arXiv subjects

E. R. Adams

Publications and source records attributed to E. R. Adams.

11 recordsLinked to original sources

arXiv2026

Measurement of dijet transverse momentum imbalance and azimuthal acoplanarity in $p$+$p$ collisions at $\sqrt{s} = 200$ GeV with the sPHENIX detector

This Letter reports on measurements of dijet transverse momentum ($p_\mathrm{T}$) imbalance and azimuthal acoplanarity in proton-proton collisions at $\sqrt{s} = 200$~GeV, using data recorded by the sPHENIX detector at the Relativistic Heavy Ion Collider corresponding to an integrated luminosity of $41$~pb$^{-1}$. Jets are reconstructed using the anti-$k_t$ algorithm with radius parameters $R = 0.3$ to $0.8$ from electromagnetic and hadronic calorimeter energy deposits. The jet $p_\mathrm{T}$ resolution is determined directly in data using two independent methods. The dijet $p_\mathrm{T}$ imbalance is characterized by the ratio $x_\mathrm{J} = p_\mathrm{T,2}/p_\mathrm{T,1}$ where $p_\mathrm{T,1(2)}$ is the highest (second-highest) jet $p_\mathrm{T}$ in the event. The dijet azimuthal acoplanarity $\Delta\phi = |\phi_1 - \phi_2|$ is also reported. Results are reported for different $p_\mathrm{T,1}$ selections and jet radius parameters, normalized per dijet pair, and compared to the results of \textsc{Pythia} and \textsc{Herwig} Monte Carlo event generators. These measurements provide a stringent quantitative test of the modeling of QCD parton shower and hadronization dynamics, place important constraints on event-generator descriptions at RHIC energies, and establish a comprehensive proton-proton baseline for forthcoming measurements of jet modification in heavy ion collisions.

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arXiv2025

Measurement of charged hadron multiplicity in Au+Au collisions at $\sqrt{\text{s}_{\text{NN}}} = 200$ GeV with the sPHENIX detector

The pseudorapidity distribution of charged hadrons produced in Au+Au collisions at a center-of-mass energy of $\sqrt{s_\mathrm{NN}} = 200$ GeV is measured using data collected by the sPHENIX detector. Charged hadron yields are extracted by counting cluster pairs in the inner and outer layers of the Intermediate Silicon Tracker, with corrections applied for detector acceptance, reconstruction efficiency, combinatorial pairs, and contributions from secondary decays. The measured distributions cover $|\eta| < 1.1$ across various centralities, and the average pseudorapidity density of charged hadrons at mid-rapidity is compared to predictions from Monte Carlo heavy-ion event generators. This result, featuring full azimuthal coverage at mid-rapidity, is consistent with previous experimental measurements at the Relativistic Heavy Ion Collider, thereby supporting the broader sPHENIX physics program.

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arXiv2025

Measurement of the transverse energy density in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV with the sPHENIX detector

This paper reports measurements of the transverse energy per unit pseudorapidity ($dE_{T}/d\eta$) produced in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV, performed with the sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The results cover the pseudorapidity range $\left|\eta\right| < 1.1$ and constitute the first such measurement performed using a hadronic calorimeter at RHIC. Measurements of $dE_{T}/d\eta$ are presented for a range of centrality intervals and the average $dE_{T}/d\eta$ as a function of the number of participating nucleons, $N_{\mathrm{part}}$, is compared to a variety of Monte Carlo heavy-ion event generators. The results are in agreement with previous measurements at RHIC, and feature an improved granularity in $\eta$ and improved precision in low-$N_{\mathrm{part}}$ events.

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arXiv2017

The Kepler Follow-Up Observation Program. I. A Catalog of Companions to Kepler Stars from High-Resolution Imaging

We present results from high-resolution, optical to near-IR imaging of host stars of Kepler Objects of Interest (KOIs), identified in the original Kepler field. Part of the data were obtained under the Kepler imaging follow-up observation program over seven years (2009 - 2015). Almost 90% of stars that are hosts to planet candidates or confirmed planets were observed. We combine measurements of companions to KOI host stars from different bands to create a comprehensive catalog of projected separations, position angles, and magnitude differences for all detected companion stars (some of which may not be bound). Our compilation includes 2297 companions around 1903 primary stars. From high-resolution imaging, we find that ~10% (~30%) of the observed stars have at least one companion detected within 1" (4"). The true fraction of systems with close (< ~4") companions is larger than the observed one due to the limited sensitivities of the imaging data. We derive correction factors for planet radii caused by the dilution of the transit depth: assuming that planets orbit the primary stars or the brightest companion stars, the average correction factors are 1.06 and 3.09, respectively. The true effect of transit dilution lies in between these two cases and varies with each system. Applying these factors to planet radii decreases the number of KOI planets with radii smaller than 2 R_Earth by ~2-23% and thus affects planet occurrence rates. This effect will also be important for the yield of small planets from future transit missions such as TESS.

