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A Spectral and Lightcurve Study of 50+ Blue Stars from the Burrell-Optical-Kepler-Survey (BOKS)
Jared Lalmansingh1, S. Howell2, D. Walter1, J. Cash1, K. Mighell2
1South Carolina State University, 2National Optical Astronomy Observatory.
BOKS used the 0.6 m Burrell-Schmidt telescope over a period of 40 nights and identified 54,687 stars between 14 < r < 19 in the Kepler Mission’s field of view. Its primary goal was to detect Jupiter-sized and Hot Jupiter (Period = 3 - 9 days) short-period exoplanets within the survey field as well as to compile high precision stellar variability data that the Kepler Mission can use for comparison purposes and to characterize the hundreds of other variable stars within the survey region.
We present the spectral classifications and light curve analysis of a sub-sample of 50+ blue stars within the BOKS field of view using BOKS lightcurve data and spectra from the Kitt Peak 2.1 meter telescope. The purpose of this study is to identify the variability of and provide characterization for the blue star population within the BOKS field.
Support for this work was provided by NOAO and the NSF PAARE program to South Carolina State University under award AST-0750814.
A Method for Determining Precise Phase Shifts of Eclipses in EB Systems: Detecting Substellar, Non-Transiting Third Bodies in Kepler Mission Eclipsing Binary Light Curves.
Robert W. Slawson1, L. R. Doyle1
A third body orbiting an eclipsing binary induces a small phase shift in the eclipses due to the light time effect as the binary system orbits about the three-body barycenter. The presence of the small third-body is revealed by a periodicity in the phase shifts consistent with a Keplerian orbit.
We present a cross-correlation method that benefits from the nearly continuously sampled light curves now becoming available from the Kepler mission. For the template, we use a model light curve of the binary system that is stationary in phase (dP/dt=0, dω/dt=0, ...). A window function slides in time along both the observed light curve and template selecting a region for cross-correlation and the phase shift as a function of time is determined from the peak in the resulting correlation function.
We examine the sensitivity limits, through numerical experiments, to the detection of substellar and planet sized masses in multi-year orbits about EBs from Kepler mission light curves.
Kepler Systems That Show Multiple Transiting Objects
Jason H. Steffen1, D. C. Fabrycky2, E. B. Ford3, M. J. Holman4, J. J. Lissauer5, D. Ragozzine4, W. F. Welsh6, Kepler Science Team
1Fermilab, 2UC Santa Cruz, 3University of Florida, 4Harvard CfA, 5NASA Ames, 6San Diego State University.
Exoplanetary systems that have multiple transiting planets provide unique and important insight into the formation, evolution, and dynamics of exoplanetary systems. Kepler has announced the discovery of a confirmed planetary system with multiple transiting planets (Kepler 9, Holman et al. 2010) as well as several candidate planetary systems that show multiple transiting objects (Steffen et al. 2010). Kepler 9 shows deviations from a constant period due to the ongoing dynamical interactions between the confirmed planets. From these transit timing variations (TTV) one can measure the planetary masses from the photometric data alone. The presence of several systems with multiple transiting candidates from the first quarter of data indicate that Kepler should continue to find systems with multiple transiting planets. Such systems will provide important, general information about the histories of planetary systems.
The Faring Behavior of G and K Dwarfs as Seen in the Kepler Q1 Data
Peiyuan Mao1, D. Soderblom2, R. Osten2, J. Valenti2
1Lafayette College, 2Space Telescope Science Institute.
The white-light photometric observations from the Kepler mission are the first ever look at the behavior of solar-type stars at ultra-high precision, and the light curves made available in the “Q1” data release show many astrophysical phenomena. Especially evident in a small fraction of the G and K dwarfs are flaring events, with rapid rises and exponential decays. These flares have much greater energies and longer decay time-scales than even the largest solar flares, which would be undetectable given Kepler’s 30-minute observing cadence. Moreover, stars that exhibit flares tend to show several flares during the 33.5 day interval covered by the Q1 data. Aside from the Kepler data itself, little is known about these stars and what sets them apart from other Kepler targets with similar rotation periods and variability amplitudes. We will show examples of flares in the Kepler light curves, describe our detection technique, and present our initial findings on this phenomenon.
