiral arm, which is traversed twice in this particular direction. Interestingly, the latter is detected for the first time. The third group, at a distance of ~12.7kpc, is probably related to the Perseus arm which lies beyond the Carina arm, and constitutes the first optical detection of this arm in the fourth Galactic quadrant. The position of this feature is consistent with both HI observations and model predictions. We also present evidence that this extremely distant group, formerly assumed to be a star cluster (Shorlin 1), is a diffuse, young population, typically found in spiral galaxies. In addition, our data-set does not support, as claimed in the literature, the possible presence of the Monoceros Ring in this direction. This study highlights how multicolor optical studies can be effective in probing the spiral structure of the outer Galactic disk. More fields need to be studied in this region of the Galaxy to constrain the spiral structure in the fourth Galactic quadrant more accurately, in particular, the shape and extent of the Perseus arm, and, possibly, to detect the even more distant Norma-Cygnus arm.