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A CRIRES-search for H <sub/>3</sub><sup>+</sup> emission from the hot Jupiter atmosphere of HD 209458 b
摘要： Close-in extrasolar giant planets are expected to cool their thermospheres by producing H+3 emission in the near-infrared (NIR), but simulations predict H+3 emission intensities that differ in the resulting intensity by several orders of magnitude. We want to test the observability of H+3 emission with CRIRES at the Very Large Telescope (VLT), providing adequate spectral resolution for planetary atmospheric lines in NIR spectra. We search for signatures of planetary H+3 emission in the L' band, using spectra of HD 209458 obtained during and after secondary eclipse of its transiting planet HD 209458 b. We searched for H+3 emission signatures in spectra containing the combined light of the star and, possibly, the planet. With the information on the ephemeris of the transiting planet, we derive the radial velocities at the time of observation and search for the emission at the expected line positions. We also apply a cross-correlation test to search for planetary signals and use a shift and add technique combining all observed spectra taken after secondary eclipse to calculate an upper emission limit. We do not find signatures of atmospheric H+3 emission in the spectra containing the combined light of HD 209458 and its orbiting planet. We calculate the emission limit for the H+3 line at 3953.0 nm [Q(1, 0)] to be 8.32 × 1018 W and a limit of 5.34 × 1018 W for the line at 3985.5 nm [Q(3, 0)]. Comparing our emission limits to the theoretical predictions suggests that we lack 1 to 3 magnitudes of sensitivity to measure H+3 emission in our target object. We show that under more favorable weather conditions the data quality can be improved significantly, reaching 5 × 1016 W for star-planet systems that are close to Earth. We estimate that pushing the detection limit down to 1015 W will be possible with ground-based observations with future instrumentation, for example, the European Extremly Large Telescope.
关键词： planetary systems,infrared: stars,stars: individual: HD 209458
更新于2025-09-04 15:30:14
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Optical spectroscopy of the microquasar GRS 1758?258: a possible intermediate mass system?
摘要： Context. GRS 1758?258 is one of two prototypical microquasars towards the Galactic center direction discovered almost a quarter of a century ago. The system remains poorly studied in the optical domain due to its counterpart being a very faint and absorbed target in a crowded region of the sky. Aims. Our aim is to investigate GRS 1758?258 in order to shed light on the nature of the stellar binary components. In particular, the main physical parameters of the donor star, such as the mass or the spectral type, are not yet well constrained. Methods. GRS 1758?258 has remained so far elusive to optical spectroscopy owing to its observational di?culties. Here, we use this traditional tool of stellar astronomy at low spectral resolution with a 10 m class telescope and a long slit spectrograph. Results. An improved spectrum is obtained as compared to previous work. The quality of the data does not allow the detection of emission or absorption features but, nevertheless, we manage to partially achieve our aims comparing the de-reddened continuum with the spectral energy distribution expected from an irradiated disc model and di?erent donor star templates. Conclusions. We tentatively propose that GRS 1758?258 does not host a giant star companion. Instead, a main sequence star with mid-A spectral type appears to better agree with our data. The main impacts of this ?nding are the possibility that we are dealing with an intermediate mass system and, in this case, the prediction of an orbital period signi?cantly shorter than previously proposed.
关键词： X-rays: binaries,stars: individual: GRS 1758-258,infrared: stars
更新于2025-09-04 15:30:14