arXiv subjects

Joseph E. Rodriguez

Publications and source records attributed to Joseph E. Rodriguez.

141 records · Page 8Linked to original sources

arXiv2017

The Mysterious Dimmings of the T Tauri Star V1334 Tau

We present the discovery of two extended $\sim$0.12 mag dimming events of the weak-lined T-Tauri star V1334. The start of the first event was missed but came to an end in late 2003, and the second began in February 2009, and continues as of November 2016. Since the egress of the current event has not yet been observed, it suggests a period of $>$13 years if this event is periodic. Spectroscopic observations suggest the presence of a small inner disk, although the spectral energy distribution shows no infrared excess. We explore the possibility that the dimming events are caused by an orbiting body (e.g. a disk warp or dust trap), enhanced disk winds, hydrodynamical fluctuations of the inner disk, or a significant increase in the magnetic field flux at the surface of the star. We also find a $\sim$0.32 day periodic photometric signal that persists throughout the 2009 dimming which appears to not be due to ellipsoidal variations from a close stellar companion. High precision photometric observations of V1334 Tau during K2 campaign 13, combined with simultaneous photometric and spectroscopic observations from the ground, will provide crucial information about the photometric variability and its origin.

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arXiv2017

The transiting dust clumps in the evolved disk of the Sun-like UXor RZ Psc

RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth mid-plane, so the disk's bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disk, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disk-related variability may arise because i) any accretion streams are transparent, and/or ii) turbulence above the inner rim is normally shadowed by a flared outer disk.

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arXiv2016

KELT-17b: A hot-Jupiter transiting an A-star in a misaligned orbit detected with Doppler tomography

We present the discovery of a hot-Jupiter transiting the V=9.23 mag main-sequence A-star KELT-17 (BD+14 1881). KELT-17b is a 1.31 -0.29/+0.28 Mj, 1.525 -0.060/+0.065 Rj hot-Jupiter in a 3.08 day period orbit misaligned at -115.9 +/- 4.1 deg to the rotation axis of the star. The planet is confirmed via both the detection of the radial velocity orbit, and the Doppler tomographic detection of the shadow of the planet over two transits. The nature of the spin-orbit misaligned transit geometry allows us to place a constraint on the level of differential rotation in the host star; we find that KELT-17 is consistent with both rigid-body rotation and solar differential rotation rates (alpha < 0.30 at 2 sigma significance). KELT-17 is only the fourth A-star with a confirmed transiting planet, and with a mass of 1.635 -0.061/+0.066 Msun, effective temperature of 7454 +/- 49 K, and projected rotational velocity v sin I_* = 44.2 -1.3/+1.5 km/s; it is amongst the most massive, hottest, and most rapidly rotating of known planet hosts.

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arXiv2016

KELT-12b: A $P \sim 5$ Day, Highly Inflated Hot Jupiter Transiting a Mildly Evolved Hot Star

We report the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting a mildly evolved host star. We identified the initial transit signal in the KELT-North survey data and established the planetary nature of the companion through precise follow-up photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the $V = 10.64$ host, TYC 2619-1057-1, has $T_{\rm eff} = 6278 \pm 51$ K, $\log{g_\star} = 3.89^{+0.054}_{-0.051}$, and [Fe/H] = $0.19^{+0.083}_{-0.085}$, with an inferred mass $M_{\star} = 1.59^{+0.071}_{-0.091} M_\odot$ and radius $R_\star = 2.37 \pm 0.18 R_\odot$. The planetary companion has $M_{\rm P} = 0.95 \pm 0.14 M_{\rm J}$, $R_{\rm P} = 1.79^{+0.18}_{-0.17} R_{\rm J}$, $\log{g_{\rm P}} = 2.87^{+0.097}_{-0.098}$, and density $ρ_{\rm P} = 0.21^{+0.075}_{-0.054}$ g cm$^{-3}$, making it one of the most inflated giant planets known. The time of inferior conjunction in ${\rm BJD_{TDB}}$ is $2457088.692055 \pm 0.0009$ and the period is $P = 5.0316144 \pm 0.0000306$ days. Despite the relatively large separation of $\sim0.07$ AU implied by its $\sim 5.03$-day orbital period, KELT-12b receives significant flux of $2.93^{+0.33}_{-0.30} \times 10^9$ erg s$^{-1}$ cm$^{-2}$ from its host. We compare the radii and insolations of transiting gas-giant planets around hot ($T_{\rm eff} \geq 6250$ K) and cool stars, noting that the observed paucity of known transiting giants around hot stars with low insolation is likely due to selection effects. We underscore the significance of long-term ground-based monitoring of hot stars and space-based targeting of hot stars with the Transiting Exoplanet Survey Satellite (TESS) to search for inflated giants in longer-period orbits.

