- ID:
- ivo://CDS.VizieR/J/AJ/160/44
- Title:
- Upper Scorpius spectroscopy and photometry
- Short Name:
- J/AJ/160/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have refined the census of stars and brown dwarfs in the Upper Sco association (~10Myr, ~145pc) by (1) updating the selection of candidate members from our previous survey to include the high-precision astrometry from the second data release of Gaia, (2) obtaining spectra of a few hundred candidate members to measure their spectral types and verify their youth, and (3) assessing the membership (largely with Gaia astrometry) of 2020 stars toward Upper Sco that show evidence of youth in this work and previous studies. We arrive at a catalog of 1761 objects that are adopted as members of Upper Sco. The distribution of spectral types among the adopted members is similar to those in other nearby star-forming regions, indicating a similar initial mass function. In previous studies, we have compiled mid-infrared photometry from the Wide-field Infrared Survey Explorer and the Spitzer Space Telescope for members of Upper Sco and used those data to identify the stars that show evidence of circumstellar disks; we present the same analysis for our new catalog of members. As in earlier work, we find that the fraction of members with disks increases with lower stellar masses, ranging from <~10% for >1M{sun} to ~22% for 0.01-0.3M{sun}. Finally, we have estimated the relative ages of Upper Sco and other young associations using their sequences of low-mass stars in M_G_RP__ versus G_BP_-G_RP_. This comparison indicates that Upper Sco is a factor of two younger than the {beta}Pic association (21-24Myr) according to both nonmagnetic and magnetic evolutionary models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/125/1352
- Title:
- Ursa Minor dSph M,T2, DDO51 photometry
- Short Name:
- J/AJ/125/1352
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large-area photometric survey of the Ursa Minor dwarf spheroidal galaxy and its environs. This survey is intended to trace the distribution of stars outside the nominal tidal radius of this system. Observations were made with the Washington M, Washington T2, and DDO51 filters, which in combination have been shown to provide reliable stellar luminosity classification for K-type stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/2474
- Title:
- USco ZYJHK1K2 photometry and proper motions
- Short Name:
- J/MNRAS/435/2474
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep ZYJ near-infrared survey of 13.5deg^2^ in the Upper Scorpius (USco) OB association. We photometrically selected ~100 cluster member candidates with masses in the range of 30-5 Jupiters, according to state-of-the-art evolutionary models. We identified 67 ZYJ candidates as bona fide members, based on complementary photometry and astrometry. We also extracted five candidates detected with Visible and Infrared Survey Telescope for Astronomy at YJ only. One is excluded using deep optical z-band imaging, while two are likely non-members, and three remain as potential members. We conclude that the USco mass function is more likely decreasing in the planetary-mass regime (although a flat mass function cannot yet be discarded), consistent with surveys in other regions.
7454. U Sgr BV light curves
- ID:
- ivo://CDS.VizieR/J/PAZh/40/221
- Title:
- U Sgr BV light curves
- Short Name:
- J/PAZh/40/221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the classical Cepheid U Sgr, we have constructed an O-C diagram spanning a time interval of 144 years. The O-C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary increase in the period, dP/dt=0.39(+/-0.10)s/yr, in agreement with the results of theoretical calculations for the third crossing of the instability strip. The available data reduced by the Eddington-Plakidis method reveal small random period fluctuations that do not distort the evolutionary trend in the O-C residuals.
- ID:
- ivo://CDS.VizieR/J/AJ/103/638
- Title:
- USNO Photographic Parallaxes. I.
- Short Name:
- J/AJ/103/638
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The U.S. Naval Observatory CCD trigonometric parallax program is described in detail, including the instrumentation employed, observing procedures followed, and reduction procedures applied. Astrometric results are presented for 72 stars ranging in apparent brightness from V=15.16 to 19.58. Photometry (V and V-I on the Kron-Cousins system) is presented for the parallax stars and for all 426 individual reference stars employed in the astrometric solutions. Corrections for differential color refraction, calibrated to the observed V-I colors, have been applied to all astrometric measures. The mean errors in the relative parallaxes range from +/-0.0005" to +/-0.0027" with a median value of +/-0.0010". Seventeen of the 23 stars with V_tan_>200km/s form a well-delineated sequence of extreme subdwarfs covering 11.5<M_V_<14.5 in the M_V_ vs V-I diagram. The transformation to the M_bol_ vs log T_eff_ plane is presented and the results are compared with various model interior computations. Within the limitations due to the uncertain T_eff_ scale for cool dwarfs and subdwarfs, the coolest members of the extreme subdwarf sequence appear to be near the hydrogen-burning minimum mass limit for stars with metallicities of [M/H]~-2.
