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1811. HATSouth-K2 C7 transiting/eclipsing systems
ID:
ivo://CDS.VizieR/J/AJ/155/119
Title:
HATSouth-K2 C7 transiting/eclipsing systems
Short Name:
J/AJ/155/119
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the result of a campaign to monitor 25 HATSouth candidates using the Kepler space telescope during Campaign 7 of the K2 mission. We discover HATS-36b (EPIC 215969174b, K2-145b), an eccentric (e=0.105+/-0.028) hot Jupiter with a mass of 3.216+/-0.062 M_J_ and a radius of 1.235+/-0.043 R_J_, which transits a solar-type G0V star (V=14.386) in a 4.1752-day period. We also refine the properties of three previously discovered HATSouth transiting planets (HATS-9b, HATS-11b, and HATS-12b) and search the K2 data for TTVs and additional transiting planets in these systems. In addition, we also report on a further three systems that remain as Jupiter-radius transiting exoplanet candidates. These candidates do not have determined masses, however pass all of our other vetting observations. Finally, we report on the 18 candidates that we are now able to classify as eclipsing binary or blended eclipsing binary systems based on a combination of the HATSouth data, the K2 data, and follow-up ground-based photometry and spectroscopy. These range in periods from 0.7 day to 16.7 days, and down to 1.5 mmag in eclipse depths. Our results show the power of combining ground-based imaging and spectroscopy with higher precision space-based photometry, and serve as an illustration as to what will be possible when combining ground-based observations with TESS data.
1812. HAT-TR-318-007: a double-lined M dwarf binary
ID:
ivo://CDS.VizieR/J/AJ/155/114
Title:
HAT-TR-318-007: a double-lined M dwarf binary
Short Name:
J/AJ/155/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery by the HATNet survey of HAT-TR-318-007, a P=3.34395390+/-0.00000020 day period detached double-lined M dwarf binary with total secondary eclipses. We combine radial velocity (RV) measurements from TRES/FLWO 1.5 m and time-series photometry from HATNet, FLWO 1.2 m, BOS 0.8 m, and NASA K2 Campaign 5, to determine the masses and radii of the component stars: M_A_=0.448+/-0.011 M_{sun}_^N^, M_B_=0.2721_-0.0042_^+0.0041^ M_{sun}_^N^, R_A_=0.4548_-0.0036_^+0.0035^ R_{sun}_^N^, and R_B_=0.2913_-0.0024_^+0.0023^ R_{sun}_^N^. We obtained a FIRE/Magellan near-infrared spectrum of the primary star during a total secondary eclipse, and we use this to obtain disentangled spectra of both components. We determine spectral types of ST_A_=M3.71+/-0.69 and ST_B_=M5.01+/-0.73 and effective temperatures of T_eff,A_=3190+/-110 K and T_eff,B_=3100+/-110 K for the primary and secondary star, respectively. We also measure a metallicity of [Fe/H]=+0.298+/-0.080 for the system. We find that the system has a small, but significant, nonzero eccentricity of 0.0136+/-0.0026. The K2 light curve shows a coherent variation at a period of 3.41315_-0.00032_^+0.00030^ days, which is slightly longer than the orbital period, and which we demonstrate comes from the primary star. We interpret this as the rotation period of the primary. We perform a quantitative comparison between the Dartmouth stellar evolution models and the seven systems, including HAT-TR-318-007, that contain M dwarfs with 0.2 M_{sun}_^N^<M<0.5 M_{sun}_^N^, have metallicity measurements, and have masses and radii determined to better than 5% precision. Discrepancies between the predicted and observed masses and radii are found for three of the systems.
1813. Havlen-Moffat No. 1 UBVRI photometry
ID:
ivo://CDS.VizieR/J/A+A/371/908
Title:
Havlen-Moffat No. 1 UBVRI photometry
Short Name:
J/A+A/371/908
Date:
21 Oct 2021
Publisher:
CDS
Description:
A deep CCD UBVRI photometric survey combined with UBVRI polarimetric observations of 21 bright stars was carried out in the region of the open cluster Havlen-Moffat No. 1. Our data reveal that the extinction law in this cluster es variable and that six cluster stars show very high polarisation values (>4%), probably because of the presence of a nearby small dust cloud. The cluster is at a distance of d=3300pc, it is 2-4Myr old and the initial mass function of its most massive stars (M>3M_{sun}_) has a flat slope of x about of 0.7. As an additional result, it was possible to reconcile the absolute magnitudes of the two WN7-type members using the R-values valid in the regions where they are located.
1814. Hawaii Infrared Parallax Program. I.
ID:
ivo://CDS.VizieR/J/ApJS/201/19
Title:
Hawaii Infrared Parallax Program. I.
Short Name:
J/ApJS/201/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
Astrometry and photometry for 318 ultracool dwarfs in 265 systems that have measured trigonometric parallaxes. To be included in this tabulation, an object must have a spectral type >=M6 or a K-band absolute magnitude >8.5mag. Parallaxes, proper motions, and coordinates at a specified epoch are given for all objects. Photometric measurements in MKO, 2MASS, Spitzer, and WISE systems are given when available. Various other flags that provide additional information about the object or photometry are included.
