Laboratory characterization (18-1893 GHz) and astronomical detection (IRAM-30m: 80-280GHz, Orion-KL) of CH_2_CHCN (vinyl cyanide) in its ground and vibrationally excited states. Improving the understanding of rotational spectra of vibrationally excited vinyl cyanide with new laboratory data and analysis. The laboratory results allow searching for these excited state transitions in the Orion-KL line survey. Furthermore, rotational lines of CH_2_CHCN contribute to the understanding of the physical and chemical properties of the cloud. Laboratory measurements of CH_2_CHCN made on several different frequency-modulated spectrometers were combined into a single broadband 50-1900GHz spectrum and its assignment was confirmed by Stark modulation spectra recorded in the 18-40GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of vinyl cyanide detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. Detailed characterisation of laboratory spectra of CH_2CHCN in 9 different excited vibrational states (v_11_=1, v_15_=1, v_11_=2, v_10_=1<==>(v_11_=1,v_15_=1), v_11_=3/v_15_=2/v_14_=1, (v_11_=1,v_10_=1)<==>(v_11_=2, v_15_=1), v_9_$=1, (v_11_=1,v_15_=2)<==>(v_10_=1, v_15_=1)<==>(v_11_=1,v_14_=1), and v_11_=4) and detection of transitions in the v_11_=2 and v_11_=3 states for the first time in Orion-KL, and of those in the v_10_=1<==>(v_11_=1,v_15_=1) dyad of states for the first time in space. The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature which trace the physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The lowest energy vibrationally excited states of vinyl cyanide such as v_11_=1 (at 328.5K), v_15_=1 (at 478.6K), v_11_=2 (at 657.8K), the v_10_=1<==>(v_11_=1,v_15_=1) dyad (at 806.4/809.9K), and v_11_=3 (at 987.9K) are populated under warm and dense conditions, so they probe the hottest parts of the Orion-KL source. The vibrational temperatures derived for the v_11_=1, v_11_=2, and v_15_=1 states are 252+/-76K, 242+/-121K, and 227+/-68K, respectively; all of them close to the mean kinetic temperature of the hot core component (210K). The total column density of CH_2_CHCN in the ground state is (3.0+/-0.9)x10^15^cm^-2^. We report the detection of methyl isocyanide (CH_3_NC) for the first time in Orion-KL and a tentative detection of vinyl isocyanide (CH_2_CHNC) and give column density ratios between the cyanide and isocyanide isomers obtaining a N(CH_3_NC)/N(CH_3_CN) ratio of 0.002. Laboratory characterisation of many previously unassigned vibrationally excited states of vinyl cyanide at microwave to THz frequencies allowed us to detect these molecular species in Orion-KL. Column density and rotational and vibrational temperatures for CH_2_CHCN in their ground and excited states, as well as for the isotopologues, have been constrained by means of a sample of more than 1000 lines in this survey.
We present VI CCD photometric observations of about 5500 stars up to a limiting magnitude of V~20 in an area of ~16'x16' around the cluster NGC 6631. The cluster parameters determined for the first time by fitting the theoretical isochrones in the V, (V-I) diagram of the cluster stars are E(V-I)=0.60+/-0.05mag, distance=2.6+/-0.5kpc, age=400+/-100Myr and metallicity, Z=0.05. The cluster diameter determined from the radial density profile is 4.8+-0.5pc. The mass function of the cluster has a slope of 2.1+/-05.
We present CCD photometry in V and I for the metal-rich globular cluster NGC 6528. A comparison with previous photometry reveals discrepancies of the order 0.1 to 0.2mag in V, emphasizing the need for independent photometry. As found previously, the giant branch (or the asymptotic giant branch, which cannot be distinguished) of the cluster extends to V-I=7. Population synthesis in V-I must take these red stars into account in order to understand integrated red colours of bulge populations. Currently available theoretical isochrones do not reproduce the shape of the RGB/AGB. The derivation of reliable values for reddening, distance and metallicity of NGC 6528 is hampered by uncertainties in the extrapolation to high metallicity, which dominate the absolute error rather than the photo metric uncertainty does. Together with other properties (old age derived from HST data, high radial velocity), this object is more likely a member of the bulge than of the disk population.
