Astronomy

Basic Testing of the Duchamp Source Finder

by Attila Popping

Observable Signatures of the low-z Circum-Galactic and Inter-Galactic Medium : UV Line Emission in Simulations

by Attila Popping

Comparison of potential ASKAP HI survey source finders

by Attila Popping

Multidimensionale Universen

by Hans-Peter Keiseler

veröffentlicht in diversen Zeitungen, Mai 2012

A Multi-Spacecraft Approach to Studying Auroral Kilometric Radiation Using the Virtual Wave Observatory

by Ravi Dinakar

For FREE pdf paper visit:

http://www.jes2s.com/pdfs/Jan2012/A%20Multi-Spacecraft%20Approach%20to%20Studying%20Auroral%20Kilometric%20Radiation%20Using%20the%20Virtual%20Wave%20Observatory.pdf


Authors:

Huy Lam1*, Teresa Petralli-Mallow2, Leonard Garcia3, and Shing Fung4
Student1, Teacher2: Poolesville High School, 17501 West Willard Road, Poolesville, Maryland 20837
Mentor/Senior Programmer3: NASA/GSFC, Greenbelt, MD 2077
Mentor/Research Astrophysicist4: NASA/GSFC, Greenbelt, MD 2077
*Correspondence: lamhuy@gmail.com

Published in The Journal of Experimental Secondary Science (www.jes2s.com)

According to the analysis of the radio wave spectrograms
captured by the IMAGE, Geotail, Polar, Wind,... more According to the analysis of the radio wave spectrograms
captured by the IMAGE, Geotail, Polar, Wind, Stereo-A,
and Stereo-B spacecraft, the correlation between the
auroral kilometric radiation (AKR) intensity and the
auroral electrojet (AE) index have been found to be
negatively correlated as well as positively correlated. These
findings raised questions against the present notion that
AKR intensity and the AE index are positively correlated.
Although the original objective of this study was to
establish a set of stable threshold values in the auroral
AE index for AKR detection, the negative correlations
found between the AKR intensity and the AE index made
these threshold calculations unattainable. Furthermore,
this study was the first attempt to establish a set of stable
threshold AE index values associated with AKR using a
multi-spacecraft approach provided by the Virtual Wave
Observatory (VWO). This approach was essential to
ensure that any changes observed in the spacecraft data
were due solely to the AKR source. The whole spectrum
of AKR was analyzed, normally 80-800 kHz in the satellite
spectrograms. The threshold value was determined by
comparing AE index plots of AKR events to corresponding
satellite spectrograms of the events. However, the poor
correlations found through this study indicated that there
may be other drivers affecting the AKR intensity other
than the strength of the auroral electrojet current. Thus, a
future multi-parameter magnetosphere investigation using
other geometric indices, such as the Dst index or the Kp
index in comparison with the AE index and AKR intensity,
could explain how unknown drivers of the AKR intensity
and the AE index synergistically caused the inconsistent
correlations. The understanding of the magnetosphere
conditions, as measured by the AE index, which trigger
the AKR emission is crucial to planetary research
because it provides a mechanism to remotely sense the
state of the Jupiter’s, Saturn’s, Neptune’s, and Uranus’s
magnetospheres.

Attraction And Repulsion from a Scientific Buddhist Perspective

by Dion Peoples

I think this was the final version published, in the Chulalongkorn University Journal of Buddhist Studies. 

17. Ulusal Astronomi Kongresi 2010 Bildiri Kitabi (s. 442-448)

by ASLI SENSOY

Letter about "El Chaco" meteorite

by Alejandro López

This is a letter made by academic researchers on cultural astronomy to reject the proyect of move the "El Chaco" meteorite from Argentina to Germany for use in the art show, Documenta 13. The transfer of this cultural treasure, without the support of the indigenous peoples as central players in this project, shows a serious lack of consideration of the inhabitants of the area.

It is very important your adhesion and the adhesion of your institution to stop this. If you wish help us please send me: name, identification number, academic degree, institution.

This is a letter made by academic researchers on cultural astronomy to reject the proyect of move the "El... more This is a letter made by academic researchers on cultural astronomy to reject the proyect of move the "El Chaco" meteorite from Argentina to Germany for use in the art show, Documenta 13. The transfer of this cultural treasure, without the support of the indigenous peoples as central players in this project, shows a serious lack of consideration of the inhabitants of the area.

