7 research outputs found
On the behaviour of spin-orbit connection of exoplanets
Star-planet interactions play, among other things, a crucial role in
planetary orbital configurations by circularizing orbits, aligning the star and
planet spin and synchronizing stellar rotation with orbital motions. This is
especially true for innermost giant planets, which can be schematized as binary
systems with a very large mass ratio. Despite a few examples where spin-orbit
synchronization has been obtained, there is no demographic study on synchronous
regimes in those systems yet. Here we use a sample of 1,055 stars with
innermost planet companions to show the existence of three observational loci
of star-planet synchronization regimes. Two of them have dominant fractions of
subsynchronous and supersynchronous star-planet systems, and a third less
populated regime of potentially synchronized systems. No synchronous
star-planet system with a period higher than 40 days has been detected yet.
This landscape is different from eclipsing binary systems, most of which are
synchronized. We suggest that planets in a stable asynchronous spin state
belonging to star-planet systems in a supersynchronized regime offer the most
favourable conditions for habitability.Comment: 15 pages, 1 figure in main paper, 6 supplementary figures. Published
in Nature Astronomy, May 202
X-ray Polarization Observations of BL Lacertae
Blazars are a class of jet-dominated active galactic nuclei with a typical
double-humped spectral energy distribution. It is of common consensus the
Synchrotron emission to be responsible for the low frequency peak, while the
origin of the high frequency hump is still debated. The analysis of X-rays and
their polarization can provide a valuable tool to understand the physical
mechanisms responsible for the origin of high-energy emission of blazars. We
report the first observations of BL Lacertae performed with the Imaging X-ray
Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization
degree 12.6\% was found in the 2-8 keV band. We contemporaneously
measured the polarization in radio, infrared, and optical wavelengths. Our
multiwavelength polarization analysis disfavors a significant contribution of
proton synchrotron radiation to the X-ray emission at these epochs. Instead, it
supports a leptonic origin for the X-ray emission in BL Lac.Comment: 17 pages, 5 figures, accepted for publication in ApJ
X-Ray Polarization Observations of BL Lacertae
International audienceBlazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus that the synchrotron emission is responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae (BL Lac) performed with the Imaging X-ray Polarimetry Explorer, from which an upper limit to the polarization degree Î X < 12.6% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton-synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac
X-Ray Polarization Observations of BL Lacertae
International audienceBlazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus that the synchrotron emission is responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae (BL Lac) performed with the Imaging X-ray Polarimetry Explorer, from which an upper limit to the polarization degree Î X < 12.6% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton-synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac
Observations of Low and Intermediate Spectral Peak Blazars with the Imaging X-Ray Polarimetry Explorer
International audienceAbstract We present X-ray polarimetry observations from the Imaging X-ray Polarimetry Explorer (IXPE) of three low spectral peak and one intermediate spectral peak blazars, namely 3C 273, 3C 279, 3C 454.3, and S5 0716+714. For none of these objects was IXPE able to detect X-ray polarization at the 3 Ï level. However, we placed upper limits on the polarization degree at âŒ10%â30%. The undetected polarizations favor models where the X-ray band is dominated by unpolarized photons upscattered by relativistic electrons in the jets of blazars, although hadronic models are not completely eliminated. We discuss the X-ray polarization upper limits in the context of our contemporaneous multiwavelength polarization campaigns