- ID:
- ivo://CDS.VizieR/J/MNRAS/463/1831
- Title:
- M67 Kepler/K2 variable stars
- Short Name:
- J/MNRAS/463/1831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the third paper of this series we continue the exploitation of Kepler/K2 data in dense stellar fields using our PSF-based method. This work is focused on a ~720-arcmin^2^ region centred on the Solar-metallicity and Solar-age open cluster M 67. We extracted light curves for all detectable sources in the Kepler channels 13 and 14, adopting our technique based on the usage of a high-angular-resolution input catalogue and target-neighbour subtraction. We detrended light curves for systematic errors, and searched for variables and exoplanets using several tools. We found 451 variables, of which 299 are new detection. Three planetary candidates were detected by our pipeline in this field. Raw and detrended light curves, catalogues, and K2 stacked images used in this work will be released to the community.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/V/69
- Title:
- MK, UBV Time and Latitude Stars
- Short Name:
- V/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- MK spectral classifications are given for 591 stars which are used for time and latitude observations at Mizusawa and Washington. The classifications in the MK system were made by slit spectrograms of dispersion 73 A/mm at H-gamma which were taken with the 91cm reflector at the Okayama Astrophysical Observatory. Photometric observations in UBV were made with the 1-meter reflector at the Flagstaff Station of U.S. Naval Observatory.
- ID:
- ivo://CDS.VizieR/J/ApJS/154/623
- Title:
- M31 Long Period Variables : Photometry
- Short Name:
- J/ApJS/154/623
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A significant fraction of the disk of M31 has been surveyed for long-period variable stars. We report the results, including near-infrared photometry of almost 2000 variables, and light curves in the i band. The period-luminosity relation suggests that most of the variables are asymptotic giant branch stars, and their luminosity function can be understood in terms of mass-loss rates, which increase with increasing luminosity on the giant branch, and star formation rates, which were a few times higher a billion years ago in M31 than they are today. We see some supergiant long-period variables, but somewhat fewer than expected based on their frequency in M33, and confined to the ring of star formation in M31 seen in the IRAS and 2MASS surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/157/231
- Title:
- MLSDSS-GaiaDR2 sample of M and L dwarfs
- Short Name:
- J/AJ/157/231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 74216 M and L dwarfs constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 (Cat. I/345) to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for late-M and L dwarfs. We also provide relations between Gaia colors and absolute magnitudes with spectral type and conclude that (G-G_RP_) has the tightest relation to spectral type for M and L dwarfs. In addition, we study magnetic activity as a function of position on the color-magnitude diagram, finding that H{alpha} magnetically active stars have, on average, redder colors and/or brighter magnitudes than inactive stars. This effect cannot be explained by youth alone and might indicate that active stars are magnetically inflated, binaries, and/or high metallicity. Moreover, we find that vertical velocity and vertical action dispersion are correlated with H{alpha} emission, confirming that these two parameters are age indicators. We also find that stars below the main sequence have high tangential velocity, which is consistent with a low metallicity and old population of stars that belong to the halo or thick disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/810/158
- Title:
- M,L,T dwarfs fundamental parameters and SEDs
- Short Name:
- J/ApJ/810/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine optical, near-infrared, and mid-infrared spectra and photometry to construct expanded spectral energy distributions for 145 field age (>500 Myr) and 53 young (lower age estimate <500 Myr) ultracool dwarfs (M6-T9). This range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. A subsample of 29 objects have well constrained ages as probable members of a nearby young moving group. We use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities (L_bol_) and radius estimates from evolutionary models give semi-empirical effective temperatures (T_eff_) for the full range of young and field age late-M, L, and T dwarfs. We construct age-sensitive relationships of luminosity, temperature, and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as T_eff_, surface gravity, and clouds on spectral morphology. We report bolometric corrections in J for both field age and young objects and find differences of up to a magnitude for late-L dwarfs. Our correction in Ks shows a larger dispersion but not necessarily a different relationship for young and field age sequences. We also characterize the NIR-MIR reddening of low gravity L dwarfs and identify a systematically cooler T_eff_ of up to 300 K from field age objects of the same spectral type and 400 K cooler from field age objects of the same M_H_ magnitude.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A119
