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Patrick J. Lowrance

Bio: Patrick J. Lowrance is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Brown dwarf & Spitzer Space Telescope. The author has an hindex of 21, co-authored 40 publications receiving 4959 citations. Previous affiliations of Patrick J. Lowrance include Association of Universities for Research in Astronomy.

Papers
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Journal ArticleDOI
TL;DR: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope as mentioned in this paper, which is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 m.
Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 � m. Two nearly adjacent 5A2 ; 5A2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 � m; 4.5 and 8 � m). All four detector arrays in the camera are 256 ; 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

3,567 citations

Journal ArticleDOI
TL;DR: In this article, the authors used data from the 2 Micron All Sky Survey All-Sky Point Source Catalogue (AASSP) to extend the census of nearby ultracool dwarfs to cover the full celestial sphere above Galactic latitude of 15°.
Abstract: Using data from the 2 Micron All Sky Survey All-Sky Point Source Catalogue, we have extended our census of nearby ultracool dwarfs to cover the full celestial sphere above Galactic latitude of 15°. Starting with an initial catalog of 2,139,484 sources, we have winnowed the sample to 467 candidate late-type M or L dwarfs within 20 pc of the Sun. Fifty-four of those sources already have spectroscopic observations confirming them as late-type dwarfs. We present optical spectroscopy of 376 of the remaining 413 sources, and identify 44 as ultracool dwarfs with spectroscopic distances less than 20 pc. Twenty-five of the 37 sources that lack optical data have near-infrared spectroscopy. Combining the present sample with our previous results and data from the literature, we catalog 94 L dwarf systems within 20 pc. We discuss the distribution of activity, as measured by Hα emission, in this volume-limited sample. We have coupled the present ultracool catalog with data for stars in the northern 8 pc sample and recent (incomplete) statistics for T dwarfs to provide a snapshot of the current 20 pc census as a function of spectral type.

300 citations

Journal ArticleDOI
TL;DR: In this paper, a large sample of optical spectra of late-type dwarfs was used to identify a subset of late M through L field dwarfs that, because of the presence of low-gravity features in their spectra, are believed to be unusually young.
Abstract: Using a large sample of optical spectra of late-type dwarfs, we identify a subset of late-M through L field dwarfs that, because of the presence of low-gravity features in their spectra, are believed to be unusually young. From a combined sample of 303 field L dwarfs, we find observationally that 7.6% ± 1.6% are younger than 100 Myr. This percentage is in agreement with theoretical predictions once observing biases are taken into account. We find that these young L dwarfs tend to fall in the southern hemisphere (decl: < 0°) and may be previously unrecognized, low-mass members of nearby, young associations like Tucana-Horologium, TW Hydrae, β Pictoris, and AB Doradus. We use a homogeneously observed sample of ~150 optical spectra to examine lithium strength as a function of L/T spectral type and further corroborate the trends noted by Kirkpatrick and coworkers. We use our low-gravity spectra to investigate lithium strength as a function of age. The data weakly suggest that for early- to mid-L dwarfs the line strength reaches a maximum for a few x 100 Myr, whereas for much older (few Gyr) and much younger (<100 Myr) L dwarfs the line is weaker or undetectable. We show that a weakening of lithium at lower gravities is predicted by model atmosphere calculations, an effect partially corroborated by existing observational data. Larger samples containing L dwarfs of well-determined ages are needed to further test this empirically. If verified, this result would reinforce the caveat first cited by Kirkpatrick and coworkers that the lithium test should be used with caution when attempting to confirm the substellar nature of the youngest brown dwarfs.

256 citations

Journal ArticleDOI
TL;DR: In this paper, the repeatability, reliability, and accuracy of differential exoplanet eclipse depth measurements made using the InfraRed Array Camera (IRAC) on the Spitzer Space Telescope during the post-cryogenic mission were examined.
Abstract: We examine the repeatability, reliability, and accuracy of differential exoplanet eclipse depth measurements made using the InfraRed Array Camera (IRAC) on the Spitzer Space Telescope during the post-cryogenic mission. We have re-analyzed an existing 4.5 μm data set, consisting of 10 observations of the XO-3b system during secondary eclipse, using seven different techniques for removing correlated noise. We find that, on average, for a given technique, the eclipse depth estimate is repeatable from epoch to epoch to within 156 parts per million (ppm). Most techniques derive eclipse depths that do not vary by more than a factor 3 of the photon noise limit. All methods but one accurately assess their own errors: for these methods, the individual measurement uncertainties are comparable to the scatter in eclipse depths over the 10 epoch sample. To assess the accuracy of the techniques as well as to clarify the difference between instrumental and other sources of measurement error, we have also analyzed a simulated data set of 10 visits to XO-3b, for which the eclipse depth is known. We find that three of the methods (BLISS mapping, Pixel Level Decorrelation, and Independent Component Analysis) obtain results that are within three times the photon limit of the true eclipse depth. When averaged over the 10 epoch ensemble, 5 out of 7 techniques come within 60 ppm of the true value. Spitzer exoplanet data, if obtained following current best practices and reduced using methods such as those described here, can measure repeatable and accurate single eclipse depths, with close to photon-limited results.

