A Ring‐shaped Embedded Young Stellar (Proto)Cluster

TheUBV photometry of 105 bright stars and theU magnitudes of 36 bright stars in M33 taken by the 2 m RCC telescope of the Rozhen Observatory at the Bulgarian Academy of Sciences were used to obtain colour-magnitude and colour-colour diagrams. A criterion forV, B-V, andU-B is suggested which facilitates the separation of the member stars from the foreground stars. The vast majority of the bright blue stars with strong negativeU-B are M33 members. The existence of objects with an unusual combination of colours (B-V>0.5 and strong negativeU-B) has been confirmed.

view Abstract Citations (51) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectral Types of Stars in the Globular Clusters Messier 3 and Messier 13. Popper, Daniel M. Abstract Spectral classifications have been obtained for fourteen stars in Messier 3 and for twenty-one stars in Messier 13. The brightest stars, which have absolute photovisual magnitudes between -2 and -3 and color indices principally between +0.9 and + 1.6 mag., are of spectral type G5-KO and luminosity class Tb. They are peculiar in that the CN absorption shortward from X 4215 is weak. This result is in agreement with an early observation by Lindblad and with Baade's grouping of the globular-cluster stars in the same population group as the high-velocity stars. Among the brightest members of each cluster is' at least one 0 or B star. Approximate magnitudes and colors have been obtained for the bright- est stars in the central regions of the two clusters. These observations augment Shapley's photometry and show that a large fraction of the brightest stars are to be found in the central regions: The dispersion in radial velocity of the most massive stars in Messier 13 is not more than a few kilometers per second Publication: The Astrophysical Journal Pub Date: January 1947 DOI: 10.1086/144893 Bibcode: 1947ApJ...105..204P full text sources ADS | data products SIMBAD (49)

We present observations of four bright stars observed with the AstroSat Soft X-ray Telescope (SXT). Visible light from bright stars like these can leak through the very thin filter in front of the CCD in the focal plane CCD camera of the SXT and thus making the extraction of X-ray events difficult. Here, we show how to extract the X-ray events without contamination by the visible light. The procedure applied to four bright stars here demonstrates how reliable X-ray information can be derived in such cases. The sample of bright stars studied here consists of two A spectral types (HIP 19265, HIP 88580), one G/K giant (Capella), and a nearby M-type dwarf (HIP 23309). No X-ray emission is observed from the A-type stars, as expected. X-ray spectra of Capella and HIP 23309 are derived and modeled here, and compared with the previous X-ray observations of these stars to show the reliability of the method used. We find that optical light can start to leak in the very soft energy bands below 0.5 keV for stars with \(V=8\) mag. In the process, we present the first X-ray spectrum of HIP 23309.

ABSTRACTThe identification of individual stars in crowded environments using photometric information alone is confounded by source confusion. However, with the addition of spectroscopic information it is possible to distinguish between blends and areas where the light is dominated by a single star, using the widths of absorption features. We describe a procedure for identifying locations in kinematically hot environments where the light is dominated by a single star, and apply this method to spectra with 0.1″ angular resolution covering the 2.1–2.3 μm interval in the central regions of M32. Targets for detailed investigation are selected as areas of localized brightness enhancement. Three locations where at least 60% of the K-band light comes from a single bright star, and another with light that is dominated by two stars with very different velocities, are identified. The dominant stars are evolving near the tip of the asymptotic giant branch (AGB), and have M5 III spectral type. The lack of a dispersion in spectral type suggests that the upper AGB within the central arcsecond of M32 has a dispersion in J - K of only a few hundredths of a magnitude, in agreement with what is seen at larger radii. One star has weaker atomic absorption lines than the others, such that [M/H] is 0.2 dex lower. Such a difference in metallicity is consistent with the metallicity dispersion inferred from the photometric width of the AGB in M32. The use of line width to distinguish between blends involving many relatively faint stars, none of which dominate the light output, and areas that are dominated by a single intrinsically bright star could be extended to crowded environments in other nearby galaxies.

Finding Characteristics of the JPCC Church in Serving Young Congregations: A Case Study of the JPCC Church Mall Kota Kasablanka, Jakarta. Contemporary churches come with pop culture that can be felt, from the concept of a room to the concept of worship. The formation of an atmosphere that is built in such a way that the congregation can feel comfortable in the worship space. The implementation of worship has several stages that are always used in every worship. These steps are carried out to foster a sense of comfort and safety for the congregation. The hallmark of JPCC in serving young congregations is the formation of Small Groups, which is another name for KomSel. In addition to Small Groups, short sermons (khutbah) and topics relevant to the lives of young people are also used in worship at JPCC Youth. This short sermon is intended so that the congregation can discuss in their respective small groups. This small group is held as a support for the sermon given and also serves as a means of discussion among Small Group members. These youths are also served by one to two Small Group Leaders or commonly called mentors. Mentors also encourage youth to be moved to serve others. In the end, several youths were also involved in ministry at JPCC. This is the main goal as well as the success of JPCC Youth, where youth can serve others in their daily lives. Keywords: Contemporary Church, Youth, Small Group, Mentor, Pop-culture

