- ID:
- ivo://CDS.VizieR/J/A+A/419/149
- Title:
- UBV(I)c photometry of NGC 6996
- Short Name:
- J/A+A/419/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and discuss broad band CCD UBV(I)c photometry and low resolution spectroscopy for stars in the region of the open cluster NGC 6996, located in the North America Nebula. The new data allow us to tightly constrain the basic properties of this object. We revise the cluster size, which in the past has been significantly underestimated. The width of the Main Sequence is mainly interpreted in terms of differential reddening, and indeed the stars' color excess E(B-V) ranges from 0.43 to 0.65, implying the presence of a significant and evenly distributed dust component. We cross-correlate our optical photometry with near infrared photometry from 2MASS, and by means of spectral classification we are able to build extinction curves for an handful of bright members. We find that the reddening slope and the total to selective absorption ratio Rv toward NGC 6996 are anomalous. Moreover the reddening-corrected colors and magnitudes allow us to derive estimates for the cluster distance and age, which turn out to be 760+/-70pc (V0-MV=9.4+/-0.2) and ~350Myr, respectively. Based on our results, we suggest that NGC 6996 is located in front of the North America Nebula, and does not seem to have any apparent relationship with it.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AN/325/307
- Title:
- UBVIc photometry of NGC 3077 center
- Short Name:
- J/AN/325/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVIc photometry of starlike objects in the central region of NGC 3077. The colour-colour and colour-magnitude diagrams of the objects are discussed. Many of the objects under consideration, starlike from the ground, are probably dense young star clusters (super star clusters, SSC). Ages spreading over ~4 to ~150Myr are estimated for most of these objects. Sakai and Madore (2001ApJ...555..280S) found enhanced star formation ~30-125Myr ago also in the halo of this galaxy; thus, high star forming activity has occurred within the entire galaxy (centre and halo) since ~130..150Myr. Having ended in the outer regions about 30Myr ago, it is going on near the centre with full vigour.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A125
- Title:
- UBVI data of open cluster Trumpler 27
- Short Name:
- J/A+A/548/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spiral structure of the Milky Way inside the solar circle is still poorly known because of the high density of the material that causes strong extinction towards the Galactic center. We present results of the first extensive and deep color-color diagram (CCD) photometric survey carried out in the field of the open cluster Trumpler 27, an object immersed in a region of extremely high visual absorption in the constellation of Sagittarius not far from the Galaxy center. The survey covers almost a quarter of square degree. We look for young stars clumps that might plausibly be associated with spiral structure. Wide-field UBVI photometry combined with infrared information allows us to reconstruct the distribution in the reddening and distance of young stars in the field using the CCD and color-magnitude diagrams (CMD).
- 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}_.
- 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/A+AS/137/233
- Title:
- UBVI imaging photometry of NGC 6231
- Short Name:
- J/A+AS/137/233
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD UBVI photometry in the field of the open cluster NGC 6231 was obtained for 1060 stars down to V=19mag. Memberships, reddening, distance and age of this cluster were investigated. Its lower sequence displays a notorious bend at V=13.5mag followed by a high number of faint stars showing a large magnitude spread at constant colour. This distribution of stars does not seem to be produced by a mere accumulation of field stars seen in the direction of the cluster but by a real star excess in the zone. The evidence suggests these stars are serious candidates to be cluster members caught in their way towards the ZAMS. Fitting them with pre main sequence isochrones an age spread of 10Myr is obtained. The luminosity and mass functions were found to be flat for -7.5<M_v_<1.5 and for 3 to 80M_{sun}_ respectively.
- 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/A+A/553/A40
- Title:
- UBVI light curves of FK Com
- Short Name:
- J/A+A/553/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply the continuous period search and carrier fit methods on long-term standard Johnson-Cousins V-observations from the years 1995-2010. The observations were carried out with two automated photometric telescopes, Phoenix-10 and Amadeus T7 located in Arizona. We identify complex phase behaviour in 6 of the 15 analysed data segments. We identify five flip-flop events and two cases of phase jumps, where the phase shift is {Delta}{phi}<0.4. In addition we see two mergers of spot regions and two cases where the apparent phase shifts are caused by spot regions drifting with respect to each other. Furthermore we detect variations in the rotation period corresponding to a differential rotation coefficient of |k|>0.031.
