- ID:
- ivo://CDS.VizieR/J/ApJ/812/158
- Title:
- Leo P RR Lyrae candidates & cumulative SFH
- Short Name:
- J/ApJ/812/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Leo P is a low-luminosity dwarf galaxy discovered through the blind HI Arecibo Legacy Fast ALFA survey. The HI and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62+/-0.15Mpc, based on the luminosity of the horizontal branch stars and 10 newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ~0.4Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the HII region is most likely an O7V or O8V spectral type, with a stellar mass >~25M_{sun}_. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ~10^-5^M_{sun}_/yr. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFHIs subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/141/53
- Title:
- Lick indices of type II Cepheid candidates
- Short Name:
- J/AJ/141/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present low-resolution spectra for variable stars in the Cepheid period range from the ROTSE-I Demonstration Project and the All Sky Automated Survey, some of which were previously identified as type II Cepheid candidates. We have derived effective temperatures, gravities, and metallicities from the spectra. Based on this, three types of variables were identified: Cepheid strip stars, cool stars that lie along the red subgiant and giant branch, and cool main-sequence stars. Many fewer type II Cepheids were found than expected and most have amplitudes less than 0.4mag. The cool variables include many likely binaries as well as intrinsic variables. Variation among the main-sequence stars is likely to be mostly due to binarity or stellar activity.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/122
- Title:
- Light curve analysis of 13 active stars
- Short Name:
- J/ApJ/838/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from light curve fits to the photometry of 13 chromospherically active stars, covering the time evolution of the rotational phase of their primary light curve minimum and the light curve amplitude.
- ID:
- ivo://CDS.VizieR/J/PASP/125/126
- Title:
- Light curve of CR Boo over 1990-2012
- Short Name:
- J/PASP/125/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two telescopes are used at the Morgan-Monroe Observatory of Indiana University for autonomous long-term photometric monitoring of stellar sources, mostly cataclysmic variable stars. The instrumentation is designed and implemented to be appropriate for multiyear automated monitoring. The capabilities and limitations of the equipment are described, along with accounts of the software, the reduction procedures, the motivations for the scientific programs, and the execution of the observing campaigns. Data on the AM CVn-type cataclysmic variable CR Boo are presented and discussed as an example of the kinds of light curves generated at this facility. The He-rich disk in CR Boo has SU UMa-type outburst behavior, with both superoutbursts and what appear to be dwarf nova outbursts. However, the light curve is quite irregular and displays a wide variety of unusual features such as switching among several superoutburst recurrence intervals, and having intervals of dwarf nova-like outbursts that seem to come and go. We discuss the likelihood that deterministic chaos is responsible for these irregularities.
- ID:
- ivo://CDS.VizieR/J/A+A/486/891
- Title:
- Light curve of EROS2 J005135-714459
- Short Name:
- J/A+A/486/891
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For seven years, the EROS-2 project obtained a mass of photometric data on variable stars. We present a peculiar Cepheid-like star, in the direction of the Small Magellanic Cloud, which demonstrates unusual photometric behaviour over a short time interval.
- ID:
- ivo://CDS.VizieR/J/A+A/468/637
- Title:
- Light curve of HD 172189
- Short Name:
- J/A+A/468/637
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The eclipsing delta-Scuti star HD 172189 is a probable member of the open cluster IC 4756 and a promising candidate target for the CoRoT mission. The detection of pulsation modes is the first step in the asteroseismological study of the star. Further, the calculation of the orbital parameters of the binary system allows us to make a dynamical determination of the mass of the star, which works as an important constraint to test and calibrate the asteroseismological models. We performed a detailed frequency analysis of 210 hours of photometric data of HD 172189 obtained from the STEPHI XIII campaign. We have identified six pulsation frequencies with a 99% confidence level and a seventh with a 65% confidence level, in the range between 100-300uHz. In addition, three eclipses were observed during the campaign, allowing us to improve the determination of the orbital period of the system.
- ID:
- ivo://CDS.VizieR/J/AJ/147/105
- Title:
- Light curve of HR Lyr over 1991-2012
- Short Name:
- J/AJ/147/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 22 yr light curve of HR Lyr, acquired with a typical cadence of 2-6 days, is examined for periodic and quasi-periodic variations. No persistent periodicities are revealed. Rather, the light curve variations often take the form of nearly linear rises and falls having typical e-folding times of about 100 days. Occasional ~0.6mag outbursts are also seen, with properties similar to those of small outbursts found in some nova-like cataclysmic variables. When the photometry is formed into yearly averages, a decline of 0.012+/-0.005mag/yr is apparent, consistent with the fading of irradiation-induced Mdot following the nova. The equivalent width of H{alpha} is tabulated at three epochs over the interval 1986-2008 in order to compare with a recent result for DK Lac in which H{alpha} was found to be fading 50 yr after the nova. However, our results for such a fading in HR Lyr are inconclusive.
