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2861. 4 transiting F-M binary systems
ID:
ivo://CDS.VizieR/J/MNRAS/437/2831
Title:
4 transiting F-M binary systems
Short Name:
J/MNRAS/437/2831
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of four transiting F-M binary systems with companions between 0.1 and 0.2M_{sun}_ in mass by the HATSouth survey. These systems have been characterized via a global analysis of the HATSouth discovery data, combined with high-resolution radial velocities and accurate transit photometry observations. We determined the masses and radii of the component stars using a combination of two methods: isochrone fitting of spectroscopic primary star parameters and equating spectroscopic primary star rotation velocity with spin-orbit synchronization. These new very low mass companions are HATS550-016B (0.110_-0.006_^+0.005^M_{sun}_, 0.147_-0.004_^+0.003^R_{sun}_), HATS551-019B (0.17_-0.01_^+0.01^M_sun}_, 0.18_-0.01_^+0.01^R_{sun}_), HATS551-021B (0.132_-0.005_^+0.014^M_sun}_, 0.154_-0.008_^+0.006^R_{sun}_) and HATS553-001B (0.20_-0.02_^+0.01^M_sun}_, 0.22_-0.01_^+0.01^R_{sun}_). We examine our sample in the context of the radius anomaly for fully convective low-mass stars. Combining our sample with the 13 other well-studied very low mass stars, we find a tentative 5 percent systematic deviation between the measured radii and theoretical isochrone models.
2862. Transiting planets in young clusters from K2
ID:
ivo://CDS.VizieR/J/AJ/154/224
Title:
Transiting planets in young clusters from K2
Short Name:
J/AJ/154/224
Date:
21 Oct 2021
Publisher:
CDS
Description:
Detection of transiting exoplanets around young stars is more difficult than for older systems owing to increased stellar variability. Nine young open cluster planets have been found in the K2 data, but no single analysis pipeline identified all planets. We have developed a transit search pipeline for young stars that uses a transit-shaped notch and quadratic continuum in a 12 or 24 hr window to fit both the stellar variability and the presence of a transit. In addition, for the most rapid rotators (P_rot_<2 days) we model the variability using a linear combination of observed rotations of each star. To maximally exploit our new pipeline, we update the membership for four stellar populations observed by K2 (Upper Scorpius, Pleiades, Hyades, Praesepe) and conduct a uniform search of the members. We identify all known transiting exoplanets in the clusters, 17 eclipsing binaries, one transiting planet candidate orbiting a potential Pleiades member, and three orbiting unlikely members of the young clusters. Limited injection recovery testing on the known planet hosts indicates that for the older Praesepe systems we are sensitive to additional exoplanets as small as 1-2 R_{Earth}_, and for the larger Upper Scorpius planet host (K2-33) our pipeline is sensitive to ~4 R_{Earth}_ transiting planets. The lack of detected multiple systems in the young clusters is consistent with the expected frequency from the original Kepler sample, within our detection limits. With a robust pipeline that detects all known planets in the young clusters, occurrence rate testing at young ages is now possible.
2863. Transition circumstellar disks in Ophiuchus
ID:
ivo://CDS.VizieR/J/ApJ/712/925
Title:
Transition circumstellar disks in Ophiuchus
Short Name:
J/ApJ/712/925
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained millimeter-wavelength photometry, high-resolution optical spectroscopy, and adaptive optics near-infrared imaging for a sample of 26 Spitzer-selected transition circumstellar disks. All of our targets are located in the Ophiuchus molecular cloud (d~125pc) and have spectral energy distributions (SEDs) suggesting the presence of inner opacity holes. We use these ground-based data to estimate the disk mass, multiplicity, and accretion rate for each object in our sample in order to investigate the mechanisms potentially responsible for their inner holes. We find that transition disks are a heterogeneous group of objects, with disk masses ranging from <0.6 to 40M_JUP_ and accretion rates ranging from <10^-11^ to 10^-7^M_{sun}_/yr, but most tend to have much lower masses and accretion rates than "full disks" (i.e., disks without opacity holes). Eight of our targets have stellar companions: six of them are binaries and the other two are triple systems. In four cases, the stellar companions are close enough to suspect they are responsible for the inferred inner holes. We find that nine of our 26 targets have low disk mass (<2.5M_JUP_) and negligible accretion (<10^-11^M_{sun}_/yr), and are thus consistent with photoevaporating (or photoevaporated) disks. Four of these nine non-accreting objects have fractional disk luminosities <10^-3^ and could already be in a debris disk stage. Seventeen of our transition disks are accreting. Thirteen of these accreting objects are consistent with grain growth. The remaining four accreting objects have SEDs suggesting the presence of sharp inner holes, and thus are excellent candidates for harboring giant planets.
