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ID:: ivo://CDS.VizieR/J/MNRAS/374/372
Title:: ZYJHK photometry in Upper Sco
Short Name:: J/MNRAS/374/372
Date:: 21 Oct 2021
Publisher:: CDS
Description:: We present first results from a deep (J=18.7), wide-field (6.5deg^2^) infrared (ZY JHK) survey in the Upper Sco association conducted within the science verification phase of the United Kingdom Infrared Telescope Infrared Deep Sky Survey Galactic Cluster Survey (GCS). Cluster members define a sequence well separated from field stars in the (Z-J, Z) colour-magnitude diagram. We have selected a total of 164 candidates with J =10.5-8.7mag from the (Z-J, Z) and (Y-J, Y) diagrams. We further investigated the location of those candidates in the other colour-magnitude and colour-colour diagrams to weed out contaminants. The cross-correlation of the GCS catalogue with the Two-Micron All-Sky Survey data base confirms the membership of 116 photometric candidates down to 20 Jupiter masses as they lie within a 2 circle centred on the association mean motion. The final list of cluster members contains 129 sources with masses between 0.3 and 0.007M_{sun}_.

ID:: ivo://CDS.VizieR/J/MNRAS/373/95
Title:: ZYJHK survey of Upper Sco association
Short Name:: J/MNRAS/373/95
Date:: 21 Oct 2021
Publisher:: CDS
Description:: We present the results of a 9.3-deg^2^ infrared (ZYJHK) survey in the Upper Scorpius association extracted from the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey Early Data Release (Dye et al., 2006MNRAS.372.1227D). We have selected a total of 112 candidates from the (Z-J, Z) colour-magnitude diagram over the Z=12.5-20.5 magnitude range, corresponding to M=0.25-0.01M_{sun}_ at an age of 5Myr and a distance of 145pc. Additional photometry in J and K filters revealed most of them as reddened stars, leaving 32 possible members. Among them, 15 have proper motion consistent with higher-mass members from Hipparcos and optical spectra with strong H{alpha} in emission and weak gravity features. We have also extracted two lower-mass candidate members for which no optical spectra are in hand. Three members exhibit strong H{alpha} equivalent widths (>20{AA}), suggesting that they could still undergo accretion, whereas two other dwarfs show signs of chromospheric activity. The likelihood of the binarity of a couple of new stellar and substellar members is discussed as well.

ID:: ivo://CDS.VizieR/J/AJ/160/252
Title:: ZZ Ceti white dwarfs and candidates in Gaia survey
Short Name:: J/AJ/160/252
Date:: 09 Mar 2022 22:00:00
Publisher:: CDS
Description:: The Gaia satellite recently released parallax measurements for ~260000 high-confidence white dwarf candidates, allowing for precise measurements of their physical parameters. By combining these parallaxes with Pan-STARRS and u-band photometry, we measured the effective temperature and stellar mass for all white dwarfs in the Northern Hemisphere within 100pc of the Sun, and identified a sample of ZZ-Ceti white dwarf candidates within the so-called instability strip. We acquired high-speed photometric observations for 90 candidates using the PESTO camera attached to the 1.6m telescope at the Mont-Megantic Observatory. We report the discovery of 38 new ZZ-Ceti stars, including two very rare ultramassive pulsators. We also identified five possibly variable stars within the strip, in addition to 47 objects that do not appear to show any photometric variability. However, several of those could be variable with an amplitude below our detection threshold, or could be located outside the instability strip due to errors in their photometric parameters. In the light of our results, we explore the trends of the dominant period and amplitude in the M--Teff plane, and briefly discuss the question of the purity of the ZZ-Ceti instability strip (i.e., a region devoid of non-variable stars).

ID:: ivo://CDS.VizieR/J/other/NewA/37.48
Title:: ZZ Cyg times of minima
Short Name:: J/other/NewA/37.
Date:: 21 Oct 2021
Publisher:: CDS
Description:: We present new photometry of the eclipsing binary ZZ Cyg. From all accumulated eclipsing times, we constructed the (O-C) curve, which can be described by a downward parabola with a possible light-time orbit. The period decrease rate is source dP/dt=-5.73(+/-0.18)d/yr. The modulated period, semi-amplitude and eccentricity for the light-time orbit are Pmod=71.4(+/-1.1)yr, A=0.0071(+/-0.0005)day and e=0.420(+/-0.053), respectively. After removing effects of the magnetic activity, this kind of cyclic oscillation may be attributed to light-time effect via an additional companion. By using the W-D code, the photometric model was updated, which identified that ZZ Cyg is a near-contact binary. We find that a hot spot may occur on the primary that explains the asymmetric light curve. The secular period decrease may possibly cause the fill-out factor of the primary to increase. Finally it will finally fill its Roche lobe. This kind of binary, ZZ Cyg, may evolve into contact binary star.

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