- Title:
- M31 luminous red nova AT 2019zhd photometry
- Short Name:
- J/A+A/646/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the follow-up campaign of the luminous red nova (LRN) AT 2019zhd, the third event of this class observed in M 31. The object was followed by several sky surveys for about five months before the outburst, during which it showed a slow luminosity rise. In this phase, the absolute magnitude ranged from M_r_=-2.8+/-0.2mag to M_r_=-5.6+/-0.1mag. Then, over a four to five day period, AT 2019zhd experienced a major brightening, reaching a peak of M_r_=-9.61+/-0.08mag and an optical luminosity of 1.4x10^39^erg/s. After a fast decline, the light curve settled onto a short-duration plateau in the red bands. Although less pronounced, this feature is reminiscent of the second red maximum observed in other LRNe. This phase was followed by a rapid linear decline in all bands. At maximum, the spectra show a blue continuum with prominent Balmer emission lines. The post-maximum spectra show a much redder continuum, resembling that of an intermediate-type star. In this phase, Halpha becomes very weak, Hbeta is no longer detectable, and a forest of narrow absorption metal lines now dominate the spectrum. The latest spectra, obtained during the post-plateau decline, show a very red continuum (Teff~3000K) with broad molecular bands of TiO, similar to those of M-type stars. The long-lasting, slow photometric rise observed before the peak resembles that of LRN V1309 Sco, which was interpreted as the signature of the common-envelope ejection. The subsequent outburst is likely due to the gas outflow following a stellar merging event. The inspection of archival HST images taken 22 years before the LRN discovery reveals a faint red source (M_F555W_=0.21+/-0.14mag, with F555W-F814W=2.96+/-0.12mag) at the position of AT 2019zhd, which is the most likely quiescent precursor. The source is consistent with expectations for a binary system including a predominant M5-type star.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A133
- Title:
- M45, M44 and M67 flare stars
- Short Name:
- J/A+A/622/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The presence and strength of a stellar magnetic field and activity is rooted in a star's fundamental parameters such as mass and age. Can flares serve as an accurate stellar "clock"? To explore if we can quantify an activity-age relation in the form of a flaring-age relation, we measured trends in the flaring rates and energies for stars with different masses and ages. We investigated the time- domain photometry provided by Kepler's follow-up mission K2 and searched for flares in three solar metallicity open clusters with well-known ages, M45 (0.125Gyr), M44 (0.63Gyr), and M67 (4.3Gyr). We updated and employed the automated flare finding and analysis pipeline Appaloosa, originally designed for Kepler. We introduced a synthetic flare injection and recovery subroutine to ascribe detection and energy recovery rates for flares in a broad energy range for each light curve. We collected a sample of 1761 stars, mostly late-K to mid-M dwarfs and found 751 flare candidates with energies ranging from 4x10^32^erg to 6x10^34^erg, of which 596 belong to M45, 155 to M44, and none to M67. We find that flaring activity depends both on Teff, and age. But all flare frequency distributions have similar slopes with alpha from 2.0 to 2.4, supporting a universal flare generation process. We discuss implications for the physical conditions under which flares occur, and how the sample's metallicity and multiplicity affect our results.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A51
- Title:
- 3mm maps of 4 transition disks
- Short Name:
