arXiv subjects

Qunfeng Jiang

Publications and source records attributed to Qunfeng Jiang.

4 recordsLinked to original sources

arXiv2026

An Outer Giant Excites and Constrains the Orbit of $\pi$ Mensae d

The nearby $\pi$ Mensae system contains the eccentric giant planet b on a 5.7 yr orbit, the 6.27 day transiting sub-Neptune c, and a candidate planet d on a 123 day orbit between them. Published estimates place the eccentricity of d between approximately 0.2 and 0.4. We reanalyze 772 published velocities with three-Keplerian fits and explore three-dimensional b-d dynamics with N-body integrations. The high-eccentricity solution persists when the phase or apsidal prior is widened; exact importance reweighting to a population-informed Beta eccentricity prior gives $e_{d}=0.378^{+0.050}_{-0.049}$. In 20 kyr integrations, 84.5% of configurations near the prograde and retrograde coplanar endpoints survive, compared with 21.3% across $60^\circ \leq I_{bd} < 120^\circ$; stellar collisions dominate the failures. Secular forcing by b moves 53 of 62 one-Myr survivors initialized with $e_{d} \leq 0.1$ into $0.3 \leq e_{d} \leq 0.5$. Representative b+d configurations remain viable for 100 Myr, whereas controls with c and general relativity retain fewer systems. The outer giant can therefore excite the observed eccentricity of d while constraining its viable orbit toward prograde or retrograde near-coplanar configurations.

astro-ph.EP↗

arXiv2026

Does Cumulative XUV Unify the Neptunian Desert?

The architecture of close-in planetary systems includes a conspicuous scarcity of Neptune-size worlds, known as the Neptunian desert. The deficit spans roughly $2$--$10\,R_{\oplus}$ at orbital periods of a few days. Atmospheric erosion by stellar X-rays and extreme-ultraviolet (XUV) radiation may shape its lower boundary, while the strong mass dependence of stellar activity complicates comparisons across spectral type. We test whether standardized cumulative XUV exposure places the lower boundaries around M-dwarf and F-, G-, and K-type (FGK) hosts on a common scale. The analysis uses 1850 Kepler and TESS planets; the primary fit contains 677 planets with $2.24 < R_p/R_{\oplus} < 7.48$. For a 5 Gyr median-rotation history, the fitted M-minus-FGK offset changes from $-1.06$ dex in present bolometric flux to $-0.37$ dex in cumulative XUV. This corresponds to $65.4\%$ compression in the point estimate and a host-bootstrap median of $73.4\%$. The convergence persists under host deletion, survey separation, unit weighting, alternative boundary definitions, and nine stellar age--rotation histories. A common-period null produces a median compression of $59.1\%$ in 2000 realizations, with $38.9\%$ at least as convergent as the data; an absolute offset-reduction statistic gives $p=0.522$. Cumulative XUV is a substantially more uniform empirical coordinate than present bolometric flux. Comparable uniformity follows from mapping a common period edge through Keplerian geometry and mass-dependent stellar activity, leaving a universal XUV erosion threshold unconstrained by the present sample.

astro-ph.EP↗

arXiv2026

Stellar tidal systematics in apsidal-motion searches for circumbinary planets: CH Ind and SW CMa

Thornton et al. (2026) reported 27 non-transiting circumbinary-planet candidates from excess apsidal motion in TESS eclipsing-binary timings. The classical stellar contribution is sensitive to target-specific radii, apsidal constants $k_2$, and rotation. We re-evaluate two evolved, double-lined eclipsing binaries in that sample: the pulsating system CH Ind and the Am system SW CMa. Their component masses and radii have been measured in dedicated binary studies, allowing the stellar contribution to be calculated directly. For CH Ind, six independent TESS sector nodes give $\dot{\omega}_{\rm obs}=1.82^{+0.99}_{-0.94}\times10^{-3}\ {\rm deg\,cycle^{-1}}$, while a coeval fit to the measured binary components predicts $\dot{\omega}_{\rm stars}=2.05^{+0.43}_{-0.34}\times10^{-3}\ {\rm deg\,cycle^{-1}}$. For SW CMa, its measured dimensions raise the classical term by a factor of about 16; the published target-specific prediction, $0.670\pm0.020\times10^{-3}\ {\rm deg\,cycle^{-1}}$, agrees with the observed $0.690\pm0.050\times10^{-3}\ {\rm deg\,cycle^{-1}}$. Neither system shows a significant excess prograde component. The comparison shows that candidates from a bulk search require target-specific binary models before a third-body interpretation is assigned.

astro-ph.EP↗

arXiv2021

Constraining the Konoplya-Rezzolla-Zhidenko deformation parameters II: limits from stellar-mass black hole X-ray data

Astrophysical black holes are thought to be the Kerr black holes predicted by general relativity, but macroscopic deviations from the Kerr solution can be expected from a number of scenarios involving new physics. In Paper I, we studied the reflection features in NuSTAR and XMM-Newton spectra of the supermassive black hole at the center of the galaxy MCG-06-30-15 and we constrained a set of deformation parameters proposed by Konoplya, Rezzolla & Zhidenko (Phys. Rev. D93, 064015, 2016). In the present work, we analyze the X-ray data of a stellar-mass black hole within the same theoretical framework in order to probe a different curvature regime. We consider a NuSTAR observation of the X-ray binary EXO 1846-031 during its outburst in 2019. As in the case of Paper I, all our fits are consistent with the Kerr black hole hypothesis, but some deformation parameters cannot be constrained well.

astro-ph.HE↗