Abstract We present the optical photometric variability of 32 planet-hosting M dwarfs within 25 pc over timescales of months to decades. The primary goal of this project—A Trail to Life Around Stars ...(ATLAS)—is to follow the trail to life by revealing nearby M dwarfs with planets that are also “quiet,” which may make them more amiable to habitability. There are 69 reported exoplanets orbiting the 32 stars discussed here, providing a rich sample of worlds for which environmental evaluations are needed. We examine the optical flux environments of these planets over month-long timescales for 23 stars observed by TESS, and find that 17 vary by less than 1% (∼11 mmag). All 32 stars are being observed at the CTIO/SMARTS 0.9 m telescope, with a median duration of 19.1 yr of optical photometric data in the VRI bands. We find over these extended timescales that six stars show optical flux variations less than 2%, 25 vary from 2% to 6% (∼22–67 mmag), and only one, Proxima Centauri, varies by more than 6%. Overall, LHS 1678 exhibits the lowest optical variability levels measured over all timescales examined, thereby providing one of the most stable photometric environments among the planets reported around M dwarfs within 25 pc. More than 600 of the nearest M dwarfs are being observed at the 0.9 m telescope in the RECONS program that began in 1999, and many more planet hosts will undoubtedly be revealed, providing more destinations to be added to the ATLAS sample in the future.
We present the optical photometric variability of 32 planet-hosting M dwarfs within 25 parsecs over timescales of months to decades. The primary goal of this project, ATLAS -- A Trail to Life Around ...Stars, is to follow the trail to life by revealing nearby M dwarfs with planets that are also "quiet", which may make them more amiable to habitability. There are 69 reported exoplanets orbiting the 32 stars discussed here, providing a rich sample of worlds for which environmental evaluations are needed. We examine the optical flux environments of these planets over month-long timescales for 23 stars observed by TESS, and find that 17 vary by less than 1% (\(\sim\)11 mmag). All 32 stars are being observed at the CTIO/SMARTS 0.9 m, with a median duration of 19.1 years of optical photometric data in the \(VRI\) bands. We find over these extended timescales that six stars show optical flux variations less than 2%, 25 vary from 2--6% (\(\sim\)22-67 mmag), and only one, Proxima Centauri, varies by more than 6%. Overall, LHS 1678 exhibits the lowest optical variability levels measured over all timescales examined, thereby providing one of the most stable photometric environments among planets reported around M dwarfs within 25 parsecs. More than 600 of the nearest M dwarfs are being observed at the 0.9 m in the RECONS program that began in 1999, and many more planet hosts will undoubtedly be revealed, providing more destinations to be added to the ATLAS sample in the future.
We present new multi-broadband transit photometry of HD 189733b obtained at the Wyoming Infrared Observatory. Using an ensemble of five-band Sloan filter observations across multiple transits we have ...created an "ultra-low" resolution transmission spectrum to discern the nature of the exoplanet atmosphere. The observations were taken over three transit events and total 108 u', 120 g', 120 r', 110 i', and 116 z' images with an average exposure cadence of seven minutes for an entire series. The analysis was performed with a Markov-Chain Monte-Carlo method assisted by a Gaussian processes regression model. We find the apparent planet radius to increase from 0.154 +0.000920-0.00096 R* at z'-band to 0.157 +0.00074-0.00078 R* at u'-band. Whether this apparent radius implies an enhanced Rayleigh scattering or clear or grey planet atmosphere is highly dependent on stellar spot modeling assumptions, but our results are consistent with the literature for HD 189733b. This set of observations demonstrates the ability of our 2.3-m ground-based observatory to measure atmospheres of large exoplanets.
The Kilodegree Extremely Little Telescope (KELT) project has been conducting a photometric survey for transiting planets orbiting bright stars for over ten years. The KELT images have a pixel scale ...of ~23"/pixel---very similar to that of NASA's Transiting Exoplanet Survey Satellite (TESS)---as well as a large point spread function, and the KELT reduction pipeline uses a weighted photometric aperture with radius 3'. At this angular scale, multiple stars are typically blended in the photometric apertures. In order to identify false positives and confirm transiting exoplanets, we have assembled a follow-up network (KELT-FUN) to conduct imaging with higher spatial resolution, cadence, and photometric precision than the KELT telescopes, as well as spectroscopic observations of the candidate host stars. The KELT-FUN team has followed-up over 1,600 planet candidates since 2011, resulting in more than 20 planet discoveries. Excluding ~450 false alarms of non-astrophysical origin (i.e., instrumental noise or systematics), we present an all-sky catalog of the 1,128 bright stars (6<V<10) that show transit-like features in the KELT light curves, but which were subsequently determined to be astrophysical false positives (FPs) after photometric and/or spectroscopic follow-up observations. The KELT-FUN team continues to pursue KELT and other planet candidates and will eventually follow up certain classes of TESS candidates. The KELT FP catalog will help minimize the duplication of follow-up observations by current and future transit surveys such as TESS.