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arXiv2016

DM Ori: A Young Star Occulted by a Disturbance in its Protoplanetary Disk

In some planet formation theories, protoplanets grow gravitationally within a young star's protoplanetary disk, a signature of which may be a localized disturbance in the disk's radial and/or vertical structure. Using time-series photometric observations by the Kilodegree Extremely Little Telescope South (KELT-South) project and the All-Sky Automated Survey for SuperNovae (ASAS-SN), combined with archival observations, we present the discovery of two extended dimming events of the young star, DM Ori. This young system faded by $\sim$1.5 mag from 2000 March to 2002 August and then again in 2013 January until 2014 September (depth $\sim$1.7 mag). We constrain the duration of the 2000-2002 dimming to be $<$ 860 days, and the event in 2013-2014 to be $<$ 585 days, separated by $\sim$12.5 years. A model of the spectral energy distribution (SED) indicates a large infrared excess consistent with an extensive circumstellar disk. Using basic kinematic arguments, we propose that DM Ori is likely being periodically occulted by a feature (possibly a warp or perturbation) in its circumstellar disk. In this scenario, the occulting feature is located $>$6 AU from the host star, moving at $\sim$14.6 km/s, and is $\sim$4.9 AU in width. This localized structure may indicate a disturbance such as may be caused by a protoplanet early in its formation.

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arXiv2016

KELT-10b: The First Transiting Exoplanet from the KELT-South Survey -- A Hot Sub-Jupiter Transiting a V = 10.7 Early G-Star

We report the discovery of KELT-10b, the first transiting exoplanet discovered using the KELT-South telescope. KELT-10b is a highly inflated sub-Jupiter mass planet transiting a relatively bright $V = 10.7$ star (TYC 8378-64-1), with T$_{eff}$ = $5948\pm74$ K, $\log{g}$ = $4.319_{-0.030}^{+0.020}$ and [Fe/H] = $0.09_{-0.10}^{+0.11}$, an inferred mass M$_{*}$ = $1.112_{-0.061}^{+0.055}$ M$_{\odot}$ and radius R$_{*}$ = $1.209_{-0.035}^{+0.047}$ R$_{\odot}$. The planet has a radius R$_{P}$ = $1.399_{-0.049}^{+0.069}$ R$_{J}$ and mass M$_{P}$ = $0.679_{-0.038}^{+0.039}$ M$_{J}$. The planet has an eccentricity consistent with zero and a semi-major axis $a$ = $0.05250_{-0.00097}^{+0.00086}$ AU. The best fitting linear ephemeris is $T_{0}$ = 2457066.72045$\pm$0.00027 BJD$_{TDB}$ and P = 4.1662739$\pm$0.0000063 days. This planet joins a group of highly inflated transiting exoplanets with a radius much larger and a mass much less than those of Jupiter. The planet, which boasts deep transits of 1.4%, has a relatively high equilibrium temperature of T$_{eq}$ = $1377_{-23}^{+28}$ K, assuming zero albedo and perfect heat redistribution. KELT-10b receives an estimated insolation of $0.817_{-0.054}^{+0.068}$ $\times$ 10$^9$ erg s$^{-1}$ cm$^{-2}$, which places it far above the insolation threshold above which hot Jupiters exhibit increasing amounts of radius inflation. Evolutionary analysis of the host star suggests that KELT-10b is unlikely to survive beyond the current subgiant phase, due to a concomitant in-spiral of the planet over the next $\sim$1 Gyr. The planet transits a relatively bright star and exhibits the third largest transit depth of all transiting exoplanets with V $<$ 11 in the southern hemisphere, making it a promising candidate for future atmospheric characterization studies.

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arXiv2016

KELT-11b: A Highly Inflated Sub-Saturn Exoplanet Transiting the V=8 Subgiant HD 93396

