- ID:
- ivo://CDS.VizieR/J/A+A/456/261
- Title:
- Differential uvby photometry of HD 239276
- Short Name:
- J/A+A/456/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The variability of HD 239276 was suspected photometrically nearly twenty years ago, but was confirmed with new observations obtained in 2001 during a two-site photometric campaign carried out from Spain, in uvby{beta} Stroemgren-Crawford photometry, and China, using the Johnson V filter. Two low-dispersion spectra were also collected. The results establish this star as a new multiperiodic gamma Dor-type pulsator with deficiency in metallicity.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/450/715
- Title:
- Differential uvby photometry of HD 218427
- Short Name:
- J/A+A/450/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 contents 845 simultaneous measurements collected in each of the four uvby colours of the Stromgren photometric system for the Gamma Doradus variable HD 218427. The data are magnitude differences (Du, Dv, Db, Dy, D(b-y), Dm1, Dc1) of the variable star minus comparison star in the standard system versus Heliocentric Julian Date. The comparison star is HD 219874. The origin in time is the Julian Day 2452839. The observations were carried out by the authors through the year 2003 using the 0.90m telescope at Sierra Nevada Observatory, Spain (Julian Days:0 to 69 in the table) and the 1.50m telescope at San Pedro Martir Observatory, Mexico (Julian Days: 122 to 128). Both telescopes are equipped with identical six-channel uvby-Hbeta spectrograph photometers for simultaneous measurements in uvby or in the narrow and wide H{beta} channels, respectively. Please note that a technical problem arose with the "u" filter in the 1.50m telescope, which made the "u" data collected with that telescope useless and they are named as 99.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/41
- Title:
- Differential V-band phot. & RVs of V506 Oph
- Short Name:
- J/ApJ/876/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report extensive differential V-band photometry and high-resolution spectroscopic observations of the early F-type, 1.06-day detached eclipsing binary V506 Oph. The observations, along with times of minimum light from the literature, are used to derive a very precise ephemeris and the physical properties for the components, with the absolute masses and radii being determined to 0.7% or better. The masses are 1.4153+/-0.0100M_{sun}_ and 1.4023+/-0.0094M_{sun}_ for the primary and secondary, the radii are 1.725+/-0.010R_{sun}_ and 1.692+/-0.012R_{sun}_, and the effective temperatures are 6840+/-150K and 6780+/-110K, respectively. The orbit is circular and the stars are rotating synchronously. The accuracy of the radii and temperatures is supported by the resulting distance estimate of 564+/-30pc, which is in excellent agreement with the value implied by the trigonometric parallax listed in the Gaia/Data Release 2 catalog. Current stellar evolution models from the Modules for Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks series for a composition of [Fe/H]=-0.04 match the properties of both stars in V506 Oph very well at an age of 1.83Gyr and indicate they are halfway through their core hydrogen-burning phase.
- ID:
- ivo://CDS.VizieR/II/242
- Title:
- Differential V photometry of V350 Peg
- Short Name:
- II/242
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present all the CCD photometric observations of the {delta} Scuti star V350 Peg performed by us until now. The data have been acquired between July 1997 and October 2002. A large part of it has been analysed and presented previously (Vidal, 2002A&A...394..585V). The new data of 2002 confirm the former conclusion that two frequencies of very similar amplitudes are excited in this star. The entire data set consists of 16191 measurements collected during 48 nights, and may be very helpful to investigate the detailed behaviour of this basically double-mode {delta} Scuti variable if future campaigns are held at a later stage.
- ID:
- ivo://CDS.VizieR/J/AJ/149/168
- Title:
- Differential VRI photometry of HI Dra
- Short Name:
- J/AJ/149/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed investigation of the low-amplitude contact binary HI Dra based on the new VR_c_I_c_ CCD photometric light curves (LCs) combined with published radial velocity (RV) curves. Our completely covered LCs were analyzed using PHOEBE and revealed that HI Dra is an overcontact binary with low fill-out factor f=24+/-4(%) and temperature difference between the components of 330K. Two spotted models are proposed to explain the LC asymmetry, between which the A subtype of W UMa type eclipsing systems, with a cool spot on the less massive and cooler component, proves to be more plausible on evolutionary grounds. The results and stability of the solutions were explored by heuristic scan and parameter perturbation to provide a consistent and reliable set of parameters and their errors. Our photometric modeling and RV curve solution give the following absolute parameters of the hot and cool components, respectively: M_h_=1.72+/-0.08M_{sun}_ and M_c_=0.43+/-0.02M_{sun}_, R_h_=1.98+/-0.03R_{sun}_ and R_c_=1.08+/-0.02R_{sun}_, and L_h_=9.6+/-0.1L_{sun}_ and L_c_=2.4+/-0.1L_{sun}_. Based on these results the initial masses of the progenitors (1.11+/-0.03M_{sun}_ and 2.25+/-0.07M_{sun}_, respectively) and a rough estimate of the age of the system of 2.4Gyr are discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/148/90
- Title:
- Differential VRI photometry of WW Gem
- Short Name:
- J/AJ/148/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WW Gem is a B-type eclipsing binary with a period of 1.2378days. The CCD photometry of this binary was performed in 2013 December using the 85cm telescope at the Xinglong Stations of the National Astronomical Observatories of China. Using the updated W-D program, the photometric model was deduced from the VRI light curves. The results imply that WW Gem is a near-contact eclipsing binary whose primary component almost fills its Roche lobe. The photometric mass ratio is q_ph_=0.48(+/-0.05). All collected times of minimum light, including two new ones, were used for the period studies. The orbital period changes of WW Gem could be described by an upward parabola, possibly overlaid by a light-time orbit with a period of P_mod_=7.41(+/-0.04)yr and a semi-amplitude of A=0.0079days(+/-0.0005days), respectively. This kind of cyclic oscillation may be attributed to the light-travel time effect via the third body. The long-term period increases at a rate of dP/dt=+3.47(+/-0.04)x10^-8^day/yr, which may be explained by the conserved mass transfer from the less massive component to the more massive one. With mass transfer, the massive binary WW Gem may be evolving into a contact binary.
