J/AJ/169/104ivo://CDS.VizieR/J/AJ/169/104doi:10.26093/cds/vizier/be-59-38CDSSaidel M.Vissapragada S.Spake J.Knutson H.A.Linssen D.Zhang M.,Greklek-McKeon M.Perez-Gonzalez J.Oklopcic A.2026-07-02T11:45:15Z2025-12-03T17:09:41ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frexoplanetswhite-dwarf-starsphotometryinfrared-astronomyspectroscopyThe lack of close-in Neptune-mass exoplanets evident in transit surveys has largely been attributed to either photoevaporative mass loss or high-eccentricity migration. To distinguish between these two possibilities, we investigate the origins of TOI-1259 A b, a Saturn-mass (0.4M_J_, 1.0R_J_) exoplanet lying along the upper edge of the Neptune desert. TOI-1259 A b's close-in (P=3.48d) orbit and low bulk density make the planet particularly vulnerable to photoevaporation. We studied the upper atmosphere of TOI-1259 A b using metastable helium 1083nm transits observed with Palomar/WIRC and Keck/NIRSPEC. We report a band-integrated excess absorption of 0.395%+/-0.072% with Palomar/WIRC and a spectroscopically resolved 5.5+/-0.94km/s blueshifted absorption of 2.4%+/-0.52% (T1-T4) and 3.5%+/-0.72% (T2-T3) with Keck/NIRSPEC. These measurements indicate the presence of an extended escaping atmosphere. Fitting these signals with a Parker wind model, we determine a corresponding atmospheric mass-loss rate of log(\dot{M})=10.2-10.65g/s for thermosphere temperatures between 7900 and 8600K. This relatively low rate suggests that this planet would not have been significantly altered by mass loss even if it formed in situ. However, the presence of a white dwarf companion, TOI-1259 B, hints that this planet may not have formed close-in, but rather migrated inward relatively late. Given the estimated parameters of the proto-white dwarf companion, we find that high-eccentricity migration is possible for the system.2025AJ....169..104Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/169/104CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/757/18 : RVs for 16 hot Jupiter host stars (Albrecht+, 2012)J/MNRAS/422/2024 : X-ray-age relation & exoplanet evaporation (Jackson+, 2012)J/ApJ/843/31 : MUSCLES Treasury Surv. IV. M dwarf UV fluxes (Youngblood+, 2017)J/AJ/159/278 : He-filter obs. of WASP-69b & WASP-52b (Vissapragada+, 2020)J/ApJ/940/L35 : HAT-P-18b JWST NIRISS transmission spectrum (Fu+, 2022)J/AJ/163/67 : 5-55000{AA} spectrum of TOI 560 (Zhang+, 2022)J/A+A/361/641 : Investigation of mass loss mechanism of LPVs (Winters+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/169/104https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/169/104http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/169/104https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/169/104https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/169/104http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/169/104GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/AJ/169/104/fig3bExcess absorption spectra in the planetary rest frame as a function of wavelength (data behind Figure 3b)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[1.081/1.085] Wavelengthumem.wldoubleExAbsT1T4[-1.6/2.5]? Excess Absorption T1-T4 (all in-transit)%phys.absorptiondoublenullablee_ExAbsT1T4Uncertainty in ExAbsT1T4%stat.error;phys.absorptiondoubleExAbsT2T3[-2.6/3.5]? Excess Absorption T2-T3 (occlusion only)%phys.absorptiondoublenullablee_ExAbsT2T3Uncertainty in ExAbsT2T3%stat.error;phys.absorptiondoubleJ/AJ/169/104/fig4Band-integrated light curve of TOI-1259 A b (data behind Figure 4)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintdT[-4.1/1.4] Time since mid-transithtime.intervaldoubleFlux[0.9/1.01] Band Integrated Relative Flux (1)phot.flux;arith.ratiodoublee_Flux[0.002/0.015] Uncertainty in Fluxstat.error;phot.fluxdoubleJ/AJ/169/104/fig5Average excess absorption during the first and second halfs of transit (data behind Figure 5)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[1.081/1.085] Wavelengthumem.wldoubleExAbs1[-2.8/2.8] Excess Absorption First Half Transit%phys.absorptiondoubleBestFit1Best Fit First Half Transit (1)%stat.fit.paramcharExAbs2[-1.9/2.9] Excess Absorption Second Half Transit%phys.absorptiondoubleBestFit2Best Fit Second Half Transit (1)%stat.fit.paramchar