- ID:
- ivo://CDS.VizieR/J/A+A/630/A119
- Title:
- Gaia DR2 distances to two clusters
- Short Name:
- J/A+A/630/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the one hand, the second data release of the Gaia mission (GaiaDR2, Cat. I/345) has opened a trove of astrometric and photometric data for Galactic clusters within a few kpc of the Sun. On the other hand, lucky imaging has been an operational technique to measure the relative positions of visual binary systems for a decade and a half, a time sufficient to apply its results to the calculation of orbits of some massive multiple systems within ~1kpc of the Sun. As part of an ambitious research program to measure distances to Galactic stellar groups (including clusters) containing O stars,I start with two of the nearest examples: Collinder 419 in Cygnus and NGC 2264 in Monoceros. The main ionizing source for both clusters is a multiple system with an O-type primary: HD 193322 and 15 Mon, respectively. For each of those two multiple systemsI aim to derive new astrometric orbits for the Aa,Ab components. First, I present a method that usesGaiaDR2 G+G_BP_+G_RP_ photometry, positions, proper motions, and parallaxes to obtain the membership and distance of a stellar group and apply it to Collinder 419 and NGC 2264. Second, I present a new code that calculates astrometric orbits by searching the whole seven-parameter orbit space and apply it to HD 193 322 Aa,Ab and 15 Mon Aa,Abusing as input literature data from the Washington Double Star Catalog (WDS) and the AstraLux measurements recently presented by Maiz Apellaniz et al. (2019, Cat. J/A+A/626/A20) I obtain GaiaDR2 distances of 1006^+37^_-34_pc for Collinder 419 and 719+/-16pc for NGC 2264, with the main contribution to the uncertainties coming from the spatial covariance of the parallaxes. The two NGC 2264 subclusters are at the same distance (within the uncertainties) and they show a significant relative proper motion. The distances are shown to be robust. HD 193322 Aa,Ab follows an eccentric (e=0.58^+0.03^_-0.04_) orbit with a period of 44+/-1 a and the three stars it contains have a total mass of 76.1^+9.9^_-7.4_M_{sun}_. The orbit of 15 Mon Aa,Ab is even more eccentric (e=0.770^+0.023^_-0.030_), with a period of 108+/-12 a and a total mass of 45.1^+3.6^_-3.3_M_{sun}_ for its two stars.
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- ID:
- ivo://CDS.VizieR/J/A+A/619/A180
- Title:
- Gaia DR2 photometric sensitivity curves
- Short Name:
- J/A+A/619/A180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second data release (DR2) from the European Space Agency mission Gaia took place on April 2018. DR2 included photometry for more than 1.3x10^9^ sources in the three bands G, G_BP_, and G_RP_. Even though the Gaia DR2 photometry is very precise, there are currently three alternative definitions of the sensitivity curves that show significative differences. The aim of this paper is to improve the quality of the input calibration data to produce new compatible definitions of the G, G_BP_, and G_RP_ bands and to identify the reasons for the discrepancies between previous definitions. We have searched the Hubble Space Telescope (HST) archive for Space Telescope Imaging Spectrograph (STIS) spectra with G430L+G750L data obtained with wide apertures and combined them with the CALSPEC library to produce a high quality spectral energy distribution (SED) library of 122 stars with a broad range of colors, including three very red stars. This library defines new sensitivity curves for G, G_BP_, and G_RP_ using a functional analytical formalism. The new sensitivity curves are significantly better than the two previous attempts we use as a reference, REV (Evans et al., 2018A&A...616A...4E, Cat. I/345) and WEI (Weiler, 2018A&A...617A.138W, Cat. J/A+A/617/A138). For G we confirm the existence of a systematic bias in magnitude and correct a color term present in REV. For G_BP_ we confirm the need to define two magnitude ranges with different sensitivity curves and measure the cut between them at G_phot_=10.87mag with a significant increase in precision. The new curves also fit the data better than either REV or WEI. For G_RP_, our new sensitivity curve fits the STIS spectra better and the differences with previous attempts reside in a systematic effect between ground-based and HST spectral libraries. Additional evidence from color-color diagrams indicate that the new sensitivity curve is more accurate. Nevertheless, there is still room for improvement in the accuracy of the sensitivity curves because of the current dearth of good-quality red calibrators: adding more to the sample should be a priority before Gaia data release 3 takes place.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/83
- Title:
- 723 Gaia DR2 White dwarfs cand. in Local Galactic Halo
- Short Name:
- J/ApJ/899/83
- Date:
- 14 Mar 2022 08:58:44
- Publisher:
- CDS
- Description:
- We present a catalog of 531 white dwarf candidates that have large apparent transverse motions relative to the Sun (v_T_>200km/s), thus making them likely members of the local Galactic halo population. The candidates were selected from the Gaia Data Release 2 and are located in a great circle with 20{deg} width running across both Galactic poles and the Galactic center and anticenter, a zone that spans 17.3% of the sky. The selection used a combination of kinematic and photometric properties, derived primarily from Gaia proper motions, G magnitudes, and G_BP_-G_RP_ color, and including parallax whenever available. Additional validation of the white dwarf candidates is made using PanSTARRS photometric (gri) data. Our final catalog includes not only stars having full kinematic and luminosity estimates from reliable Gaia parallax, but also stars with presently unreliable or no available Gaia parallax measurements. We argue that our method of selecting local halo objects with and without reliable parallax data leads us to round up all possible halo white dwarfs in the Gaia catalog (in that particular section of the sky) with recorded proper motions >40mas/yr and that pass our v_T_>200km/s threshold requirement. We expect this catalog will be useful for the study of the white dwarf population of the local Galactic halo.
