arXiv subjects

Jan-Niklas Pippert

Publications and source records attributed to Jan-Niklas Pippert.

7 recordsLinked to original sources

arXiv2026

Discovery of an extremely narrow trail-like feature crossing the Veil Supernova Remnant in deep amateur observations

We report the discovery of an extremely narrow and highly collimated gaseous trail-like structure crossing the eastern region of the Veil Nebula (Cygnus Loop). The feature was first identified in deep narrow-band H-alpha images obtained by a small telescope and was confirmed in more than a dozen publicly available amateur and professional images in the last two decades, rejecting the possibility of being an artifact (e.g., artificial satellite trail). To characterize its structural and luminosity parameters, we applied a model-fitting code originally developed for the analysis of extragalactic stellar tidal streams. The structure is only detected in H-alpha emission, with no detectable counterpart in [SII] or in visible observations, and shows an almost constant brightness and width along its extension. It exhibits a surface brightness of 22.32+/- 0.13 H-alpha mag arcsec^2. Model fitting yields a median width of 1.63", which corresponds to a physical scale of approximately 1200 UA, assuming it is at the same distance (2400 light-years) as the Veil Nebula remnant. We discuss several potential scenarios for the origin of this feature: a Herbig-Haro-like jet, the trail of a high-velocity object, or a non-radiative shock associated with the supernova remnant. We rule out the Herbig-Haro scenario, given the absence of a driving stellar source and the lack of [S II] emission. A high-velocity-object wake cannot yet be excluded, particularly if the driver is a compact remnant, but the absence of an obvious source or bow-shock apex and the extremely small, nearly constant width of the structure make a normal runaway-star origin unlikely. The current evidence instead favours a Balmer-dominated non-radiative shock associated with the Cygnus Loop, generated as the SNR blast wave encounters a dense material layer or magnetic structure viewed nearly edge-on.

astro-ph.GA↗

arXiv2026

TOI-2147 b and TOI-6019 b: Two eccentric warm Jupiters detected and characterized with TESS and MaHPS

The population of Jupiter-sized exoplanets with orbital periods between 10 and 200 days (WJs) exhibits a broad range of orbital eccentricities and system architectures, suggesting a diversity of formation and migration pathways. In this work, we report the detection and characterization of two new eccentric WJs, TOI-2147 b and TOI-6019 b, initially identified as planet candidates by the Transiting Exoplanet Survey Satellite (TESS). We combined TESS photometry with ground-based follow-up observations, including multiband photometry from LCOGT and MuSCAT2, high-angular-resolution speckle imaging, and high-precision radial velocity measurements from the high-resolution Manfred Hirt Planet Finder Spectrograph (MaHPS). Using these data, we were able to confirm the planetary nature of both candidates. TOI-2147 b has a radius of $10.5 \pm 0.3\,\mathrm{R}_\oplus$ and a mass of $116 \pm 22\,\mathrm{M}_\oplus$. It orbits its slightly metal-poor ($\mathrm{[Fe/H]} = -0.29^{+0.07}_{-0.08}$) G-type host star on an eccentric orbit ($e = 0.29 \pm 0.07$) with a period of 26.2 days. TOI-6019 b has a radius of $12.3 \pm 0.3\,\mathrm{R}_\oplus$ and a mass of $149 \pm 15\,\mathrm{M}_\oplus$. It orbits a slightly evolved, solar-metallicity G-type sub-giant with a period of 14.5 days on a significantly eccentric orbit ($e = 0.48^{+0.05}_{-0.04}$). Both planets have bulk densities below that of Jupiter, indicating mildly inflated radii, with interior structure modeling using GASTLI. This suggests that tidal heating from the nonzero eccentricities likely contributes to this inflation and disfavors large atmospheric metal enrichment. No significant signals from additional companions were detected in the radial velocity time series or transit timing variations. Together with the elevated eccentricities, this is consistent with a high-eccentricity migration origin for both systems.

astro-ph.EP↗

arXiv2025

Galaxy Luminosity Function of the Coma Cluster from Deep $u'-g'-r'$ Wendelstein Imaging Data