We report the discovery of a transiting exoplanet, KELT-11b, orbiting the bright ($V=8.0$) subgiant HD 93396. A global analysis of the system shows that the host star is an evolved subgiant star with $T_{\rm eff} = 5370\pm51$ K, $M_{*} = 1.438_{-0.052}^{+0.061} M_{\odot}$, $R_{*} = 2.72_{-0.17}^{+0.21} R_{\odot}$, log $g_*= 3.727_{-0.046}^{+0.040}$, and [Fe/H]$ = 0.180\pm0.075$. The planet is a low-mass gas giant in a $P = 4.736529\pm0.00006$ day orbit, with $M_{P} = 0.195\pm0.018 M_J$, $R_{P}= 1.37_{-0.12}^{+0.15} R_J$, $ρ_{P} = 0.093_{-0.024}^{+0.028}$ g cm$^{-3}$, surface gravity log ${g_{P}} = 2.407_{-0.086}^{+0.080}$, and equilibrium temperature $T_{eq} = 1712_{-46}^{+51}$ K. KELT-11 is the brightest known transiting exoplanet host in the southern hemisphere by more than a magnitude, and is the 6th brightest transit host to date. The planet is one of the most inflated planets known, with an exceptionally large atmospheric scale height (2763 km), and an associated size of the expected atmospheric transmission signal of 5.6%. These attributes make the KELT-11 system a valuable target for follow-up and atmospheric characterization, and it promises to become one of the benchmark systems for the study of inflated exoplanets.

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arXiv2016

An Extreme Analogue of $ε$ Aurigae: An M-giant Eclipsed Every 69 Years by a Large Opaque Disk Surrounding a Small Hot Source

We present TYC 2505-672-1 as a newly discovered and remarkable eclipsing system comprising an M-type red giant that undergoes a ~3.45 year long, near-total eclipse (depth of ~4.5 mag) with a very long period of ~69.1 yr. TYC 2505-672-1 is now the longest-period eclipsing binary system yet discovered, more than twice as long as that of the currently longest-period system, $ε$ Aurigae. We show from analysis of the light curve including both our own data and historical data spanning more than 120 yr and from modeling of the spectral energy distribution, both before and during eclipse, that the red giant primary is orbited by a moderately hot source (T$_{eff}$~8000 K) that is itself surrounded by an extended, opaque circumstellar disk. From the measured ratio of luminosities, the radius of the hot companion must be in the range 0.1-0.5 Rsun (depending on the assumed radius of the red giant primary), which is an order of magnitude smaller than that for a main sequence A star and 1-2 orders of magnitude larger than that for a white dwarf. The companion is therefore most likely a "stripped red giant" subdwarf-B type star destined to become a He white dwarf. It is however somewhat cooler than most sdB stars, implying a very low mass for this "pre-He-WD" star. The opaque disk surrounding this hot source may be a remnant of the stripping of its former hydrogen envelope. However, it is puzzling how this object became stripped, given that it is at present so distant (orbital semi-major axis of ~24 AU) from the current red giant primary star. Extrapolating from our calculated ephemeris, the next eclipse should begin in early UT 2080 April and end in mid UT 2083 September (eclipse center UT 2081 December 24). This system is poised to become an exemplar of a very rare class of systems, even more extreme in several respects than the well studied archetype $ε$ Aurigae.

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arXiv2016

KELT-14b and KELT-15b: An Independent Discovery of WASP-122b and a New Hot Jupiter

We report the discovery of KELT-14b and KELT-15b, two hot Jupiters from the KELT-South survey. KELT-14b, an independent discovery of the recently announced WASP-122b, is an inflated Jupiter mass planet that orbits a $\sim5.0^{+0.3}_{-0.7}$ Gyr, $V$ = 11.0, G2 star that is near the main sequence turnoff. The host star, KELT-14 (TYC 7638-981-1), has an inferred mass $M_{*}$=$1.18_{-0.07}^{+0.05}$$M_{\odot}$ and radius $R_{*}$=$1.37\pm{-0.08}$$R_{\odot}$, and has $T_{eff}$=$5802_{-92}^{+95}$K, $\log{g_*}$=$4.23_{-0.04}^{+0.05}$ and =$0.33\pm{0.09}$. The planet orbits with a period of $1.7100588 \pm 0.0000025$ days ($T_{0}$=2457091.02863$\pm$0.00047) and has a radius R$_{p}$=$1.52_{-0.11}^{+0.12}$$R_{J}$ and mass M$_{p}$=$1.196\pm0.072$$M_{J}$, and the eccentricity is consistent with zero. KELT-15b is another inflated Jupiter mass planet that orbits a $\sim$ $4.6^{+0.5}_{-0.4}$ Gyr, $V$ = 11.2, G0 star (TYC 8146-86-1) that is near the "blue hook" stage of evolution prior to the Hertzsprung gap, and has an inferred mass $M_{*}$=$1.181_{-0.050}^{+0.051}$$M_{\odot}$ and radius $R_{*}$=$1.48_{-0.04}^{+0.09}$$R_{\odot}$, and $T_{eff}$=$6003_{-52}^{+56}$K, $\log{g_*}$=$4.17_{-0.04}^{+0.02}$ and [Fe/H]=$0.05\pm0.03$. The planet orbits on a period of $3.329441 \pm 0.000016$ days ($T_{0}$ = 2457029.1663$\pm$0.0073) and has a radius R$_{p}$=$1.443_{-0.057}^{+0.11}$$R_{J}$ and mass M$_{p}$=$0.91_{-0.22}^{+0.21}$$M_{J}$ and an eccentricity consistent with zero. KELT-14b has the second largest expected emission signal in the K-band for known transiting planets brighter than $K<10.5$. Both KELT-14b and KELT-15b are predicted to have large enough emission signals that their secondary eclipses should be detectable using ground-based observatories.

