Subtracting Starlight: A Spitzer Search for Substellar... Sidekicks?

The abundance of discovered exoplanets show that our solar system may not be typical. We have several small rocky bodies close to our star, surrounded by large gaseous planets farther out, all on nearly circular orbits. In contrast, exoplanetary systems have been revealed to have extraordinary features: massive gas giants have been discovered both exceptionally close to their star (so-called ``hot Jupiters\u27\u27), as well as much farther away than thought possible (hundreds to thousands of times farther than Earth is from the sun); the average exoplanet\u27s orbit is not circular, but quite elliptical, with an eccentricity of 0.2. These features may be connected: it is possible that undiscovered far-separated giant planets could disrupt the orbits of inner planets. We performed direct imaging surveys of nearby stars using the Spitzer space telescope, making use of advanced point spread function subtraction techniques, to look for giant planets or brown dwarfs in the typical range of 10-100 projected AU (using IRAC\u27s sub-array mode) and 100-1000 projected AU (using IRAC\u27s full array). We found several infrared-color-selected potential companions around HD 76151, HR 8799, GJ 86, HD 160691, and GJ 581. These will require follow-up observations to test for common proper motion and confirmation of spectral type

KIC 8462852 - The Infrared Flux

We analyzed the warm Spitzer/IRAC data of KIC 8462852. We found no evidence of infrared excess at 3.6 micron and a small excess of 0.43 +/- 0.18 mJy at 4.5 micron, below the 3 sigma threshold necessary to claim a detection. The lack of strong infrared excess 2 years after the events responsible for the unusual light curve observed by Kepler, further disfavors the scenarios involving a catastrophic collision in a KIC 8462852 asteroid belt, a giant impact disrupting a planet in the system or a population of a dust-enshrouded planetesimals. The scenario invoking the fragmentation of a family of comets on a highly elliptical orbit is instead consistent with the lack of strong infrared excess found by our analysis.Comment: Published on The Astrophysical Journal Letter

The Prototypical Young L/T-Transition Dwarf HD 203030B Likely Has Planetary Mass

Upon its discovery in 2006, the young L7.5 companion to the solar analog HD 203030 was found to be unusual in being $\approx$200 K cooler than older late-L dwarfs. HD 203030B offered the first clear indication that the effective temperature at the L-to-T spectral type transition depends on surface gravity: now a well-known characteristic of low-gravity ultra-cool dwarfs. An initial age analysis of the G8V primary star indicated that the system was 130--400 Myr old, and so the companion between 12--31 $M_{\rm Jup}$. Using moderate resolution near-infrared spectra of HD 203030B, we now find features of very low gravity comparable to those of 10--150 Myr-old L7--L8 dwarfs. We also obtained more accurate near infrared and {\sl Spitzer}/IRAC photometry, and find a $(J-K)_{\rm MKO}$ color of $2.56\pm0.13$ mag---comparable to those observed in other young planetary-mass objects---and a luminosity of log($L_{\rm bol}/L_{\odot}$)$\,=\,-4.75\pm0.04$ dex. We further reassess the evidence for the young age of the host star, HD 203030, with a more comprehensive analysis of the photometry and updated stellar activity measurements and age calibrations. Summarizing the age diagnostics for both components of the binary, we adopt an age of 100 Myr for HD 203030B and an age range of 30--150 Myr. Using cloudy evolutionary models, the new companion age range and luminosity result in a mass of 11 $M_{\rm Jup}$ with a range of 8--15 $M_{\rm Jup}$, and an effective temperature of $1040\pm50$ K.Comment: 12 pages, 7 figures, accepted for publication in A

The Size Frequency Distribution of Small Main-Belt Asteroids

The asteroid size distribution informs us about the formation and composition of the Solar System. We build on our previous work in which we harvest serendipitously observed data of the Taurus region and measure the brightness and size distributions of Main-belt asteroids. This is accomplished with the highly sensitive MIPS 24 micron channel. We expect to catalog 104 asteroids, giving us a statistically significant data set. Results from this investigation will allow us to characterize the total population of small, Main-belt asteroids. Here we will present new results on the completeness of our study; on the presence of size distribution variations with inclination and radial distance in the belt; and early result on other archival fields

Subtracting Starlight: A Spitzer Search for Substellar... Sidekicks?

The abundance of discovered exoplanets show that our solar system may not be typical. We have several small rocky bodies close to our star, surrounded by large gaseous planets farther out, all on nearly circular orbits. In contrast, exoplanetary systems have been revealed to have extraordinary features: massive gas giants have been discovered both exceptionally close to their star (so-called ``hot Jupiters''), as well as much farther away than thought possible (hundreds to thousands of times farther than Earth is from the sun); the average exoplanet's orbit is not circular, but quite elliptical, with an eccentricity of 0.2. These features may be connected: it is possible that undiscovered far-separated giant planets could disrupt the orbits of inner planets. We performed direct imaging surveys of nearby stars using the Spitzer space telescope, making use of advanced point spread function subtraction techniques, to look for giant planets or brown dwarfs in the typical range of 10-100 projected AU (using IRAC's sub-array mode) and 100-1000 projected AU (using IRAC's full array). We found several infrared-color-selected potential companions around HD 76151, HR 8799, GJ 86, HD 160691, and GJ 581. These will require follow-up observations to test for common proper motion and confirmation of spectral type.</p