We derive the $g'$ band galaxy luminosity function (GLF) of quenched resolved galaxies in the Coma cluster from a deep-imaging survey with $\approx1.5\,\mathrm{deg^2}$ around the cluster center. The dataset comprises deep $u'$-, $g'$-, and $r'$-band data obtained with the Wendelstein Wide Field Imager on the $2.1\,$m Fraunhofer Wendelstein Telescope reaching median $3\sigma$ surface brightness limits in 10" $\times$ 10" boxes of $\mathrm{ (30.0\,u',\,\,29.6\,g',\,\,28.7\,r')\,mag\,arcsec^{-2}}$. We measure structural parameters across a large dynamic range in galaxy brightness ($-24.5\,g'\,\mathrm{mag} \lessapprox M\lessapprox-11.3\,g'\,\mathrm{mag}$), from the brightest cluster galaxy to low-luminosity dwarfs, including compact dwarf galaxies and ultra-diffuse galaxies. We automatically identify more than 6000 cluster member candidates based on their membership on the quiescent sequence in the $u'-g'$ versus $g'-r'$ color-color diagram. The structural parameters of bright galaxies are obtained via isophotal modeling, and fully automated parametric image fitting for faint ones. Injection-recovery tests and two identically analyzed reference fields provide statistical corrections for completeness and contamination, yielding a representative GLF that reliably probes the faint end and may serve as a benchmark for future studies. We report a best-fit single Schechter $g'$ band GLF with $M^\star=-21.71^{+0.26}_{-0.29}\,g'\,\mathrm{mag}$, $\log_{10}(\phi^\star\,[\mathrm{deg}^{-2}\,\mathrm{mag}^{-1}])=1.355^{+0.076}_{-0.079}$, and a comparatively steep faint-end slope $\alpha=-1.444^{+0.015}_{-0.015}$. A directly matched comparison with the Coma counterpart in SLOW, a constrained cosmological simulation using CDM, shows broad agreement between the GLFs down to the simulation limit of $M = -15.5\,g'\,\mathrm{mag}$, despite a deficit of bright galaxies.

astro-ph.GA↗

arXiv2025

Living the stream: Properties and progenitors of tidal shells and streams around galaxies from Magneticum

Stellar shells and streams are remnants of satellite galaxies visible around galaxies. Advances in low-surface-brightness observations and increasing resolution of cosmological simulations now allow investigating the properties and origin of these features. The metallicity, age, and velocity dispersion of shells and streams are investigated to infer their progenitor galaxies properties. We employed the hydrodynamical cosmological simulations Magneticum Pathfinder to extract these properties and identify the progenitors of the shells and streams. We compared to observational results from surveys and individual galaxies, matching and testing the methodology used in observations. Mock observations of shells and streams agree well with observational data regarding their morphology and spatial distribution. We find that both types of features are associated with localized depressions in stellar velocity dispersion compared to the surrounding regions. They are not as clearly distinct in metallicity and ages, though overall shells and more metal rich and streams are younger. We confirm results from idealized models that shells form commonly from radial major mergers but also through minor mergers, while streams usually form from minor mergers on circular orbits. We do not find the widths of streams to correlate with the half-mass radii of their progenitors, but the progenitors follow the mass-metallicity relation. On average, the masses measured for shells and streams approximately corresponds to 20% of the progenitor mass. We introduce a class of star-forming streams, which originate from in-situ star formation rather than the disruption of a satellite galaxy. Measuring stellar population properties of shells and streams provides the means to reconstruct the progenitor properties, and especially distinguish those streams that are not made through the disruption of a galaxy but formed in-situ.

astro-ph.GA↗

arXiv2025

Modeling Tidal Streams and Tidal Tails around Galaxies Using Deep Wendelstein Imaging Data

