- ID:
- ivo://CDS.VizieR/J/AJ/126/175
- Title:
- M31Y eclipsing binaries and Cepheids
- Short Name:
- J/AJ/126/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The DIRECT Project aims to obtain direct distances to two Local Group galaxies, M31 and M33, which occupy a crucial position near the base of the cosmological distance ladder. The first step is to search for detached eclipsing binaries (DEBs) and Cepheids using 1m class telescopes to select good candidates, which will be followed up spectroscopically on 6.510m class telescopes. In this ninth paper, we present a catalog of variable stars discovered with image subtraction in field M31Y (RA=10.97{deg}, DE=41.69{deg}; J2000.0). The data were obtained with the Fred Lawrence Whipple Observatory 1.2m telescope on 25 nights, over a period of 6 months. In our search covering 22x22, we discovered 41 eclipsing binaries, 126 Cepheids, and 97 other periodic or nonperiodic variables, including a luminous blue variable candidate, a nova, and a Galactic cataclysmic variable. The catalog of variables, as well as their photometry and finding charts, is available electronically via anonymous ftp and the World Wide Web, at http://cfa-www.harvard.edu/~kstanek/DIRECT . The complete set of the CCD frames is available upon request.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/791/54
- Title:
- Nearby M Dwarfs parameters
- Short Name:
- J/ApJ/791/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Comparisons between the planet populations around solar-type stars and those orbiting M dwarfs shed light on the possible dependence of planet formation and evolution on stellar mass. However, such analyses must control for other factors, i.e., metallicity, a stellar parameter that strongly influences the occurrence of gas giant planets. We obtained infrared spectra of 121 M dwarfs stars monitored by the California Planet Search and determined metallicities with an accuracy of 0.08 dex. The mean and standard deviation of the sample are -0.05 and 0.20 dex, respectively. We parameterized the metallicity dependence of the occurrence of giant planets on orbits with a period less than two years around solar-type stars and applied this to our M dwarf sample to estimate the expected number of giant planets. The number of detected planets (3) is lower than the predicted number (6.4), but the difference is not very significant (12% probability of finding as many or fewer planets). The three M dwarf planet hosts are not especially metal rich and the most likely value of the power-law index relating planet occurrence to metallicity is 1.06 dex per dex for M dwarfs compared to 1.80 for solar-type stars; this difference, however, is comparable to uncertainties. Giant planet occurrence around both types of stars allows, but does not necessarily require, a mass dependence of ~1 dex per dex. The actual planet-mass-metallicity relation may be complex, and elucidating it will require larger surveys like those to be conducted by ground-based infrared spectrographs and the Gaia space astrometry mission.
- ID:
- ivo://CDS.VizieR/V/101
- Title:
- Nearest stars until 10pc
- Short Name:
- V/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The given catalogue is a revised version of the catalogue (Zakhozhaj, 1987). The previous numeration is preserved, and the stars, with trigonometric, photometric and spectral parallaxes >0.100" are presented. The catalogue contains data on new components of multiple visual systems, on the components of spectral-binary systems, on invisible components with masses >0.08 solar mass. New data are obtained in 90s and contained in the articles [2-6]. The catalogue contains the main characteristics of stars such as the positions, proper motions, radial velocities, parallaxes, photometrical data and also new data of masses and radii of stars. The completeness of the catalogue is about 70%.
- ID:
- ivo://CDS.VizieR/J/AJ/153/25
- Title:
- Near-infrared observations of 84 KOI systems
- Short Name:
- J/AJ/153/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine probabilities of physical association for stars in blended Kepler Objects of Interest (KOIs), and find that 14.5%_-3.4%_^+3.8%^ of companions within ~4'' are consistent with being physically unassociated with their primary. This produces a better understanding of potential false positives in the Kepler catalog and will guide models of planet formation in binary systems. Physical association is determined through two methods of calculating multi-band photometric parallax using visible and near-infrared adaptive optics observations of 84 KOI systems with 104 contaminating companions within ~4''. We find no evidence that KOI companions with separations of less than 1'' are more likely to be physically associated than KOI companions generally. We also reinterpret transit depths for 94 planet candidates, and calculate that 2.6%+/-0.4% of transits have R>15R_{oplus}_, which is consistent with prior modeling work.