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arXiv2015

TraMoS IV: Discarding the Quick Orbital Decay Hypothesis for OGLE-TR-113b

In the context of the TraMoS project we present nine new transit observations of the exoplanet OGLE-TR-113b observed with the Gemini South, Magellan Baade, Danish-1.54m and SOAR telescopes. We perform a homogeneous analysis of these new transits together with ten literature transits to probe into the potential detection of an orbital decay for this planet reported by \citet{adams2010}. Our new observations extend the transit monitoring baseline for this system by 6 years, to a total of more than 13 years. With our timing analysis we obtained a $\dot{P}=-1.0 \pm 6.0$ ms~yr$^{-1}$, which rejects previous hints of a larger orbital decay for OGLE-TR-113b. With our updated value of $\dot{P}$ we can discard tidal quality factors of $Q_{\star} < 10^{5}$ for its host star. Additionally, we calculate a 1$σ$ dispersion of the Transit Timing Variations (TTVs) of 42 seconds over the 13 years baseline, which discards additional planets in the system more massive than $0.5-3.0~M_{\oplus}$ in 1:2, 5:3, 2:1 and 3:1 Mean Motion Resonances with OGLE-TR-113b. Finally, with the joint analysis of the 19 light curves we update transit parameters, such as the relative semi-major axis $a / R_s = 6.44^{+0.04}_{-0.05}$, the planet-to-star radius ratio $R_p / R_s =0.14436^{+0.00096}_{-0.00088}$, and constrains its orbital inclination to $i =89.27^{+0.51}_{-0.68}$~degrees.

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arXiv2014

De-biased Populations of Kuiper Belt Objects from the Deep Ecliptic Survey

The Deep Ecliptic Survey (DES) discovered hundreds of Kuiper Belt objects from 1998-2005. Follow-up observations yielded 304 objects with good dynamical classifications (Classical, Scattered, Centaur, or 16 mean-motion resonances with Neptune). The DES search fields are well documented, enabling us to calculate the probability of detecting objects with particular orbital parameters and absolute magnitudes at a randomized point in each orbit. Grouping objects together by dynamical class leads, we estimate the orbital element distributions (a, e, i) for the largest three classes (Classical, 3:2, and Scattered) using maximum likelihood. Using H-magnitude as a proxy for the object size, we fit a power law to the number of objects for 8 classes with at least 5 detected members (246 objects). The best Classical slope is alpha=1.02+/-0.01 (observed from 5<=H<=7.2). Six dynamical classes (Scattered plus 5 resonances) are consistent in slope with the Classicals, though the absolute number of objects is scaled. The exception to the power law relation are the Centaurs (non-resonant with perihelia closer than Neptune, and thus detectable at smaller sizes), with alpha=0.42+/-0.02 (7.5<H<11). This is consistent with a knee in the H-distribution around H=7.2 as reported elsewhere (Bernstein et al. 2004, Fraser et al. 2014). Based on the Classical-derived magnitude distribution, the total number of objects (H<=7) in each class are: Classical (2100+/-300 objects), Scattered (2800+/-400), 3:2 (570+/-80), 2:1 (400+/-50), 5:2 (270+/-40), 7:4 (69+/-9), 5:3 (60+/-8). The independent estimate for the number of Centaurs in the same H range is 13+/-5. If instead all objects are divided by inclination into "Hot" and "Cold" populations, following Fraser et al. (2014), we find that alphaHot=0.90+/-0.02, while alphaCold=1.32+/-0.02, in good agreement with that work.

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arXiv2011

Twenty-One New Light Curves of OGLE-TR-56b: New System Parameters and Limits on Timing Variations

Although OGLE-TR-56b was the second transiting exoplanet discovered, only one light curve, observed in 2006, has been published besides the discovery data. We present twenty-one light curves of nineteen different transits observed between July 2003 and July 2009 with the Magellan Telescopes and Gemini South. The combined analysis of the new light curves confirms a slightly inflated planetary radius relative to model predictions, with R_p = 1.378 +/- 0.090 R_J. However, the values found for the transit duration, semimajor axis, and inclination values differ significantly from the previous result, likely due to systematic errors. The new semimajor axis and inclination, a = 0.01942 +/- 0.00015 AU and i = 73.72 +/- 0.18 degrees, are smaller than previously reported, while the total duration, T_14 = 7931 +/- 38 s, is 18 minutes longer. The transit midtimes have errors from 23 s to several minutes, and no evidence is seen for transit midtime or duration variations. Similarly, no change is seen in the orbital period, implying a nominal stellar tidal decay factor of Q_* = 10^7, with a three-sigma lower limit of 10^5.7.

