- ID:
- ivo://CDS.VizieR/J/AJ/149/194
- Title:
- Differential BVR light curves of DK Cyg
- Short Name:
- J/AJ/149/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD photometry is presented for the hot overcontact binary DK Cyg together with reasonable explanations for the light and period variations. Historical light and velocity curves from 1962 to 2012 were simultaneously analyzed with the Wilson-Devinney (W-D) synthesis code. The brightness disturbances were satisfactorily modeled by applying a magnetic cool spot on the primary star. Based on 261 times of minimum light that include 116 new timings and span more than 87 years, a period study reveals that the orbital period has varied due to a periodic oscillation superimposed on an upward parabola. The period and semi-amplitude of the modulation are about 78.1years and 0.0037days, respectively. This detail is interpreted as a light-travel-time effect due to a circumbinary companion with a minimum mass of M_3_=0.065M_{sun}_, within the theoretical limit of ~0.07M_{sun}_ for a brown dwarf star. The observed period increase at a fractional rate of +2.74x10^-10^ is in excellent agreement with that calculated from our W-D synthesis. Mass transfer from the secondary to the primary component is mainly responsible for the secular period change. We examined the evolutionary status of the DK Cyg system from the absolute dimensions.
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- ID:
- ivo://CDS.VizieR/J/AJ/145/100
- Title:
- Differential BVR light curves of EP And
- Short Name:
- J/AJ/145/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new long-term CCD photometry for EP And acquired during the period 2007-2012. The light curves display total eclipses at primary minima and season-to-season light variability. Our synthesis for all available light curves indicates that the eclipsing pair is a W-type overcontact binary with parameters of q=2.578, i=83.3{deg}, {Delta}T=27K, f=28%, and l_3_=2%-3%. The asymmetric light curves in 2007 were satisfactorily modeled by a cool spot on either of the eclipsing components from a magnetic dynamo. Including our 95 timing measurements, a total of 414 times of minimum light spanning about 82yr was used for a period study. A detailed analysis of the eclipse timing diagram revealed that the orbital period of EP And has varied as a combination of an upward-opening parabola and two periodic variations, with cycle lengths of P_3_=44.6yr and P_4_=1.834yr and semi-amplitudes of K_3_=0.0100days and K_4_=0.0039days, respectively. The observed period increase at a fractional rate of +1.39*10^-10^ is in excellent agreement with that calculated from the W-D code and can be plausibly explained by some combination of mass transfer from the primary to the secondary star and angular momentum loss due to magnetic braking. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of a third and fourth component with projected masses of M_3_=0.25M_{sun}_ and M_4_=0.90M_{sun}_. The more massive companion could be revealed using high-resolution spectroscopic data extending over the course of a few years and could also be a binary itself. It is possible that the circumbinary objects may have played an important role in the formation and evolution of the eclipsing pair, which would cause it to have a short initial orbital period and thus evolve into an overcontact configuration by angular momentum loss.
- ID:
- ivo://CDS.VizieR/J/AJ/147/91
- Title:
- Differential BVR light curves of V407 Peg
- Short Name:
- J/AJ/147/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New multiband CCD photometry is presented for V407 Peg; the R_C_ light curves are the first ever compiled. Our light curves, displaying a flat bottom at secondary minimum and an O'Connell effect, were simultaneously analyzed with the radial velocity (RV) curves given by Rucinski et al. The light changes of the system are best modeled using both a hot spot on the secondary star and a third light. The model also represents historical light curves. All available minimum epochs, including our six timing measurements, have been examined and they indicate that the eclipse timing variation is mainly caused by light asymmetries due to the spot activity detected in the light-curve synthesis. The hot spot may be produced as a result of the impact of the gas stream from the primary star. Our light and velocity solutions indicate that V407 Peg is a totally eclipsing A-type overcontact binary with values of q=0.251, i=87.6{deg}, {Delta}T=496K, f=61%, and l_3_=11~16%. Individual masses and radii of both components are determined to be M_1_=1.72M_{sun}_, M_2_=0.43M_{sun}_, R_1_=2.15R_{sun}_, and R_2_=1.21R_{sun}_. These results are very different from previous ones, which is probably caused by the light curves with distorted and inclined eclipses used in those other analyses. The fact that there are no objects optically related to the system and that the seasonal RVs show a large discrepancy in systemic velocity indicates that the third light source most likely arises from a tertiary component orbiting the eclipsing pair.
- ID:
- ivo://CDS.VizieR/J/AJ/146/113
- Title:
- Differential griz photometry of HATS-3
- Short Name:
- J/AJ/146/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery by the HATSouth survey of HATS-3b, a transiting extrasolar planet orbiting a V=12.4 F dwarf star. HATS-3b has a period of P=3.5479days, mass of M_p_=1.07M_J_, and radius of R_p_=1.38R _J_. Given the radius of the planet, the brightness of the host star, and the stellar rotational velocity (vsini=9.0km/s), this system will make an interesting target for future observations to measure the Rossiter-McLaughlin effect and determine its spin-orbit alignment. We detail the low-/medium-resolution reconnaissance spectroscopy that we are now using to deal with large numbers of transiting planet candidates produced by the HATSouth survey. We show that this important step in discovering planets produces logg and T_eff_ parameters at a precision suitable for efficient candidate vetting, as well as efficiently identifying stellar mass eclipsing binaries with radial velocity semi-amplitudes as low as 1km/s.