- ID:
- ivo://CDS.VizieR/J/AJ/158/38
- Title:
- New substellar discoveries from Kepler and K2
- Short Name:
- J/AJ/158/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discoveries of a brown dwarf (BD) and a low-mass star from the Kepler and K2 missions. The newly discovered BD is EPIC 212036875b and the low-mass star is KOI-607b. EPIC 212036875b has a mass of M_b_=52.3+/-1.9 M_J_, a radius of R_b_=0.874+/-0.017 R_J_, and orbits its host star in P=5.169885+/-0.000027 days. Its host star is a late F-type star with M_*_=1.288+/-0.065 M_{sun}_, R_*_= 1.498+/-0.025 R_{sun}_, and T_eff_=6238+/-60 K. KOI-607b has a mass of M_b_=95.1+/-3.4 M_J_, a radius of R_b_=1.089+/-0.089 R_J_, and an orbital period of P=5.89399148+/-0.00000060 days. The primary star in the KOI-607 system is a G dwarf with M_*_=0.993+/-0.052 M_{sun}_, R_*_= 0.915+/-0.031 R_{sun}_, and T_eff_=5418+/-87 K. We also revisit a BD, CWW 89Ab, that was previously published by Nowak et al. 2017AJ....153..131N (under the designation EPIC 219388192b). CWW 89Ab is one of two known transiting BDs associated with a star cluster, which illustrates the need for more BDs with accurate masses, radii, and reliable age determinations to test theoretical models. We find that the newly discovered BD, EPIC 212036875b, falls in the middle of the so-called BD desert, indicating that EPIC 212036875b is either a particularly rare object, or the BD desert may not be so dry after all.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A52
- Title:
- NGC 2264, NGC 2547 and NGC 2516 stellar radii
- Short Name:
- J/A+A/586/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rapidly rotating, low-mass members of eclipsing binary systems have measured radii that are significantly larger than predicted by standard evolutionary models. It has been proposed that magnetic activity is responsible for this radius inflation. By estimating the radii of low-mass stars in three young clusters (NGC 2264, NGC 2547, NGC 2516, with ages of ~5, ~35 and ~140Myr respectively), we aim to establish whether similar radius inflation is seen in single, magnetically active stars. We use radial velocities from the Gaia-ESO Survey (GES) and published photometry to establish cluster membership and then combine GES measurements of projected equatorial velocities with published rotation periods to estimate the average radii for groups of fast-rotating cluster members as a function of their luminosity and age. The average radii are compared with the predictions of both standard evolutionary models and variants that include magnetic inhibition of convection and starspots.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/23
- Title:
- NUV and FUV measurements of planet host stars
- Short Name:
- J/ApJ/890/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for evidence of the cause of the exoplanet radius gap, i.e., the dearth of planets with radii near 1.8R_{Earth}_. If the cause were photoevaporation, the radius gap should trend with proxies for the early-life high-energy emission of the planet-hosting stars. If, alternatively, the cause were core-powered mass loss, no such trends should exist. Critically, spurious trends between the radius gap and stellar properties arise from an underlying correlation with instellation. After accounting for this underlying correlation, we find that no trends remain between the radius gap and stellar mass or present-day stellar activity as measured by near-UV emission. We dismiss the nondetection of a radius gap trend with near-UV emission because present-day near-UV emission is unlikely to trace early-life high-energy emission, but we provide a catalog of Galaxy Evolution Explorer near-UV and far-UV emission measurements for general use. We interpret the nondetection of a radius gap trend with stellar mass by simulating photoevaporation with mass-dependent evolution of stellar high-energy emission. The simulation produces an undetectable trend between the radius gap and stellar mass under realistic sources of error. We conclude that no evidence, from this analysis or others in the literature, currently exists that clearly favors either photoevaporation or core-powered mass loss as the primary cause of the exoplanet radius gap. However, repeating this analysis once the body of well-characterized <4R_{Earth}_ planets has roughly doubled could confirm or rule out photoevaporation.
