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users:mhooton:start [2018/10/10 14:55]
Matthew Hooton
users:mhooton:start [2018/11/12 12:37] (current)
Matthew Hooton
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 ===== Papers ===== ===== Papers =====
  
-<WRAP indent> **{{kelt9_u_apjl.pdf|A ground-based NUV secondary eclipse observation of KELT-9b - ApJL (submitted)}}** \\ +<WRAP indent> **{{kelt9_u_apjl.pdf|A ground-based NUV secondary eclipse observation of KELT-9b - ApJL (accepted)}}** \\ 
 KELT-9b is a recently discovered exoplanet with a 1.49 d orbit around a B9.5/​A0-type star. The unparalleled levels of UV irradiation it receives from its host star put KELT-9b in its own unique class of ultra-hot Jupiters, with an equilibrium temperature > 4000 K. The high quantities of dissociated hydrogen and atomic metals present in the dayside atmosphere of KELT-9b bear more resemblance to a K-type star than a gas giant. We present a single observation of KELT-9b during its secondary eclipse, taken with the Wide Field Camera on the Isaac Newton Telescope (INT). This observation was taken in the U-band, a bandpass particularly sensitive to Rayleigh scattering. We do not detect a secondary eclipse signal, but our 3σ upper limit of 192 ppm on the depth allows us to constrain the dayside temperature of KELT-9b at pressures of ~30 mbar to 5035 K (3σ). Our models suggest that the scattering from the dayside of KELT-9b is negligible due to H<​sup>​-</​sup>​ opacity in the optical and NUV. This places KELT-9b squarely in the albedo regime populated by its cooler cousins, almost all of which reflect very small components of the light incident on their daysides. This work demonstrates the ability of ground-based 2m-class telescopes like the INT to perform secondary eclipse studies in the NUV, which to date have only been conducted from space-based facilities. KELT-9b is a recently discovered exoplanet with a 1.49 d orbit around a B9.5/​A0-type star. The unparalleled levels of UV irradiation it receives from its host star put KELT-9b in its own unique class of ultra-hot Jupiters, with an equilibrium temperature > 4000 K. The high quantities of dissociated hydrogen and atomic metals present in the dayside atmosphere of KELT-9b bear more resemblance to a K-type star than a gas giant. We present a single observation of KELT-9b during its secondary eclipse, taken with the Wide Field Camera on the Isaac Newton Telescope (INT). This observation was taken in the U-band, a bandpass particularly sensitive to Rayleigh scattering. We do not detect a secondary eclipse signal, but our 3σ upper limit of 192 ppm on the depth allows us to constrain the dayside temperature of KELT-9b at pressures of ~30 mbar to 5035 K (3σ). Our models suggest that the scattering from the dayside of KELT-9b is negligible due to H<​sup>​-</​sup>​ opacity in the optical and NUV. This places KELT-9b squarely in the albedo regime populated by its cooler cousins, almost all of which reflect very small components of the light incident on their daysides. This work demonstrates the ability of ground-based 2m-class telescopes like the INT to perform secondary eclipse studies in the NUV, which to date have only been conducted from space-based facilities.
  
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 g cm<​sup>​−3</​sup>;​ therefore one of the lowest density exoplanets currently known. With a relatively deep 1.0% transit around a bright V=10.96 host star, NGTS-2b is a prime target for probing giant planet composition via atmospheric transmission spectroscopy. The rapid rotation (v sin i=15.2 ± 0.8 km s,<​sup>​−1</​sup>​) also makes this system an excellent candidate for Rossiter-McLaughlin follow-up observations,​ to measure the sky-projected stellar obliquity. NGTS-2b was confirmed without the need for follow-up photometry, due to the high precision of the NGTS photometry. g cm<​sup>​−3</​sup>;​ therefore one of the lowest density exoplanets currently known. With a relatively deep 1.0% transit around a bright V=10.96 host star, NGTS-2b is a prime target for probing giant planet composition via atmospheric transmission spectroscopy. The rapid rotation (v sin i=15.2 ± 0.8 km s,<​sup>​−1</​sup>​) also makes this system an excellent candidate for Rossiter-McLaughlin follow-up observations,​ to measure the sky-projected stellar obliquity. NGTS-2b was confirmed without the need for follow-up photometry, due to the high precision of the NGTS photometry.
  
-**{{extreme-asteroids-pan-aas.pdf|Extreme asteroids in the Pan-STARRS 1 Survey - AJ (submitted)}}** \\ +**{{extreme-asteroids-pan-final.pdf|Extreme asteroids in the Pan-STARRS 1 Survey - AJ (accepted)}}** \\ 
 Using the first 18 months of the Pan-STARRS 1 survey we have identified 33 candidate high-amplitude objects for follow-up observations and carried out observations of 22 asteroids. 4 of the observed objects were found to have observed amplitude A<​sub>​obs</​sub>​ ≥ 1.0 mag. We find that these high amplitude objects are most simply explained by single rubble pile objects with some density-dependent internal strength, allowing them to resist mass shedding even at their highly elongated shapes. 3 further objects although below the cut-off for `high-amplitude’ had a combination of elongation and rotation period which also may require internal cohesive strength, depending on the density of the body. We find that none of the `high-amplitude asteroids’ identified here require any unusual cohesive strengths to resist rotational fission. 3 asteroids were sufficiently observed to allow for shape and spin pole models to be determined through light curve inversion. 45864 was determined to have retrograde rotation with spin pole axes λ = 218±10◦,​β = −82±5◦ and asteroid 206167 was found to have best fit spin pole axes λ = 57 ± 5◦, β = −67 ± 5◦. An additional object not initially measured with A<​sub>​obs</​sub>​ > 1.0 mag, 49257, was determined to have a shape model which does suggest a high-amplitude object. Its spin pole axes were best fit for values λ = 112 ± 6◦, β = 6 ± 5◦. In the course of this project to date no large super-fast rotators (Prot < 2.2 h) have been identified.</​WRAP>​ Using the first 18 months of the Pan-STARRS 1 survey we have identified 33 candidate high-amplitude objects for follow-up observations and carried out observations of 22 asteroids. 4 of the observed objects were found to have observed amplitude A<​sub>​obs</​sub>​ ≥ 1.0 mag. We find that these high amplitude objects are most simply explained by single rubble pile objects with some density-dependent internal strength, allowing them to resist mass shedding even at their highly elongated shapes. 3 further objects although below the cut-off for `high-amplitude’ had a combination of elongation and rotation period which also may require internal cohesive strength, depending on the density of the body. We find that none of the `high-amplitude asteroids’ identified here require any unusual cohesive strengths to resist rotational fission. 3 asteroids were sufficiently observed to allow for shape and spin pole models to be determined through light curve inversion. 45864 was determined to have retrograde rotation with spin pole axes λ = 218±10◦,​β = −82±5◦ and asteroid 206167 was found to have best fit spin pole axes λ = 57 ± 5◦, β = −67 ± 5◦. An additional object not initially measured with A<​sub>​obs</​sub>​ > 1.0 mag, 49257, was determined to have a shape model which does suggest a high-amplitude object. Its spin pole axes were best fit for values λ = 112 ± 6◦, β = 6 ± 5◦. In the course of this project to date no large super-fast rotators (Prot < 2.2 h) have been identified.</​WRAP>​
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users/mhooton/start.1539183324.txt.gz · Last modified: 2018/10/10 14:55 by Matthew Hooton

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