- ID:
- ivo://CDS.VizieR/J/AJ/105/1571
- Title:
- USNO Photographic Parallaxes IX
- Short Name:
- J/AJ/105/1571
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Trigonometric parallaxes, relative proper motions, and photometry are presented for 122 stars in 111 systems. Of these stars, 70 are brighter than V = 10.0.
- ID:
- ivo://CDS.VizieR/J/other/JAD/13.2
- Title:
- UU Cnc UBVRI differential photometry
- Short Name:
- J/other/JAD/13.2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present UBVR photometric observations of the 96-day binary system UU Cancri (K4 III) obtained in 1972-1994. A relatively large scatter in the orbital light curves turned out to be intrinsic with a modulating cycle lasting at least 8000 days. Using all available archived photographic and visual observations covering nearly 100 years, we find the orbital period of the system to be constant. This fact, together with the pattern of the colour curves, makes the existence of a powerful accretion disk in the system improbable.
- ID:
- ivo://CDS.VizieR/J/ApJ/757/52
- Title:
- UV and IR observations for SINGS galaxies. I.
- Short Name:
- J/ApJ/757/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color (or ultraviolet spectral slope), i.e., the IRX-UV (or IRX-{beta}) relation, found in studies of starburst galaxies is a prevalent recipe for correcting extragalactic dust attenuation. Considerable dispersion in this relation discovered for normal galaxies, however, complicates its usability. In order to investigate the cause of the dispersion and to have a better understanding of the nature of the IRX-UV relation, in this paper, we select five nearby spiral galaxies, and perform spatially resolved studies on each of the galaxies, with a combination of ultraviolet and infrared imaging data. We measure all positions within each galaxy and divide the extracted regions into young and evolved stellar populations. By means of this approach, we attempt to discover separate effects of dust attenuation and stellar population age on the IRX-UV relation for individual galaxies. In this work, in addition to dust attenuation, stellar population age is interpreted to be another parameter in the IRX-UV function, and the diversity of star formation histories is suggested to disperse the age effects. At the same time, strong evidence shows the need for more parameters in the interpretation of observational data, such as variations in attenuation/extinction law. Fractional contributions of different components to the integrated luminosities of the galaxies suggest that the integrated measurements of these galaxies, which comprise different populations, would weaken the effect of the age parameter on IRX-UV diagrams. The dependence of the IRX-UV relation on luminosity and radial distance in galaxies presents weak trends, which offers an implication of selective effects. The two-dimensional maps of the UV color and the infrared-to-ultraviolet ratio are displayed and show a disparity in the spatial distributions between the two galaxy parameters, which offers a spatial interpretation of the scatter in the IRX-UV relation.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/76
- Title:
- UV and IR properties for galaxies
- Short Name:
- J/ApJ/789/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-{beta} relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 {AA} bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 {AA} bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.
- ID:
- ivo://CDS.VizieR/J/ApJ/446/622
- Title:
- UV and optical imagery of LH 52 and LH 53
- Short Name:
- J/ApJ/446/622
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A 40' field including the stellar associations LH 52 and LH 53 and the supernova remnant N49 in the Large Magellanic Cloud was observed by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Space Shuttle mission in 1990 December. The image in the 162 nm bandpass is discussed together with ground-based BV data on subfields containing LH 52 and LH 53. Point-spread function photometry in the 162nm, B, and V bands is presented in the form of color-magnitude diagrams and two-color diagrams, which are compared with stellar models. The far-ultraviolet extinction curve of the dust in LH 52 is unusually steep for the LMC. The most probable age of both associations is ~10 Myr, which constrains the scenario for the evolution of the supergiant Halpha shell LMC 4 by stochastic self-propagated star formation. The initial mass function (IMF) slope for LH 52 is Gamma~-1, in agreement with previous work, and the slope for LH 53, which is less densely populated, is Gamma~-2. A similar relationship between surface density of stars and IMF slope is reported for a UIT field near 30 Dor. The ultraviolet morphology of N49, which is contained in LH 53, is dominated by two bright features that straddle an X-ray bright spot, consistent with an encounter between the blast wave and a cloud. The estimated age of ~10Myr for LH 53 implies an initial mass of ~20M_{sun}_ for the N49 progenitor star.