2864. Transition disks. II. Southern MoC
ID:
ivo://CDS.VizieR/J/ApJ/749/79
Title:
Transition disks. II. Southern MoC
Short Name:
J/ApJ/749/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
Transition disk objects are pre-main-sequence stars with little or no near-IR excess and significant far-IR excess, implying inner opacity holes in their disks. Here we present a multifrequency study of transition disk candidates located in Lupus I, III, IV, V, VI, Corona Australis, and Scorpius. Complementing the information provided by Spitzer with adaptive optics (AO) imaging (NaCo, VLT), submillimeter photometry (APEX), and echelle spectroscopy (Magellan, Du Pont Telescopes), we estimate the multiplicity, disk mass, and accretion rate for each object in our sample in order to identify the mechanism potentially responsible for its inner hole. We find that our transition disks show a rich diversity in their spectral energy distribution morphology, have disk masses ranging from <~1 to 10M_JUP_, and accretion rates ranging from <~10^-11^ to 10^-7.7^M_{sun}_/yr. Of the 17 bona fide transition disks in our sample, three, nine, three, and two objects are consistent with giant planet formation, grain growth, photoevaporation, and debris disks, respectively. Two disks could be circumbinary, which offers tidal truncation as an alternative origin of the inner hole.
2865. Transit light curves of TRAPPIST-1 planets
ID:
ivo://CDS.VizieR/J/AJ/156/218
Title:
Transit light curves of TRAPPIST-1 planets
Short Name:
J/AJ/156/218
Date:
21 Oct 2021
Publisher:
CDS
Description:
The TRAPPIST-1 planetary system provides an exceptional opportunity for the atmospheric characterization of temperate terrestrial exoplanets with the upcoming James Webb Space Telescope (JWST). Assessing the potential impact of stellar contamination on the planets' transit transmission spectra is an essential precursor to this characterization. Planetary transits themselves can be used to scan the stellar photosphere and to constrain its heterogeneity through transit depth variations in time and wavelength. In this context, we present our analysis of 169 transits observed in the optical from space with K2 and from the ground with the SPECULOOS and Liverpool telescopes. Combining our measured transit depths with literature results gathered in the mid-/near-IR with Spitzer/IRAC and HST/WFC3, we construct the broadband transmission spectra of the TRAPPIST-1 planets over the 0.8-4.5 {mu}m spectral range. While planet b, d, and f spectra show some structures at the 200-300 ppm level, the four others are globally flat. Even if we cannot discard their instrumental origins, two scenarios seem to be favored by the data: a stellar photosphere dominated by a few high-latitude giant (cold) spots, or, alternatively, by a few small and hot (3500-4000 K) faculae. In both cases, the stellar contamination of the transit transmission spectra is expected to be less dramatic than predicted in recent papers. Nevertheless, based on our results, stellar contamination can still be of comparable or greater order than planetary atmospheric signals at certain wavelengths. Understanding and correcting the effects of stellar heterogeneity therefore appears essential for preparing for the exploration of TRAPPIST-1 with JWST.
2866. Transit times of 11 hot Jupiters
ID:
ivo://CDS.VizieR/J/AJ/159/150
Title:
Transit times of 11 hot Jupiters
Short Name:
J/AJ/159/150
Date:
21 Oct 2021
Publisher:
CDS
Description:
Many of the known hot Jupiters are formally unstable to tidal orbital decay. The only hot Jupiter for which orbital decay has been directly detected is WASP-12, for which transit-timing measurements spanning more than a decade have revealed that the orbital period is decreasing at a rate of dP/dt~10^-9^, corresponding to a reduced tidal quality factor of about 2x10^5^. Here, we present a compilation of transit-timing data for WASP-12 and 11 other systems that are especially favorable for detecting orbital decay: KELT-16; WASP-18, 19, 43, 72, 103, 114, and 122; HAT-P-23; HATS-18; and OGLE-TR-56. For most of these systems we present new data that extend the time baseline over which observations have been performed. None of the systems besides WASP-12 display convincing evidence for period changes, with typical upper limits on dP/dt on the order of 10^-9^ or 10^-10^, and lower limits on the reduced tidal quality factor on the order of 10^5^. One possible exception is WASP-19, which shows a statistically significant trend, although it may be a spurious effect of starspot activity.