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arXiv2011

First results from the MIT Optical Rapid Imaging System (MORIS) on the IRTF: a stellar occultation by Pluto and a transit by exoplanet XO-2b

We present a high-speed, visible-wavelength imaging instrument: MORIS (the MIT Optical Rapid Imaging System). MORIS is mounted on the 3-m Infrared Telescope Facility (IRTF) on Mauna Kea, HI. Its primary component is an Andor iXon camera, a nearly 60 arcsec square field of view with high quantum efficiency, low read noise, low dark current, and full-frame readout rates ranging from as slow as desired to a maximum of between 3.5 Hz and 35 Hz (depending on the mode; read noise of 6e-/pixel and 49 e-/pixel with electron-multiplying gain=1, respectively). User-selectable binning and subframing can increase the cadence to a few hundred Hz. An electron-multiplying mode can be employed for photon counting, effectively reducing the read noise to sub-electron levels at the expense of dynamic range. Data cubes, or individual frames, can be triggered to several nanosecond accuracy using the Global Positioning System. MORIS is mounted on the side-facing exit window of SpeX (Rayner et al. 2003), allowing simultaneous near-infrared and visible observations. Here we describe the components, setup, and measured characteristics of MORIS. We also report results from the first science observations: the 24 June 2008 stellar occultation by Pluto and an extrasolar planetary transit by XO-2b. The Pluto occultation, of a 15.8 R magnitude star, has signal-to-noise ratio of 35 per atmospheric scale height and a midtime error of 0.32 s. The XO-2b transit reaches photometric precision of 0.5 millimagnitudes in 2 minutes and has a midtime timing precision of 23 seconds.

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arXiv2010

Six High-Precision Transits of OGLE-TR-113b

We present six new transits of the hot Jupiter OGLE-TR-113b observed with MagIC on the Magellan Telescopes between January 2007 and May 2009. We update the system parameters and revise the planetary radius to R_p=1.084 pm 0.029 R_J, where the error is dominated by stellar radius uncertainties. The new transit midtimes reveal no transit timing variations from a constant ephemeris of greater than 13 pm 28 seconds over two years, placing an upper limit of 1-2 M_Earth on the mass of any perturber in a 1:2 or 2:1 mean-motion resonance with OGLE-TR-113b. Combining the new transit epochs with five epochs published between 2002 and 2006, we find hints that the orbital period of the planet may not be constant, with the best fit indicating a decrease of dP/dt=-60 pm 15 milliseconds per year. If real, this change in period could result from either a long-period (more than 8 years) timing variation due to a massive external perturber, or more intriguingly from the orbital decay of the planet. The detection of a changing period is still tentative and requires additional observations, but if confirmed it would enable direct tests of tidal stability and dynamical models of close-in planets.

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arXiv2010

Lack of Transit Timing Variations of OGLE-TR-111b: A re-analysis with six new epochs

We present six new transits of the exoplanet OGLE-TR-111b observed with the Magellan Telescopes in Chile between April 2008 and March 2009. We combine these new transits with five previously published transit epochs for this planet between 2005 and 2006 to extend the analysis of transit timing variations reported for this system. We derive a new planetary radius value of 1.019 +/- 0.026 R_J, which is intermediate to the previously reported radii of 1.067 +/- 0.054 R_J (Winn et al. 2007) and 0.922 +/- 0.057 R_J (Diaz et al. 2008). We also examine the transit timing variation and duration change claims of Diaz et al. (2008). Our analysis of all eleven transit epochs does not reveal any points with deviations larger than 2 sigma, and most points are well within 1 sigma. Although the transit duration nominally decreases over the four year span of the data, systematic errors in the photometry can account for this result. Therefore, there is no compelling evidence for either a timing or a duration variation in this system. Numerical integrations place an upper limit of about 1 M_E on the mass of a potential second planet in a 2:1 mean-motion resonance with OGLE-TR-111b.

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arXiv2007

Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres

The bulk composition of an exoplanet is commonly inferred from its average density. For small planets, however, the average density is not unique within the range of compositions. Variations of a number of important planetary parameters--which are difficult or impossible to constrain from measurements alone--produce planets with the same average densities but widely varying bulk compositions. We find that adding a gas envelope equivalent to 0.1%-10% of the mass of a solid planet causes the radius to increase 5-60% above its gas-free value. A planet with a given mass and radius might have substantial water ice content (a so-called ocean planet) or alternatively a large rocky-iron core and some H and/or He. For example, a wide variety of compositions can explain the observed radius of GJ 436b, although all models require some H/He. We conclude that the identification of water worlds based on the mass-radius relationship alone is impossible unless a significant gas layer can be ruled out by other means.

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