- ID:
- ivo://CDS.VizieR/J/ApJ/896/81
- Title:
- HST survey of ONC in H2O 1.4um abs. band. III.
- Short Name:
- J/ApJ/896/81
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- We present new results concerning the substellar binary population in the Orion Nebula Cluster (ONC). Using the Karhunen-Loeve Image Projection algorithm, we have reprocessed images taken with the IR channel of the Wide Field Camera 3 mounted on the Hubble Space Telescope to unveil faint, close companions in the wings of the stellar point-spread functions. Starting with a sample of 1392 bona fide unsaturated cluster members, we detect 39 close-pair cluster candidates with separation 0.16"-0.77". The primary masses span a range Mp~0.015-1.27M_{sun}_, whereas for the companions we derive Mc~0.004-0.54M_{sun}_. Of these 39 binary systems, 18 were already known, while the remaining 21 are new detections. Correcting for completeness and combining our catalog with previously detected ONC binaries, we obtain an overall binary fraction of 11.5%+/-0.9%. Compared to other star-forming regions, our multiplicity function is ~2 times smaller than, for example, Taurus, while compared to the binaries in the field we obtain comparable values. We analyze the mass functions of the binaries, finding differences between the mass distributions of binaries and single stars and between primary and companion mass distributions. The mass ratio shows a bottom-heavy distribution with median value Mc/Mp~0.25. Overall, our results suggest that ONC binaries may represent a template for the typical population of field binaries, supporting the hypothesis that the ONC may be regarded as a most typical star-forming region in the Milky Way.
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- ID:
- ivo://CDS.VizieR/J/ApJ/818/176
- Title:
- HST/WFC3 NIR photometry of 2M1207b
- Short Name:
- J/ApJ/818/176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotational modulations of brown dwarfs have recently provided powerful constraints on the properties of ultra-cool atmospheres, including longitudinal and vertical cloud structures and cloud evolution. Furthermore, periodic light curves directly probe the rotational periods of ultra-cool objects. We present here, for the first time, time-resolved high-precision photometric measurements of a planetary-mass companion, 2M1207b. We observed the binary system with Hubble Space Telescope/Wide Field Camera 3 in two bands and with two spacecraft roll angles. Using point-spread function-based photometry, we reach a nearly photon-noise limited accuracy for both the primary and the secondary. While the primary is consistent with a flat light curve, the secondary shows modulations that are clearly detected in the combined light curve as well as in different subsets of the data. The amplitudes are 1.36% in the F125W and 0.78% in the F160W filters, respectively. By fitting sine waves to the light curves, we find a consistent period of 10.7_-0.6_^+1.2^hr and similar phases in both bands. The J- and H-band amplitude ratio of 2M1207b is very similar to a field brown dwarf that has identical spectral type but different J-H color. Importantly, our study also measures, for the first time, the rotation period for a directly imaged extra-solar planetary-mass companion.
- ID:
- ivo://CDS.VizieR/J/ApJ/747/35
- Title:
- HST/WFC3 transit observation of GJ1214b
- Short Name:
- J/ApJ/747/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Capitalizing on the observational advantage offered by its tiny M dwarf host, we present Hubble Space Telescope/Wide Field Camera 3 (WFC3) grism measurements of the transmission spectrum of the super-Earth exoplanet GJ1214b. These are the first published WFC3 observations of a transiting exoplanet atmosphere. After correcting for a ramp-like instrumental systematic, we achieve nearly photon-limited precision in these observations, finding the transmission spectrum of GJ1214b to be flat between 1.1 and 1.7{mu}m. Inconsistent with a cloud-free solar composition atmosphere at 8.2{sigma}, the measured achromatic transit depth most likely implies a large mean molecular weight for GJ1214b's outer envelope. A dense atmosphere rules out bulk compositions for GJ1214b that explain its large radius by the presence of a very low density gas layer surrounding the planet. High-altitude clouds can alternatively explain the flat transmission spectrum, but they would need to be optically thick up to 10 mbar or consist of particles with a range of sizes approaching 1 {mu}m in diameter.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1118
- Title:
- HU Aqr planetary system mid-egress moments
- Short Name:
- J/MNRAS/448/1118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the mid-egress eclipse timing data gathered for the cataclysmic binary HU Aquarii during the years 1993-2014. The (O-C) residuals were previously attributed to a single ~7 Jupiter mass companion in ~5 AU orbit or to a stable two-planet system with an unconstrained outermost orbit. We present 22 new observations gathered between 2011 June and 2014 July with four instruments around the world. They reveal a systematic deviation of ~60-120 s from the older ephemeris. We re-analyse the whole set of the timing data available. Our results provide an erratum to the previous HU Aqr planetary models, indicating that the hypothesis for a third and fourth body in this system is uncertain. The dynamical stability criterion and a particular geometry of orbits rule out coplanar two-planet configurations. A putative HU Aqr planetary system may be more complex, e.g. highly non-coplanar. Indeed, we found examples of three-planet configurations with the middle planet in a retrograde orbit, which are stable for at least 1 Gyr, and consistent with the observations. The (O-C) may be also driven by oscillations of the gravitational quadrupole moment of the secondary, as predicted by the Lanza et al. modification of the Applegate mechanism. Further systematic, long-term monitoring of HU Aqr is required to interpret the (O-C) residuals.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1118
- Title:
- i-band photometry of HAT-P-16
- Short Name:
- J/ApJ/720/1118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of HAT-P-16b, a transiting extrasolar planet orbiting the V=10.8mag F8 dwarf GSC 2792-01700, with a period P=2.775960+/-0.000003 days, transit epoch T_c_=2455027.59293+/-0.00031 (BJD10), and transit duration 0.1276+/-0.0013 days. The host star has a mass of 1.22+/-0.04M_{sun}_, radius of 1.24+/-0.05R_{sun}_, effective temperature 6158+/-80K, and metallicity [Fe/H]=+0.17+/-0.08. The planetary companion has a mass of 4.193+/-0.094M_J_ and radius of 1.289+/-0.066R_J_, yielding a mean density of 2.42+/-0.35g/cm^3^. Comparing these observed characteristics with recent theoretical models, we find that HAT-P-16b is consistent with a 1Gyr H/He-dominated gas giant planet. HAT-P-16b resides in a sparsely populated region of the mass-radius diagram and has a non-zero eccentricity of e=0.036 with a significance of 10{sigma}.
