- ID:
- ivo://CDS.VizieR/J/A+A/365/545
- Title:
- Remnant disks around main-sequence stars IR flux
- Short Name:
- J/A+A/365/545
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometric ISO 60 and 170{mu}m measurements, complemented by some IRAS data at 60{mu}m, of a sample of 84 nearby main-sequence stars of spectral class A, F, G and K in order to determine the incidence of dust disks around such main-sequence stars. Fifty stars were detected at 60{mu}m; 36 of these emit a flux expected from their photosphere while 14 emit significantly more. The excess emission we attribute to a circumstellar disk like the ones around Vega and {beta} Pictoris. Thirty four stars were not detected at all; the expected photospheric flux, however, is so close to the detection limit that the stars cannot have an excess stronger than the photospheric flux density at 60{mu}m. Of the stars younger than 400Myr one in two has a disk; for the older stars this is true for only one in ten. We conclude that most stars arrive on the main sequence surrounded by a disk; this disk then decays in about 400Myr. Because (i) the dust particles disappear and must be replenished on a much shorter time scale and (ii) the collision of planetesimals is a good source of new dust, we suggest that the rapid decay of the disks is caused by the destruction and escape of planetesimals. We suggest that the dissipation of the disk is related to the heavy bombardment phase in our Solar System. Whether all stars arrive on the main sequence surrounded by a disk cannot be established: some very young stars do not have a disk. And not all stars destroy their disk in a similar way: some stars as old as the Sun still have significant disks.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/416/125
- Title:
- RI photometry in alpha Per and Pleiades
- Short Name:
- J/A+A/416/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photographic astrometry (proper motions and accurate positions), photometry (in the photographic R and I passbands) and membership probabilities for high probability proper motion members of the clusters Alpha Persei and The Pleiades are presented, along with cross-identifications with names from previously known members in the compilation of Prosser & Stauffer (The Stauffer & Prosser Open Cluster Catalogue, priv.comm.) and their corresponding proper motion membership probabilities according to our study. The SuperCOSMOS facility at the Royal Observatory Edinburgh has (using plates from the United Kingdom Schmidt Telescope) produced complete southern sky surveys in BJ, R and I with an additional second epoch R survey. These surveys are now publicly available (Hambly et al. 2001MNRAS.326.1279H). The scanning program has now moved on to the northern hemisphere, using film and glass copies of plates taken by the Oschin Schmidt Telescope on Mount Palomar, California. These data will soon be publicly available.
- ID:
- ivo://CDS.VizieR/J/ApJS/94/749
- Title:
- RI photometry of cool dwarfs
- Short Name:
- J/ApJS/94/749
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosity function at the end of the main sequence is determined from V, R, and I data taken by the CCD/Transit Instrument (CTI), a dedicated telescope surveying an 8.25' wide strip of sky centered at {delta}=+28{deg}, thus sampling Galactic latitudes of +90{deg} down to -35{deg}. A selection of 133 objects chosen via R-I and V-I colors has been observed spectroscopically at the 4.5m Multiple Mirror Telescope to assess contributions by giants and subdwarfs and to verify that the reddest targets are objects of extremely late spectral class. Eighteen dwarfs of type M6 or later have been discovered, with the latest being of type M8.5. Data used for the determination of the luminosity function cover 27.3{deg}^2^ down to a completeness limit of R=19.0.
- ID:
- ivo://CDS.VizieR/J/PASP/118/659
- Title:
- RI photometry of 2MASS late M and L dwarfs
- Short Name:
- J/PASP/118/659
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report R and I band observations for 201 late M and L dwarfs selected on the basis of Two Micron All Sky Survey (Cat. II/246) JHKs and photographic red colors, made with a telescope of modest aperture. It is shown that deep surveys covering these red bands can provide data sets that complement JHKs, permitting a fairly good photometric classification system for L dwarfs. Due primarily to the disappearance of strong TiO opacities, R-I reaches a maximum at late M type and turns blueward for subtypes M9 to about L3. Apart from a small plateau at L0-L2, the I-Ks color remains as a monotonic measure of spectral type or temperature over this range, and likewise for M dwarfs. For late L types, both colors probably get redder again, although the accuracy of our data and number of objects do not give us robust conclusions by L6-L8. It is also interesting to look at the dispersions of the IJKs bands at a given spectral type. It is widely believed that this dispersion is caused by object-to-object variations in the amount, location, or other properties of dust or clouds. We find a moderately larger spread for the J-Ks color than for I-J.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A115
- Title:
- Rotating massive MS stars evolutionary models
- Short Name:
- J/A+A/530/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a dense grid of evolutionary tracks and isochrones of rotating massive main-sequence stars. We provide three grids with different initial compositions tailored to compare with early OB stars in the Small and Large Magellanic Clouds and in the Galaxy. Each grid covers masses ranging from 5 to 60M_{sun}_ and initial rotation rates between 0 and about 600km/s. To calibrate our models we used the results of the VLT-FLAMES Survey of Massive Stars. We determine the amount of convective overshooting by using the observed drop in rotation rates for stars with surface gravities logg<3.2 to determine the width of the main sequence. We calibrate the efficiency of rotationally induced mixing using the nitrogen abundance determinations for B stars in the Large Magellanic cloud. We describe and provide evolutionary tracks and the evolution of the central and surface abundances.
