- ID:
- ivo://CDS.VizieR/J/MNRAS/443/454
- Title:
- UBVIH{alpha} photometry in NGC 1893
- Short Name:
- J/MNRAS/443/454
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a UBVI and H{alpha} photometric study of the young open cluster NGC 1893 in the HII region W8 (IC 410 or Sh 2-236). A total of 65 early-type members are selected from photometric diagrams. A mean reddening of the stars is <E(B-V)>=0.563+/-0.083mag. The published photometric data in the near- and mid-infrared passbands are used to test the reddening law towards the cluster, and we confirm that the reddening law is normal (R_V_=3.1). Zero-age main-sequence fitting gives a distance modulus of V_0_-M_V_= 12.7+/-0.2mag, equivalent to 3.5+/-0.3kpc. From H{alpha} photometry, 125 H{alpha} emission stars and candidates are identified as pre-main-sequence (PMS). The lists of young stellar objects and X-ray sources published by previous studies allow us to select a large number of PMS members down to 1M_{sun}_. Isochrone fitting in the Hertzsprung-Russell diagram gives a turn-off age of 1.5Myr and the median age of 1.9Myr from the PMS members with a spread of ~5Myr. We derive the initial mass function (IMF) for stars with mass larger than 1M_{sun}_. The slope of the IMF ({Gamma}=-1.3+/-0.1) is well consistent with the Salpeter/Kroupa IMF. A total mass of the cluster appears to be in excess of 1300M_{sun}_. Finally, we estimate the mass accretion rate of 82 PMS members in the mass range of 0.6-5M_{sun}_.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/438/1451
- Title:
- UBVIH{alpha} photometry of IC 1848
- Short Name:
- J/MNRAS/438/1451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IC 1848 is one of the young open clusters in the giant star-forming Cas OB6 association. Several interesting aspects relating to star formation processes in giant star-forming regions attracted us to study the initial mass function (IMF), star formation mode and properties of pre-main-sequence (PMS) stars. A UBVI and H{alpha} photometric study of the young open cluster IC 1848 was conducted as part of the 'Sejong Open Cluster Survey'. We have selected 10^5^ early-type members from photometric diagrams. Their mean reddening is <E(B-V)>=0.660+/-0.054mag. Using the published photometric data with near- and mid-infrared archival data we confirmed the normal reddening law (R_V_=3.1) towards the cluster (IC 1848). A careful zero-age main-sequence fitting gives a distance modulus of V_0_-M_V_=11.7+/-0.2mag, equivalent to 2.2+/-0.2kpc. H{alpha} photometry and the list of young stellar objects identified by Koenig et al. permitted us to select a large number of PMS stars comprising 196 H{alpha} emission stars, 35 H{alpha} emission candidates, 5 Class I, 368 Class II and 24 transition disc candidates. From the Hertzsprung-Russell diagram using stellar evolution models, we estimate an age of 5Myr from several evolved stars and 3Myr from the PMS stars. The IMF was derived from stars with mass larger than 3M_{sun}_, and the slope is slightly steeper ({Gamma}=-1.6+/-0.2) than the Salpeter/Kroupa IMF. Finally, we estimated the mass accretion rate of PMS stars with an ultraviolet excess. The mean mass accretion rate is about 1.4x10^-8^M_{sun}_/yr in the mass range of 0.5-2M_{sun}_, whereas intermediate-mass stars (>=2.5M_{sun}_) exhibit a much higher accretion rate of dM/dt>10^-6^M_{sun}/yr.
- ID:
- ivo://CDS.VizieR/J/AJ/123/1411
- Title:
- UBVIHalpha photometry of NGC 4314 star clusters
- Short Name:
- J/AJ/123/1411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hubble Space Telescope (HST) WFPC2 images, we have obtained U, B, V, I, and H{alpha} photometry for 76 star clusters in the nuclear star-forming ring of the barred spiral galaxy NGC 4314. These clusters are likely associated with an inner inner Lindblad resonance (IILR). The blue colors and H{alpha} emission for most of these clusters imply very young ages of 115 Myr. Age estimates based on several reddening-free parameters indicate that the present epoch of star formation has lasted at least 30Myr. By estimating the masses of stars in the clusters and comparing with the H{alpha} luminosity, we conclude that a significant fraction of ongoing star formation in the nuclear ring of NGC 4314 occurs in clusters. The cluster masses identify these as young open clusters, not young globular clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/398/221
- Title:
- UBVIJHK photometry towards (l=305{deg},b=0{deg})
- Short Name:
- J/MNRAS/398/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical (UBVIc) observations of a rich and complex field in the Galactic plane towards l~305{deg} and b~0{deg}.
- ID:
- ivo://CDS.VizieR/J/PASP/122/288
- Title:
- UBVI_KC_ photometry in NGC 2309
- Short Name:
- J/PASP/122/288
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained CCD UBVI_KC_ photometry down to V~22.0 for the open cluster NGC 2309 and its surrounding field. Twenty three probable cluster members have been identified for the first time on the basis of sound photometric criteria. Because NGC 2309 is a relatively poor cluster projected onto a rich star field showing density fluctuations, the frequently used membership criteria based on stellar density profiles or proper motion measurements would not be enough to assess the star membership status if employed independently. We estimated a cluster radius of 7.9' and a radius at half the maximum of the cluster density profile of 1.7'. Based on the best fits of isochrones computed by the Geneva group to the cluster color-magnitude and color-color diagrams, previously shifted by the cluster reddening (E(B-V)=0.32) and distance (d=2.5kpc), we derived the cluster age (250Myr) and metallicity ([Fe/H]~0.0). If an 8.5kpc distance from the Sun to the center of the Galaxy is assumed, then NGC 2309 is found to be located just in front of the Perseus spiral arm.
