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22921. UBVR photometry of Nova Mon 2002 (V838 Mon)
ID:
ivo://CDS.VizieR/J/PAZh/28/764
Title:
UBVR photometry of Nova Mon 2002 (V838 Mon)
Short Name:
J/PAZh/28/764
Date:
21 Oct 2021
Publisher:
CDS
Description:
UBVR photometric and spectroscopic observations of V838 Mon during the outbursts.
22922. UBVR photometry of the open cluster King 2
ID:
ivo://CDS.VizieR/J/A+A/240/262
Title:
UBVR photometry of the open cluster King 2
Short Name:
J/A+A/240/262
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we present the Johnson-Cousins UBVR CCD photometry of the stars in King 2, an old open cluster towards the galactic anticenter. We have obtained the colour-magnitude diagram, the colour excess, the reddening, an estimate of the metallicity, and the distance modulus. The comparison of the observational colour-magnitude diagram with the theoretical simulations based on stellar models with convective overshoot shows that a major revision of the model structure is required. To this aim, we explore the possibility that the formulation of convective overshoot for stars in the mass range 1 to 2M_{sun}_ ought to be different from the one currently in use. The point of major uncertainty that we see to affect the stars in this domain is whether or not convective overshoot may erode the gradient in molecular weight in the regions surrounding the convective core. We find that models, in which this is not allowed to occur, better fit the overall morphology of the colour-magnitude diagram of King 2. In addition to this, analyzing the width of the main sequence band we suggest that a significant fraction of the stars are members of binary systems, and evaluate the range spanned by their mass ratios. Finally, we derive the luminosity function and the mass function for the main sequence stars of the cluster.
22923. UBVR photometry of the T Tauri binary DQ Tau
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.
22924. UBVR photometry of V1481 Cyg
ID:
ivo://CDS.VizieR/J/PAZh/24/145
Title:
UBVR photometry of V1481 Cyg
Short Name:
J/PAZh/24/145
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a UBVR photometry observations are presented for eclipsing binary V1481 Cyg in the open cluster NGC 7128. The binary was observed between 1993 and 1995 with the 1m and 0.6m telescopes at Maidanak Observatory (Uzbekistan).
22925. UBVR(UIT) photometry of O and OB stars in SMC
ID:
ivo://CDS.VizieR/J/AJ/127/1632
Title:
UBVR(UIT) photometry of O and OB stars in SMC
Short Name:
J/AJ/127/1632
Date:
21 Oct 2021
Publisher:
CDS
Description:
The distribution of N*, the number of OB stars per association or cluster, appears to follow a universal power-law form (N*)^-2^ in the local universe. We evaluate the distribution of N* in the Small Magellanic Cloud using recent broadband optical and space-ultraviolet data, with special attention to the lowest values of N*. We find that the power-law distribution in N* continues smoothly down to N*=1. This strongly suggests that the formation of field massive stars is a continuous process with those in associations and that the field stars do not originate from a different star formation mode.
22926. UBV sequences in Cen
ID:
ivo://CDS.VizieR/J/A+A/14/164
Title:
UBV sequences in Cen
Short Name:
J/A+A/14/164
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photoelectric UBV observations were made with the ESO 1m telescope and the ESO photometer on 6 nights between 1970-04-01 and 1970-05-03. The observations were centered around (B1950)13:24-62:23 The positions and identifications of the 3 sequences were computed by B. Skiff (Lowell Obs.) in September 2010, from a comparison of the published charts with the computer screen-plots of UCAC2.
22927. UBV sequences near 3 globulars
ID:
ivo://CDS.VizieR/J/AJ/75/167
Title:
UBV sequences near 3 globulars
Short Name:
J/AJ/75/167
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results concerning photoelectrically observed UBV magnitudes and colors of bright to intermediately faint stars near three globular clusters (NGC 2808, 5927, and 6101) are assembled.
22928. UBV & V(RI)c photometry of 23 active stars
ID:
ivo://CDS.VizieR/J/A+AS/125/11
Title:
UBV & V(RI)c photometry of 23 active stars
Short Name:
J/A+AS/125/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the progress of our ongoing photometric monitoring program of spotted late-type stars with automatic photoelectric telescopes (APTs) on Mt. Hopkins in Arizona and on Mt. Etna in Sicily. We present 9250 differential UBV and/or V(RI)c observations for altogether 23 chromospherically active stars, singles and binaries, pre-main-sequence and post-main-sequence, taken between 1991 and 1996. For a description of the UBV and (RI)c photometric system, see e.g. <GCPD/01> and <GCPD/54>
22929. ubvy{beta} photometry in Puppis-Vela
ID:
ivo://CDS.VizieR/J/A+A/543/A39
Title:
ubvy{beta} photometry in Puppis-Vela
Short Name:
J/A+A/543/A39
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the distribution of the interstellar dust towards six small volumes of the sky in the region of the Gum nebula. New high-quality four-colour uvby and H-beta Stromgren photometry obtained for 352 stars in six selected areas of Kapteyn, complemented with data obtained in a previous investigation for two of these areas, were used to estimate the colour excess and distance to these objects. The obtained colour excess versus distance diagrams, complemented with other information, when available, were analysed in order to infer the properties of the interstellar medium permeating the observed volumes. On the basis of the overall standard deviation in the photometric measurements, we estimate that colour excesses and distances are determined with an accuracy of 0.010mag and better than 30%, respectively, for a sample of 520 stars. A comparison with 37 stars in common with the new Hipparcos catalogue attests to the high quality of the photometric distance determination. The obtained colour excess versus distance diagrams testify to the low density volume towards the observed lines-of-sight. Very few stars out to distances of 1kpc from the Sun have colour excesses larger than E(b-y)=0.1mag. In spite of the low density character of the interstellar medium towards the Puppis-Vela direction, the obtained reddening as a function of the distance indicates that two or more interstellar structures are crossed towards the observed lines-of-sight. One of these structures may be associated with the very low density wall of the Local Cavity, which has a distance of 100-150pc from the Sun. Another structure might be related to the Gum nebula, and if so, its front face would be located at about 350pc from the Sun.
22930. ubvy{beta} photometry in the Lupus dark cloud
ID:
ivo://CDS.VizieR/J/MNRAS/331/474
Title:
ubvy{beta} photometry in the Lupus dark cloud
Short Name:
J/MNRAS/331/474
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stroemgren uvby{beta} photometry observations obtained for 205 stars in the general direction of a void in the IRAS 100-{mu}m emission from the Lupus dark cloud complex are presented and analysed. The colour excess versus distance diagram confirms the existence of a region depleted from interstellar material, which is also seen in the ROSAT soft X-ray background emission map. The distance to the surrounding material is estimated as being within the interval from 60 to 100pc. This result is in disagreement with previous distance estimates to the supposed supernova that has been suggested as responsible for clearing the region from dust. As an alternative, the data presented support the suggestion that the void may have been produced by the detachment of material from the interface between LoopI and the Local Bubble as a consequence of hydromagnetic instabilities. Moreover, the distribution of colour excess as a function of distance supports a value of ~150pc as the most probable distance to the dark cloud known as Lupus1.

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