- ID:
- ivo://CDS.VizieR/II/360
- Title:
- Gaia DR2 x AllWISE catalogue
- Short Name:
- II/360
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second Gaia Data Release (DR2) contains astrometric and photometric data for more than 1.6 billion objects with mean Gaia G magnitude <20.7, including many Young Stellar Objects (YSOs) in different evolutionary stages. In order to explore the YSO population of the Milky Way, we combined the Gaia DR2 database with WISE and Planck measurements and made an all-sky probabilistic catalogue of YSOs using machine learning techniques, such as Support Vector Machines, Random Forests, or Neural Networks. Our input catalogue contains 103 million objects from the DR2xAllWISE cross-match table. We classified each object into four main classes: YSOs, extragalactic objects, main-sequence stars and evolved stars. At a 90% prob- ability threshold we identified 1 129 295 YSO candidates. To demonstrate the quality and potential of our YSO catalogue, here we present two applications of it. (1) We explore the 3D structure of the Orion A star forming complex and show that the spatial distribution of the YSOs classified by our procedure is in agreement with recent results from the literature. (2) We use our catalogue to classify published Gaia Science Alerts. As Gaia measures the sources at multiple epochs, it can efficiently discover transient events, including sudden brightness changes of YSOs caused by dynamic processes of their circumstellar disk. However, in many cases the physical nature of the published alert sources are not known. A cross-check with our new catalogue shows that about 30% more of the published Gaia alerts can most likely be attributed to YSO activity. The catalogue can be also useful to identify YSOs among future Gaia alerts.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A3
- Title:
- Gaia Early Data Release 3 photometric passbands
- Short Name:
- J/A+A/649/A3
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Gaia Early Data Release 3 (Gaia EDR3) contains astrometry and photometry results for about 1.8 billion sources based on observations collected by the European Space Agency Gaia satellite during the first 34 months of its operational phase. In this paper, we focus on the photometric content, describing the input data, the algorithms, the processing, and the validation of the results. Particular attention is given to the quality of the data and to a number of features that users may need to take into account to make the best use of the Gaia EDR3 catalogue. The processing broadly followed the same procedure as for Gaia DR2, but with significant improvements in several aspects of the blue and red photometer (BP and RP) preprocessing and in the photometric calibration process. In particular, the treatment of the BP and RP background has been updated to include a better estimation of the local background, and the detection of crowding effects has been used to exclude affected data from the calibrations. The photometric calibration models have also been updated to account for flux loss over the whole magnitude range. Significant improvements in the modelling and calibration of the Gaia point and line spread functions have also helped to reduce a number of instrumental effects that were still present in DR2. Gaia EDR3 contains 1.806 billion sources with G-band photometry and 1.540 billion sources with GBP and GRP photometry. The median uncertainty in the G-band photometry, as measured from the standard deviation of the internally calibrated mean photometry for a given source, is 0.2mmag at magnitude G=10 to 14, 0.8mmag at G~17, and 2.6mmag at G~19. The significant magnitude term found in the Gaia DR2 photometry is no longer visible, and overall there are no trends larger than 1mmag/mag. Using one passband over the whole colour and magnitude range leaves no systematics above the 1% level in magnitude in any of the bands, and a larger systematic is present for a very small sample of bright and blue sources. A detailed description of the residual systematic effects is provided. Overall the quality of the calibrated mean photometry in Gaia EDR3 is superior with respect to DR2 for all bands.
