Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/4322
- Title:
- Orbital parameters of 341 new binaries
- Short Name:
- J/MNRAS/474/4322
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The orbital parameters of binaries at intermediate periods (10^2^-10^3^d) are difficult to measure with conventional methods and are very incomplete. We have undertaken a new survey, applying our pulsation timing method to Kepler light curves of 2224 main-sequence A/F stars and found 341 non-eclipsing binaries. We calculate the orbital parameters for 317 PB1 systems (single-pulsator binaries) and 24 PB2s (double-pulsators), tripling the number of intermediate-mass binaries with full orbital solutions. The method reaches down to small mass ratios q~0.02 and yields a highly homogeneous sample. We parametrize the mass-ratio distribution using both inversion and MCMC forward-modelling techniques, and find it to be skewed towards low-mass companions, peaking at q~0.2. While solar-type primaries exhibit a brown dwarf desert across short and intermediate periods, we find a small but statistically significant (2.6{sigma}) population of extreme-mass-ratio companions (q<0.1}) to our intermediate-mass primaries. Across periods of 100-1500d and at q>0.1, we measure the binary fraction of current A/F primaries to be 15.4%+/-1.4%, though we find that a large fraction of the companions (21%+/-6%) are white dwarfs in post-mass-transfer systems with primaries that are now blue stragglers, some of which are the progenitors of Type Ia supernovae, barium stars, symbiotics, and related phenomena. Excluding these white dwarfs, we determine the binary fraction of original A/F primaries to be 13.9%+/-2.1% over the same parameter space. Combining our measurements with those in the literature, we find the binary fraction across these periods is a constant 5% for primaries M_1_<0.8M_{sun}_, but then increases linearly with logM_1_, demonstrating that natal discs around more massive protostars M_1_>~1M_{sun}_} become increasingly more prone to fragmentation. Finally, we find the eccentricity distribution of the main-sequence pairs to be much less eccentric than the thermal distribution.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A78
- Title:
- Orphan stream RR Lyrae and non-variables
- Short Name:
- J/A+A/648/A78
- Date:
- 07 Dec 2021 13:05:58
- Publisher:
- CDS
- Description:
- We present a chemo-dynamical study of the Orphan stellar stream using a catalog of RR Lyrae pulsating variable stars for which photometric, astrometric, and spectroscopic data are available. Employing low-resolution spectra from the Sloan Digital Sky Survey (SDSS), we determined line-of-sight velocities for individual exposures and derived the systemic velocities of the RR Lyrae stars. In combination with the stars' spectroscopic metallicities and Gaia EDR3 astrometry, we investigated the northern part of the Orphan stream. In our probabilistic approach, we found 20 single mode RR Lyrae variables likely associated with the Orphan stream based on their positions, proper motions, and distances. The acquired sample permitted us to expand our search to nonvariable stars in the SDSS dataset, utilizing line-of-sight velocities determined by the SDSS. We found 54 additional nonvariable stars linked to the Orphan stream. The metallicity distribution for the identified red giant branch stars and blue horizontal branch stars is, on average, -2.13+/-0.05dex and -1.87+/-0.14dex, with dispersions of 0.23 and 0.43dex, respectively. The metallicity distribution of the RR Lyrae variables peaks at -1.80+/-0.06dex and a dispersion of 0.25dex. Using the collected stellar sample, we investigated a possible link between the ultra-faint dwarf galaxy Grus II and the Orphan stream. Based on their kinematics, we found that both the stream RR Lyrae and Grus II are on a prograde orbit with similar orbital properties, although the large uncertainties on the dynamical properties render an unambiguous claim of connection difficult. At the same time, the chemical analysis strongly weakens the connection between both. We argue that Grus II in combination with the Orphan stream would have to exhibit a strong inverse metallicity gradient, which to date has not been detected in any Local Group system.