114 citations

Journal ArticleDOI
Peter Plavchan1, Thomas Barclay2, Thomas Barclay3, Jonathan Gagné4, Peter Gao5, Bryson Cale1, William Matzko1, Diana Dragomir6, Diana Dragomir7, S. N. Quinn8, Dax L. Feliz9, Keivan G. Stassun9, Ian J. M. Crossfield10, Ian J. M. Crossfield7, David Berardo7, David W. Latham8, Ben Tieu1, Guillem Anglada-Escudé11, George R. Ricker7, Roland Vanderspek7, Sara Seager7, Joshua N. Winn, Jon M. Jenkins12, Stephen A. Rinehart3, Akshata Krishnamurthy7, Scott Dynes7, John P. Doty3, Fred C. Adams13, Dennis Afanasev3, Chas Beichman14, Michael Bottom15, Brendan P. Bowler16, Carolyn Brinkworth17, Carolyn Brown18, Andrew Cancino19, David R. Ciardi14, Mark Clampin3, Jake T. Clark18, Karen A. Collins8, Cassy Davison20, Daniel Foreman-Mackey, Elise Furlan14, Eric Gaidos15, Claire Geneser21, Frank Giddens19, Emily A. Gilbert22, Ryan Hall20, Coel Hellier23, Todd J. Henry, Jonathan Horner18, Andrew W. Howard14, Chelsea X. Huang7, Joseph Huber19, Stephen R. Kane24, Matthew A. Kenworthy25, John F. Kielkopf26, David M. Kipping27, Chris Klenke19, Ethan Kruse3, Natasha Latouf1, Patrick J. Lowrance14, Bertrand Mennesson14, Matthew W. Mengel18, Sean M. Mills14, Timothy D. Morton28, Norio Narita, Elisabeth R. Newton29, America Nishimoto19, Jack Okumura18, Enric Palle30, Joshua Pepper31, Elisa V. Quintana3, Aki Roberge3, Veronica Roccatagliata32, Joshua E. Schlieder3, Angelle Tanner21, Johanna Teske33, C. G. Tinney34, Andrew Vanderburg16, Kaspar von Braun35, Bernie Walp, Jason J. Wang5, Jason J. Wang14, Sharon X. Wang33, Denise Weigand19, Russel J. White20, Robert A. Wittenmyer18, Duncan J. Wright18, Allison Youngblood3, Hui Zhang36, Perri Zilberman37 
24 Jun 2020-Nature
TL;DR: In this paper, the authors reported observations of a planet transiting AU Microscopii (AU Mic b), which has an orbital period of 846 days, an orbital distance of 007-astronomical units, a radius of 04-Jupiter radii, and a mass of less than 18 Jupiter masses at 3σ confidence.
Abstract: AU Microscopii (AU Mic) is the second closest pre-main-sequence star, at a distance of 979 parsecs and with an age of 22 million years1 AU Mic possesses a relatively rare2 and spatially resolved3 edge-on debris disk extending from about 35 to 210 astronomical units from the star4, and with clumps exhibiting non-Keplerian motion5-7 Detection of newly formed planets around such a star is challenged by the presence of spots, plage, flares and other manifestations of magnetic 'activity' on the star8,9 Here we report observations of a planet transiting AU Mic The transiting planet, AU Mic b, has an orbital period of 846 days, an orbital distance of 007 astronomical units, a radius of 04 Jupiter radii, and a mass of less than 018 Jupiter masses at 3σ confidence Our observations of a planet co-existing with a debris disk offer the opportunity to test the predictions of current models of planet formation and evolution

92 citations


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Journal ArticleDOI
TL;DR: The Spitzer Space Telescope, NASA's great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit as mentioned in this paper.
Abstract: The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected, and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical, and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first 6 months of the Spitzer mission.