From the $\Lambda$ cold dark matter paradigm it is expected that galaxies merge and grow in their environments. These processes form various tidal features depending on the merger mass ratio, orbital parameters, and gas richness. We inspected 170 $g'$-band Abell cluster observations from the 2.1m Fraunhofer-Teleskop Wendelstein and identify 111 of such features from which we select nine streams and five tails. A fast and innovative technique was developed for determining their photometric properties. The model is a Gaussian, including higher-order moments to describe the light profile in slices perpendicular to the elongation direction. From these models, FWHM apertures are generated. The method was developed, tested, and applied on the selected features and corresponding $g$- and $r$-band data from the Legacy Survey DR10. Regarding the novel modeling approach, we can measure surface and total brightnesses with precisions of 4% and 7%, respectively. Mean stream width precision, which also translates to the mean $R_\mathrm{e}$ along the feature is on average within 3% uncertainty. The measured streams have on average a surface brightness of $\sim26.25$ $g'$ mag arcsec$^{-2}$ and are dimmer than the tails in our sample ($\sim25.14$ $g'$ mag arcsec$^{-2}$). We infer that the progenitors of our streams can come from dwarfs, early-type galaxies or disks, based on the streams structural parameters. Furthermore, brightnesses and colors of the streams and tails are consistent with those of galaxies that populate the red sequence in the Coma cluster within $2\sigma$.

astro-ph.GA↗

arXiv2025

Confirmation of four hot Jupiters detected by TESS using follow-up spectroscopy from MaHPS at Wendelstein together with NEID and TRES

We report the confirmation and characterization of four hot Jupiter-type exoplanets initially detected by TESS: TOI-1295 b, TOI-2580 b, TOI-6016 b, and TOI-6130 b. Using observations with the high-resolution echelle spectrograph MaHPS on the 2.1m telescope at Wendelstein Observatory, together with NEID at Kitt Peak National Observatory and TRES at the Fred Lawrence Whipple Observatory, we confirmed the planetary nature of these four planet candidates. We also performed precise mass measurements. All four planets are found to be hot Jupiters with orbital periods between 2.4 and 4.0 days. The sizes of these planets range from 1.29 to 1.64 Jupiter radii, while their masses range from 0.6 to 1.5 Jupiter masses. Additionally, we investigated whether there are signs of other planets in the systems but have found none. Lastly, we compared the radii of our four objects to the results of an empirical study of radius inflation and see that all four demonstrate a good fit with the current models. These four planets belong to the first array of planets confirmed with MaHPS data, supporting the ability of the spectrograph to detect planets around fainter stars as faint as V=12.

astro-ph.EP↗

arXiv2025

TOI-5108 b and TOI 5786 b: Two transiting sub-Saturns detected and characterized with TESS, MaHPS and SOPHIE

We report the discovery and characterization of two sub-Saturns from the Transiting Exoplanet Survey Satellite (\textit{TESS}) using high-resolution spectroscopic observations from the MaHPS spectrograph at the Wendelstein Observatory and the SOPHIE spectrograph at the Haute-Provence Observatory. Combining photometry from TESS, KeplerCam, LCOGT, and MuSCAT2 with the radial velocity measurements from MaHPS and SOPHIE we measure precise radii and masses for both planets. TOI-5108 b is a sub-Saturn with a radius of $6.6 \pm 0.1$ $R_\oplus$ and a mass of $32 \pm 5$ $M_\oplus$. TOI-5786 b is similar to Saturn with a radius of $8.54 \pm 0.13$ $R_\oplus$ and a mass of $73 \pm 9$ $M_\oplus$. The host star for TOI-5108 b is a moderately bright (Vmag 9.75) G-type star. TOI-5786 is a slightly dimmer (Vmag 10.2) F-type star. Both planets are close to their host stars with periods of 6.75 days and 12.78 days respectively. This puts TOI-5108 b just inside the bounds of the Neptune desert while TOI-5786 b is right above the upper edge. We estimate hydrogen-helium envelope mass fractions of $38 \%$ for TOI-5108 b and $74 \% $ for TOI-5786 b. However, using a model for the interior structure that includes tidal effects the envelope fraction of TOI-5108 b could be much lower ($\sim 20\,\%$) depending on the obliquity. We estimate mass-loss rates between 1.0 * $10^9$ g/s and 9.8 * $10^9$ g/s for TOI-5108 b and between 3.6 * $10^8$ g/s and 3.5 * $10^9$ g/s for TOI-5786 b. Given their masses, this means that both planets are stable against photoevaporation. We also detect a transit signal for a second planet candidate in the TESS data of TOI-5786 with a period of 6.998 days and a radius of $3.83 \pm 0.16$ $R_\oplus$. Using our RV data and photodynamical modeling, we are able to provide a 3-$\sigma$ upper limit of 26.5 $M_\oplus$ for the mass of the potential inner companion to TOI-5786 b.

astro-ph.EP↗