We present a detailed study of an eclipsing binary which had been classified Ap SrCrEu (Hartoog, 1976ApJ...205..807H) before being known as a binary. Radial velocities measured at the times of both quadratures allow us to obtain precise masses for both components, while the light curve yields the radii. The following ephemeris and fundamental parameters of the system were obtained: HJD=(2447999.7656+/-0.0041) +(3.174990+/-0.000001) E, e=0.00, i=81.9+/-0.1{deg}, M_1_=1.90+/-0.02M_{sun}_, M_2_=1.85+/-0.02M_{sun}_, R_1_=1.63+/-0.03R_{sun}_, R_2_=1.60+/-0.03R_{sun}_, vsini_1_=27.6+/-3.5km/s, vsini_2_=23.6+/-3.6km/s. The projected rotational velocities were determined by fitting a synthetic spectrum convolved with a rotational profile to the observed spectrum. A comparison of the spectra of V392 Car and of the normal A star Cox 98, which has the same colour indices, shows that Sr is not overabundant and the metallicity of V392 Car is the same as that of the other cluster members. Therefore, V392 Car is a normal A2 star rather than an Ap star. The position of V392 Car in the HR diagram is entirely consistent with membership of the cluster NGC 2516. An independent estimate of the distance to this cluster was done using the parameters of the eclipsing system, and found to be in agreement with the Hipparcos one. A comparison of the parameters obtained from observations with predictions of internal structure models leads to a metallicity estimate [M/H]=0+/-0.10dex for NGC 2516. This estimate is completely independent of any spectroscopic or photometric method (except for the T_eff_ determination) but relies on stellar structure models.
Using extended multicolour CCD photometry of the triple-mode radial pulsator V823 Cas we studied the properties of the coupling frequencies invoked by nonlinear processes. Our results support that a resonance connection affects the mode coupling behaviour. The P1/P0 period ratio of V823 Cas has an "out of range" value if compared with the period ratios of the known double mode pulsators, while the P2/P1 period ratio is normal. The periods and period ratios cannot be consistently interpreted without conflict with pulsation and/or evolution models. We describe this failure with the suggestion that at present, the periods of V823 Cas are in a transient, resonance affected state, thus do not reflect the true parameters of the object. The anomalous period change behaviour of the fundamental and second overtone modes supports this idea. We have also raised the possibility that a f0+f2=2f1 resonance may act in triple mode pulsators.
The monitoring of spectral evolution of the very slow nova V723 Cas started at the Asiago Astrophysical Observatory just on the announcement of discovery. In this paper the spectral evolution during the long pre-maximum stage, which lasted from August to December 1995, is reported. Emission lines of H I and Fe II were prominent in the early stage. Most of the lines were accompanied by P Cygni type absorption components. The emission lines gradually weakened with time and the absorption components developed. The mean of the blue-shifts of the absorption components with respect to the emissions was about -126km/s in September and -96km/s in December 1995. Some lines of Fe I, Fe II, Y II, Sc II, Ba II, etc. appeared in the later stage. All emission lines, except for H{alpha}, once nearly disappeared in November when the nova slightly brightened to V=~8.6. Some emission lines appeared again several days before the beginning of the final rise to maximum luminosity, then a pure absorption spectrum of F type supergiant was seen on the maximum of V=~7.1 at the middle of December. The absorption components of Si II lines at 634.7 and 637.1nm showed fairly different profiles from those of the other metallic lines, which suggests a complicated gas motion in the atmosphere. The distance and the absolute magnitude at maximum are estimated to be 2.95+/-0.7kpc and M_V_(max)=-6.1+/-0.5, respectively. The mass of the white dwarf in this system may be about 0.58+/-0.07M_{sun}_.
We report on the ongoing outburst of the young variable V1180 Cas, which is known to display characteristics in common with EXor eruptive variables. We present results that support the scenario of an accretion-driven nature of the brightness variations of the object and provide the first evidence of jet structures around the source. We monitored the recent flux variations of the target in the R_C_, J, H, and K bands. New optical and near-IR spectra taken during the current high state of V1180 Cas are presented, in conjunction with H_2_ narrow-band imaging of the source.