- ID:
- ivo://CDS.VizieR/J/AJ/158/88
- Title:
- Oscillations in KOI-976's Kepler photometry
- Short Name:
- J/AJ/158/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the bulk system parameters of the seismically active, rapidly rotating {delta}-Scuti KOI-976 and constrain the orbit geometry of its transiting binary companion using a combined approach of asteroseismology and gravity-darkening light curve analysis. KOI-976 is a 1.62+/-0.2 M_{sun}_ star with a measured v sin(i) of 120+/-2 km/s and seismically induced variable signal that varies by ~0.6% of the star's total photometric brightness. We take advantage of the star's oblate shape and seismic activity to perform three measurements of its obliquity angle relative to the plane of the sky. We first apply a rotational splitting theory to the star's variable signal observed in short-cadence Kepler photometry to constrain KOI-976's obliquity angle, and then subtract off variability from that data set using the linear algorithm for significance reduction software LASR. We perform gravity-darkened fits to Kepler variability-subtracted short-cadence photometry and to Kepler's phase-folded long-cadence photometry to obtain two more measurements of the star's obliquity. We find that the binary system transits in a grazing configuration with measured obliquity values of 36{deg}+/-17{deg}, 46{deg}+/-16{deg}, and 43{deg}+/-20{deg}, respectively, for the three measurements. We perform these analyses as a way to demonstrate overcoming the challenges high-mass stars can present to transit light curve fitting and to prepare for the large number of exoplanets that the Transiting Exoplanet Survey Satellite will discover orbiting A/F stars.
- ID:
- ivo://CDS.VizieR/J/A+A/399/271
- Title:
- Oscillations in the PMS star V346 Ori
- Short Name:
- J/A+A/399/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of periodicities in the light curve of the Pre-Main Sequence (PMS) Herbig Ae star V346 Ori. We interpret variations in the light curve of the star as the superposition of at least two periodic signals that result from delta Scuti-type stellar oscillations. The computation of linear non-adiabatic radial pulsation models for PMS stars reproduces these periods for a 1.55M_{sun}_ star with Teff=7410K and log(L/L_{sun}_)=0.74 pulsating in the fundamental and in the second overtone. If our assumption of radial oscillations is indeed correct, the star's location on the HR diagram places it at a distance significantly smaller than that of the Orion star forming region, hence raising questions regarding the evolutionary status of V346 Ori. Observations with better time sampling and spanning a longer period of time are needed if the latter question is to be addressed fully.
- ID:
- ivo://CDS.VizieR/J/AJ/160/6
- Title:
- OSMOS & modspec RVs of 30 cataclysmic variables
- Short Name:
- J/AJ/160/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopy and orbital periods Porb for 30 apparently nonmagnetic cataclysmic binaries with periods below ~3hr, nearly all of which are dwarf novae, mostly of the SU Ursae Majoris subclass. We then turn to the evidence supporting the prediction that short-period dwarf novae evolve toward longer periods after passing through a minimum period-the "period bounce" phenomenon. Plotting data from the literature reveals that for superhump period excess {epsilon}=(P_sh_-P_orb_)/P_orb_ below ~0.015, the period appears to increase with decreasing {epsilon}, agreeing at least qualitatively with the predicted behavior. Next, motivated by the long (decadal) outburst intervals of the WZ Sagittae subclass of short-period dwarf novae, we ask whether there could be a sizable population of "lurkers"-systems that resemble dwarf novae at minimum light, but which do not outburst over accessible timescales (or at all) and therefore do not draw attention to themselves. By examining the outburst history of the Sloan Digital Sky Survey sample of Cataclysmic Variables (CVs), which were selected by color and not by outburst, we find that a large majority of the color-selected dwarf-nova-like objects have been observed to outburst, and we conclude that "lurkers," if they exist, are a relatively minor part of the CV population.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A13
- Title:
- Outburst of V1318 Cyg S (LkHa 225)
- Short Name:
- J/A+A/625/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young double star V1318 Cyg, which is associated with a small isolated star-forming region around HAeBe star BD+40 4124, has very unusual photometric and spectral behavior. We present results of photometric and spectroscopic observations in the optical range. We carried out BVRI CCD photometric observations of V1318 Cyg from 2015 Sept. to 2017 July. For the same period we acquired medium- and low-resolution spectra. Observations were performed with the 2.6 m telescope of the Byurakan observatory. We also analyzed the images of this field in IPHAS and other surveys. We analyze the historical light curve for V1318 Cyg and demonstrate that the southern component, V1318 Cyg S, after being rather bright in the 1970s (V~14 mag) started to lower its brightness and in 1990 became practically invisible in the optical. After its reappearance in the second half of the 1990s the star started to become very slowly brighter. Between 2006 and 2010 V1318 Cyg S started brightening more quickly, and in 2015 had become brighter by more than five magnitudes in visible light. Since this time V1318 Cyg S has remained at this maximum. Its spectrum shows little variability and consists of a mixture of emission and absorption lines, which has allowed for estimates of its spectral type as early Ae, with obvious evidence of matter outflow. We derive its current A(V)~7.2 and L=750L_(sun)_ thus confirming that V1318 Cyg S should belong to the Herbig Ae stars, making it, along with BD+40 4124 and V1686 Cyg, the third luminous young star in the group. It is very probable that we observe V1318 Cyg S near the pole and that the inclination of its dense and slow (<100km/s) outflow is low. The unusual variability and other features of V1318 Cyg S make it difficult to classify this star among known types of eruptive young stars. It could be an extreme, higher-mass example of an EXor, or an object of intermediate class between EXors and FUors, like V1647 Ori.
