- ID:
- ivo://CDS.VizieR/J/A+A/608/L8
- Title:
- Calibration of G passband for Gaia DR1
- Short Name:
- J/A+A/608/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On September 2016 the first data from Gaia were released (DR1). The first release included photometry for over 109 sources in the very broad G system. To test the correspondence between G magnitudes in DR1 and the synthetic equivalents derived using spectral energy distributions from observed and model spectrophotometry. To correct the G passband curve and to measure the zero point in the Vega system. Methods. I have computed the synthetic G and Tycho-2 BTVT photometry for a sample of stars using the Next Generation Spectral Library (NGSL) and the Hubble Space Telescope (HST) CALSPEC spectroscopic standards. I have found that the nominal G passband curve is too blue for the DR1 photometry, as shown by the presence of a color with an exponent of 0.783 eliminates the color term. The corrected passband has a Vega zero point of 0.070+/-0.004 magnitudes.
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- ID:
- ivo://CDS.VizieR/J/AJ/129/1642
- Title:
- Calibration of synthetic photometry
- Short Name:
- J/AJ/129/1642
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new calibration of optical (UBV, Stroemgren uvby{beta}, and Geneva) and near-IR (Johnson RIJHK and Two Micron All Sky Survey) photometry for B and early A stars derived from Kurucz ATLAS9 model atmospheres. These models are then used to calibrate the synthetic photometry.
- ID:
- ivo://CDS.VizieR/III/29
- Title:
- Catalog of H{gamma} measures
- Short Name:
- III/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue of equivalent widths of H{gamma} measured by R.M. Petrie in the spectra of 1171 stars is presented. The catalogue represents a compilation of all the published and unpublished values available to us. It is shown that no systematic differences exist between the equivalent widths by Petrie and those currently being derived at the Dominion Astrophysical Observatory.
- ID:
- ivo://CDS.VizieR/V/24
- Title:
- Catalogue of Geneva Photometric Boxes
- Short Name:
- V/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue of the Geneva photometric boxes (or Golay's boxes) is announced.
- ID:
- ivo://CDS.VizieR/J/ApJS/115/185
- Title:
- 3C 390.3 BVRI and H photometry
- Short Name:
- J/ApJS/115/185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V, R, and I), the spectrophotometric optical continuum flux F_{lambda}_(5177{AA}), and the integrated emission-line fluxes of H{alpha}, H{beta}, H{gamma}, He I 5876, and He II {lambda}4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000{AA}). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the cross-correlation functions, typically around 5 days, but with uncertainties also typically around 5 days; zero time delay between the high-energy and low-energy continuum variations cannot be ruled out. The strong optical emission lines H{alpha}, H{beta}, H{gamma}, and He I {lambda}5876 respond to the high-energy continuum variations with time delays typically about 20 days, with uncertainties of about 8 days. There is some evidence that He II {lambda}4686 responds somewhat more rapidly, with a time delay of around 10 days, but again, the uncertainties are quite large (~8 days). The mean and rms spectra of the H{alpha} and H{beta} line profiles provide indications for the existence of at least three distinct components located at +/-4000 and 0km/s relative to the line peak. The emission-line profile variations are largest near line center.
- ID:
- ivo://CDS.VizieR/J/A+A/371/L5
- Title:
- CCD {Delta}a-photometry of NGC 1866
- Short Name:
- J/A+A/371/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the detection of the first extragalactic, classical chemically peculiar (CP) stars more than 100 years after the discovery of this group. Using the tool of CCD {Delta}a-photometry, eight definite positive detections in the globular-like stellar cluster NGC 1866 and its surrounding in the Large Magellanic Cloud were made. More than 1950 objects within a radius of 9.5' of the cluster center down to 20.5 magnitude were observed in this three filter, narrow band photometric system. Averaging more than 70 individual frames for all three filters yielded a 3{sigma} detection limit of 0.015mag for stars with V=20mag. Furthermore we found three objects with significantly negative {Delta}a-values indicating either an Ae/shell or {lambda} Bootis nature. The overall percentage of chemically peculiar stars for NGC 1866 (1.5%) seems lower than for the majority of open clusters in our Milky Way whereas the incidence within the LMC field is decisively less (0.3%). For a description of the {Delta}a photometric system, see e.g. <GCPD/75>
- ID:
- ivo://CDS.VizieR/J/A+A/395/823
- Title:
- CCD {Delta}a-photometry of 5 open clusters
- Short Name:
- J/A+A/395/823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The time scale on which chemical peculiarity in upper main sequence stars begins is unknown. Results from the Hipparcos measurements indicate that the classical chemically peculiar (CP) stars occupy the whole area from the zero age main sequence to the terminal age main sequence. Hubrig et al. (2000ApJ...539..352H) reported that the magnetic fields appear only in stars that have already completed at least approximately 30% of their main sequence life time. Previous observations in the very young Orion OB1 and Scorpio Centaurus associations reveal a percentage of chemically peculiar stars that is significantly smaller (less than 5%) than that of the galactic field (up to 25%). This already indicates that the phenomenon needs at least several Myr to appear. Since no further observations have been published since then, we have observed the five very young (1Myr<Age<25Myr) open clusters Collinder 272, Pismis 20, Lynga 14, NGC 6396 and NGC 6611. Photometry from 250 CCD frames in the three filter Delta a-system results in very low detection limits (0.008 to 0.015mag). We find no single photometrically chemically peculiar candidate in approximately 460 observed cluster members in the five program clusters. From the number of observed objects we deduce upper limits between 0.6% and 2.4% for the incidence of CP stars for the five observed aggregates.The tables presented here include all photometric observations of these five clusters. For a description of the (Delta a) photometric system, see e.g. <GCPD/75>: a = g2 - (g1+y)/2 g1 and g2 centered at 502 and 524nm.