2867. Triggered star formation in SFO 38
ID:
ivo://CDS.VizieR/J/ApJ/717/1067
Title:
Triggered star formation in SFO 38
Short Name:
J/ApJ/717/1067
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have investigated the young stellar population in and around SFO 38, one of the massive globules located in the northern part of the Galactic HII region IC 1396, using the Spitzer IRAC and MIPS observations (3.6-24um), and followed up with ground-based optical photometric and spectroscopic observations. Based on the IRAC and MIPS colors and H{alpha} emission, we identify ~45 young stellar objects (Classes 0/I/II) and 13 probable pre-main-sequence candidates. We derive the spectral types (mostly K- and M-type stars), effective temperatures, and individual extinction of the relatively bright and optically visible Class II objects. Using the width of the H{alpha} emission line measured at 10% peak intensity, we derive the mass accretion rates of individual objects to be between 10^-10^ and 10^-8^M_{sun}_/yr.
2868. Trigonometric parallaxes of 134 low-mass stars
ID:
ivo://CDS.VizieR/J/AJ/152/24
Title:
Trigonometric parallaxes of 134 low-mass stars
Short Name:
J/AJ/152/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report trigonometric parallaxes for 134 low-mass stars and brown dwarfs, of which 38 have no previously published measurement and 79 more have improved uncertainties. Our survey focused on nearby targets, so 119 are closer than 30pc. Of the 38 stars with new parallaxes, 14 are within 20pc and seven are likely brown dwarfs (spectral types later than L0). These parallaxes are useful for studies of kinematics, multiplicity, and spectrophotometric calibration. Two objects with new parallaxes are confirmed as young stars with membership in nearby young moving groups: LP 870-65 in AB Doradus and G161-71 in Argus. We also report the first parallax for the planet-hosting star GJ3470; this allows us to refine the density of its Neptune-mass planet. T-dwarf 2MASSJ12590470-4336243, previously thought to lie within 4pc, is found to be at 7.8pc, and the M-type star 2MASSJ01392170-3936088 joins the ranks of nearby stars as it is found to be within 10pc. Five stars that are overluminous and/or too red for their spectral types are identified and deserve further study as possible young stars.
2869. Triple systems (cool primary + hot binary)
ID:
ivo://CDS.VizieR/J/AJ/127/2915
Title:
Triple systems (cool primary + hot binary)
Short Name:
J/AJ/127/2915
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the course of comparing parameters of evolved cool star plus hot main-sequence star binaries with theoretical isochrones, some discrepancies are found between implied stellar masses and the spectroscopic binary mass function or the measured angular separation. These are naturally explained if there is a third star in the system. Multiplicity is also required to explain some comparisons of "cool plus hot binary" IUE and optical spectral energy distribution analysis with measured flux ratios, especially Tycho's two-color photometry of separate components. Out of a sample of 136 cool-plus-hot binary star systems under study, measurements are now indicating several systems considered double (HD 5373, 23089, 26673, 29094, 49126, 71129, 149379, 179002, 187299), and probably a few others (including HD 136415), to have at least three stellar components. Several other cases of suspected triple systems are confirmed. For comparison, there are eight known triples included in the project. In all, about 25% of the systems contain three or more components within a few arcseconds. Estimated separations are provided, which may be of use when not known from interferometry. In general, the triple systems have one post-main-sequence component and two upper main-sequence components, usually revolving around each other. One new triple system, HD 149379, has as its middle component an F giant in the brief first crossing of the Hertzsprung gap.
2870. Trumpler 5 photometric BV catalog
ID:
ivo://CDS.VizieR/J/MNRAS/446/1411
Title:
Trumpler 5 photometric BV catalog
Short Name:
J/MNRAS/446/1411
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of a long-term programme, we analyse the evolutionary status and properties of the old and populous open cluster Trumpler 5 (Tr 5), located in the Galactic anticentre direction, almost on the Galactic plane. Tr 5 was observed with Wide Field Imager@MPG/ESO Telescope using the Bessel U, B, and V filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMD with a library of synthetic CMDs generated with different stellar evolution sets (Padova, FRANEC, and FST). Age, reddening, and distance are derived through the synthetic CMD method using stellar evolutionary models with subsolar metallicity (Z=0.004 or Z=0.006). Additional spectroscopic observations with Ultraviolet VLT Echelle Spectrograph@Very Large Telescope of three red clump stars of the cluster were used to determine more robustly the chemical properties of the cluster. Our analysis shows that Tr 5 has subsolar metallicity, with [Fe/H]=-0.403+/-0.006 dex (derived from spectroscopy), age between 2.9 and 4 Gyr (the lower age is found using stellar models without core overshooting), reddening E(B-V) in the range 0.60-0.66 mag complicated by a differential pattern (of the order of ~+/-0.1mag), and distance modulus (m-M)_0_=12.4+/-0.1mag.