- ID:
- ivo://CDS.VizieR/J/AJ/155/53
- Title:
- Outbursts and disk variability in Be stars
- Short Name:
- J/AJ/155/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to study the growth and evolution of circumstellar disks around classical Be stars, we analyze optical time-series photometry from the KELT survey with simultaneous infrared and visible spectroscopy from the Apache Point Observatory Galactic Evolution Experiment survey and Be Star Spectra database for a sample of 160 Galactic classical Be stars. The systems studied here show variability including transitions from a diskless to a disk-possessing state (and vice versa), and persistent disks that vary in strength, being replenished at either regularly or irregularly occurring intervals. We detect disk-building events (outbursts) in the light curves of 28% of our sample. Outbursts are more commonly observed in early- (57%), compared to mid- (27%) and late-type (8%) systems. A given system may show anywhere between 0 and 40 individual outbursts in its light curve, with amplitudes ranging up to ~0.5 mag and event durations between ~2 and 1000 days. We study how both the photometry and spectroscopy change together during active episodes of disk growth or dissipation, revealing details about the evolution of the circumstellar environment. We demonstrate that photometric activity is linked to changes in the inner disk, and show that, at least in some cases, the disk growth process is asymmetrical. Observational evidence of Be star disks both growing and clearing from the inside out is presented. The duration of disk buildup and dissipation phases are measured for 70 outbursts, and we find that the average outburst takes about twice as long to dissipate as it does to build up in optical photometry. Our analysis hints that dissipation of the inner disk occurs relatively slowly for late-type Be stars.
- ID:
- ivo://CDS.VizieR/J/A+A/401/271
- Title:
- Outbursts in the Be star HR 2501
- Short Name:
- J/A+A/401/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Several mostly unrelated periods or time scales characterize the variability of HR 2501. This star is a new lambda Eri star with a period of 0.79187d. This star also exhibits a mid- to long-term variability of characteristic time ~500d, most probably a consequence of the recurrent outbursts of matter from the rapidly rotating Be star towards its disk.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/2216
- Title:
- Outer bulge O-rich Mira's JHKL photometry
- Short Name:
- J/MNRAS/455/2216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report periods and JHKL observations for 643 oxygen-rich Mira variables found in two outer bulge fields at b=-7{deg} and l=+/-8{deg} and combine these with data on 8057 inner bulge Miras from the OGLE, Macho and 2MASS surveys, which are concentrated closer to the Galactic centre. Distance moduli are estimated for all these stars. Evidence is given showing that the bulge structure is a function of age. The longer period Miras (LogP>2.6, age~5Gyr and younger) show clear evidence of a bar structure inclined to the line of sight in both the inner and outer regions. The distribution of the shorter period (metal-rich globular cluster age) Miras, appears spheroidal in the outer bulge. In the inner region these old stars are also distributed differently from the younger ones and possibly suggest a more complex structure. These data suggest a distance to the galactic centre R_0_, of 8.9kpc, with an estimated uncertainty of ~0.4kpc. The possible effect of helium enrichment on our conclusions is discussed.
