Polarization in NGC2244

Hoag, A. A.; Smith, Elske V. P.

doi:10.1086/127327

Cited by 15 publications

(8 citation statements)

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“…9 as candidate member stars of the cluster. Among these stars, spectral types of 47 stars were determined by Verschueren (1991), two stars (OI 142 and 178) by Hoag & Smith (1959), and one star (OI 123) by Morgan et al (1965). Using these data, we excluded 27 stars based on their positions in photometric diagrams and their spectral types, leaving only 23 stars as members.…”

Section: Ob Membersmentioning

confidence: 99%

“…A higher value of E(BÀV ) = 0.58 was derived by Dufour & Lee (1970), but as Turner (1976) indicated, their large value may be affected by the extrapolation of their data to obtain A V and E(BÀV ). Because the cluster consists of relatively bright stars, spectral types of many stars have been determined by several authors (Hoag & Smith 1959;Morgan et al 1965;Verschueren 1991). The largest number of stars was observed by Verschueren, with 193 stars classified down to V % 13.5 mag.…”

Section: Introductionmentioning

confidence: 99%

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[ITAL]UBVI[/ITAL] and Hα Photometry of the Young Open Cluster NGC 2244

Park¹,

Sung²

2002

The Astronomical Journal

129

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New UBVI and H photometry has been performed for the young open cluster NGC 2244. We classified 30 OB stars as being members of the cluster using proper-motion data and spectral types from previous investigators, along with photometric diagrams obtained in this study. We measured H emission strength of the stars by H photometry and set up a selection criterion to select pre-main-sequence (PMS) stars with H emission. Fourteen PMS stars and seven PMS candidates were found using the criterion. In addition, six stars found near the positions of ROSAT HRI X-ray sources were assumed to be PMS stars and the optical counterparts of these X-ray sources. We determined a reddening of hE(BÀV )i = 0.47 AE 0.04 for the cluster and a total-to-selective extinction ratio of R V = 3.1 AE 0.2. The distance modulus derived was V 0 À M V = 11.1. By comparing our photometric results with theoretical evolution models, we derived a main-sequence turnoff age of 1.9 Myr and a PMS age spread of about 6 Myr. The slope of the initial mass function, C, calculated in the mass range 0.5 log m 2.0 could be flat (C = À0.7 AE 0.1).

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Section: Ob Membersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

[ITAL]UBVI[/ITAL] and Hα Photometry of the Young Open Cluster NGC 2244

Park¹,

Sung²

2002

The Astronomical Journal

129

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“…McNamara 1976; (25) Levato & Abt 1976; (26) Schild & Chaffee 1971; (27) Borgman 1960; (28) Warren & Hesser 1977; (29) Sharpless 1952; (30) Racine 1968a; (31) Crawford et al 1955; (32) Johnson & Morgan 1953; (33) Meadows 1961; (34) Johnson 1962; (35)Hoag & Smith 1959; (36) …”

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confidence: 99%

An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR‐through‐UV Curve Morphology

Fitzpatrick

Massa

2007

ApJ

692

844

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We study the IR-through-UV wavelength dependence of 328 Galactic interstellar extinction curves affecting normal, near-main-sequence B and late O stars. We derive the curves using a new technique that employs stellar atmosphere models in lieu of unreddened ''standard'' stars. Under ideal conditions, this technique is capable of virtually eliminating spectral mismatch errors in the curves. In general, it lends itself to a quantitative assessment of the errors and enables a rigorous testing of the significance of relationships between various curve parameters, regardless of whether their uncertainties are correlated. Analysis of the curves gives the following results:1. In accord with our previous findings, the central position of the 2175 8 extinction bump is mildly variable, its width is highly variable, and the two variations are unrelated.2. Strong correlations are found among some extinction properties within the UV region, and within the IR region.3. With the exception of a few curves with extreme (i.e., large) values of R(V ), the UVand IR portions of Galactic extinction curves are not correlated with each other.4. The large sight lineYtoYsight line variation seen in our sample implies that any average Galactic extinction curve will always reflect the biases of its parent sample.5. The use of an average curve to deredden a spectral energy distribution (SED) will result in significant errors, and a realistic error budget for the dereddened SED must include the observed variance of Galactic curves.While the observed large sight lineYtoYsight line variations, and the lack of correlation among the various features of the curves, make it difficult to meaningfully characterize average extinction properties, they demonstrate that extinction curves respond sensitively to local conditions. Thus, each curve contains potentially unique information about the grains along its sight line.

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“…Notes. N tot is the total number of studied stars and N ST refers to those having available spectral type, the respective references to photometric and spectroscopic catalogues are: (a) Deeg & Ninkov (1996); (b) Park & Sung (2002); (c) Sung et al (1997); (d) Sung et al (2000); (e) Forbes et al (1992); ( f ) Johnson (1962), Morgan et al (1965), Conti & Leep (1974), Hoag & Smith (1959), Wolff et al (2007); (g) Morgan et al (1965), Walker (1956), Young (1978); (h) Hiltner et al (1965). The extinction law references are: (i) Bhavya et al (2007); ( j) Ogura & Ishida (1981), Pérez et al (1987); (k) Walker (1956), Pérez et al (1987); (l) Neckel & Chini (1981), Arias et al (2007).…”

Section: Main-sequence Fitting Algorithmmentioning

confidence: 99%

Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

Fernandes

Gregorio-Hetem

Hetem

2012

A&A

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Aims. We studied four young star clusters to characterise their anomalous extinction or variable reddening and asses whether they could be due to contamination by either dense clouds or circumstellar effects. Methods. We evaluated the extinction law (R V ) by adopting two methods: (i) the use of theoretical expressions based on the colourexcess of stars with known spectral type; and (ii) the analysis of two-colour diagrams, where the slope of the observed colour distribution was compared to the normal distribution. An algorithm to reproduce the zero-age main-sequence (ZAMS) reddened colours was developed to derive the average visual extinction (A V ) that provides the closest fit to the observational data. The structure of the clouds was evaluated by means of a statistical fractal analysis, designed to compare their geometric structure with the spatial distribution of the cluster members. Results. The cluster NGC 6530 is the only object of our sample affected by anomalous extinction. On average, the other clusters suffer normal extinction, but several of their members, mainly in NGC 2264, seem to have high R V , probably because of circumstellar effects. The ZAMS fitting provides A V values that are in good agreement with those found in the literature. The fractal analysis shows that NGC 6530 has a centrally concentrated distribution of stars that differs from the substructures found in the density distribution of the cloud projected in the A V map, suggesting that the original cloud was changed by the cluster formation. However, the fractal dimension and statistical parameters of Berkeley 86, NGC 2244, and NGC 2264 indicate that there is a good cloud-cluster correlation, when compared to other works based on an artificial distribution of points.

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Polarization in NGC2244

Cited by 15 publications

References 8 publications

[ITAL]UBVI[/ITAL] and Hα Photometry of the Young Open Cluster NGC 2244

[ITAL]UBVI[/ITAL] and Hα Photometry of the Young Open Cluster NGC 2244

An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR‐through‐UV Curve Morphology

Probing the anomalous extinction of four young star clusters: the use of colour-excess, main-sequence fitting and fractal analysis

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