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601. Kapteyn's star spectroscopic measurements
ID:
ivo://CDS.VizieR/J/MNRAS/443/L89
Title:
Kapteyn's star spectroscopic measurements
Short Name:
J/MNRAS/443/L89
Date:
21 Oct 2021
Publisher:
CDS
Description:
Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this paper, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object to the Sun. The observations comprise archival and new HARPS, HIRES and PFS Doppler measurements. Two Doppler signals are detected at periods of 48 and 120 days using likelihood periodograms and a Bayesian analysis of the data. Using the same techniques, the activity indices and archival ASAS-3 photometry show evidence for low-level activity periodicities of the order of several hundred days. However, there are no significant correlations with the radial velocity variations on the same time-scales. The inclusion of planetary Keplerian signals in the model results in levels of correlated and excess white noise that are remarkably low compared to younger G, K and M dwarfs. We conclude that Kapteyn's star is most probably orbited by two super-Earth mass planets, one of which is orbiting in its circumstellar habitable zone, becoming the oldest potentially habitable planet known to date. The presence and long-term survival of a planetary system seems a remarkable feat given the peculiar origin and kinematic history of Kapteyn's star. The detection of super-Earth mass planets around halo stars provides important insights into planet-formation processes in the early days of the Milky Way.
602. Karle observations of V505 Sgr
ID:
ivo://CDS.VizieR/J/AJ/106/2058
Title:
Karle observations of V505 Sgr
Short Name:
J/AJ/106/2058
Date:
21 Oct 2021
Publisher:
CDS
Description:
V505 Sgr is a classical Algol system consisting of an A2 V primary and a G5 IV secondary that fills its Roche lobe. New times of minimum light are presented. The period of the eclipsing system (1.18287d) varies, due in part to an orbital light-time effect. A third component has been detected that orbits the eclipsing pair. This investigation uses the SIMPLEX algorithm [Kallrath & Linnell, ApJ, 313, 346 (1987)] and the Differential Correction code [Wilson, ApJ, 234, 1054 (1979)] to analyze two separate datasets. The results indicate the third component, an F8 V star, contributes about 5% of the light to the system. The minimum projected distance between the third component and the eclipsing pair is 37 AU. This implies an orbital period of about 105 years, a value that differs with the O-C data. The photometric solution, combined with recent spectroscopic data, yields R(1)=2.14R(Sun) and R(2)=2.24R(Sun) and M(1)=2.20M(Sun) and M(2)=1.15M(Sun).
603. K2 Campaign 9 added events
ID:
ivo://CDS.VizieR/J/PASP/128/L4401
Title:
K2 Campaign 9 added events
Short Name:
J/PASP/128/L4401
Date:
21 Oct 2021
Publisher:
CDS
Description:
K2's Campaign 9 (K2C9) will conduct a ~3.7 deg^2^ survey toward the Galactic bulge from 2016 April 22 through July 2 that will leverage the spatial separation between K2 and the Earth to facilitate measurement of the microlens parallax {pi}_E_ for >~170 microlensing events. These will include several that are planetary in nature as well as many short-timescale microlensing events, which are potentially indicative of free-floating planets (FFPs). These satellite parallax measurements will in turn allow for the direct measurement of the masses of and distances to the lensing systems. In this article we provide an overview of the K2C9 space- and ground-based microlensing survey. Specifically, we detail the demographic questions that can be addressed by this program, including the frequency of FFPs and the Galactic distribution of exoplanets, the observational parameters of K2C9, and the array of resources dedicated to concurrent observations. Finally, we outline the avenues through which the larger community can become involved, and generally encourage participation in K2C9, which constitutes an important pathfinding mission and community exercise in anticipation of WFIRST.