Carta sobre el proyecto de trasladar el meteorito "El Chaco"

by Alejandro López

Esta es una carta redactada por investigadores académicos en astronomía cultural para oponerse al traslado a Alemania del meteorito "El Chaco" de Argentina. El proyecto de trasladarlo en prestamo para la muestra de arte "Documenta 13" no respeta la cosmovisión de los aborígenes chaqueños para quienes este meteorito es importantísimo. Debería haberse pensado en los habitantes de la zona, especialmente los pueblos originarios como protagonistas centrales de cualquier proyecto, sin cuya participación y acuerdo amplio ningún traslado tiene sentido.

Quien quiera adherir a la carta, envíeme su nombre, algún número de identidad, grado académico e institución de pertenencia.

Esta es una carta redactada por investigadores académicos en astronomía cultural para oponerse al traslado a Alemania... more Esta es una carta redactada por investigadores académicos en astronomía cultural para oponerse al traslado a Alemania del meteorito "El Chaco" de Argentina. El proyecto de trasladarlo en prestamo para la muestra de arte "Documenta 13" no respeta la cosmovisión de los aborígenes chaqueños para quienes este meteorito es importantísimo. Debería haberse pensado en los habitantes de la zona, especialmente los pueblos originarios como protagonistas centrales de cualquier proyecto, sin cuya participación y acuerdo amplio ningún traslado tiene sentido.

Descubriendo el Universo

by Maximiliano Isi

N. Boroffka, Review: Wolfhard Schlosser, Jan Cierny, Sterne und Steine. Eine praktische Astronomie der Vorzeit (Darmstadt 1996). European Archaeology - online www.archaeology.ro, Dez. 2000.

by Nikolaus Boroffka

Book review

Searching for Extra-Solar Planets Using the PIRATE Telescope

by Samantha Rolfe

Detection of visible light from the darkest world

by David Kipping

First-authored, published in MNRAS (2011)

We present the detection of visible light from the planet TrES-2b, the darkest exoplanet currently known. By analysis... more We present the detection of visible light from the planet TrES-2b, the darkest exoplanet currently known. By analysis of the orbital photometry from publicly available Kepler data (0.4-0.9 microns), we determine a day-night contrast amplitude of (6.5 +/- 1.9 ppm), constituting the lowest amplitude orbital phase variation discovered. The signal is detected to 3.7 sigma confidence and persists in six different methods of modelling the data and thus appears robust. In contrast, we are unable to detect ellipsoidal variations or beaming effects, but we do provide confidence intervals for these terms. If the day-night contrast is interpreted as being due to scattering, it corresponds to a geometric albedo of Ag = 0.0253 +/- 0.0072. However, our models indicate that there is a significant emission component to day-side brightness, and the true albedo is even lower (<1%). By combining our measurement with Spitzer and ground-based data, we show that a model with moderate redistribution (Pn ~ 0.3) and moderate extra optical opacity (kappa' ~ 0.3-0.4) provide a compatible explanation to the data.

HAT-P-31b,c: A Transiting, Eccentric, Hot Jupiter and a Long-Period, Massive Third-Body

by David Kipping

First-authored, published in AJ (2011), 142, 95

We report the discovery of HAT-P-31b, a transiting exoplanet orbiting the V=11.660 dwarf star GSC 2099-00908.... more We report the discovery of HAT-P-31b, a transiting exoplanet orbiting the V=11.660 dwarf star GSC 2099-00908. HAT-P-31b is the first HAT planet discovered without any follow-up photometry, demonstrating the feasibility of a new mode of operation for the HATNet project. The 2.17 Mj, 1.1Rj planet has a period P = 5.0054 days and maintains an unusually high eccentricity of e = 0.2450+/-0.0045, determined through Keck, FIES and Subaru high precision radial velocities. Detailed modeling of the radial velocities indicates an additional quadratic residual trend in the data detected to very high confidence. We interpret this trend as a long-period outer companion, HAT-P-31c, of minimum mass 3.4Mj and period >2.8 years. Since current RVs span less than half an orbital period, we are unable to determine the properties of HAT-P-31c to high confidence. However, dynamical simulations of two possible configurations show that orbital stability is to be expected. Further, if HAT-P-31c has non-zero eccentricity, our simulations show that the eccentricity of HAT-P-31b is actively driven by the presence of c, making HAT-P-31 a potentially intriguing dynamical laboratory.