- ID:
- ivo://CDS.VizieR/J/AJ/122/1383
- Title:
- DIRECT BVI photometry in M31
- Short Name:
- J/AJ/122/1383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- DIRECT is a project to directly obtain the distances to two important galaxies in the cosmological distance ladder, M31 and M33, using detached eclipsing binaries and Cepheids. As part of our search for these variables, we have obtained photometry and positions for thousands of stellar objects within the monitored fields, covering an area of 557.8arcmin^2^. Here we present the equatorial coordinates and BVI photometry for 26,712 stars in the M31 galaxy, along the eastern arm and in the vicinity of the star-forming region NGC 206.
- ID:
- ivo://CDS.VizieR/J/PASP/122/162
- Title:
- Direct imaging of exoplanets
- Short Name:
- J/PASP/122/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-contrast imaging can find and characterize gas giant planets around nearby young stars and the closest M stars, complementing radial velocity and astrometric searches by exploring orbital separations inaccessible to indirect methods. Ground-based coronagraphs are already probing within 25AU of nearby young stars to find objects as small as 3M_{Jup}_. This paper contrasts near-term and future ground-based capabilities with high-contrast imaging modes of the James Webb Space Telescope (JWST). Monte Carlo modeling reveals that JWST can detect planets with masses as small as 0.2M_{Jup}_ across a broad range of orbital separations. We present new calculations for planet brightness as a function of mass and age for specific JWST filters and extending to 0.1M_{Jup}_.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A76
- Title:
- DIRECT lightcurves of 21 luminous YSGs in M33
- Short Name:
- J/A+A/601/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of massive stars surviving the red supergiant (RSG) stage remains unexplored due to the rarity of such objects. The yellow hypergiants (YHGs) appear to be the warm counterparts of post-RSG classes located near the Humphreys-Davidson upper luminosity limit, which are characterized by atmospheric instability and high mass-loss rates. We aim to increase the number of YHGs in M33 and thus to contribute to a better understanding of the pre-supernova evolution of massive stars. Optical spectroscopy of five dust-enshrouded YSGs selected from mid-IR criteria was obtained with the goal of detecting evidence of extensive atmospheres. We also analyzed BVIc photometry for 21 of the most luminous YSGs in M33 to identify changes in the spectral type. To explore the properties of circumstellar dust, we performed SED-fitting of multi-band photometry of the 21 YSGs. We find three luminous YSGs in our sample to be YHG candidates, as they are surrounded by hot dust and are enshrouded within extended, cold dusty envelopes. Our spectroscopy of star 2 shows emission of more than one H{alpha} component, as well as emission of CaII, implying an extended atmospheric structure. In addition, the long-term monitoring of the star reveals a dimming in the visual light curve of amplitude larger than 0.5mag that caused an apparent drop in the temperature that exceeded 500K. We suggest the observed variability to be analogous to that of the Galactic YHG {rho} Cas. Five less luminous YSGs are suggested as post-RSG candidates showing evidence of hot or/and cool dust emission. We demonstrate that mid-IR photometry, combined with optical spectroscopy and time-series photometry, provide a robust method for identifying candidate YHGs. Future discovery of YHGs in Local Group galaxies is critical for the study of the late evolution of intermediate-mass massive stars.
- ID:
- ivo://CDS.VizieR/J/AJ/121/2032
- Title:
- Direct variables in M33A field
- Short Name:
- J/AJ/121/2032
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- DIRECT is a project to directly obtain the distances to two Local Group galaxies, M31 and M33, which occupy a crucial position near the bottom of the cosmological distance ladder. As the first step of the DIRECT project, we have searched for detached eclipsing binaries (DEBs) and new Cepheids in the M31 and M33 galaxies with 1 m class telescopes. In this paper, we present a catalog of variable stars discovered in the data from the follow-up observations of the DEB system D33J013346.2+304439.9 in field M33A (RA=23.55{deg}, DE=30.72{deg}; J2000.0), collected with the Kitt Peak National Observatory's 2.1 m telescope. In our search covering an area of 108arcmin^2^, we have found 434 variable stars: 63 eclipsing binaries, 305 Cepheids, and 66 other periodic, possible long-period, or nonperiodic variables. Of these variables, 280 are newly discovered, mainly short-period and/or faint Cepheids. Their light curves were extracted using the ISIS image subtraction package. For 85% of the variables, we present light curves in standard V and B magnitudes, with the remaining 15% expressed in units of differential flux. We have discovered a population of first-overtone Cepheid candidates, and for eight of them we present strong arguments in favor of this interpretation. We also report on the detection of a nonlinearity in the KPNO T2KA and T1KA cameras.