604. K2 Campaign 2: young disk-bearing stars in Sco & Oph
ID:
ivo://CDS.VizieR/J/AJ/156/71
Title:
K2 Campaign 2: young disk-bearing stars in Sco & Oph
Short Name:
J/AJ/156/71
Date:
21 Oct 2021
Publisher:
CDS
Description:
The K2 Mission has photometrically monitored thousands of stars at high precision and cadence in a series of ~80-day campaigns focused on sections of the ecliptic plane. During its second campaign, K2 targeted over 1000 young stellar objects (YSOs) in the ~1-3 Myr {rho} Ophiuchus and 5-10 Myr Upper Scorpius regions. From this set, we have carefully vetted photometry from WISE and Spitzer to identify those YSOs with infrared excess indicative of primordial circumstellar disks. We present here the resulting comprehensive sample of 288 young disk-bearing stars from B through M spectral types and analysis of their associated K2 light curves. Using statistics of periodicity and symmetry, we categorize each light curve into eight different variability classes, notably including "dippers" (fading events), "bursters" (brightening events), stochastic, and quasi-periodic types. Nearly all (96%) of disk-bearing YSOs are identified as variable at 30-minute cadence with the sub-1% precision of K2. Combining our variability classifications with (circum)stellar properties, we find that the bursters, stochastic sources, and the largest amplitude quasi-periodic stars have larger infrared colors, and hence stronger circumstellar disks. They also tend to have larger H{alpha} equivalent widths, indicative of higher accretion rates. The dippers, on the other hand, cluster toward moderate infrared colors and low H{alpha}. Using resolved disk observations, we further find that the latter favor high inclinations, except for a few notable exceptions with close to face-on disks. These observations support the idea that YSO time-domain properties are dependent on several factors, including accretion rate and view angle.
605. KELT 2006-2013 photometry of V409 Tau and AA Tau
ID:
ivo://CDS.VizieR/J/AJ/150/32
Title:
KELT 2006-2013 photometry of V409 Tau and AA Tau
Short Name:
J/AJ/150/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
AA Tau is a well studied young stellar object (YSO) that presents many of the photometric characteristics of a Classical T Tauri star (CTTS), including short-timescale stochastic variability attributed to spots and/or accretion as well as long-duration dimming events attributed to occultations by vertical features (e.g., warps) in its circumstellar disk. We present new photometric observations of AA Tau from the Kilodegree Extremely Little Telescope North (KELT-North) which reveal a deep, extended dimming event in 2011, which we show supports the interpretation by Bouvier et al. of an occultation by a high-density feature in the circumstellar disk located >8AU from the star. We also present KELT-North observations of V409 Tau, a relatively unstudied YSO also in Taurus-Auriga, showing short timescale erratic variability, along with two separate long and deep dimming events, one from 2009 January through late 2010 October, and the other from 2012 March until at least 2013 September. We interpret both dimming events to have lasted more than 600 days, each with a depth of ~1.4mag. From a spectral energy distribution analysis, we propose that V409 Tau is most likely surrounded by a circumstellar disk viewed nearly edge-on, and using Keplerian timescale arguments we interpret the deep dimmings of V409 Tau as occultations from one or more features within this disk >~10AU from the star. In both AA Tau and V409 Tau, the usual CTTS short-timescale variations associated with accretion processes close to the stars continue during the occultations, further supporting the distant occulting material interpretation. Like AA Tau, V409 Tau serves as a laboratory for studying the detailed structure of the protoplanetary environments of T Tauri disks, specifically disk structures that may be signposts of planet formation at many AU out in the disk. We also provide a table of all currently known disk-occulting young stars as a convenient reference for future work on such objects.
606. Kepler compact pulsator candidates
ID:
ivo://CDS.VizieR/J/MNRAS/414/2860
Title:
Kepler compact pulsator candidates
Short Name:
J/MNRAS/414/2860
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from the final 6 months of a survey to search for pulsations in white dwarfs (WDs) and hot subdwarf stars with the Kepler spacecraft. Spectroscopic observations are used to separate the objects into accurate classes, and we explore the physical parameters of the subdwarf B (sdB) stars and white dwarfs in the sample. From the Kepler photometry and our spectroscopic data, we find that the sample contains five new pulsators of the V1093 Her type, one AM CVn type cataclysmic variable and a number of other binary systems.