- J/A+A/564/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transition disks are protoplanetary disks with inner depleted dust cavities and excellent candidates to investigate the dust evolution under the existence of a pressure bump. A pressure bump at the outer edge of the cavity allows dust grains from the outer regions to stop their rapid inward migration towards the star and efficiently grow to millimetre sizes. Dynamical interactions with planet(s) have been one of the most exciting theories to explain the clearing of the inner disk. We look for evidence of the presence of millimetre dust particles in transition disks by measuring their spectral index {alpha}_mm_ with new and available photometric data. We investigate the influence of the size of the dust depleted cavity on the disk integrated millimetre spectral index. We present the 3-millimetre (100GHz) photometric observations carried out with Plateau de Bure Interferometer of four transition disks: LkH{alpha} 330, UX Tau A, LRLL 31, and LRLL 67. We use available values of their fluxes at 345GHz to calculate their spectral index, as well as the spectral index for a sample of twenty transition disks. We compare the observations with two kind of models. In the first set of models, we consider coagulation and fragmentation of dust in a disk in which a cavity is formed by a massive planet located at different positions. The second set of models assumes disks with truncated inner parts at different radius and with power-law dust size distributions, where the maximum size of grains is calculated considering turbulence as the source of destructive collisions. We show that the integrated spectral index is higher for transition disks (TD) than for regular protoplanetary disks (PD) with mean values of <{alpha}_mm_^TD^>=2.70+/-0.13 and <{alpha}_mm_^PD^>=2.20+/-0.07 respectively. For transition disks, the probability that the measured spectral index is positively correlated with the cavity radius is 95%. High angular resolution imaging of transition disks is needed to distinguish between the dust trapping scenario and the truncated disk case.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/55
- Title:
- MMT hypervelocity star survey. II.
- Short Name:
- J/ApJ/751/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of five new unbound hypervelocity stars (HVSs) in the outer Milky Way halo. Using a conservative estimate of Galactic escape velocity, our targeted spectroscopic survey has now identified 16 unbound HVSs as well as a comparable number of HVSs ejected on bound trajectories. A Galactic center origin for the HVSs is supported by their unbound velocities, the observed number of unbound stars, their stellar nature, their ejection time distribution, and their Galactic latitude and longitude distribution. Other proposed origins for the unbound HVSs, such as runaway ejections from the disk or dwarf galaxy tidal debris, cannot be reconciled with the observations. An intriguing result is the spatial anisotropy of HVSs on the sky, which possibly reflects an anisotropic potential in the central 10-100pc region of the Galaxy. Further progress requires measurement of the spatial distribution of HVSs over the southern sky. Our survey also identifies seven B supergiants associated with known star-forming galaxies; the absence of B supergiants elsewhere in the survey implies there are no new star-forming galaxies in our survey footprint to a depth of 1-2Mpc.
- ID:
- ivo://CDS.VizieR/J/ApJ/849/L36
- Title:
- mm-wave size study of ALMA submm galaxies
- Short Name:
- J/ApJ/849/L36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the study of the far-infrared (IR) sizes of submillimeter galaxies (SMGs) in relation to their dust-obscured star formation rate (SFR) and active galactic nuclei (AGN) presence, determined using mid-IR photometry. We determined the millimeter-wave ({lambda}_obs_=1100um) sizes of 69 Atacama Large Millimeter/submillimeter Array (ALMA)-identified SMGs, selected with >=10{sigma} confidence on ALMA images (F_1100um_=1.7-7.4mJy). We found that all of the SMGs are located above an avoidance region in the size-flux plane, as expected by the Eddington limit for star formation. In order to understand what drives the different millimeter-wave sizes in SMGs, we investigated the relation between millimeter-wave size and AGN fraction for 25 of our SMGs at z=1-3. We found that the SMGs for which the mid-IR emission is dominated by star formation or AGN have extended millimeter-sizes, with respective median R_c,e_=1.6_-0.21_^+0.34^ and 1.5_-0.24_^+0.93^kpc. Instead, the SMGs for which the mid-IR emission corresponds to star-forming/AGN composites have more compact millimeter-wave sizes, with median R_c,e_=1.0_-0.20_^+0.20^kpc. The relation between millimeter-wave size and AGN fraction suggests that this size may be related to the evolutionary stage of the SMG. The very compact sizes for composite star-forming/AGN systems could be explained by supermassive black holes growing rapidly during the SMG coalescing, star-formation phase.