- ID:
- ivo://CDS.VizieR/J/A+A/373/153
- Title:
- CCD {Delta}a-photometry of 5 open clusters
- Short Name:
- J/A+A/373/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High accurate photometric data in the three filter, narrow band Delta a-system for five open clusters (NGC 2489, NGC 2567, NGC 2658, NGC 5281 and NGC 6208) are presented permitting one to detect apparent chemically peculiar stars. The ages and distances are wide spread to improve the statistics of peculiar stars in our Milky Way. A total of 235 stars within these clusters have been observed. We have detected ten apparent peculiar objects (six with significant positive and four with negative {Delta}a-values) in four open clusters. Although three of them within the boundaries of NGC 2567 are probably not members of this cluster. Since no Stromgren uvbybeta data are available from the literature, Johnson UB-Vphotometry was used to test and calibrate our photometric data. The results from a comparison of both systems are excellent. The tables presented here include all photometric observations of these five clusters. For a description of the {Delta}a photometric system, see e.g. <GCPD/75>
- ID:
- ivo://CDS.VizieR/J/A+A/412/721
- Title:
- CCD {Delta}a-photometry of 5 open clusters
- Short Name:
- J/A+A/412/721
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated 1008 objects in the area of five intermediate age open clusters (NGC 2099, NGC 3114, NGC 6204, NGC 6705 and NGC 6756) via the narrow band {Delta}a-system. The detection limit for photometric peculiarity is very low (always less than 0.009mag) due to the high number of individual frames used (193 in total). We have detected six peculiar objects in NGC 6705 and NGC 6756 from which one in the latter is almost certainly an unreddened late type foreground star. The remaining five stars are probably cluster members and bona fide chemically peculiar objects (two are {lambda} Bootis type candidates). Furthermore, we have investigated NGC 3114, a cluster for which already photoelectric {Delta}a-measurements exist. A comparison of the CCD and photoelectric values shows very good agreement. Again, the high capability of our CCD {Delta}a-photometric system to sort out true peculiar objects together with additional measurements from broad or intermediate band photometry is demonstrated.
- ID:
- ivo://CDS.VizieR/J/A+A/385/867
- Title:
- CCD {Delta}a-photometry of 5 open clusters
- Short Name:
- J/A+A/385/867
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In total, more than 550 objects within the fields of five open clusters (NGC 2439, NGC 3960, NGC 6134, NGC 6192 and NGC 6451) were investigated in order to find classical chemically peculiar stars. One bona-fide CP candidate was detected in each of the open clusters NGC 3960, NGC 6192 and NGC 6451. All three objects seem to be members of the corresponding cluster taking the results from our photometry as well as from the literature. For NGC 6192 and NGC 6451 we found widely different interstellar reddening values and therefore distances and ages in the literature. From an analysis of published Johnson UBVRI photometry, we were able to rule out a rather old age for NGC 6451. This is also supported by the finding of one peculiar object in this cluster with spectral type of about A2. Five variable objects within the field of NGC 6134 were detected. The variability exceeds 10 times (or typically 0.03 mag) the standard deviation of the weighted individual measurements. But since our observations were obtained mostly during one hour (typical integration times of five minutes per filter) on several nights within 45 days, no light curves could yet be derived. For this cluster some Am candidates were reported for which we were not able to detect a significant positive {Delta} a-value. For a description of the {Delta}a photometric system, see e.g. <GCPD/75>