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arXiv2015

Recurring Occultations of RW Aurigae by Coagulated Dust in the Tidally Disrupted Circumstellar Disk

We present photometric observations of RW Aurigae, a Classical T Tauri system, that reveal two remarkable dimming events. These events are similar to that which we observed in 2010-2011, which was the first such deep dimming observed in RW Aur in a century's worth of photometric monitoring. We suggested the 2010-2011 dimming was the result of an occultation of the star by its tidally disrupted circumstellar disk. In 2012-2013, the RW Aur system dimmed by ~0.7 mag for ~40 days and in 2014/2015 the system dimmed by ~2 mag for >250 days. The ingress/egress duration measurements of the more recent events agree well with those from the 2010-2011 event, providing strong evidence that the new dimmings are kinematically associated with the same occulting source. Therefore, we suggest that both the 2012-2013 and 2014-2015 dimming events, measured using data from the Kilodegree Extremely Little Telescope and the Kutztown University Observatory, are also occultations of RW Aur A by tidally disrupted circumstellar material. Recent hydrodynamical simulations of the eccentric fly-by of RW Aur B suggest the occulting body to be a bridge of material connecting RW Aur A and B. These simulations suggest the possibility of additional occultations, supported by the observations presented in this work. The color evolution of the dimmings suggest that the tidally stripped disk material includes dust grains ranging in size from small grains at the leading edge, typical of star forming regions, to large grains, ices or pebbles producing grey or nearly grey extinction deeper within the occulting material. It is not known whether this material represents arrested planet building prior to the tidal disruption event, or perhaps accelerated planet building as a result of the disruption event, but in any case the evidence suggests the presence of advanced planet building material in the space between RW Aur A and B.

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arXiv2015

KELT-8b: A highly inflated transiting hot Jupiter and a new technique for extracting high-precision radial velocities from noisy spectra

We announce the discovery of a highly inflated transiting hot Jupiter discovered by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly evolved, G dwarf with $T_{\rm eff} = 5754_{-55}^{+54}$ K, $\log{g} = 4.078_{-0.054}^{+0.049}$, $[Fe/H] = 0.272\pm0.038$, an inferred mass $M_{*}=1.211_{-0.066}^{+0.078}$ M$_{\odot}$, and radius $R_{*}=1.67_{-0.12}^{+0.14}$ R$_{\odot}$. The planetary companion has mass $M_P = 0.867_{-0.061}^{+0.065}$ $M_{J}$, radius $R_P = 1.86_{-0.16}^{+0.18}$ $R_{J}$, surface gravity $\log{g_{P}} = 2.793_{-0.075}^{+0.072}$, and density $ρ_P = 0.167_{-0.038}^{+0.047}$ g cm$^{-3}$. The planet is on a roughly circular orbit with semimajor axis $a = 0.04571_{-0.00084}^{+0.00096}$ AU and eccentricity $e = 0.035_{-0.025}^{+0.050}$. The best-fit linear ephemeris is $T_0 = 2456883.4803 \pm 0.0007$ BJD$_{\rm TDB}$ and $P = 3.24406 \pm 0.00016$ days. This planet is one of the most inflated of all known transiting exoplanets, making it one of the few members of a class of extremely low density, highly-irradiated gas giants. The low stellar $\log{g}$ and large implied radius are supported by stellar density constraints from follow-up light curves, plus an evolutionary and space motion analysis. We also develop a new technique to extract high precision radial velocities from noisy spectra that reduces the observing time needed to confirm transiting planet candidates. This planet boasts deep transits of a bright star, a large inferred atmospheric scale height, and a high equilibrium temperature of $T_{eq}=1675^{+61}_{-55}$ K, assuming zero albedo and perfect heat redistribution, making it one of the best targets for future atmospheric characterization studies.