A program has been initiated at the Yerkes Observatory to determine more accurately the mean direction of the interstellar magnetic field in the vicinity of the sun by observing the interstellar polarization of bright nearby stars in the direction of the galactic poles and in the galactic plane. Spectroscopic parallaxes are needed for the program stars. Spectrograms have been taken therefore for those stars for which no MK spectral types are given either in the Catalogue of Bright Stars (HofBeit 1964) or the Catalogue of Stellar Spectra Classified in the Morgan-Keenan System (Jaschek, Conde, afnd de Sierra 1964). Since accurate spectral types in the MK system may be useful for other investigations as well, the spectral classifications are published in advance of the extended polarimetrie program. All spectrograms were obtained on Kodak Ila-O plates with the Cassegrain spectrograph and the 110-mm camera on the 82-inch reflector at the McDonald Observatory. The dispersion was about 120 A/mm at Hy. Spectrograms of 54 standard stars of the MK system from the revised list of 1953 were obtained during the same observing period. The standard spectra and the criteria of the Yerkes Atlas of Stellar Spectra (Morgan, Keenan, and Kellman 1943) were used to determine the spectral types. When the line ratios were intermediate between those of two standards, interpolated spectral types were given. No attempt was made to determine luminosity classes for peculiar spectra. Spectra with only slight deviation from standard spectra were labeled (p)- The luminosity of these (p)-stars is assumed to be not much different from ordinary stars of corresponding spectral type. The results of the classification are given in Table I. An asterisk following the HR number refers to a remark on the classification at the end of the table.

Aims. We study the links possibly existing between the lithium content of bright giant stars and their rotational velocity. Methods. We performed a spectral analysis of 145 bright giant stars (luminosity class II) spanning the spectral range from F3 to K5. All these stars have homogeneous rotational velocity measurements available in the literature. Results. For all the stars of the sample, we provide consistent lithium abundances (A Li ), effective temperatures (T eff ), projected rotational velocity (u sin i), mean metallicity ([Fe/H]), stellar mass, and an indication of the stellar multiplicity. The gradual decrease in lithium abundance with T eff is confirmed for bright giant stars, and it points to a dilution factor that is at least as significant as in giant stars. From the F to K spectral types, the A Li spans at least three orders of magnitude, reflecting the effects of stellar mass and evolution on dilution. Conclusions. We find that the behavior of A Li as a function of v sin i in bright giant stars presents the same trend as is observed in giants and subgiants: stars with high A Li are moderate or fast rotators, while stars with low A Li show a wide range of v sin i values.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic Discriminant for O-Type Star Clusters. Hiltner, W. A. ; Morgan, W. W. Abstract Some 20 years ago it was noticed at the Yerkes Observatory that the brightest stars in the Orion Nebula cluster possessed unusually strong and broad hydrogen lines for their spectral types; the effect is most clearly visible at H~. A similar phenomenon has now been observed, on McDonald spectrograms, for a number of early B stars in the cluster associated with M8, which has been investigated by Merle F. Walker at the Lick Observatory. It seems possible that the abnormally strong hydrogen lines may be a discriminant for very young 0-type clusters. Publication: The Astronomical Journal Pub Date: 1963 DOI: 10.1086/109039 Bibcode: 1963AJ.....68Q.281H full text sources ADS |