- ID:
- ivo://CDS.VizieR/J/A+A/325/167
- Title:
- Geneva photometry in NGC 6231
- Short Name:
- J/A+A/325/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photoelectric (127 stars) and CCD (168 stars) Geneva photometry for the very young open cluster NGC 6231. We have searched for new cluster members out to a distance of ~13arcmin, extending the Seggewiss area (~8arcmin), and we found at least 64 new probable members in this extended field. Differential reddening is clearly measured across the cluster area. We determine the cluster distance (1800pc) and age (3.8+/-0.6x10^6^yr). The probable presence of pre-main sequence stars and the consequence of this population on the cluster formation history is analysed. We also found that the O8.5III star S161 is a long term variable and we present its light curve extending over more than 20 years. Finally we discuss the existence of Ap stars in the cluster. For a description of the Geneva photometric system, see e.g. <GCPD/13>
- ID:
- ivo://CDS.VizieR/J/A+A/343/847
- Title:
- Geneva Photometry of Eta Car
- Short Name:
- J/A+A/343/847
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss 24yr of optical photometry of {eta} Carinae, among which new Geneva photometry made between 1994 and 1998. Various conclusions from our previous photometric studies are confirmed. The core hides a normal S Dor variable (or LBV): it shows light variations on a time scale of 1-4yr, with superimposed micro oscillations whose quasi-period indicates a temperature in the order of 22000K. Therefore, a more complicated model for {eta} Car is necessary to explain its extraordinary appearance and phenomena exhibited in the past and at present.
- ID:
- ivo://CDS.VizieR/J/A+A/415/241
- Title:
- Geneva photometry of HD 129929
- Short Name:
- J/A+A/415/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have gathered and analysed a timeseries of 1493 high-quality multicolour Geneva photometric data of the B3V {beta} Cep star Hd 129929. The dataset has a time base of 21.2 years. The occurrence of a beating phenomenon is evident from the data. We find evidence for the presence of at least six frequencies, among which we see components of two frequency multiplets with an average spacing of ~0.0121c/d which points towards very slow rotation. This result is in agreement with new spectroscopic data of the star and also with previously taken UV spectra. We provide the amplitudes of the six frequencies in all seven photometric filters. The metal content of the star is Z=0.018+/-0.004. All these observational results will be used to perform detailed seismic modelling of this massive star in a subsequent paper.
- ID:
- ivo://CDS.VizieR/J/A+A/463/579
- Title:
- Geneva photometry of HD 23642
- Short Name:
- J/A+A/463/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 23642 is the only known eclipsing binary in the Pleiades, and therefore of importance in determining the distance to this cluster. To use new photometric and spectroscopic data in combination with existing data in the literature in order to improve the determination of the parameters of the system, its distance and reddening. New photometric and spectroscopic data are presented for HD 23642. The spectroscopic data are ``spectrally disentangled'' using the KOREL code. The new and literature photometric and radial velocity data are simultaneously analysed using the FOTEL code to obtain the orbital solution and derive the fundamental parameters of the two stars. The distance and reddening are determined by fitting 7-colour Geneva, B,V and Stroemgren colours, and considering surface-brightness relations for the two components in (B-V) and Stroemgren c_1_-index. The preferred distance is 138.0+/-1.5pc for a reddening of E(B-V)=0.025+/-0.003. The reddening value is larger than the 0.012 adopted in the recent works on this stars by Munari et al. (2004A&A...418L..31M) and Southworth et al. (2005A&A...429..645S), and smaller than other values in the literature for the cluster reddening. The distance is in agreement with other recent works on the distance to the Pleiades. A comparison with evolutionary models suggests that the inclusion of convective core overshoot gives a much better fit to the empirical mass-radius relationship obtained from the binary analysis. Both this comparison and the "spectral disentangling" are consistent with HD 23642 having [Fe/H]=+0.06, a value determined by the most recent spectroscopical analyses of Pleiades stars.
- ID:
- ivo://CDS.VizieR/J/A+A/364/689
- Title:
- Geneva photometry of HDE 318107
- Short Name:
- J/A+A/364/689
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rotation period of the Ap star HDE 318107 has been determined from magnetic and photometric observations obtained between August 1992 and September 1998
