We carry out a project to independently measure the distances of supernova remnants (SNRs) in the first quadrant of the Galaxy. In this project, red clump (RC) stars are used as standard candles and extinction probes to build the optical extinction (A V ) -distance(D) relation in each direction of extinction-known SNRs. The distances of 15 SNRs are well determined. Among them, the distances of G65.8-0.5, G66.0-0.0 and G67.6+0.9 are given for the first time. We also obtain 32 upper/lower limits of distances, and the distances to G5.7-0.1, G15.1-1.6, G28.8+1.5 and G78.2+2.1 are constrained. Most of the distances measured by the RC method are consistent with previous results. The RC method provides an independent access to the distances of SNRs.

Binaries play key roles in determining stellar parameters and exploring stellar evolution models. We build a catalog of 88 eclipsing binaries with spectroscopic information, taking advantage of observations from both the Large Sky Area Multi-Object fiber Spectroscopic Telescope and the Palomar Transient Factory surveys. A software pipeline is constructed to identify binary candidates by examining their light curves. The orbital periods of binaries are derived from the Lomb-Scargle method. The key distinguishing features of eclipsing binaries are recognized by a new filter, Flat Test. We classify the eclipsing binaries by applying a Fourier analysis on the light curves. Among all the binary stars, 13 binaries are identified as eclipsing binaries for the first time. The catalog contains the following information: the position, primary eclipsing magnitude and time, eclipsing depth, the number of photometry and radial velocity observations, largest radial velocity difference, binary type, the effective temperature of the observable star T eff , and surface gravity of the observable star log g. The false-positive probability is calculated by using both a Monte Carlo simulation and real data from the Sloan Digital Sky Survey Stripe 82 Standard Catalog. The binaries in the catalog are mostly with a period of less than one day. The period distribution shows a 0.22 day cutoff, which is consistent with the low probability of an eclipsing binary rotating with such a period.

A precise transit ephemeris serves as the premise for follow-up exoplanet observations. The transit timing variation (TTV) as an important scientific output potentially reveals planetary orbital evolution. We compare transit timings of 262 hot Jupiters from TESS with the archival ephemeris and find 31 of them having significant TESS timing offsets, among which WASP-161b shows the most significant offset of -203.7±4.1 minutes. The median value of these offsets is 17.8 minutes, equivalent to 3.4 σ. We evaluate the timing precision of TESS Objects of Interest (TOI) which provides the TESS timings in this work. The evaluation is applied by deriving TESS transit timing from a self-generated pipeline. We refine and update the previous ephemeris, based on precise timing (uncertainty within 1 minute) and a long timing baseline (∼ 10 years). Our refined ephemeris gives the transit timing at a median precision of 1.11 minutes until 2025 and 1.86 minutes until 2030. All the targets with timing offset larger than 10σ present earlier timings than the prediction, which cannot be due to underestimated ephemeris uncertainty, apsidal precision, or Rømer effect as those effects should be unsigned. We regard the timing offsets mainly originating from the underestimated ephemeris uncertainty. For some particular targets, timing offsets are due to tidal dissipation. We find a tentative TTV of XO-3b (timing offset > 10 σ) yielding a period derivative of 5.8±0.9×10 −9 . The TTV may be explained by tidal dissipation. Our result provides direct observational support for the tidal dissipation of XO-3b, reported in previous work.

We present a novel, iterative method using an empirical Bayesian approach for modeling the limb-darkened WASP-121b transit from the TESS light curve. Our method is motivated by the need to improve R p /R * estimates for exoplanet atmosphere modeling and is particularly effective with the limb-darkening (LD) quadratic law requiring no prior central value from stellar atmospheric models. With the nonlinear LD law, the method has all the advantages of not needing atmospheric models but does not converge. The iterative method gives a different R p /R * for WASP-121b at a significance level of 1σ when compared with existing noniterative methods. To assess the origins and implications of this difference, we generate and analyze light curves with known values of the LD coefficients (LDCs). We find that noniterative modeling with LDC priors from stellar atmospheric models results in an inconsistent R p /R * at a 1.5σ level when the known LDC values are the same as those previously found when modeling real data by the iterative method. In contrast, the LDC values from the iterative modeling yield the correct value of R p /R * to within 0.25σ. For more general cases with different known inputs, Monte Carlo simulations show that the iterative method obtains unbiased LDCs and correct R p /R * to within a significance level of 0.3σ. Biased LDC priors can cause biased LDC posteriors and lead to bias in the R p /R * of up to 0.82%, 2.5σ for the quadratic law and 0.32%, 1.0σ for the nonlinear law. Our improvement in R p /R * estimation is important when analyzing exoplanet atmospheres.

Double radio lobes are generally believed to be produced by active nuclei of elliptical galaxies. However, several double-lobed radio sources have been solidly found to be associated with spiral galaxies. By cross-matching ~9 x 10^5 spiral galaxies selected from the SDSS DR8 data with the full 1.4GHz radio source catalogs of NVSS and FIRST, we identify three new spiral galaxies: J0326-0623, J1110+0321 and J1134+3046 that produce double radio lobes, in addition to five double-lobed spirals previously known. By combining the newly discovered and all the other known cases in literature, we find that most of these spiral galaxies are located in a galaxy group or a poor cluster, in which the environment is denser than in the field, and about half of them are the central brightest galaxies in their parent system. We therefore suggest that the environment is one of the key factors for a spiral to produce double radio lobes.