- ID:
- ivo://CDS.VizieR/J/AJ/147/144
- Title:
- Differential griz photometry of HATS-5
- Short Name:
- J/AJ/147/144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of HATS-5b, a transiting hot Saturn orbiting a G-type star, by the HATSouth survey. HATS-5b has a mass of M_p_{approx}0.24M_J_, radius of R_p_{approx}0.91R_J_, and transits its host star with a period of P{approx}4.7634days. The radius of HATS-5b is consistent with both theoretical and empirical models. The host star has a V-band magnitude of 12.6, mass of 0.94M_{sun}_, and radius of 0.87R_{sun}_. The relatively high scale height of HATS-5b and the bright, photometrically quiet host star make this planet a favorable target for future transmission spectroscopy follow-up observations. We reexamine the correlations in radius, equilibrium temperature, and metallicity of the close-in gas giants and find hot Jupiter-mass planets to exhibit the strongest dependence between radius and equilibrium temperature. We find no significant dependence in radius and metallicity for the close-in gas giant population.
- ID:
- ivo://CDS.VizieR/J/AJ/137/226
- Title:
- Differential light curves of TV Tri
- Short Name:
- J/AJ/137/226
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry for the Algol-type binary RV Trianguli observed during three nights in 2007 November. The photometric solution was derived from our VR observations by using the Wilson-Devinny program. The results indicated that RV Tri is a semidetached binary with a mass ratio of q=0.306+/-0.005. Based on 236 light minimum times, the orbital period change of RV Tri was analyzed in detail.
- ID:
- ivo://CDS.VizieR/J/A+A/476/881
- Title:
- Differential photometry of FK Com
- Short Name:
- J/A+A/476/881
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the present work we publish new photometric observations of the very active single giant, FK Com for the time period between the 1st of January 2002 and the 8th of July 2004. The observations have been carried out with three different automatic photometric telescopes: Phoenix 10, Wolfgang and Amadeus, all located in Arizona, USA. Observations contain measurements at the following bands: Johnson U, B and V, Cousins I and Stroemgren b and y. The observations are differential photometry in respect to the primary comparison star HD 117567.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2026
- Title:
- Differential photometry of HD 8801
- Short Name:
- J/AJ/129/2026
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have discovered the first example of a star pulsating intrinsically with both {gamma} Doradus and {delta} Scuti frequencies. HD 8801 is an Am metallic-line star that appears to be single. Since the vast majority of Am stars are members of binary systems with periods less than 1000 days and also do not pulsate, HD 8801 possesses a very unusual, if not unique, combination of physical properties. Our photometry, acquired with an automatic telescope at Fairborn Observatory, resolves six independent pulsation periods between 0.048 and 0.404 days. The two longest periods lie within the range of {gamma} Dor variables, while the four shorter periods are within the range of {delta} Sct stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/2263
- Title:
- Differential photometry of the EB* HATS551-027
- Short Name:
- J/MNRAS/451/2263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery and characterization of a new M-dwarf binary, with component masses and radii of M_1_=0.244_-0.003_^+0.003^M_{sun}_, R_1_=0.261_-0.009_^+0.006^R_{sun}_, M_2_=0.179_-0.001_^+0.002^M_{sun}_, R_2_=0.218_-0.011_^+0.007^R_{sun}_, and orbital period of ~4.1 d. The M-dwarf binary HATS551-027 (LP 837-20) was identified as an eclipsing binary by the HATSouth survey, and characterized by a series of high-precision photometric observations of the eclipse events, and spectroscopic determinations of the atmospheric parameters and radial velocity orbits. HATS551-027 is one of few systems with both stellar components lying in the fully convective regime of very low mass stars, and can serve as a test for stellar interior models. The radius of HATS551-027A is consistent with models to 1{sigma}, whilst HATS551-027B is inflated by 9 percent at 2{sigma} significance. We measure the effective temperatures for the two stellar components to be T_eff,1_=3190+/-100K and T_eff,2_=2990+/-110K; both are slightly cooler than theoretical models predict, but consistent with other M-dwarfs of similar masses that have previously been studied. We also measure significant H{alpha} emission from both components of the binary system, and discuss this in the context of the correlation between stellar activity and the discrepancies between the observed and model temperatures.
- ID:
- ivo://CDS.VizieR/J/AJ/153/211
- Title:
- Differential photometry of the F-subgiant HAT-P-67
- Short Name:
- J/AJ/153/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of HAT-P-67b, which is a hot-Saturn transiting a rapidly rotating F-subgiant. HAT-P-67b has a radius of R_p_=2.085_-0.071_^+0.096^ R_J_, and orbites a M_*_=1.642_-0.072_^+0.155^ M_{sun}_, R_*_=2.546_-0.084_^+0.099^ R_{sun}_ host star in a ~4.81 day period orbit. We place an upper limit on the mass of the planet via radial velocity measurements to be M_p_<0.59 M_J_, and a lower limit of >0.056 M_J_ by limitations on Roche lobe overflow. Despite being a subgiant, the host star still exhibits relatively rapid rotation, with a projected rotational velocity of vsini_*_=35.8+/-1.1 km/s, which makes it difficult to precisely determine the mass of the planet using radial velocities. We validated HAT-P-67b via two Doppler tomographic detections of the planetary transit, which eliminate potential eclipsing binary blend scenarios. The Doppler tomographic observations also confirm that HAT-P-67b has an orbit that is aligned to within 12{deg}, in projection, with the spin of its host star. HAT-P-67b receives strong UV irradiation and is among one of the lowest density planets known, which makes it a good candidate for future UV transit observations in the search for an extended hydrogen exosphere.