LUNA: An algorithm for generating dynamic planet-moon transits

by David Kipping

Solo-authored, published in MNRAS (2011), 416, 689

It has been previously shown that moons of extrasolar planets may be detectable with the Kepler Mission, for moon... more It has been previously shown that moons of extrasolar planets may be detectable with the Kepler Mission, for moon masses above ~0.2 Earth masses Kipping et al. 2009c. Transit timing effects have been formerly identified as a potent tool to this end, exploiting the dynamics of the system. In this work, we explore the simulation of transit light curves of a planet plus a single moon including not only the transit timing effects but also the light curve signal of the moon itself. We introduce our new algorithm, LUNA, which produces transit light curves for both bodies, analytically accounting for shadow overlaps, stellar limb darkening and planet-moon dynamical motion. By building the dynamics into the core of LUNA, the routine automatically accounts for transit timing/duration variations and ingress/egress asymmetries for not only the planet, but also the moon. We then generate some artificial data for two feasibly detectable hypothetical systems of interest: a i) prograde and ii) retrograde Earth-like moon around a habitable-zone Neptune for a M-dwarf system. We fit the hypothetical systems using LUNA and demonstrate the feasibility of detecting these cases with Kepler photometry.

The Transits of Extrasolar Planets with Moons

by David Kipping

Solo-authored, PhD thesis (2011), University College London

The search for extrasolar planets is strongly motivated by the goal of characterizing how frequent habitable worlds... more The search for extrasolar planets is strongly motivated by the goal of characterizing how frequent habitable worlds and life may be within the Galaxy. Whilst much effort has been spent on searching for Earth-like planets, large moons may also be common, temperate abodes for life as well. The methods to detect extrasolar moons, or "exomoons" are more subtle than their planetary counterparts and in this thesis I aim to provide a method to find such bodies in transiting systems, which offer the greatest potential for detection. Before one can search for the tiny perturbations to the planetary signal, an understanding of the planetary transit must be established. Therefore, in Chapters 3 to 5 I discuss the transit model and provide several new insights. Chapter 4 presents new analytic expressions for the times of transit minima and the transit duration, which will be critical in the later search for exomoons. Chapter 5 discusses two sources of distortion to the transit signal, namely blending (with a focus on the previously unconsidered self-blending scenario) and light curve smearing due to long integration times. I provide methods to compensate for both of these effects, thus permitting for the accurate modelling of the planetary transit light curve. In Chapter 6, I discuss methods to detect exomoons through their gravitational influence on the host planet, giving rise to transit timing and duration variations (TTV and TDV). The previously known TTV effect is updated with a new model and the associated critical problems are outlined. I then predict a new effect, TDV, which solves these problems, making exomoon detection viable. Chapter 7 presents a feasibility study for detecting habitable-zone exomoons with Kepler, where it is found that moons down to 0.2 Earth masses are detectable. Finally, conclusions and future work are discussed in Chapter 8.

How to Weigh a Star Using a Moon

by David Kipping

Solo-authored, published in MNRAS (2011), 409, L119

We show that for a transiting exoplanet accompanied by a moon which also transits, the absolute masses and radii of... more We show that for a transiting exoplanet accompanied by a moon which also transits, the absolute masses and radii of the star, planet and moon are determinable. For a planet-star system, it is well known that the density of the star is calculable from the lightcurve by manipulation of Kepler's Third Law. In an analogous way, the planetary density is calculable for a planet-moon system which transits a star, and thus the ratio-of-densities is known. By combining this ratio with the observed ratio-of-radii and the radial velocity measurements of the system, we show that the absolute dimensions of the star and planet are determinable. This means such systems could be used as calibrators of stellar evolution. The detection of dynamical effects, such as transit timing variations, allows the absolute mass of the moon to be determined as well, which may be combined with the radius to infer the satellite's composition.

HAT-P-26b: A Low-Density Neptune-Mass Planet Transiting a K Star

by David Kipping

Co-authored, published in ApJ (2011), 728, 138

We report the discovery of HAT-P-26b, a transiting extrasolar planet orbiting the moderately bright V=11.744 K1 dwarf... more We report the discovery of HAT-P-26b, a transiting extrasolar planet orbiting the moderately bright V=11.744 K1 dwarf star GSC 0320-01027, with a period P = 4.234516 +- 0.000015 d, transit epoch Tc = 2455304.65122 +- 0.00035 (BJD), and transit duration 0.1023 +- 0.0010 d. The host star has a mass of 0.82 +- 0.03 Msun, radius of 0.79 + 0.10 - 0.04 Rsun, effective temperature 5079 +- 88 K, and metallicity [Fe/H] = -0.04 +- 0.08. The planetary companion has a mass of 0.059 +- 0.007 MJ, and radius of 0.565 + 0.072 - 0.032 RJ yielding a mean density of 0.40 +- 0.10 g cm-3. HAT-P-26b is the fourth Neptune-mass transiting planet discovered to date. It has a mass that is comparable to those of Neptune and Uranus, and slightly smaller than those of the other transiting Super-Neptunes, but a radius that is ~65% larger than those of Neptune and Uranus, and also larger than those of the other transiting Super-Neptunes. HAT-P-26b is consistent with theoretical models of an irradiated Neptune-mass planet with a 10 Mearth heavy element core that comprises >~ 50% of its mass with the remainder contained in a significant hydrogen-helium envelope, though the exact composition is uncertain as there are significant differences between various theoretical models at the Neptune-mass regime. The equatorial declination of the star makes it easily accessible to both Northern and Southern ground-based facilities for follow-up observations.