1815. Hawaii infrared parallax program. II. Ultracool dwarfs
ID:
ivo://CDS.VizieR/J/ApJ/833/96
Title:
Hawaii infrared parallax program. II. Ultracool dwarfs
Short Name:
J/ApJ/833/96
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a large, uniform analysis of young (~10-150Myr) ultracool dwarfs, based on new high-precision infrared (IR) parallaxes for 68 objects. We find that low-gravity (VL-G) late-M and L dwarfs form a continuous sequence in IR color-magnitude diagrams, separate from the field population and from current theoretical models. These VL-G objects also appear distinct from young substellar (brown dwarf and exoplanet) companions, suggesting that the two populations may have a different range of physical properties. In contrast, at the L/T transition, young, old, and spectrally peculiar objects all span a relatively narrow range in near-IR absolute magnitudes. At a given spectral type, the IR absolute magnitudes of young objects can be offset from ordinary field dwarfs, with the largest offsets occurring in the Y and J bands for late-M dwarfs (brighter than the field) and mid-/late-L dwarfs (fainter than the field). Overall, low-gravity (VL-G) objects have the most uniform photometric behavior, while intermediate gravity (INT-G) objects are more diverse, suggesting a third governing parameter beyond spectral type and gravity class. We examine the moving group membership for all young ultracool dwarfs with parallaxes, changing the status of 23 objects (including 8 previously identified planetary-mass candidates) and fortifying the status of another 28 objects. We use our resulting age-calibrated sample to establish empirical young isochrones and show a declining frequency of VL-G objects relative to INT-G objects with increasing age. Notable individual objects in our sample include high-velocity (>~100km/s) INT-G objects, very red late-L dwarfs with high surface gravities, candidate disk-bearing members of the MBM20 cloud and {beta} Pic moving group, and very young distant interlopers. Finally, we provide a comprehensive summary of the absolute magnitudes and spectral classifications of young ultracool dwarfs, using a combined sample of 102 objects found in the field and as substellar companions to young stars.
1816. Hawaii IR parallax program. IV. L0-T8 BDs with UKIRT
ID:
ivo://CDS.VizieR/J/AJ/159/257
Title:
Hawaii IR parallax program. IV. L0-T8 BDs with UKIRT
Short Name:
J/AJ/159/257
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present parallaxes, proper motions, and J-band photometry for 348 L and T dwarfs measured using the wide-field near-infrared camera (WFCAM) on the United Kingdom Infrared Telescope (UKIRT). This is the largest single batch of infrared parallaxes for brown dwarfs to date. Our parallaxes have a median uncertainty of 3.5mas, similar to most previous ground-based infrared parallax surveys. Our target list was designed to complete a volume-limited parallax sample of L0-T8 dwarfs out to 25pc spanning declinations -30{deg} to +60{deg} (68% of the sky). We report the first parallaxes for 165 objects, and we improve on previous measurements for another 53 objects. Our targets include 104 objects (mostly early-L dwarfs) having Gaia DR2 parallax measurements with which our parallaxes are consistent. We include an extensive comparison of previous literature parallaxes for L and T dwarfs with both our results and Gaia DR2 measurements, identifying systematic offsets for some previous surveys. Our parallaxes confirm that 14 objects previously identified as wide common proper motion companions to main-sequence stars have distances consistent with companionship. We also report new J_MKO_ photometry for our targets, including the first measurements for 193 of our targets and improvements over previously published J_MKO_ photometry for another 60 targets. Altogether, our parallaxes will enable the first population studies using a volume-limited sample spanning spectral types L0-T8 defined entirely by parallaxes.
1817. Hawaii redshifts in the ACS-GOODS region
ID:
ivo://CDS.VizieR/J/AJ/127/3137
Title:
Hawaii redshifts in the ACS-GOODS region
Short Name:
J/AJ/127/3137
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results of an extensive spectroscopic survey of galaxies in the roughly 160 arcmin^2^ ACS-GOODS region surrounding the Hubble Deep Field North (HDF-N). We have identified 892 galaxies or stars with z<24, R<24.5, or B<25 in the region. The spectra were obtained with either the DEIMOS or LRIS spectrographs on the Keck 10m telescopes. The results are compared with photometric redshift estimates and with redshifts from the literature, as well as with the redshifts of a parallel effort led by a group at Keck. Our sample, when combined with the literature data, provides identifications for 1324 sources. We use our results to determine the redshift distributions with magnitude, to analyze the rest-frame color distributions with redshift and spectral type, and to investigate the dependence of the X-ray galaxy properties on the local galaxy density in the redshift interval z=0-1.5. We find the rather surprising result that the galaxy X-ray properties are not strongly dependent on the local galaxy density for galaxies in the same luminosity range.
