- ID:
- ivo://CDS.VizieR/J/A+A/531/A49
- Title:
- UBV and spectroscopic variations of V2368 Oph
- Short Name:
- J/A+A/531/A49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The A-type star HR 6412 = V2368 Oph was used by several investigators as a photometric comparison star for the known eclipsing binary U Oph but was found to be variable by three independent groups, including us. By analysing series of new spectral and photometric observations and a critical compilation of available radial velocities, we were able to find the correct period of light and radial-velocity variations and demonstrate that the object is an eclipsing and double-lined spectroscopic binary moving in a highly eccentric orbit. We derived a linear ephemeris Tmin.I=HJD(2454294.67+/-0.01)+(38.32712+/-0.00004)d*E and estimated preliminary basic physical properties of the binary.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/405/1087
- Title:
- UBV photometry and radial velocities of V497 Cep
- Short Name:
- J/A+A/405/1087
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New light and radial-velocity curves of V497 Cep, a binary in the open cluster NGC 7160, were obtained and the linear ephemeris of the system was refined to HJD(Min I)=(2446299.1596+/-0.0064)+(1.2028287d+/-0.0000015)dxE. The first light and radial-velocity curve solutions allowed us to derive the basic physical properties of this astrophysically important binary.
- ID:
- ivo://CDS.VizieR/J/AJ/113/2104
- Title:
- UBV photometry of 163 stars around SU Cyg
- Short Name:
- J/AJ/113/2104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric, CCD, and photographic photometry is presented for a sample of 163 stars in the field of the short-period Cepheid SU Cyg for the purpose of searching for a putative cluster that might be associated with the Cepheid. Although the variable is situated in a clump of stars that has the appearance of a sparse cluster, the photometric evidence indicates that they are not a physical group. About two dozen B and A-type stars randomly distributed in the field lie at a common distance of 1086+/-60pc (V_0_-M_V_= 10.18+/-0.12 for R=2.94+/-0.38), but they are likely to represent at best a segment of the Vul OB4 association, which overlaps the region. SU Cyg is unlikely to be a member of that group. The close optical companion to SU Cyg, an A2 V star with a radial velocity (<VR>=-23.6+/-7.1km/s) close to the systemic velocity of the Cepheid, is a spectroscopic binary that might be physically related to the variable. Its primary importance is for helping to establish a space reddening of E_(B-V_)=0.15+/-0.01 for SU Cyg. Despite the lack of related cluster stars to SU Cyg, its two unresolved companions can be used to place restrictions on the likely luminosity of the Cepheid. The resulting value of <M_V_><=-3.02+/-0.23 relative to its companions agrees closely with a value of <MV>(PLC)=-3.03+/-0.07 obtained from the Cepheid PLC relation.
- ID:
- ivo://CDS.VizieR/J/A+AS/138/87
- Title:
- UBVRI photometry of EUV stellar sources
- Short Name:
- J/A+AS/138/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of high-precision UBV(RI)_c_ photometric observations and of spectroscopic radial velocity measurements obtained at the European Southern Observatory for a sample of 51 cool stars detected in the EUV by the ROSAT Wide Field Camera (WFC). Using also recent results from HIPPARCOS, we infer spectral types and investigate the single or binary nature of the sample stars. Optical variability, with periods in the 0.4-13 day range, has been detected for the first time in 15 of these stars.
- ID:
- ivo://CDS.VizieR/J/A+A/364/205
- Title:
- UBVy photometry of cool stars
- Short Name:
- J/A+A/364/205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-precision photometry, high- and medium-resolution spectroscopy for a sample of 32 stars likely to be the optical counterparts of X-ray sources serendipitously detected by the EXOSAT satellite. Using also recent results from the Hipparcos satellite, we infer spectral types, compute X-ray luminosities and Li abundances and investigate the single or binary nature of the sample stars. We found eleven new variable stars, whose photometric periods fall in the 1.2-27.5 day range, for most of which the optical variability is consistent with the presence of photospheric cool spots. For our sample of X-ray selected stars we confirm the existence of a strong correlation between the stellar rotation rate and the level of activity, and also between the X-ray and bolometric luminosities. Two stars in our sample are likely to be pre-main sequence objects, one is likely to be a previously unknown M-type star within 25pc.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/86
- Title:
- UCD galaxies in the Coma cluster
- Short Name:
- J/ApJ/737/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a spectroscopic search for ultra-compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within the ACS images, and the known properties of Fornax and Virgo UCDs. Follow-up spectroscopy with Keck/Low-Resolution Imaging Spectrometer confirmed 27 candidates as members of the Coma cluster, a success rate >60% for targeted objects brighter than M_R_=-12. Another 14 candidates may also prove to be Coma members, but low signal-to-noise spectra prevent definitive conclusions.
