- ID:
- ivo://CDS.VizieR/J/ApJ/710/1664
- Title:
- BV photometry in Leo IV and Leo V dSphs
- Short Name:
- J/ApJ/710/1664
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained deep photometry in two 1{deg}x1{deg} fields covering the close pair of dwarf spheroidal galaxies Leo IV and Leo V and part of the area in between. From the distribution of likely red giant branch (RGB) and horizontal-branch (HB) stars in the data set, we find that both Leo IV and Leo V are significantly larger than indicated by previous measurements based on shallower data. With a half-light radius of r_h_=4.6'+/-0.8' (206+/-36pc) and r_h_=2.6'+/-0.6' (133+/-31pc), respectively, both systems are now well within the physical size bracket of typical dwarf spheroidal Milky Way satellites. Both are also found to be significantly elongated with an ellipticity of {epsilon}~0.5, a characteristic shared by many of the fainter (M_V_>-8) Milky Way dwarf spheroidals. The large spatial extent of our survey allows us to search for extra-tidal features in the area between the two dwarf galaxies with unprecedented sensitivity. The spatial distribution of candidate RGB and HB stars in this region is found to be non-uniform at the ~3{sigma} level. We investigate different scenarios to explain the close proximity of Leo IV and Leo V, and the possible tidal bridge between them.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/117/2868
- Title:
- BV photometry in M2 (NGC 7089)
- Short Name:
- J/AJ/117/2868
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BV CCD photometry for 30 RR Lyrae variables, including 13 newly discovered, in the Oosterhoff type II globular cluster M2. New light curves and ephemerides are presented. Our observations cover magnitudes ranging from the red giant branch tip to ~3mag below the turnoff, allowing us to determine accurate fundamental photometric parameters. With the discovery of new RR Lyrae variables, the mean periods of the RRab and RRc variables are <P_ab_>=0.685+/-0.022days and <P_c_>=0.333+/-0.013days, respectively. The number ratio of the RRc type variables to the total number of RR Lyrae type variables is n(c)/n(ab+c)=0.40. The RR Lyrae pulsational mode transition occurs between the fundamental period of 0.528-days and 0.556-days. From star counts along the horizontal branch (HB), we obtain two HB color distribution indices, (B-R)/(B+V+R)=0.92 and B2/(B+V+R)=0.46. The period-change rates are also derived. The mean period-change rate from six RRab variables is <{beta}>=0.06+/-0.04days/Myr, which agrees well with the predictions of Lee's 1991 model. Our color-magnitude diagram shows a very extended blue HB tail, and there are no significant blue HB gaps in M2.
- ID:
- ivo://CDS.VizieR/J/AJ/121/318
- Title:
- BV photometry in NGC 5986
- Short Name:
- J/AJ/121/318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained new CCD BV photometry of the little-studied southern Galactic globular cluster NGC 5986, including light curves of five of its RR Lyrae variables. The cluster's red giant branch bump is detected for the first time, at V=16.47 +/-0.03. We derive a reddening and true distance modulus of E(B-V)=0.29+/-0.02 and (m-M)_0_=15.15+/-0.10, respectively. The cluster's color-magnitude diagram reveals a mostly blue horizontal branch, like that of M13 or M2, and quite unlike M3; yet all of these clusters have nearly identical metallicities ([Fe/H]_CG97_=-1.35). We show that the RR Lyrae variables in NGC 5986 are about 0.2mag brighter on average than those in M3, an important exception to the often-employed, universal M_V_(RR)-[Fe/H] relation. Finally, we note that NGC 5986 contains two luminous stars with spectral types A-F, which are likely to be post-asymptotic giant branch (PAGB) objects. The V-band luminosity function of such yellow PAGB stars is a promising standard candle. We suggest that the luminosity function is sharply peaked at M_V_(PAGB)=-3.28+/-0.07.
- ID:
- ivo://CDS.VizieR/J/AJ/106/1024
- Title:
- BV photometry in NGC 288
- Short Name:
- J/AJ/106/1024
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/328/167
- Title:
- BV photometry in supergiant shell LMC4
- Short Name:
- J/A+A/328/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The youngest stellar populations of a 'J'-shaped region inside the supergiant shell (SGS) LMC4 have been analysed with CCD photometry in B, V passbands. This region consists of 2 coherent strips, one from the east to the west reaching about 400pc across the OB superassociation LH 77 and another extending about 850pc from south to north. The standard photometric methods yield for each of the 25 CCD fields a colour-magnitude diagram (CMD) which is used for age determination of the youngest star population by isochrone fitting. The resultant ages lie in the range from 9Myr to 16Myr without correlation with the distance to the LMC 4 centre. We therefore conclude that there must have been one triggering event for star formation inside this large LMC SGS with a diameter of 1.4kpc.