Parameterizing and Modeling Eclipsing Binaries in The Kepler Field Using Kepler Quarter 2 and 3 Data
Sean Morrison1, K. Mighell2, S. Howell2, D. Bradstreet3
1Appalachian State University, 2National Optical Astronomy Observatory, 3Eastern University.
We present a preliminary analysis of Quarter 2 and Quarter 3 Kepler light curves for 56 eclipsing binary star systems from the Kepler Cycle 1 program 08-KEPLER08-0014, ";A Calibration Study of Variable Stars in the Kepler Field"; (PI: Mighell). We developed a C program to phase these long cadence (30 minute) data that determines the period and zero point with a typical precision of 0.0864 seconds for an orbital period of 1.019949 days. We have developed 3D models of the systems using Binary Maker 3 (BM3) by David Bradstreet. Spectra of 32 of the systems were obtained at the Kitt Peak National Observatory 2.1 m telescope using the GoldCam spectrometer. We have determined temperatures for some of the stars from the temperature ratios, based on the BM3 models, and the average temperatures for the spectral classifications of the stars which were derived from the 2.1-m spectra. The high photometric precision of the Kepler light curves allows us to identify significant star spots on a subset of the systems. Morrison was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program and the Department of Defense ASSURE program through Scientific Program Order No. 13 (AST-0754223) of the Cooperative Agreement No. AST-0132798 between the Association of Universities for Research in Astronomy (AURA) and the NSF.
Cross Matching of Available GALEX Objects with Kepler Targets at MAST
Myron Smith1, B. Shiao2, Kepler
1Computer Sciences Corp., 2Space Telescope Science Institute.
The recent release of the GALEX Release 6 dataset includes 72 sky ";tiles"; overlapping some 60% of the Kepler Field of View. MAST (Multi-Mission Archive at Space Telescope Science Institute) has constructed a cross-match catalog of all matches of GALEX objects with 5"; of the coordinates for objects in the Kepler Input Catalog (KIC) and vice-versa.
The results permit the addition of UV colors (near-UV and/or far-UV, centered at about 2300 Angstroms and 1500 Angstroms, respectively) to
the SDSS program's griz filters that the Kepler ground-based support photometric program emulated. Until now the absence of an ultraviolet filter for this ground survey of KIC objects has meant that it was not possible to clearly identify hot (OBA-type) objects. The addition of the GALEX UV magnitudes will address this deficiency. In addition, the (FUV-NUV) vectors for ISM reddening and stellar temperature are very different, allowing the former degeneracy of the two terms to be lifted. We exhibit on-line tools to enable users to obtain UV, griz, and 2MASS colors to aid in the search of targets and to investigate general distributions of objects in the KIC. We discuss completeness of the cross-match survey with the KIC catalog. We point out that the numbers of detections are primarily limited by the far-UV and near-UV effective apertures of GALEX.
Kepler Light Curves of AGN
Michael T. Carini1, W. Welsh2
1Western Kentucky University, 2San Diego State University.
The Kepler mission is observing the same region of the sky for its entire mission lifetime, allowing virtually uninterrupted optical observations of any object in its field of view. This provides the opportunity to obtain optical light curves of AGN of unprecedented duration and sampling. During cycle 1, we obtained observations of two bright AGN in the Kepler field of view: the Seyfert 1 galaxy ZW 229.015 and the Seyfert 2 galaxy IGR J19473+4452. We present the light curves of these sources and discuss their variability properties. Because the Kepler Pipeline is optimized for detecting transiting planets, not photometry of extended sources, we also discuss potential systematic problems and cautions one must have when interpreting these light curves.
Mining the Kepler Mission Database: Rotations, Starspots, Ages and Possible Tidal Interactions of Stars with Close-in Planets
Greg Feiden1, E. Guinan2, T. Boyajian3, Y. Kok4, O. Basturk5, A. Roberson6, I. Ribas7
1Dartmouth College, 2Villanova University, 3Georgia State University, 4University of Sydney, Australia, 5Ankara University, Turkey, 6Pennsylvania State University, 7Institut de Ciencies de l'Espai, Spain.