- ID:
- ivo://CDS.VizieR/J/A+A/390/585
- Title:
- Light curve of R Cygni
- Short Name:
- J/A+A/390/585
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed analysis of the century long visual light curve of the long-period Mira star R Cygni is presented and discussed. The data were collected from the publicly available databases of the AFOEV, the BAAVSS and the VSOLJ. The full light curve consists of 26655 individual points obtained between 1901 and 2001. The light curve and its periodicity were analysed with help of the O-C diagram, Fourier analysis and time-frequency analysis. The results demonstrate the limitations of these linear methods. The next step was to investigate the possible presence of low-dimensional chaos in the light curve. For this, a smoothed and noise-filtered signal was created from the averaged data and with the help of time delay embedding, we have tried to reconstruct the attractor of the system. The main result is that R Cygni shows such period-doubling events that can be interpreted as being caused by a repetitive bifurcation of the chaotic attractor between a period 2T orbit and chaos. The switch between these two states occurs in a certain compact region of the phase space, where the light curve is characterized by ~1500-day long transients. The Lyapunov spectrum was computed for various embedding parameters confirming the chaotic attractor, although the exponents suffer from quite high uncertainty because of the applied approximation. Finally, the light curve is compared with a simple one zone model generated by a third-order differential equation which exhibits well-expressed period-doubling bifurcation. The strong resemblance is another argument for chaotic behaviour. Further studies should address the problem of global flow reconstruction, including the determination of the accurate Lyapunov exponents and dimension.
- ID:
- ivo://CDS.VizieR/J/AJ/147/10
- Title:
- Light curve of V794 Aql over 1990-2012
- Short Name:
- J/AJ/147/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 1990-2012 light curve of the nova-like (NL) cataclysmic variable V794 Aql is studied in order to characterize and better understand the transitions to and from the faint state, and the variations within the bright state. Investigations of earlier portions of this data had concluded that the transitions to the low state were much slower than the rapid recovery, giving a sawtoothed appearance to the light curve. This behavior differs from that of most other VY Scl stars, which led to an interpretation of the large amplitude sawtooths as being due to an accretion disk (AD) instability. However, more recent photometry strongly suggests that the bright state itself has transitions of 1-1.5mag, and that earlier studies had intermixed these bright state variations with the transitions to the low state. These newly recognized variations within the bright state sometimes appear as small outbursts (OBs) with typical amplitudes of 0.5-1.5mag and spacings of ~15-50days. The rise times of the OBs are 2-3 times faster than the decline times. We argue that the V794 Aql bright state variations are due to AD behavior similar to that seen in dwarf novae, but with varying degrees of stability. Similar regular small OBs have also been reported in other NL CVs, which we compare with V794 Aql. The true deep low states in V794 Aql appear to be normal, having transition speeds and shapes very similar to the transitions in other VY Scl stars.
- ID:
- ivo://CDS.VizieR/J/AJ/160/155
- Title:
- Light curve segments of 22 host stars with TESS
- Short Name:
- J/AJ/160/155
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- We present a systematic phase curve analysis of known transiting systems observed by the Transiting Exoplanet Survey Satellite (TESS) during year one of the primary mission. Using theoretical predictions for the amplitude of the planetary longitudinal atmospheric brightness modulation, stellar ellipsoidal distortion and Doppler boosting, as well as brightness considerations to select targets with likely detectable signals, we applied a uniform data processing and light-curve modeling framework to fit the full-orbit phase curves of 22 transiting systems with planet-mass or brown dwarf companions, including previously published systems. Statistically significant secondary eclipse depths and/or atmospheric brightness modulation amplitudes were measured for HIP65A, WASP-18, WASP-19, WASP-72, WASP-100, WASP-111, WASP-121, and WASP-122/KELT-14. For WASP-100b, we found marginal evidence that the brightest region of the atmosphere is shifted eastward away from the substellar point. We detected significant ellipsoidal distortion signals in the light curves of HIP65A, TOI-503, WASP-18, and WASP-30, with HIP65A, TOI-503 and WASP-18 also exhibiting Doppler boosting. The measured amplitudes of these signals agree with the predictions of theoretical models. Combining the optical secondary eclipse depths with previously published Spitzer 3.6 and 4.5{mu}m measurements, we derived dayside brightness temperatures and visible-light geometric albedos for a subset of the analyzed systems. We also calculated updated transit ephemerides combining the transit timings from the TESS light curves with previous literature values.