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arXiv2015

First Results from the Disk Eclipse Search with KELT (DESK) Survey

Using time-series photometry from the Kilodegree Extremely Little Telescope (KELT) exoplanet survey, we are looking for eclipses of stars by their protoplanetary disks, specifically in young stellar associations. To date, we have discovered two previously unknown, large dimming events around the young stars RW Aurigae and V409 Tau. We attribute the dimming of RW Aurigae to an occultation by its tidally disrupted disk, with the disruption perhaps resulting from a recent flyby of its binary companion. Even with the dynamical environment of RW Aurigae, the distorted disk material remains very compact and presumably capable of forming planets. This system also shows that strong binary interactions with disks can also influence planet and core composition by stirring up and mixing materials during planet formation. We interpret the dimming of V409 Tau to be due to a feature, possibly a warp or perturbation, lying at least 10 AU from the host star in its nearly edge-on circumstellar disk.

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arXiv2015

V409 Tau As Another AA Tau: Photometric Observations of Stellar Occultations by the Circumstellar Disk

AA Tau is a well studied young stellar object that presents many of the photometric characteristics of a Classical T Tauri star (CTTS), including short-timescale stochastic variability attributed to spots and/or accretion as well as long duration dimming events attributed to occultations by vertical features (e.g., warps) in its circumstellar disk. We present new photometric observations of AA Tau from the Kilodegree Extremely Little Telescope North (KELT-North) which reveal a deep, extended dimming event in 2011, which we show supports the interpretation by Bouvier et al. (2013) of an occultation by a high-density feature in the circumstellar disk located >8 AU from the star. We also present KELT-North observations of V409 Tau, a relatively unstudied young stellar object also in Taurus-Auriga, showing short timescale erratic variability, along with two separate long and deep dimming events, one from January 2009 through late October 2010, and the other from March 2012 until at least September 2013. We interpret both dimming events to have lasted more than 600 days, each with a depth of ~1.4 mag. From a spectral energy distribution analysis, we propose that V409 Tau is most likely surrounded by a circumstellar disk viewed nearly edge-on, and using Keplerian timescale arguments we interpret the deep dimmings of V409 Tau as occultations from one or more features within this disk >10 AU from the star. In both AA Tau and V409 Tau, the usual CTTS short-timescale variations associated with accretion processes close to the stars continue during the occultations, further supporting the distant occulting material interpretation. Like AA Tau, V409 Tau serves as a laboratory for studying the detailed structure of the protoplanetary environments of T Tauri disks, specifically disk structures that may be signposts of planet formation at many AU out in the disk.

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arXiv2014

New Red Jewels in Coma Berenices

We have used Sloan Digital Sky Survey-III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) radial velocity observations in the near-infrared $H$-band to explore the membership of the nearby ($86.7 \pm 0.9$ pc) open cluster Coma Berenices (Melotte 111), concentrating on the poorly-populated low-mass end of the main sequence. Using SDSS-III APOGEE radial velocity measurements, we confirm the membership of eight K/M dwarf members, providing the first confirmed low-mass members of the Coma Berenices cluster. Using $R\sim2000$ spectra from IRTF-SpeX, we confirm the independently luminosity classes of these targets, and find their metallicities to be consistent with the known solar mean metallicity of Coma Berenices and of M dwarfs in the Solar neighborhood. In addition, the APOGEE spectra have enabled measurement of $v\sin i$ for each target and detection for the first time of the low-mass secondary components of the known binary systems Melotte 111 102 and Melotte 111 120, as well as identification of the previously unknown binary system 2MASS J12214070+2707510. Finally, we use Kilodegree Extremely Little Telescope (KELT) photometry to measure photometric variability and rotation periods for a subset of the Coma Berenices members.

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arXiv2013

Occultation of the T Tauri Star RW Aurigae A by its Tidally Disrupted Disk

RW Aur A is a classical T Tauri star, believed to have undergone a reconfiguration of its circumstellar environment as a consequence of a recent fly-by of its stellar companion, RW Aur B. This interaction stripped away part of the circumstellar disk of RW Aur A, leaving a tidally disrupted arm and a short truncated circumstellar disk. We present photometric observations of the RW Aur system from the Kilodegree Extremely Little Telescope (KELT) survey showing a long and deep dimming that occurred from September 2010 until March 2011. The dimming has a depth of ~2 magnitudes, a duration of ~180 days and was confirmed by archival observations from American Association of Variable Star Observers (AAVSO). We suggest that this event is the result of a portion of the tidally disrupted disk occulting RW Aur A, specifically a fragment of the tidally disrupted arm. The calculated transverse linear velocity of the occulter is in excellent agreement with the measured relative radial velocity of the tidally disrupted arm. Using simple kinematic and geometric arguments, we show that the occulter cannot be a feature of the RW Aur A circumstellar disk, and we consider and discount other hypotheses. We also place constraints on the thickness and semi-major axis of the portion of the arm that occulted the star.

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