The first public data release from the Kepler Space Telescope contained over 156,000 stars which had been monitored continuously for approximately 33 days. With continuous photometric monitoring and unprecedented ultra-high precision, the Kepler dataset is an splendid resource for investigating stellar rotation (and age) via starspots as well as for investigating starspot fractional coverage and distributions, starspot lifetime and differential rotation as a function of spectral type and rotation/age. Here, we narrowed our focus to the ~306 planetary candidates, mostly main sequence late F, G and K stars, released during June 2010 (see Boruki et al. 2010). This is an attractive data set for the study of starspots properties since these stars host transiting planets with orbital planes almost exactly aligned with our line-of-sight and will generally have the host stars' rotation axes perpendicular to the planetary orbital plane. Thus, the inclination of the star's rotation axis can be assumed known and should (in most cases) be at right angles to our line-of-sight. Using a Lomb-Scargle Periodogram analysis, we have extracted reliable rotation periods and spot coverages for stars which showed evidence for starspots. From the measured rotation periods, we were able to determine, empirically, the age of the stellar system (using Villanova rotation-age relations) and investigate the potential tidal evolution of the planet-star system. However, we found good evidence that rotation-age relations do not apply to stars that host short-period, Jupiter sized planets. The aforementioned stars show a definite tendency towards star-rotation-planet orbital synchronization. The initial results of this exploratory program will be discussed.
This project was initiated at the 2010 Sagan Exoplanet Summer Workshop hosted by NExScI at Caltech. We wish to thank NASA and the organizers of the workshop - in particular Dawn Gelino and Carolyn Brinkworth. EG wishes also to acknowledge support from NSF/RUI Grant AST-10-09903.
Piecing Together Planet Populations: How RV Super-Earth Frequency Predictions Measure up to Kepler’s Planet Candidates
Angie Wolfgang1, G. Laughlin1
1University of California, Santa Cruz.
Based on the mass and period distributions of the super-Earths discovered by the Geneva Extrasolar Planet Search, there are expected to be planets less massive than Neptune orbiting a large fraction of main sequence stars in periods of 50 days or less. Expanding on this prediction, we employ a Monte Carlo method to create populations of super-Earths with varying compositions, mass distributions, and period distributions. We then compare the results of these simulations with the planet candidates announced by Kepler on June 15, 2010, calculating a statistical best fit to identify the radial velocity super-Earth population which is most likely to reproduce Kepler’s population of planet candidates.
Kepler Measurements of M Star Variability
Geoffrey Bryden1, J. Stauffer2, D. R. Ciardi3, NStED Science Team
1JPL, 2Caltech, 3NExScI.
Late-type stars may be ideal candidates for detection of Earth-mass planets - lower stellar mass corresponds to larger radial-velocity amplitude and deeper transit depth for a given planet mass/size. Low-mass stars are only good targets, however, if they can be observed at noise levels similar to those for solar-type stars. As an exploration of the inherent variability of low-mass stars, we have identified a sample of 63 nearby M dwarfs within the Kepler field of view. The Kepler lightcurves for these stars generally vary by ~1% over the 33-day observational window. After subtraction of gradual long-term trends, only a handful of the stars exhibit variability above the photon-noise limit (typically 0.1-1.0 mmag). We conclude that >90% of M dwarfs are quiet within the several hour timeframe appropriate for detection of planetary transits.
Confirming sub-Neptunian Transiting Exoplanets with Kepler
Natalie M. Batalha1, Kepler Science Team
1San Jose State University.
NASA's Kepler Mission, launched in March 2009, uses transit photometry to detect and characterize exoplanets with the objective of determining the frequency of earth-size planets in the habitable zone. The instrument is a wide field-of-view (115 square degrees) photometer comprised of a 0.95-meter effective aperture Schmidt telescope feeding an array of 42 CCDs that continuously and simultaneously monitors the brightness of up to 170,000 stars. In January, 2010, the team announced its first 5 planet discoveries identified in the first 43 days of data and confirmed by radial velocity follow-up. The ";first five"; are all short-period giant planets, the smallest being comparable in size to Neptune. Collectively, they are similar to the sample of transiting exoplanets that have been identified to date, the roster of which currently hovers around 100. In August 2010, an additional two planets, each orbiting the star Kepler-9, were confirmed by a combination of radial velocity and transit timing measurements. A third, smaller planet in the same system was validated stastistically by probing the parameter space for potential false-positives. Throughout 2010, a concerted effort was made to push radial velocity confirmation down toward the smaller planets. Recent progress on our efforts to confirm such candidates is discussed.