3,177 citations

Journal ArticleDOI
TL;DR: In this paper, the star formation efficiency (SFE) per unit of gas in 23 nearby galaxies and compare it with expectations from proposed star formation laws and thresholds was measured, and the authors interpreted this decline as a strong dependence of giant molecular cloud (GMC) formation on environment.
Abstract: We measure the star formation efficiency (SFE), the star formation rate (SFR) per unit of gas, in 23 nearby galaxies and compare it with expectations from proposed star formation laws and thresholds. We use H I maps from The H I Nearby Galaxy Survey (THINGS) and derive H2 maps of CO measured by HERA CO-Line Extragalactic Survey and Berkeley-Illinois-Maryland Association Survey of Nearby Galaxies. We estimate the SFR by combining Galaxy Evolution Explorer (GALEX) far-ultraviolet maps and the Spitzer Infrared Nearby Galaxies Survey (SINGS) 24 ?m maps, infer stellar surface density profiles from SINGS 3.6 ?m data, and use kinematics from THINGS. We measure the SFE as a function of the free fall and orbital timescales, midplane gas pressure, stability of the gas disk to collapse (including the effects of stars), the ability of perturbations to grow despite shear, and the ability of a cold phase to form. In spirals, the SFE of H2 alone is nearly constant at (5.25 ? 2.5) ? 10?10 yr?1 (equivalent to an H2 depletion time of 1.9 ? 109 yr) as a function of all of these variables at our 800 pc resolution. Where the interstellar medium (ISM) is mostly H I, however, the SFE decreases with increasing radius in both spiral and dwarf galaxies, a decline reasonably described by an exponential with scale length 0.2r 25-0.25r 25. We interpret this decline as a strong dependence of giant molecular cloud (GMC) formation on environment. The ratio of molecular-to-atomic gas appears to be a smooth function of radius, stellar surface density, and pressure spanning from the H2-dominated to H I-dominated ISM. The radial decline in SFE is too steep to be reproduced only by increases in the free-fall time or orbital time. Thresholds for large-scale instability suggest that our disks are stable or marginally stable and do not show a clear link to the declining SFE. We suggest that ISM physics below the scales that we observe?phase balance in the H I, H2 formation and destruction, and stellar feedback?governs the formation of GMCs from H I.

1,888 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the relationship between the local environment of galaxies and their star formation rate (SFR) in the Great Observatories Origins Deep Survey, GOODS, at z∼1.
Abstract: Aims We study the relationship between the local environment of galaxies and their star formation rate (SFR) in the Great Observatories Origins Deep Survey, GOODS, at z∼1 Methods We use ultradeep imaging at 24� m with the MIPS camera onboard Spitzer to determine the contribution of obscured light to the SFR of galaxies over the redshift range 08≤ z ≤12 Accurate galaxy densities are measured thanks to the large sample of ∼1200 spectroscopic redshifts with high (∼70 %) spectroscopic completeness Morphology and stellar masses are derived from deep HST-ACS imaging, supplemented by ground based imaging programs and photometry from the IRAC camera onboard Spitzer Results We show that the star formation‐density relation observed locally was reversed at z∼ 1: the average SFR of an individual galaxy increased with local galaxy density when the universe was less than half its present age Hierarchical galaxy for mation models (simulated lightcones from the Millennium model) predicted such a reversal to occur only at earlier epochs (z>2) and at a lower level We present a remarkable structure at z∼ 1016, containing X-ray traced galaxy concentrations, which will eventually merge into a Virgo-like cluster This structure illustrates how the ind ividual SFR of galaxies increases with density and shows that it is the∼1‐2 Mpc scale that affects most the star formation in galaxies at z∼ 1 The SFR of z∼ 1 galaxies is found to correlate with stellar mass suggesting that mass plays a role in the observed star formation‐density trend However the specific SFR ( =SFR/M⋆) decreases with stellar mass while it increases with galaxy density, which i mplies that the environment does directly affect the star formation activity of galaxies Major mergers do not appear to be the unique or even major cause for this effect since nearly half (46 %) of the luminous infrared galaxies (LIRGs) at z∼ 1 present the HST-ACS morphology of spirals, while only a third present a clear signature of major mergers The remaining galaxies are divided into compact (9 %) and irregular (14 %) galaxies Moreover, the specific SFR o f major mergers is only marginally stronger than that of spirals Conclusions These findings constrain the influence of the growth of large- scale structures on the star formation history of galaxies Reproducing the SFR‐density relation at z∼ 1 is a new challenge for models, requiring a correct balance between mass assembly through mergers and in-situ star formation at early epochs

1,696 citations

Journal ArticleDOI
TL;DR: The Infrared Spectrograph (IRS) as discussed by the authors is one of the three science instruments on the Spitzer Space Telescope and is optimized to take full advantage of the very low background in the space environment.
Abstract: The Infrared Spectrograph (IRS) is one of three science instruments on the Spitzer Space Telescope .T he IRS comprises four separate spectrograph modules covering the wavelength range from 5.3 to 38 � m with spectral resolutions, R ¼ k=� k � 90 and 600, and it was optimized to take full advantage of the very low background in the space environment. The IRS is performing at or better than the prelaunch predictions. An autonomous target acquisition capability enables the IRS to locate the mid-infrared centroid of a source, providing the information so that the spacecraft can accurately offset that centroid to a selected slit. This feature is particularly useful when taking spectra of sources with poorly known coordinates. An automated data-reduction pipeline has been developed at the Spitzer Science Center. Subject headingg infrared: general — instrumentation: spectrographs — space vehicles: instruments

1,628 citations

Journal ArticleDOI
23 Feb 2017-Nature
TL;DR: The observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1, and the six inner planets form a near-resonant chain, such that their orbital periods are near-ratios of small integers.
Abstract: One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away. The transiting configuration of these planets, combined with the Jupiter-like size of their host star—named TRAPPIST-1—makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities. Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces.

1,476 citations