- ID:
- ivo://CDS.VizieR/J/AJ/106/637
- Title:
- ICCD speckle observations. IX
- Short Name:
- J/AJ/106/637
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiplicity of stars within clusters is a well-studied phenomenon. However, recent survey work done on the Hyades by Mason et al. [1993AJ....105..220M] would seem to indicate that even in the most often studied clusters, there may be binaries yet undiscovered. In order to expand the sample of cluster binaries with potentially short-period visual orbits, a speckle survey of 45 Pleiades, 54 Praesepe, and 22 IC 4665 bright stars (V < 10) for possible multiplicity was conducted at the KPNO 4 m Mayall telescope between 1987 October and 1991 November. Of these, three new binaries have been discovered: one in the Pleiades where the new component may be spectroscopic, another in Praesepe which has been confirmed from examinations of archival observations and also has been resolved by occultation, and the third in IC 4665. Continued study of these new binary stars could further refine the cluster distance moduli as well as the cluster mass-luminosity relations.
- ID:
- ivo://CDS.VizieR/J/AJ/108/2299
- Title:
- ICCD speckle observations of binary stars. XI.
- Short Name:
- J/AJ/108/2299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One-thousand one-hundred ninety-seven observations of 730 binary star systems, observed by means of speckle interferometry with the 4m telescope on Kitt Peak, are presented. Included in these binary stars are new interferometric companions to five visual binaries. These measurements, made mostly during the period 1991 to 1993, comprise the 11th installment of results stemming from our speckle program at the 4m class telescopes on Kitt Peak, Cerro Tololo, and Mauna Kea.
- ID:
- ivo://CDS.VizieR/J/AJ/111/936
- Title:
- ICCD Speckle obs. of binary stars. XIII
- Short Name:
- J/AJ/111/936
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nine hundred eighty-nine observations of 694 binary star systems, observed by means of speckle interferometry with the 4m telescope on Cerro Tololo, are presented. Included in these observations are three new interferometric binaries and new interferometric companions to four visual binaries. These measurements, made during the period 1989-1994, comprise the 13th installment of digital results stemming from our speckle program at several major observatories, and the 23rd list since the program's inception in 1975.
- ID:
- ivo://CDS.VizieR/J/AJ/119/3084
- Title:
- ICCD speckle obs. of binary stars. XXIII.
- Short Name:
- J/AJ/119/3084
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 2017 observations of 1286 binary stars, observed by means of speckle interferometry using six telescopes over a 15 year period from 1982 April to 1997 June. These measurements constitute the 23d installment in CHARA's speckle program at 2 to 4 m class telescopes and include the second major collection of measurements from the Mount Wilson 100 inch (2.5 m) Hooker Telescope. Orbital elements are also presented for 14 systems, seven of which have had no previously published orbital analyses.
- ID:
- ivo://CDS.VizieR/J/AJ/157/169
- Title:
- Identifying exoplanets with deep learning in K2
- Short Name:
- J/AJ/157/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For years, scientists have used data from NASA's Kepler Space Telescope to look for and discover thousands of transiting exoplanets. In its extended K2 mission, Kepler observed stars in various regions of the sky all across the ecliptic plane, and therefore in different galactic environments. Astronomers want to learn how the populations of exoplanets are different in these different environments. However, this requires an automatic and unbiased way to identify exoplanets in these regions and rule out false-positive signals that mimic transiting planet signals. We present a method for classifying these exoplanet signals using deep learning, a class of machine learning algorithms that have become popular in fields ranging from medical science to linguistics. We modified a neural network previously used to identify exoplanets in the Kepler field to be able to identify exoplanets in different K2 campaigns that exist in a range of galactic environments. We train a convolutional neural network, called AstroNet-K2, to predict whether a given possible exoplanet signal is really caused by an exoplanet or a false positive. AstroNet-K2 is highly successful at classifying exoplanets and false positives, with accuracy of 98% on our test set. It is especially efficient at identifying and culling false positives, but for now, it still needs human supervision to create a complete and reliable planet candidate sample. We use AstroNet-K2 to identify and validate two previously unknown exoplanets. Our method is a step toward automatically identifying new exoplanets in K2 data and learning how exoplanet populations depend on their galactic birthplace.