X, Y pixel coordinates and V, I CCD photometric magnitudes of stars in cluster region NGC 6553. DAOPHOT photometric errors in V and (V-I) are also given.
CCD observations in the Johnson V, Kron-Cousins I and the Washington system C and T_1_ passbands have been used to generate colour-magnitude diagrams (CMDs) reaching down to V~21.0mag and T_1_~19.0 for Trumpler 5, an old open cluster located towards the Galactic anticentre. Our data analysis confirms the existence of non-uniform extinction over the face of the cluster, the mean E(V-I) and E(C-T_1_) values being 0.80+/-0.05 and 1.17+/-0.15, respectively. Through comparison of the cluster CMDs with theoretical isochrones of the Geneva group, Washington Standard Giant Branches and measures of V and T_1_ indices, we derive the following values for the cluster apparent distance modulus, age, and metallicity: V-M_V_=13.80+/-0.30 (corresponding to a distance from the Sun of 2.4+/-0.5 kpc and 0.04kpc above the Galactic plane), t=5.0+/-0.5Gyr and [Fe/H]=-0.30+/-0.15. We estimate the cluster angular radius to be about 7.7 arcmin (=5.4pc) from star counts carried out within and outside the cluster field.
Using H{alpha} grism spectroscopy and optical and Two-Micron All-Sky Survey photometry of the fields containing NGC 1893 and two emission nebulae, Sim 129 and Sim 130, we show the presence of a number of H{alpha} and near-infrared excess sources towards the region between HD 242935 and the two emission nebulae. Among them a large majority of these pre-main-sequence candidate sources are concentrated towards regions closer to Sim 129 and Sim 130.
We wish to determine accurate ages for open clusters and use this, in conjunction with colour-magnitude diagrams, to constrain models of stellar structure and evolution. The detached eclipsing binary V20 in the old, metal-rich ([Fe/H]=+0.40) open cluster NGC6791 is studied in order to determine highly accurate masses and radii of its components. This allows the cluster age to be established with high precision, using isochrones in the mass-radius diagram. Methods. We employ high-resolution UVES spectroscopy of V20 to determine the spectroscopic orbit and time-series V, Ic photometry to obtain the photometric elements.
We present CCD VI_KC_ photometry down to V~21mag in the field of the rich open cluster NGC 2194, which is projected towards the Galactic anticentre direction. We measured V magnitudes and V-I colours for a total of 2515 stars in a field of 13.6x13.6arcmin^2^, supplemented with CCD photometry in the C, M and T_1_ filters of the Washington system and photoelectric CMT_1_T_2_ photometry of 20 red giant candidates, using the 0.9-m telescope at the Cerro Tololo Inter-American Observatory (CTIO), Chile, on 1997 December 23-24.
We report deep (V~24.0) VI CCD photometry of three fields centred in the regions of the old open clusters Saurer A, B and C. In the case of Saurer A, which is considered one of the oldest known open clusters, we also provide a comparison field.
Attention is given to a population of 110 stars in the NGC 6611 cluster of the Eagle nebula that have prominent near-infrared excess and optical colours typical of pre-main-sequence (PMS) stars older than 8Myr. At least half of those for which spectroscopy exists have a H{alpha} emission line profile revealing active accretion. In principle, the V-I colours of all these stars would be consistent with those of young PMS objects (<1Myr) whose radiation is heavily obscured by a circumstellar disc seen at high inclination and in small part scattered towards the observer by the back side of the disc. However, using theoretical models it is shown here that objects of this type can only account for a few percent of this population. In fact, the spatial distribution of these objects, their X-ray luminosities, their optical brightness, their positions in the colour-magnitude diagram and the weak Li absorption lines of the stars studied spectroscopically suggest that most of them are at least eight times older than the ~1Myr-old PMS stars already known in this cluster and could be as old as ~30Myr. This is the largest homogeneous sample to date of Galactic PMS stars considerably older than 8Myr that are still actively accreting from a circumstellar disc and it allows us to set a lower limit of 7 percent to the disc frequency at ~16Myr in NGC 6611. These values imply a characteristic exponential lifetime of ~6Myr for disc dissipation.