•Amorphous nanosilica isprepared from rice husk (agriculture waste) by employing cost-effective and environment-friendly method.•TheXRD analysis reveals the small crystallite size. The SEM, TEM and ...SAED patterns support the XRD pattern analysis.•Nanosilica exhibits excellent optical properties in the visible range and band gap found to be 3.35 eV, which is slightly higher than its bulk value.•The amorphous nanosilica is found to be a diamagnetic material. The magnetic polymers are found to be ferrimagnetic nature.•The magnetic hysteresis loops of amorphous nanosilica/Ferrite/PVDF composites reveal that these materials can be used as polymer magnet.
Amorphous nanosilica (SiO2) was prepared from rice husk by a cost-effective and environment-friendly method. Magnetic nanocomposite has been prepared by using injection molding equipment from amorphous nanosilica, ferrites, and PVDF. The XRD pattern analysis reveals the amorphous nature of the silica. The particle size of SiO2 was observed from the SEM and TEM analysis and found to be very small, which suggests the formation of amorphous nanosilica from the rice husk. FTIR spectra show the absorption peaks of SiOiSi (silanol) functional group. The photoluminescence spectrum reveals the broad excitation of radiation in the visible region. A characteristics peak in UV–Vis absorption spectra occurs at 365 nm, and the optical band gap was found to be 3.35 eV. Magnetic study shows the diamagnetic nature of amorphous nanosilica. The nanocomposite of amorphous nano silica-Ferrite-PVDF exhibits ferromagnetic nature due to the presence of ferrite in the nanocomposite. The magnetic hysteresis loop of nanocomposite reveals that the materials can be used as polymer magnet. The physical properties of amorphous nansilica and its composite with PVDF and ferrite have been explored in the present article. The present study may help to use prepared nanosilica materials in technological applications.
Background: Measurement of regional cerebral oxygen saturation (rSO_2) is a safe, noninvasive, and portable optical method that can be used to monitor activity within the cortical areas of the human ...brain. Making use of specific wavelengths of light, near‑infrared spectroscopy (NIRS) provides measurements of oxygenated hemoglobin (Hb) and deoxygenated Hb that is in direct relation with hemodynamic changes in the brain. Aim: The aim of this study was to compare the changes in rSO_2 at different time points between propofol and sevoflurane anesthesia during gynecological laparoscopic surgery. After approval by the institutional ethics committee, written informed consent was taken from all eligible patients. Methods: This randomized clinical study was conducted in a gynecology operation theater complex. Thirty‑four patients aged between 18 and 60 years categorized between the American Society of Anesthesiologists (ASA) class I I and II who are scheduled for gynecological laparoscopic surgery under general anesthesia were randomized into two groups with 17 patients in each group. The Group 1 patients receive sevoflurane anesthesia and Group 2 patients receive total intravenous anesthesia using an infusion of propofol. The rSO_2 values were continuously monitored using NIRS. The bispectral index target range during maintenance was 40-50. Results: The sevoflurane group showed significantly higher rSO_2 values than the propofol group in gynecological laparoscopic surgery. Conclusion: It can be inferred that the sevoflurane group showed significantly higher rSO_2 values than the propofol group in gynecological laparoscopic surgery not only during pneumoperitoneum in the Trendelenburg position but also after desufflation of the abdomen in the neutral position (supine).
Management of groundwater resources needs continuous and efficient monitoring networks. Sparsity of in situ measurements both spatially and temporally creates hindrance in framing groundwater ...management policies. Remotely sensed data can be a possible alternative. GRACE satellites can trace groundwater changes globally. Moreover, gridded rainfall (RF) and soil moisture (SM) data can shed some light on the hydrologic system. The present study attempts to use GRACE, RF and SM data at a local scale to predict groundwater level. Ground referencing of satellite data were done by using three machine learning techniques- Support Vector Regression (SVR), Random Forest Method (RFM) and Gradient Boosting Mechanism (GBM). The performance of the developed methodology was tested on a part of the Indo-Gangetic basin. The analyses were carried out for nine GRACE pixels to identify relationship between individual well measurements and satellite-derived data. These nine pixels are classified on the basis of presence or absence of hydrological features. Pixels with the presence of perennial streams showed reasonably good results. However, pixels with wells located mostly near the stream gave relatively poorer predictions. These results help in identifying wells which can reasonably represent the regional shallow groundwater dynamics.
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