2057. U Gem spectroscopy
- ID:
- ivo://CDS.VizieR/J/MNRAS/361/1091
- Title:
- U Gem spectroscopy
- Short Name:
- J/MNRAS/361/1091
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a phase-resolved spectroscopic study of the secondary star in the cataclysmic variable (CV) U Gem. We use our data to measure the radial velocity semi-amplitude, systemic velocity and rotational velocity of the secondary star. Combining this with literature data allows us to determine masses and radii for both the secondary star and white dwarf, which are independent of any assumptions about their structure. We use these to compare their properties to those of field stars and find that both components follow field mass-radius relationships. The secondary star has the mass, radius, luminosity and photometric temperature of an M2 star, but a spectroscopic temperature of M4. The latter may well be due to a high metallicity. There is a troubling inconsistency between the radius of the white dwarf inferred from its gravitational redshift and inclination and that inferred from its temperature, flux and astrometric distance.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A50
- Title:
- Ultra compact dwarf galaxies catalog
- Short Name:
- J/A+A/625/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric surveys of galaxy clusters have revealed a large number of ultra compact dwarfs (UCDs) around predominantly massive elliptical galaxies. Their origin is still debated as some UCDs are considered to be the remnant nuclei of stripped dwarf galaxies while others seem to mark the high-mass end of the star cluster population. We aim to characterize the properties of a UCD found at very close projected distance (r_wproj_=1.1kpc) from the centre of the low-mass (M~10^10^M_{sun}_) early-type galaxy FCC 47. This is a serendipitous discovery from MUSE adaptive optics science verification data. We explore the potential origin of this UCD as either a massive cluster or the remnant nucleus of a dissolved galaxy. We used archival Hubble Space Telescope data to study the photometric and structural properties of FCC 47-UCD1. In the MUSE data, the UCD is unresolved, but we used its spectrum to determine the radial velocity and metallicity. The surface brightness of FCC 47-UCD1 is best described by a single King profile with low concentration C=Rt/Rc~10 and large effective radius (r_eff_=24pc). Its integrated magnitude and blue colour (Mg=-10.55mag, (g-z)=1.46mag) combined with a metallicity of [M/H]=-1.12+/-0.10dex and an age >8Gyr obtained from the full fitting of the MUSE spectrum suggests a stellar population mass of M*=4.87x10^6^M_{sun}_. The low S/N of the MUSE spectrum prevents detailed stellar population analysis. Due to the limited spectral resolution of MUSE, we can only give an upper limit on the velocity dispersion ({sigma}<17km/s), and consequently on its dynamical mass (M_dyn_<1.3x10^7^M_{sun}_). The origin of the UCD cannot be constrained with certainty. The low metallicity, old age, and magnitude are consistent with a star cluster origin, whereas the extended size is consistent with an origin as the stripped nucleus of a dwarf galaxy with a initial stellar mass of a few 10^8^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/18
- Title:
- Ultra-compact HII regions & methanol masers. I.
- Short Name:
- J/ApJ/833/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted Very Large Array C-configuration observations to measure positions and luminosities of Galactic Class II 6.7GHz methanol masers and their associated ultra-compact HII regions. The spectral resolution was 3.90625kHz and the continuum sensitivity reached 45{mu}Jy/beam. We mapped 372 methanol masers with peak flux densities of more than 2Jy selected from the literature. Absolute positions have nominal uncertainties of 0.3". In this first paper on the data analysis, we present three catalogs; the first gives information on the strongest feature of 367 methanol maser sources, and the second provides information on all detected maser spots. The third catalog presents derived data of the 127 radio continuum counterparts associated with maser sources. Our detection rate of radio continuum counterparts toward methanol masers is approximately one-third. Our catalogs list properties including distance, flux density, luminosity, and the distribution in the Galactic plane. We found no significant relationship between luminosities of masers and their associated radio continuum counterparts, however, the detection rate of radio continuum emission toward maser sources increases statistically with the maser luminosities.
- ID:
- ivo://CDS.VizieR/J/MNRAS/301/640
- Title:
- Ultracompact H II regions studies. II.
- Short Name:
- J/MNRAS/301/640
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High spatial resolution radio continuum and 6.67-GHz methanol spectral line data are presented for methanol masers previously detected by Walsh et al. (1997, Cat. <J/MNRAS/291/261>). Methanol maser and/or radio continuum emission is found in 364 cases towards IRAS-selected regions. For those sources with methanol maser emission, relative positions have been obtained to an accuracy of typically 0.05arcsec, with absolute positions accurate to around 1arcsec. Maps of selected sources are provided. The intensity of the maser emission does not seem to depend on the presence of a continuum source. The coincidence of water and methanol maser positions in some regions suggests there is overlap in the requirements for methanol and water maser emission to be observable. However, there is a striking difference between the general proximity of methanol and water masers to both cometary and irregularly shaped ultracompact (UC) HII regions, indicating that, in other cases, there must be differing environments conductive to stimulating their emission. We show that the methanol maser is most likely present before an observable UC HII region is formed around a massive star and is quickly destroyed as the UC HII region evolves. There are 36 out of 97 maser sites that are linearly extended. The hypothesis that the maser emission is found in a circumstellar disc is not inconsistent with these 36 maser sites, but is unlikely. It cannot, however, account for all other maser sites. An alternative model which uses shocks to create the masing spots can more readily reproduce the maser spot distributions.