607. Kepler cycle 1 observations of low-mass stars
ID:
ivo://CDS.VizieR/J/AJ/143/4
Title:
Kepler cycle 1 observations of low-mass stars
Short Name:
J/AJ/143/4
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have analyzed Kepler light curves for 849 stars with Teff<=5200K from our Cycle 1 Guest Observer program. We identify six new eclipsing binaries, one of which has an orbital period of 29.91 days and two of which are probably W UMa variables. In addition, we identify a candidate "warm Jupiter" exoplanet. We further examine a subset of 670 sources for variability. Of these objects, 265 stars clearly show periodic variability that we assign to rotation of the low-mass star. At the photometric precision level provided by Kepler, 251 of our objects showed no evidence for variability. We were unable to determine periods for 154 variable objects. We find that 79% of stars with Teff<=5200K are variable. The rotation periods we derive for the periodic variables span the range 0.31days<=Prot<=126.5days. A considerable number of stars with rotation periods similar to the solar value show activity levels that are 100 times higher than the Sun.
608. Kepler Data Search
ID:
ivo://archive.stsci.edu/kepler
Title:
Kepler Data Search
Short Name:
Kepler CS
Date:
22 Jul 2020 21:17:20
Publisher:
Space Telescope Science Institute Archive
Description:
Launched in 2009, the Kepler Mission is surveying a region of our galaxy to determine what fraction of stars in our galaxy have planets and measure the size distribution of those exoplanets. Although Kepler completed its primary mission to determine the fraction of stars that have planets in 2013, it is continuing the search, using a more limited survey mode, under the new name K2. This service is the main Kepler data search.
609. Kepler Data Search
ID:
ivo://archive.stsci.edu/kepler_ktc
Title:
Kepler Data Search
Short Name:
KTC
Date:
22 Jul 2020 21:12:32
Publisher:
Space Telescope Science Institute Archive
Description:
This interface joins the Kepler Target Catalog (KTC) with other tables to allow users to access the Kepler data archive. Observed Kepler targets are included with their associated data set names. Since most of the Kepler light curve data is still proprietary, public data can be found by searching for release dates earlier than todays date.
610. Kepler {delta} Sct stars amplitude modulation
ID:
ivo://CDS.VizieR/J/MNRAS/460/1970
Title:
Kepler {delta} Sct stars amplitude modulation
Short Name:
J/MNRAS/460/1970
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a thorough search for amplitude modulation of pulsation modes in 983 {delta} Sct stars, which have effective temperatures between 6400<T_eff_<10000K in the Kepler Input Catalogue and were continuously observed by the Kepler Space Telescope for 4yr. We demonstrate the diversity in pulsational behaviour observed, in particular non-linearity, which is predicted for {delta} Sct stars. We analyse and discuss examples of {delta} Sct stars with constant amplitudes and phases; those that exhibit amplitude modulation caused by beating of close-frequency pulsation modes; those that exhibit pure amplitude modulation (with no associated phase variation); those that exhibit phase modulation caused by binarity; and those that exhibit amplitude modulation caused by non-linearity. Using models and examples of individual stars, we demonstrate that observations of the changes in amplitude and phase of pulsation modes can be used to distinguish among the different scenarios. We find that 603 {delta} Sct stars (61.3 per cent) exhibit at least one pulsation mode that varies significantly in amplitude over 4yr. Conversely, many {delta} Sct stars have constant pulsation amplitudes so short-length observations can be used to determine precise frequencies, amplitudes and phases for the most coherent and periodic {delta} Sct stars. It is shown that amplitude modulation is not restricted to a small region on the HR diagram, therefore not necessarily dependent on stellar parameters such as T_eff_, logg or [Fe/H]. Our catalogue of 983 {delta} Sct stars will be useful for comparisons to similar stars observed by K2 and TESS, because the length of the 4-yr Kepler data set will not be surpassed for some time.

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