The cool, overcontact, close binary, V523 Cassiopeiae was observed with the 1 m reflector at the US Naval Observatory, Flagstaff Station. The photometry was very good, with a precision on the order of a few millimagnitudes, but not numerous enough for complete light-curve analyses (e.g., differential corrections). A conventional published synthesis has been found acceptable as a fiducial model, and most of the observational weight has been used to develop a spot model for the stars and to support the validity of theoretical limb-darkening coefficients. Both photospheres and chromospheres contribute to the model. This result indicates that multifilter measures of this and similarly cool binaries are necessary for fuller descriptions of stellar activity cycles. A number of newly determined times of minimum light solidify the published rate of period variability.
The physical mechanisms driving star formation (SF) in galaxies are still not fully understood. Tidal dwarf galaxies (TDGs), made of gas ejected during galaxy interactions, seem to be devoid of dark matter and have a near-solar metallicity. The latter makes it possible to study molecular gas and its link to SF using standard tracers (CO, dust) in a peculiar environment. We present a detailed study of a nearby TDG in the Virgo Cluster, VCC 2062, using new high-resolution CO(1-0) data from the Plateau de Bure, deep optical imaging from the Next Generation Virgo Cluster Survey (NGVS), and complementary multiwavelength data. Until now, there was some doubt whether VCC 2062 was a true TDG, but the new deep optical images from the NGVS reveal a stellar bridge between VCC 2062 and its parent galaxy, NGC 4694, which is clear proof of its tidal origin. Several high-resolution tracers (H{alpha}, UV, 8um, and 24um) of the star formation rate (SFR) are compared to the molecular gas distribution as traced by the CO(1-0). Coupled with the SFR tracers, the NGVS data are used with the CIGALE code to model the stellar populations throughout VCC 2062, yielding a declining SFR in the recent past, consistent with the low H{alpha}/UV ratio, and a high burst strength. HI emission covers VCC 2062, whereas the CO is concentrated near the HI maxima. The CO peaks correspond to two very distinct regions: one with moderate SF to the NE and one with only slightly weaker CO emission but with nearly no SF. Even where SF is clearly present, the SFR is below the value expected from the surface density of the molecular and the total gas as compared to spiral galaxies and other TDGs. After discussing different possible explanations, we conclude that the low surface brightness is a crucial parameter to understand the low SFR.
From a quantitative analysis of 413 Virgo Cluster early-type dwarf galaxies (dEs) with SDSS imaging data, we find that the dE class can be divided into multiple subpopulations that differ significantly in their morphology and clustering properties. Three dE subclasses are shaped like thick disks and show no central clustering: (1) dEs with disk features like spiral arms or bars, (2) dEs with central star formation, and (3) ordinary, bright dEs that have no or only a weak nucleus.
We study the dust content of a large optical input sample of 910 early-type galaxies (ETG) in the Virgo cluster, also extending to the dwarf ETG, and examine the results in relation to those on the other cold ISM components. We have searched for far-infrared emission in all galaxies in the input sample using the 250um image of the Herschel Virgo Cluster Survey (HeViCS). This image covers a large fraction of the cluster with an area of ~55 square degrees. For the detected ETG we measured fluxes in five bands from 100 to 500um, and estimated the dust mass and temperature with modified black-body fits. Dust is detected above the completeness limit of 25.4mJy at 250um in 46 ETG, 43 of which are in the optically complete part of the input sample. In addition, dust is present at fainter levels in another six ETG. We detect dust in the four ETG with synchrotron emission, including M 87.
We present an analysis of the globular cluster (GC) system of the nucleated dwarf elliptical galaxy VCC 1087 in the Virgo Cluster based on Keck LRIS spectroscopy and archival Hubble Space Telescope Advanced Camera for Surveys imaging. We estimate that VCC 1087 hosts a total population of 77+/-19 GCs, which corresponds to a relatively high V-band specific frequency of 5.8+/-1.4. The g_475_-z_850_ color distribution of the GCs shows a blue (metal-poor) peak with a tail of redder (metal-rich) clusters similar in color to those seen in luminous elliptical galaxies.
The database contains some outputs of the VCD for the scenarios : {1)
Standard cloud albedo Scenario, solar EUV average conditions ; 2)
Standard cloud albedo Scenario, solar EUV minimum conditions ; 3)
Standard cloud albedo Scenario, solar EUV maximum conditions ; 4) Low
cloud albedo Scenario, solar EUV average conditions ; 5) High cloud
albedo Scenario, solar EUV average conditions available}, at different
positions of latitude and longitude. These VCD outputs are provided as
Votables containing profiles of temperatures, pressures, density and
abundances of main species for altitudes between 0 and 349.5 km from
the surface.
