- ID:
- ivo://CDS.VizieR/J/ApJ/541/841
- Title:
- UBV photometry and ages of Trapezium systems
- Short Name:
- J/ApJ/541/841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We sought to determine the maximum age of Trapezium systems by studying possible trapezium systems that were selected independently of their occurrence in H II regions. We started with the unpublished catalog by Allen, Tapia & Parrao (1977RMxAA...3..119A) of all the known visual systems having three or more stars in which the maximum separation is less than 3.0 times the minimum separation. Their catalog has 968 such systems whose most frequent primary type is F, which does not describe young systems. With a CCD on the Kitt Peak 0.9m telescope we obtained UBV frames for 265 systems accessible with our equipment on Kitt Peak. The frames were used to obtain UBV photometry for about 1500 stars with an accuracy of 0.04mag between V=7 and 14mag. Also these frames were used to obtain astrometry with an accuracy of +/-0.015{deg} in position angle and +/-0.01" in separation. For the brightest star in each system we obtained a spectral type to determine the distance and reddening to the system.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/119/483
- Title:
- UBV photometry of double stars.
- Short Name:
- J/A+AS/119/483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBV photometric observations of 55 wide visual double stars with K- and M- type primaries. Our observations have been compared and combined with information available in the literature. At least 58% of them are optical pairs.
- ID:
- ivo://CDS.VizieR/J/A+A/386/237
- Title:
- UBV(RI)c photometry of 7 symbiotic stars
- Short Name:
- J/A+A/386/237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Asiago photographic archive has been searched for plates containing the symbiotic stars Hen 2-468, QW Sge, LT Del, V407 Cyg, K 3-9, V335 Vul, FG Ser and Draco C-1. A total of 635 plates imaging the program stars have been found and the brightness estimated using the Henden & Munari (2000A&AS..143..343H) UBV(RI) photometric sequences. These historical data have allowed for the first time the determination of the orbital periods of Hen 2-468 (774 days) and QW Sge (390.5 days), a significant improvement in the orbital period of LT Del (465.6 days) and for V407 Cyg an evaluation of the Mira's pulsation period and complex lightcurve shape in the red (R and I bands). Some previously unknown outbursts have been discovered too.
- ID:
- ivo://CDS.VizieR/J/AJ/159/214
- Title:
- UBVRI linear polarisation in Wolf-Rayet winds
- Short Name:
- J/AJ/159/214
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- Wolf-Rayet (WR) stars have strong, hot winds, with mass-loss rates at least a factor of 10 greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper, we use the technique of multiband linear polarimetry to extract information on the global asymmetry of the wind in a sample of 47 bright Galactic WR stars. Our observations also include time-dependent observations of 17 stars in the sample. The path to our goal includes removing the dominating component of wavelength-dependent InterStellar Polarization (ISP), which normally follows the well-known Serkowski law. We include a wavelength-dependent ISP position angle parameter in our ISP law and find that 15 stars show significant results for this parameter. We detect a significant component of wavelength-independent polarization due to electron scattering in the wind for 10 cases, with most WR stars showing none at the ~0.05% level precision of our data. The intrinsically polarized stars can be explained with binary interaction, large-scale wind structure, and clumping. We also found that 5 stars out of 19 observed with the Stromgren b filter (probing the complex {lambda}4600-4700{AA} emission-line region) have significant residuals from the ISP law and propose that this is due to wind asymmetries. We provide a useful catalog of ISP for 47 bright Galactic WR stars and upper limits on the possible level of intrinsic polarization.
- ID:
- ivo://CDS.VizieR/J/A+A/448/1075
- Title:
- UBVRI photometry and polarimetry of DF Tau
- Short Name:
- J/A+A/448/1075
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of multi-year photometric and polarimetric observations of the young binary system DF Tau in UBVRI bands as well as bispectrum speckle interferometric observations in the H and K bands are presented. The photometric and polarimetric observations suggest the linear poarization variation has substantially a stochastic character.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/8
- Title:
- UBVR photometry of the T Tauri binary DQ Tau
- Short Name:
- J/ApJ/835/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The theory of binary star formation predicts that close binaries (a<100au) will experience periodic pulsed accretion events as streams of material form at the inner edge of a circumbinary disk (CBD), cross a dynamically cleared gap, and feed circumstellar disks or accrete directly onto the stars. The archetype for the pulsed accretion theory is the eccentric, short-period, classical T Tauri binary DQ Tau. Low-cadence (~daily) broadband photometry has shown brightening events near most periastron passages, just as numerical simulations would predict for an eccentric binary. Magnetic reconnection events (flares) during the collision of stellar magnetospheres near periastron could, however, produce the same periodic, broadband behavior when observed at a one-day cadence. To reveal the dominant physical mechanism seen in DQ Tau's low-cadence observations, we have obtained continuous, moderate-cadence, multiband photometry over 10 orbital periods, supplemented with 27 nights of minute-cadence photometry centered on four separate periastron passages. While both accretion and stellar flares are present, the dominant timescale and morphology of brightening events are characteristic of accretion. On average, the mass accretion rate increases by a factor of five near periastron, in good agreement with recent models. Large variability is observed in the morphology and amplitude of accretion events from orbit to orbit. We argue that this is due to the absence of stable circumstellar disks around each star, compounded by inhomogeneities at the inner edge of the CBD and within the accretion streams themselves. Quasiperiodic apastron accretion events are also observed, which are not predicted by binary accretion theory.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A205
- Title:
- Ultra-hot Jupiter WASP-121b transits
- Short Name:
- J/A+A/635/A205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultra-hot Jupiters offer interesting prospects for expanding our theories on dynamical evolution and the properties of extremely irradiated atmospheres. In this context, we present the analysis of new optical spectroscopy for the transiting ultra-hot Jupiter WASP-121b. We first refine the orbital properties of WASP-121b, which is on a nearly polar (obliquity Psi^North^=88.1+/-0.25{deg} or Psi^South^=91.11+/-0.20{deg}) orbit, and exclude a high differential rotation for its fast-rotating (P<1.13-days), highly inclined (i*^North_=8.1^+3.0^_-2.6_{deg} or i*_South_=171.9^+2.5^_-3.4_{deg}) star. We then present a new method that exploits the reloaded Rossiter-McLaughlin technique to separate the contribution of the planetary atmosphere and of the spectrum of the stellar surface along the transit chord. Its application to HARPS transit spectroscopy of WASP-121b reveals the absorption signature from metals, likely atomic iron, in the planet atmospheric limb. The width of the signal (14.3+/-1.2km/s) can be explained by the rotation of the tidally locked planet. Its blueshift (-5.2+/-0.5km/s) could trace strong winds from the dayside to the nightside, or the anisotropic expansion of the planetary thermosphere.