- ID:
- ivo://CDS.VizieR/J/ApJS/162/49
- Title:
- UBV imaging of irregular galaxies
- Short Name:
- J/ApJS/162/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of UBV imaging of a large sample of irregular galaxies: 94 Im systems, 24 blue compact dwarfs (BCDs), and 18 Sm galaxies. We also include JHK imaging of 42 of these galaxies. The sample spans a large range in galactic parameters. Ellipse fit axial ratios, inclinations, and position angles are derived, integrated photometry and azimuthally averaged surface photometry profiles are determined, and exponential fits give the central surface brightnesses, scale lengths, and isophotal and half-power radii.
- ID:
- ivo://CDS.VizieR/J/A+A/345/505
- Title:
- UBVI magnitudes of NGC 869 B-type pulsators
- Short Name:
- J/A+A/345/505
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the course of the search for B-type pulsators in the central region of h Persei, we discovered two {beta} Cephei stars, Oo692 and Oo992, and one SPB star, Oo893. The first two stars are monoperiodic pulsators with periods of 0.1716946 and 0.1326359 d respectively, and semi-amplitudes smaller than 0.01mag. The light curve of Oo893 can be described by a single 1.193633-day period, slightly non-sinusoidal in shape, and having semi-amplitudes from 19 mmag in I to 48 mmag in U. Oo893 is the first SPB star found in h and {chi} Persei. In addition, we discovered seven other variables, including three eclipsing binaries and one {lambda} Eri star. One of the binaries is a W UMa-type star and a likely cluster member. We also present new UBV photometry for 258 stars in the field. The average reddening, estimated from the cluster colour-colour diagram, amounts to E(B-V)=0.52mag. A 0.1mag dispersion of reddenings within the cluster is also seen.
- ID:
- ivo://CDS.VizieR/J/ApJ/641/763
- Title:
- UBVI photometry for Arp 220 star clusters
- Short Name:
- J/ApJ/641/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new optical observations of young massive star clusters in Arp 220, the nearest ultraluminous infrared galaxy, taken in UBVI with the Hubble Space Telescope ACS HRC camera. We find a total of 206 probable clusters whose spatial distribution is centrally concentrated toward the nucleus of Arp 220. We use model star cluster tracks to determine ages, luminosities, and masses for 14 clusters with complete UBVI indices or previously published near-infrared data. We estimate rough masses for 24 additional clusters with I<24mag from BVI indices alone.
- ID:
- ivo://CDS.VizieR/J/other/BASI/29.53
- Title:
- UBVI photometry in Berkeley 32
- Short Name:
- J/other/BASI/29.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new CCD photometry of the distant old open star cluster Berkeley 32 in Johnson V and Cousins I passbands. A total of about 3200 stars have been observed in a field of about 13'x13'. The colour-magnitude diagram (CMD) in V, (V-I) has been generated down to V=22mag. A broad but well defined main sequence is clearly visible. Some blue stragglers, a well developed subgiant branch and a Red Clump are also seen. By fitting isochrones to this CMD as well as to other CMDs available in the literature, and using the Red Clump location, the reddening, distance and age of the star cluster have been determined. The cluster has a distance of about 3.3kpc, its radius is about 2.4pc; the reddening E(B-V) is 0.08 mag and the age is about 6.3Gyr. By comparison with theoretical isochrones, a metallicity of [Fe/H]~-0.2dex has been estimated.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A70
- Title:
- UBVI photometry in 3 globular clusters
- Short Name:
- J/A+A/573/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric analysis of the external regions of three Galactic Globular Clusters: NGC 6121, NGC 6397 and NGC 6752. The main goal is the characterization of the multiple stellar populations along the main sequence (MS) and the study of the radial trend of the different populations hosted by the target clusters. The data have been collected using FORS2 mounted at the ESO/VLT@UT1 telescope in UBVI filters. From these data sets we extracted high-accuracy photometry and constructed color-magnitude diagrams. We exploit appropriate combination of colors and magnitudes which are powerful tools to identify multiple stellar populations, like B versus U-B and V versus c_U,B,I_=(U-B)-(B-I) CMDs. We confirm previous findings of a split MS in NGC 6752 and NGC 6121. Apart from the extreme case of omega Centauri, this is the first detection of multiple MS from ground-based photometry. For NGC 6752 and NGC 6121 we compare the number ratio of the blue MS to the red MS in the cluster outskirts with the fraction of first and second generation stars measured in the central regions. There is no evidence for significant radial trend. The MS of NGC 6397 is consistent with a simple stellar population. We propose that the lack of multiple sequences is due both to observational errors and to the limited sensitivity of U,B,V,I photometry to multiple stellar populations in metal-poor GCs. Finally, we compute the helium abundance for the stellar populations hosted by NGC 6121 and NGC 6752, finding a mild ({Delta}Y~0.02) difference between stars in the two sequences.