view Abstract Citations (268) References (77) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Asymptotic Giant Branch of Magellanic Cloud Clusters Frogel, Jay A. ; Mould, Jeremy ; Blanco, V. M. Abstract Thirty-nine clusters in the Magellanic Clouds have been surveyed for carbon and M-type asymptotic giant branch (AGB) stars. We identified and obtained near-infrared photometry for about 400 such stars in and around the clusters. The cluster classification scheme of Searle, Wilkinson, and Bagnuolo (SWB), which we show to be closely correlated with cluster age, is a key element in the analysis of our data. The principal results of our investigation are as follows. In a C-M diagram the cluster M stars shift steadily redward in J-K as one goes from clusters of SWB type I to VI. This is due to the increasing age of the clusters along the sequence. There are two peaks in the color distribution of the M stars which could indicate two epochs of enhanced cluster formation: one about 100 Myr ago, the other about 1 Gyr ago. These correspond to similar enhancements deduced for M stars in the Bar West region of the LMC. For LMC clusters in the 1 Gyr old group we estimate the spread in [Fe/H] to be on the order of 0.2-0.3 dex. This implies that chemical enrichment was fairly uniform throughout the LMC at that epoch. The brightest stars in SWB type VII clusters have luminosities and colors that are closely comparable to the brightest stars in Galactic globular clusters; with one possible exception they have no luminous AGB stars. We deduce that the SWB VII clusters in the Clouds are as old as Galactic globular clusters and have a range in metallicity of about a factor of 10. Luminous carbon stars are present only in SWB IV-VI clusters. They are easily distinguished from M stars by their color and luminosity. The effects of age and metallicity are apparent in luminosity functions for C stars: for those in SWB type VI clusters the luminosity function is several tenths of a magnitude fainter than that for earlier type clusters: both cluster and field SMC C stars are intrinsically fainter than their LMC counterparts. The shape of the luminosity functions for C stars from the various types of clusters are consistent with each being drawn from the same sample of field stars in the Clouds, so that the latter is clearly a composite population with a range in age and metallicity that must closely overlap that for the clusters. For the SWB-type clusters in which C stars are present, they are almost always brighter than the M stars in the same clusters. The transition luminosity between the two types of stars gets systematically brighter as one passes from the latest to the earliest type clusters. The existence of such a transition luminosity is an important prediction of the theory of carbon star formation and evolution. The youngest clusters in which C stars are found have an age of about 100 Myr implying a maximum initial mass for these stars of 3-5 M_sun_. In clusters younger than 100 Myr, the brightest stars are M giants; even though these are the brightest stars in the entire sample, they still cannot account for the missing luminous AGB stars. Therefore, the hypothesis that luminous C stars turn back into M stars appears to be ruled out. Convective overshooting or high mass-loss rates are promising hypotheses for the absence of luminous C stars. The former could also explain the fact that we see luminous C stars in clusters with turnoff masses as low as 1.0 M_sun_ in the SMC. In intermediate-age clusters, ~40% of the bolometric luminosity is contributed by C and M type AGB stars, a somewhat smaller fraction than predicted by Renzini and Buzzoni. However, because the C star luminosity function is shifted to fainter magnitudes than predicted, the age range in which AGB stars make a significant contribution is shifted to substantially older ages. If the contribution of AGB stars is removed from a cluster's light, the resulting distribution of integrated J-K colors shows a jump at types IV-V. This corresponds to the age at which the helium core switches from being degenerate to nondegenerate and is in reasonable agreement with theory. Publication: The Astrophysical Journal Pub Date: March 1990 DOI: 10.1086/168518 Bibcode: 1990ApJ...352...96F Keywords: Asymptotic Giant Branch Stars; Carbon Stars; Globular Clusters; M Stars; Magellanic Clouds; Color-Magnitude Diagram; Hertzsprung-Russell Diagram; Interstellar Extinction; Metallicity; Star Formation; Stellar Luminosity; Stellar Spectrophotometry; Astrophysics; CLUSTERS: GLOBULAR; GALAXIES: MAGELLANIC CLOUDS; STARS: CARBON; STARS: EVOLUTION; STARS: LATE-TYPE full text sources ADS | data products SIMBAD (301) NED (40)

We present the first results from an ongoing survey for multiplicity among the bright stars using the Navy Precision Optical Interferometer (NPOI). We first present a summary of NPOI observations of known multiple systems, including the first detection of the companion of β Scuti with precise relative astrometry, to illustrate the instrument’s detection sensitivity for binaries at magnitude differences Δm ⪅ 3 over the range of angular separation 3–860 milliarcseconds (mas). A limiting Δm 700 ∼ 3.5 is likely for binaries where the component spectral types differ by less than two. Model fits to these data show good agreement with published orbits, and we additionally present a new orbit solution for one of these stars, σ Her. We then discuss early results of the survey of bright stars at δ −20°. This survey, which complements previous surveys of the bright stars using speckle interferometry, initially emphasizes bright stars of spectral types F0 through K2. We report observations of 41 stars of apparent visual magnitude m V , all having been observed on multiple nights. Analysis of these data produces fitted angular separations, position angles, and component magnitude differences for six previously known visual binaries. Three additional systems were examined as possible binaries, but no conclusive detection could be made. No evidence of close stellar companions within our detection limit of Δm ≈3 was found for the remaining 32 stars observed; however, uniform-disk angular diameters are reported for 11 of the resolved stars in this last group.