- ID:
- ivo://CDS.VizieR/J/AJ/155/177
- Title:
- Obliquities of planetary & eclipsing binary systems
- Short Name:
- J/AJ/155/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The light curve of an eclipsing system shows anomalies whenever the eclipsing body passes in front of active regions on the eclipsed star. In some cases, the pattern of anomalies can be used to determine the obliquity {Psi} of the eclipsed star. Here we present a method for detecting and analyzing these patterns, based on a statistical test for correlations between the anomalies observed in a sequence of eclipses. Compared to previous methods, ours makes fewer assumptions and is easier to automate. We apply it to a sample of 64 stars with transiting planets and 24 eclipsing binaries for which precise space-based data are available, and for which there was either some indication of flux anomalies or a previously reported obliquity measurement. We were able to determine obliquities for 10 stars with hot Jupiters. In particular we found {Psi}~<10{deg} for Kepler-45, which is only the second M dwarf with a measured obliquity. The other eight cases are G and K stars with low obliquities. Among the eclipsing binaries, we were able to determine obliquities in eight cases, all of which are consistent with zero. Our results also reveal some common patterns of stellar activity for magnetically active G and K stars, including persistently active longitudes.
- ID:
- ivo://CDS.VizieR/J/ApJ/612/481
- Title:
- Optical brightness of {epsilon} Eri dust ring
- Short Name:
- J/ApJ/612/481
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The STIS CCD camera on the Hubble Space Telescope (HST) was used to take deep optical images near the K2 V main-sequence star {epsilon} Eridani in an attempt to find an optical counterpart of the dust ring previously imaged by submillimeter observations. Upper limits for the optical brightness of the dust ring are determined and discussed in the context of the scattered starlight expected from plausible dust models.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/209
- Title:
- Orbital nature of 81 ellipsoidal red giant binaries
- Short Name:
- J/ApJ/835/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we collect a sample of 81 ellipsoidal red giant binaries in the Large Magellanic Cloud (LMC), and we study their orbital natures individually and statistically. The sample contains 59 systems with circular orbits and 22 systems with eccentric orbits. We derive orbital solutions using the 2010 version of the Wilson-Devinney code (Wilson & Devinney 1971ApJ...166..605W ; Wilson 1979ApJ...234.1054W, 1990ApJ...356..613W ; Wilson+ 2009, J/ApJ/702/403). The sample is selection-bias corrected, and the orbital parameter distributions are compared to model predictions for the LMC and to observations in the solar vicinity. The masses of the red giant primaries are found to range from about 0.6 to 9M_{sun}_ with a peak at around 1.5M_{sun}_, in agreement with studies of the star formation history of the LMC, which find a burst of star formation beginning around 4 Gyr ago. The observed distribution of mass ratios q=m_2_/m_1_ is more consistent with the flat q distribution derived for the solar vicinity by Raghavan+ (2010, J/ApJS/190/1) than it is with the solar vicinity q distribution derived by Duquennoy & Mayor (1991A&A...248..485D). There is no evidence for an excess number of systems with equal mass components. We find that about 20% of the ellipsoidal binaries have eccentric orbits, twice the fraction estimated by Soszynski+ (2004, J/AcA/54/347). Our eccentricity evolution test shows that the existence of eccentric ellipsoidal red giant binaries on the upper parts of the red giant branch (RGB) can only be explained if tidal circularization rates are ~1/100 the rates given by the usual theory of tidal dissipation in convective stars.