- ID:
- ivo://CDS.VizieR/J/A+AS/61/473
- Title:
- BV photometry in the LMC bar
- Short Name:
- J/A+AS/61/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present B, V magnitudes and relative positions for all brighter than V=18.3 in a field of 0.02 square degrees near the north west end of the Large Magellanic Cloud bar. These star are the bright tail of a larger sample of about 18000 stars previously presented in the form color-magnitude diagram; they form a set of data free from selection effects and, therefore, valuable for further studies.
- ID:
- ivo://CDS.VizieR/J/AZh/79/542
- Title:
- BV photometry of active K-M dwarfs
- Short Name:
- J/AZh/79/542
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variability of the photospheric radiation of 40 (dKe-dMe) dwarfs due to variations in the spottedness of their surfaces is analyzed based on the behavior of their mean annual brightnesses over long time intervals.
- ID:
- ivo://CDS.VizieR/J/AJ/127/318
- Title:
- BV photometry of Andromeda II variables
- Short Name:
- J/AJ/127/318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a variable star search in Andromeda II, a dwarf spheroidal galaxy companion to M31, using Hubble Space Telescope Wide Field Planetary Camera 2 observations. Seventy-three variables were found, one of which is an anomalous Cepheid while the others are RR Lyrae stars. The anomalous Cepheid has properties consistent with those found in other dwarf spheroidal galaxies. For the RR Lyrae stars, the mean periods are 0.571 and 0.363 days for the fundamental mode and first-overtone mode stars, respectively. With this fundamental mode mean period and the mean metallicity determined from the red giant branch (<[Fe/H]>=-1.49), Andromeda II follows the period-metallicity relation defined by the Galactic globular clusters and other dwarf spheroidal galaxies. We also find that the properties of the RR Lyrae stars themselves indicate a mean abundance that is consistent with that determined from the red giants.
- ID:
- ivo://CDS.VizieR/J/A+A/429/607
- Title:
- BV photometry of Berkeley 36, 73 and 34
- Short Name:
- J/A+A/429/607
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BV photometry of the faint open clusters Berkeley 36, Berkeley 73 and Biurakan 13 are studied. For these clusters no colour-magnitude analyses were previously available. The colour-magnitude Diagrams indicate that they are all old open clusters. The derived ages are ~4Gyr for Berkeley 36, and ~2.3Gyr for both Berkeley 73 and Biurakan 13. The clusters are not very reddened, with E(B-V)=0.25, 0.10 and 0.30 respectively for Berkeley 36, Berkeley 73 and Biurakan 13. Berkeley 36 and Berkeley 73 are located at a distance from the Galactic center of 10kpc, while Biurakan 13 is much farther, at 15kpc. A peak in the age distribution appears at 5Gyr suggesting a distinct star forming event in the disk.
- ID:
- ivo://CDS.VizieR/J/A+AS/121/213
- Title:
- BV photometry of Blanco 1 stars
- Short Name:
- J/A+AS/121/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of H{alpha}(6562A) and Li I(6708A) observations of 114 low-mass stars of the young open cluster Blanco 1. We also present observations of 30 stars in Ca II(K). This work extends the first Blanco 1 spectroscopic study of Panagi et al. (1994A&A...285..233D). From a sample of four well-studied clusters, including Blanco 1, we find that the fraction of H{alpha} emission-line stars amongst K dwarfs is a good indicator of relative age, with a smaller fraction indicative of older age. Blanco 1 shows a relatively small fraction of emitters, inconsistent with previous age estimates for the cluster. We estimate the cluster age to to be 90+/-25Myr, slightly older than the Pleiades. The method is shown to be more sensitive to age than lithium and a useful alternative to other age measurement techniques. The variation of H{alpha} with (B-V) is similar to that observed in the older solar neighbourhood dwarfs, suggesting that, at least for the absorption-line stars, the contribution of stellar rotation to the equivalent width is unclear. We combine both spectroscopy and photometry to revise cluster membership and give accurate positions for all these stars.