HAT-P-24b: An inflated hot-Jupiter on a 3.36d period transiting a hot, metal-poor star

by David Kipping

First-authored, published in ApJ (2011), 725, 2017

We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting the moderately bright V=11.818 F8 dwarf... more We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting the moderately bright V=11.818 F8 dwarf star GSC 0774-01441, with a period P = 3.3552464 +/- 0.0000071 d, transit epoch Tc = 2455216.97669 +/- 0.00024 (BJD_UTC), and transit duration 3.653 +/- 0.025 hours. The host star has a mass of 1.191 +/- 0.042 Msun, radius of 1.317 +/- 0.068 Rsun, effective temperature 6373 +/- 80 K, and a low metallicity of [Fe/H] = -0.16 +/- 0.08. The planetary companion has a mass of 0.681 +/- 0.031 MJ, and radius of 1.243 +/- 0.072 RJ yielding a mean density of 0.439 +/- 0.069 g cm-3 . By repeating our global fits with different parameter sets, we have performed a critical investigation of the fitting techniques used for previous HAT planetary discoveries. We find that the system properties are robust against the choice of priors. The effects of fixed versus fitted limb darkening are also examined. HAT-P-24b probably maintains a small eccentricity of e = 0.052 +0.022 -0.017, which is accepted over the circular orbit model with false alarm probability 5.8%. In the absence of eccentricity pumping, this result suggests HAT-P-24b experiences less tidal dissipation than Jupiter. Due to relatively rapid stellar rotation, we estimate that HAT-P-24b should exhibit one of the largest known Rossiter-McLaughlin effect amplitudes for an exoplanet (deltaVRM ~ 95 m/s) and thus a precise measurement of the sky-projected spin-orbit alignment should be possible.

HAT-P-20b--HAT-P-23b: Four Massive Transiting Extrasolar Planets

by David Kipping

Co-authored, published in ApJ (2011)

We report the discovery of four relatively massive (2-7MJ) transiting extrasolar planets. HAT-P-20b orbits a V=11.339... more We report the discovery of four relatively massive (2-7MJ) transiting extrasolar planets. HAT-P-20b orbits a V=11.339 K3 dwarf star with a period P=2.875317+/-0.000004d. The host star has a mass of 0.760+/-0.03 Msun, radius of 0.690+/-0.02 Rsun, Teff=4595+/-80 K, and metallicity [Fe/H]=+0.35+/-0.08. HAT-P-20b has a mass of 7.246+/-0.187 MJ, and radius of 0.867+/-0.033 RJ yielding a mean density of 13.78+/-1.50 gcm^-3 , which is the second highest value among all known exoplanets. HAT-P-21b orbits a V=11.685 G3 dwarf on an eccentric (e=0.2280+/-0.016) orbit, with a period of P=4.1244810+/-000007d. The host star has a mass of 0.95+/-0.04Msun, radius of 1.10+/-0.08Rsun, Teff=5588+/-80K, and [Fe/H]=+0.01+/-0.08. HAT-P-21b has a mass of 4.063+/-0.161MJ, and radius of 1.024+/-0.092RJ. HAT-P-22b orbits the V=9.732 G5 dwarf HD233731, with P=3.2122200+/-0.000009d. The host star has a mass of 0.92+/-0.03Msun, radius of 1.04+/-0.04Rsun, Teff=5302+/-80K, and metallicity of +0.24+/-0.08. The planet has a mass of 2.147+/-0.061 MJ, and compact radius of 1.080+/-0.058RJ. The host star also harbors an M-dwarf companion at a wide separation. Finally, HAT-P-23b orbits a V=12.432 G0 dwarf star, with a period P=1.212884+/-0.000002d. The host star has a mass of 1.13+/-0.04sun, radius of 1.20+/-0.07Rsun, Teff=5905+/-80K, and [Fe/H]=+0.15+/-0.04. The planetary companion has a mass of 2.090+/-0.111MJ, and radius of 1.368+/-0.090RJ (abridged).