Gamma Ray Bursts
High Metallicity LGRB Hosts
John Graham1, A. Fruchter2, E. Levesque3, L. Kewley3, J. Brinchmann4, S. Charlot5, A. Levan6, N. Tanvir7, S. Patel8, K. Misra2, K. Huang9, D. Reichart10, M. Nysewander2
1STScI & JHU, 2STScI, 3IFA, 4Leiden, Netherlands, 5Bordeaux, France, 6Warwick, United Kingdom, 7Leicester, United Kingdom, 8National Space Science & Technology Center, 9JHU, 10UNC.
One of the most powerful means to study the formation and evolution of gamma-ray bursts is by observing there environments. While short bursts have been detected in nearby galaxies of all types, long burst hosts are dominated by blue irregulars leading to speculation of metal poor host galaxies, a result which has now been confirmed via emission line metallicity diagnostics. However beginning with LGRB 051022 at log(O/H)+12 = 8.77 (using the R23 method with Kobulnicky & Kewley 2004 scale) three exceptions to this trend have been found. This extends the metallicity range of LGRB hosts to that found throughout the Milky Way, challenges conventional wisdom that LGRBs require low metallicity progenitor environments and has significant implications in understanding LGRB formation. Here I present the results of our observations of two of these super-solar metallicity host galaxies, analysis of the high Z host population with respect to various comparison samples, and ongoing efforts to more directly probe the metallicities of the burst progenitors.
The Stellar Ages and Masses of Short GRB Host Galaxies: Investigating the Progenitor Delay Time Distribution and the Role of Mass and Star Formation in the Short GRB Rate
Camille N. Leibler1, E. Berger1
We present multi-band optical and near-infrared observations of 19 short γ-ray burst (GRB) host galaxies, aimed at measuring their stellar masses and population ages. The goals of this study are to evaluate whether short GRBs track the stellar mass distribution of galaxies, to investigate the progenitor delay time distribution, and to explore any connection between long and short GRB progenitors. Comparing the distribution of stellar masses found using a single-stellar population model to the general galaxy mass function, we find that short GRBs track the cosmic stellar mass distribution only if the late-type hosts generally have maximal masses. However, there is an apparent dearth of early-type short GRB hosts compared to the equal contribution of early- and late-type galaxies to the cosmic stellar mass budget. These results suggest that stellar mass may not be the sole parameter controlling the short GRB rate, and raise the possibility of a two-component model with both mass and star formation playing a role (reminiscent of the case for Type Ia supernovae). If short GRBs in late-type galaxies indeed track star formation activity, the resulting typical delay time is ∼ 0.2 Gyr, while those in early-type hosts have a typical delay of ∼ 3 Gyr. Using the same stellar population models to fit 22 long GRB host galaxies in a similar redshift range we find that they have significantly lower masses and younger population ages. Most importantly, the two GRB host populations remain distinct even if we consider only the star-forming hosts of short GRBs, supporting our previous findings (based on star formation rates and metallicities) that the progenitors of long GRBs and short GRBs in late-type galaxies are distinct.
This work was partially supported by Swift AO5 grant #5080010 and AO6 grant #6090612. Additional support was provided by the Harvard College Research Program.
A Beaming-Independent Estimate of the Distribution of Gamma Ray Burst Energies
Isaac S. Shivvers1, E. Berger1
AAS 217 Winter Meeting Abstract Submission
Dr. Edo Berger
A Beaming-Independent Estimate of the Distribution of Gamma Ray Burst Energies
The single most important parameter of any cosmological explosion is the energy release. Energy measurements provide insight into the progenitor object and the explosion mechanism. The measurement of gamma-ray burst (GRB) energies has, traditionally, been a complicated problem due to highly non-spherical energy distributions and relativistic beaming effects. However, on timescales of >100 days GRBs become roughly non-relativistic and spherical. Using radio observations from the Very Large Array at times >100 days after the burst, we are able to calculate the energies of 20 bursts free from the large corrections needed when using early-time observations. We find a median energy in good agreement with results calculated through detailed analysis of multi-wavelength light curves. The similarity between methods provides further evidence that the bulk of the energy budget of GRBs is in the relativistic outflow and not in slower, lagging material. Our results were achieved economically, with only a few radio-wavelength flux measurements per GRB. We suggest that similar future observations with the Expanded VLA will provide unique insight into GRB energetics.