- ID:
- ivo://CDS.VizieR/J/AJ/156/275
- Title:
- Rotational evolution of young, binary M dwarfs
- Short Name:
- J/AJ/156/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed K2 light curves for more than 3000 low-mass stars in the ~8 Myr old Upper Sco association, the ~125 Myr age Pleiades open cluster, and the ~700 Myr old Hyades and Praesepe open clusters to determine stellar rotation rates. Many of these K2 targets show two distinct periods, and for the lowest-mass stars in these clusters, virtually all of these systems with two periods are photometric binaries. The most likely explanation is that we are detecting the rotation periods for both components of these binaries. We explore the evolution of the rotation rate in both components of photometric binaries relative to one another and to nonphotometric binary stars. In Upper Sco and the Pleiades, these low-mass binary stars have periods that are much shorter on average and much closer to each other than would be true if drawn at random from the M dwarf single stars. In Upper Sco, this difference correlates strongly with the presence or absence of infrared excesses due to primordial circumstellar disks-the single-star population includes many stars with disks, and their rotation periods are distinctively longer on average than their binary star cousins of the same mass. By Praesepe age, the significance of the difference in rotation rate between the single and binary low-mass M dwarf stars is much less, suggesting that angular momentum loss from winds for fully convective zero-age main-sequence stars erases memory of the rotation rate dichotomy for binary and single very low mass stars at later ages.
- ID:
- ivo://CDS.VizieR/J/A+A/568/L12
- Title:
- Rotational frequency splitting in Sun-like stars
- Short Name:
- J/A+A/568/L12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Asteroseismology offers the prospect of constraining differential rotation in Sun-like stars. Here we have identified six high signal-to-noise main-sequence Sun-like stars in the Kepler field, which all have visible signs of rotational splitting of their p-mode frequencies. For each star, we extract the rotational frequency splitting and inclination angle from separate mode sets (adjacent modes with l=2, 0, and 1) spanning the p-mode envelope. We use a Markov chain Monte Carlo method to obtain the best fit and errors associated with each parameter. We are able to make independent measurements of rotational splittings of ~8 radial orders for each star. For all six stars, the measured splittings are consistent with uniform rotation, allowing us to exclude large radial differential rotation. This work opens the possibility of constraining internal rotation of Sun-like stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/704/975
- Title:
- Rotational velocities for M dwarfs
- Short Name:
- J/ApJ/704/975
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic rotation velocities (vsini) for 56 M dwarf stars using high-resolution Hobby-Eberly Telescope High Resolution Spectrograph red spectroscopy. In addition, we have also determined photometric effective temperatures, masses, and metallicities ([Fe/H]) for some stars observed here and in the literature where we could acquire accurate parallax measurements and relevant photometry. We have increased the number of known vsini values for mid M stars by around 80% and can confirm a weakly increasing rotation velocity with decreasing effective temperature. Our sample of vsini is peak at low velocities (~3km/s). We find a change in the rotational velocity distribution between early M and late M stars, which is likely due to the changing field topology between partially and fully convective stars. There is also a possible further change in the rotational distribution toward the late M dwarfs where dust begins to play a role in the stellar atmospheres. We also link vsini to age and show how it can be used to provide mid-M star age limits. When all literature velocities for M dwarfs are added to our sample, there are 198 with vsini<=10km/s and 124 in the mid-to-late M star regime (M3.0-M9.5) where measuring precision optical radial velocities is difficult. In addition, we also search the spectra for any significant Half emission or absorption. Forty three percent were found to exhibit such emission and could represent young, active objects with high levels of radial-velocity noise. We acquired two epochs of spectra for the star GJ1253 spread by almost one month and the Half profile changed from showing no clear signs of emission, to exhibiting a clear emission peak. Four stars in our sample appear to be low-mass binaries (GJ1080, GJ3129, Gl802, and LHS3080), with both GJ3129 and Gl802 exhibiting double Half emission features. The tables presented here will aid any future M star planet search target selection to extract stars with low vsini.
- ID:
- ivo://CDS.VizieR/J/AJ/143/93
- Title:
- Rotational velocities in early-M stars
- Short Name:
- J/AJ/143/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of rotation and chromospheric activity in a sample of 334 M dwarfs of spectral types M0-M4.5 populating the parameter space around the boundary to full convection. We obtain high-resolution optical spectra for 206 targets and determine projected rotational velocity, vsin i, and H{alpha} emission. The data are combined with measurements of vsin i in field stars of the same spectral type from the literature. Our sample adds 157 new rotation measurements to the existing literature and almost doubles the sample of available vsin i. The final sample provides a statistically meaningful picture of rotation and activity at the transition to full convection in the solar neighborhood. Finally, we compare projected rotational velocities of 33 stars to rotational periods derived from photometry in the literature and determine inclinations for a few of them.
- ID:
- ivo://CDS.VizieR/J/other/NatAs/4.03
- Title:
- Rotation and activity across HR diagram
- Short Name:
- J/other/NatAs/4.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present mean chromospheric CaII H and K activity levels and rotation periods, derived from the Mount Wilson Observatory HK Project time series. These are combined with theoretically calculated convective turnover times to derive Rossby numbers and connect the rotational scaling of chromospheric activity of main sequence and post-main sequence stars with each other.