The bright stars for 15 SMC clusters were classified in order to derive the distribution of various spectral types. The studied clusters represent all evolutionary ages (disk, intermediate and halo) and are located at various places of the parent galaxy. The spectal classification of the stars was carried out using film copies of the 1.2 m Schmidt telescope objective prism plates. Low dispersion (2440 Å at Hγ) and medium dispersion (830 Å at Hγ) unwidewed UJ and RI spectra were examined by means of a binocular microscope. Short exposure plates were used as well for the most bright stars and particularly for the stars at the central areas where crowding is more severe. More details about the used material and the criteria used for the classification are described by Kontizas et al (1985). For each cluster a circular area was examined inside its tidal radius. (Kontizas, 1984). The stars in the innermost part of the populous clusters were not classified because of the overlapped images. Stars of fields in the vicinity of each cluster were also classified to find the contribution of field stars in the cluster area. The magnitude range of the studied stars is 14.5<V<17.50.

Bright stars, stars with visual magnitude smaller than 6.5, can be studied using small telescope. In general, if stars are assumed as black body radiator, then the color in infrared (IR) region is usually equal to zero. Infrared data from IRAS observations at 12 and 25μm (micron) with good flux quality are used to search for bright stars (from Bright Stars Catalogues) with infrared excess. In magnitude scale, stars with IR excess is defined as stars with IR color m12−m25>0; where m12−m25 = −2.5log(F12/F25)+1.56, where F12 and F25 are flux density in Jansky at 12 and 25μm, respectively. Stars with similar spectral type are expected to have similar color. The existence of infrared excess in the same spectral type indicates the existence of circum-stellar dust, the origin of which is probably due to the remnant of pre main-sequence evolution during star formation or post AGB evolution or due to physical process such as the rotation of those stars.

We present and discuss new CCD-based photometric material in the UBVI pass-bands for nine Galactic star clusters located inside the solar ring, for which no CCD data are currently available. They are: IC 2714, NGC 4052, ESO131SC09, NGC 5284, NGC 5316, NGC 5715, VdB-Hagen ~164, NGC 6268, and Czernik 38. We first perform star counts by combining our optical photometry wi th 2MASS, and derive cluster sizes and radial density profiles. The fundamental parameters - age, reddening and distance- are then inferred from the analysis of the star distribution in color-color and color-magnitude diagrams of only the spatially selected likely members. Our analysis shows that ESO131SC09, NGC 5284, and VdB-Hagen 164 are most probably not clusters, but random enhancements of a few bright stars along the line of sight, with prop erties much similar to open cluster remnants. The remaining clusters are physical groups, and are all younger than about 1 Gyr . We use the newly derived set of parameters, in particular distance and reddening, to investigate their position in the Galaxy in the context of the spiral structure of the Milky Way. We find that the youngest clusters (IC 2714, NGC 5316, and NGC 6268) are located close to or inside the Carina-Sagittarius arm, and are therefore {\i t bona fide} spiral structure tracers. On the other hand, the oldest (Czernik 38, NGC 4052, and NGC 5715) are floating in the inter-arm space between the Carina-Sagittarius and the more distant Scutum-Crux arm. Interestingly enough, the oldest clusters of this sample - Czernik 38 and NGC 5715- are among the few known open clusters to be older or as old as the Hyades in the inner Galactic disk, where star clusters are not expected to survive for a long time, because of the strong tidal field and the higher probability of close encounters .

IRAS stars with reliable fluxes at 12, 25, and 60 microns were investigated which fell into three main types: (1) bright; (2) O-rich; and (3) C-rich. The three star types had a tendency to separate in the IRAS color-color diagram such that almost nonoverlapping zones could be defined for the groups with about 70 percent of the stars included. The O-rich stars tended to be redder in (12) - (25) than bright stars, and C-rich stars tended to be redder in (25) - (60) than bright and O-rich stars. It is suggested that the flattening of the underlying continuum slope may be the dominant cause of the change in (12) - (25). Of the 4300 unassociated IRAS point sources considered, amost 50 percent are late-type stars.

Background: The formation of small groups and education with an active learning approach is among the basics of problem-based learning (PBL).Objectives: The present study aimed at determining the effect of the PBL approach with virtualsmall groups on academic achievement and participatory learning in midwifery students of Islamic Azad University, Jahrom Branch, Iran.Methods: The present interventional study was performed on 50 midwifery students of Islamic Azad University, Jahrom Branch, studying at internal and gynecologic surgery course in the academic year of 2018-19. The subjects were randomly assigned to the intervention and control groups. The intervention and control groups underwent PBL and the conventional methods, respectively. The academic success of the participants and the active and collaborative learning was assessed. Data were analyzed using the Mann-Whitney U and Wilcoxon tests in SPSS.Results: There was a significant increase in the mean score of academic achievement in the intervention group compared to controls (P <0.05). The active and collaborative learning (ACL) score of the intervention group was above average and significantly higher compared to the control group (P=0.03).Conclusion: PBL virtual with small groups, in addition to academic success, affects ACL. This technology can be used for educational purposes, such as participation and interaction in small groups in the PBL.