1818. HAWK-I JHK photometry of the Orion Nebula Cloud
ID:
ivo://CDS.VizieR/J/MNRAS/461/1734
Title:
HAWK-I JHK photometry of the Orion Nebula Cloud
Short Name:
J/MNRAS/461/1734
Date:
21 Oct 2021
Publisher:
CDS
Description:
Due to its youth, proximity and richness, the Orion nebula cloud (ONC) is an ideal testbed to obtain a comprehensive view on the initial mass function (IMF) down to the planetary mass regime. Using the HAWK-I camera at the VLT, we have obtained an unprecedented deep and wide near-infrared JHK mosaic of the ONC (90 per cent completeness at K ~19.0mag, 22x28 arcmin^2^). Applying the most recent isochrones and accounting for the contamination of background stars and galaxies, we find that ONC's IMF is bimodal with distinct peaks at about 0.25 and 0.025M_{sun}_ separated by a pronounced dip at the hydrogen burning limit (0.08M_{sun}_), with a depth of about a factor of 2-3 below the log-normal distribution. Apart from ~920 low-mass stars (M<1.4M_{sun}_) the IMF contains ~760 brown dwarf candidates and ~160 isolated planetary mass object candidates with M>0.005M_{sun}_, hence about 10 times more substellar candidates than known before. The substellar IMF peak at 0.025M_{sun}_ could be caused by brown dwarfs and isolated planetary mass objects which have been ejected from multiple systems during the early star formation process or from circumstellar discs.
1819. HAZMAT. III. Low-mass stars GALEX photometry
ID:
ivo://CDS.VizieR/J/AJ/155/122
Title:
HAZMAT. III. Low-mass stars GALEX photometry
Short Name:
J/AJ/155/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
Low-mass stars are currently the most promising targets for detecting and characterizing habitable planets in the solar neighborhood. However, the ultraviolet (UV) radiation emitted by such stars can erode and modify planetary atmospheres over time, drastically affecting their habitability. Thus, knowledge of the UV evolution of low-mass stars is critical for interpreting the evolutionary history of any orbiting planets. Shkolnik & Barman (2014, J/AJ/148/64) used photometry from the Galaxy Evolution Explorer (GALEX) to show how UV emission evolves for early-type M stars (>0.35 M_{sun}_). In this paper, we extend their work to include both a larger sample of low-mass stars with known ages as well as M stars with lower masses. We find clear evidence that mid- and late-type M stars (0.08-0.35 M_{sun}_) do not follow the same UV evolutionary trend as early-Ms. Lower-mass M stars retain high levels of UV activity up to field ages, with only a factor of 4 decrease on average in GALEX NUV and FUV flux density between young (<50 Myr) and old (~5 Gyr) stars, compared to a factor of 11 and 31 for early-Ms in NUV and FUV, respectively. We also find that the FUV/NUV flux density ratio, which can affect the photochemistry of important planetary biosignatures, is mass- and age-dependent for early-Ms, but remains relatively constant for the mid- and late-type Ms in our sample.
1820. HAZMAT. II. Low-mass stars with GALEX UV observations
ID:
ivo://CDS.VizieR/J/AJ/154/67
Title:
HAZMAT. II. Low-mass stars with GALEX UV observations
Short Name:
J/AJ/154/67
Date:
21 Oct 2021
Publisher:
CDS
Description:
The ultraviolet (UV) light from a host star influences a planet's atmospheric photochemistry and will affect interpretations of exoplanetary spectra from future missions like the James Webb Space Telescope. These effects will be particularly critical in the study of planetary atmospheres around M dwarfs, including Earth-sized planets in the habitable zone. Given the higher activity levels of M dwarfs compared to Sun-like stars, time-resolved UV data are needed for more accurate input conditions for exoplanet atmospheric modeling. The Galaxy Evolution Explorer (GALEX) provides multi-epoch photometric observations in two UV bands: near-ultraviolet (NUV; 1771-2831{AA}) and far-ultraviolet (FUV; 1344-1786{AA}). Within 30pc of Earth, there are 357 and 303 M dwarfs in the NUV and FUV bands, respectively, with multiple GALEX observations. Simultaneous NUV and FUV detections exist for 145 stars in both GALEX bands. Our analyses of these data show that low-mass stars are typically more variable in the FUV than the NUV. Median variability increases with later spectral types in the NUV with no clear trend in the FUV. We find evidence that flares increase the FUV flux density far more than the NUV flux density, leading to variable FUV to NUV flux density ratios in the GALEX bandpasses.The ratio of FUV to NUV flux is important for interpreting the presence of atmospheric molecules in planetary atmospheres such as oxygen and methane as a high FUV to NUV ratio may cause false-positive biosignature detections. This ratio of flux density in the GALEX bands spans three orders of magnitude in our sample, from 0.008 to 4.6, and is 1 to 2 orders of magnitude higher than for G dwarfs like the Sun. These results characterize the UV behavior for the largest set of low-mass stars to date.