- ID:
- ivo://CDS.VizieR/J/AJ/157/211
- Title:
- Unresolved binaries in TESS with speckle imaging
- Short Name:
- J/AJ/157/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) is conducting a two-year wide-field survey searching for transiting exoplanets around nearby bright stars that will be ideal for follow-up characterization. To facilitate studies of planet compositions and atmospheric properties, accurate and precise planetary radii need to be derived from the transit light curves. Since 40%-50% of exoplanet host stars are in multiple star systems, however, the observed transit depth may be diluted by the flux of a companion star, causing the radius of the planet to be underestimated. High angular resolution imaging can detect companion stars that are not resolved in the TESS Input Catalog, or by seeing-limited photometry, to validate exoplanet candidates and derive accurate planetary radii. We examine the population of stellar companions that will be detectable around TESS planet candidate host stars, and those that will remain undetected, by applying the detection limits of speckle imaging to the simulated host star populations of Sullivan et al. (2015, J/ApJ/809/77) and Barclay et al. (2018, J/ApJS/239/2). By detecting companions with contrasts of {Delta}m~<7-9 and separations of ~0.02"-1.2", speckle imaging can detect companion stars as faint as early M stars around A-F stars and stars as faint as mid-M around G-M stars, as well as up to 99% of the expected binary star distribution for systems located within a few hundred parsecs.
- ID:
- ivo://CDS.VizieR/J/ApJS/235/6
- Title:
- Updated Multiple Star Catalog (MSC): Sept 2021
- Short Name:
- J/ApJS/235/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog of hierarchical stellar systems with three or more components is an update of the original 1997 version (Tokovinin, 1997-1999, J/A+AS/124/75). For 2000 hierarchies, the new Multiple Star Catalog (MSC) provides distances, component masses and periods, and supplementary information (astrometry, photometry, identifiers, orbits, notes). The MSC content and format are explained, and its incompleteness and strong observational selection are stressed. Nevertheless, the MSC can be used for statistical studies and is a valuable source for planning observations of multiple stars. Rare classes of stellar hierarchies found in the MSC (with six or seven components, extremely eccentric orbits, planar and possibly resonant orbits, hosting planets) are briefly presented. High-order hierarchies have smaller velocity dispersion compared to triples and are often associated with moving groups. The paper concludes with an analysis of the ratio of periods and separations between inner and outer subsystems. In wide hierarchies, the ratio of semimajor axes, estimated statistically, is distributed between 3 and 300, with no evidence of dynamically unstable systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/715/1203
- Title:
- {upsilon} Andromedae system with HST
- Short Name:
- J/ApJ/715/1203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used high-cadence radial velocity (RV) measurements from the Hobby-Eberly Telescope with existing velocities from the Lick, Elodie, Harlan J. Smith, and Whipple 60" telescopes combined with astrometric data from the Hubble Space Telescope Fine Guidance Sensors to refine the orbital parameters and determine the orbital inclinations and position angles of the ascending node of components {upsilon} And A c and d. With these inclinations and using M*=1.31M_{sun}_ as a primary mass, we determine the actual masses of two of the companions: {upsilon} And A c is 13.98^+2.3^_-5.3_M_Jup_, and {upsilon} And A d is 10.25^+0.7^_-3.3_M_Jup_. These measurements represent the first astrometric determination of mutual inclination between objects in an extrasolar planetary system, which we find to be 29.9+/-1{deg}. The combined RV measurements also reveal a long-period trend indicating a fourth planet in the system. We investigate the dynamic stability of this system and analyze regions of stability, which suggest a probable mass of {upsilon} And A b. Finally, our parallaxes confirm that u And B is a stellar companion of {upsilon} And A.