Quantifying GRB Pulse Shape Evolution to Study the Pulse Scale Conjecture
Daniel Miller1, R. J. Nemiroff1, J. Holmes1, A. Shahmoradi1
1Michigan Technology University.
The asymmetry of isolated gamma ray burst pulses is quantified by a simple ratio of rising to decaying fluence. This ratio can be defined in a background independent way by using only the peak of the pulse. This ratio is used to explore the prevalence of the Pulse Scale Conjecture (PSC; Nemiroff 2000) for a series of the brightest isolated BATSE GRB pulses known. The PSC posits that the shape of a GRB pulse is invariant across energy channels, scaling only in time and brightness. Within statistical uncertainties, it is found that some GRB pulses hold well to the PSC, whereas others do not. Moreover, for some GRB pulses, the PSC appears to hold only between specific energy channels. Examples will be shown and discussed.
Evidence for a Correlation Between Gamma-Ray Burst Variability and the Optical Afterglow Onset
1St John's Univ..
The intrinsic variability (V) of prompt gamma-ray emission from gamma-ray burst (GRB) events is compared to the properties of the subsequent afterglow onset, yielding evidence of a correlation between V and the the optical onset's peak. We used Liang et al.'s (2009) fitted properties of the optical onset bump in 16 events with an observed optical rise and known redshift, and calculated V from the lightcurves in the Swift gamma-ray data archive. The optical onset properties are known to be mutually correlated; comparing these optical bump properties to V shows positive correlations at the 3-sigma level with (de-redshifted) width, peak time, rise, and decay times and negative correlations with peak flux and the ratio of rise to decay times. When the bump peak time or width are expressed as a ratio of the GRB duration (T90), the correlation evidence with V is weaker.
Pulse Scaling Properties of Gamma-Ray Bursts
Justin Holmes1, R. J. Nemiroff1, D. Miller1
1Michigan Technological University.
Gamma-ray bursts (GRBs) hold potential as standard candles for the high redshift universe. To help identify relationships which may arise in GRBs that could lead to a standard candle, isolated pulses from a number of very bright GRBs were inspected regarding their pulse scaling nature. A direct test of the pulse scale conjecture was conducted using energy channel data from the Burst and Transient Source Experiment (BATSE). The test consisted of taking a light curve for a bright GRB pulse from a specific BATSE energy channel, scaling it in brightness and time, and finding the best statistical fit for the same GRB pulse in a different BATSE energy channel. Many of the GRB pulses tested showed a statistically acceptable scaling between at least two BATSE energy channels.
Search for Late Jet Breaks in X-ray Afterglows of Gamma-Ray Bursts
David N. Burrows1, J. Racusin2
1Penn State Univ., 2NASA/GSFC.
Gamma-ray bursts are the most energetic events known since the Big Bang. Because both the prompt emission and the afterglow of GRBs is highly beamed, determination of their actual explosion energies depends on measurement of the beaming angle, which can be estimated on the basis of the detection of an achromatic jet break in the light curve. Jet break measurements for Swift GRBs have been rare; as a result, we have undertaken a program of studying X-ray GRB afterglows using the Chandra observatory to obtain very late-time flux measurements. When compared with earlier Swift XRT flux measurements, these allow the measurements of late jet breaks in some bursts, and allow strict limits to be placed on jet break times in other cases. We will present a progress report on this work and its implication for GRB energetics.
AGN, QSO, Blazars
15 GHz Radio Variability of Gamma-Ray Blazars
Joseph Richards1, W. Max-Moerbeck1, V. Pavlidou1, T. J. Pearson1, A. C. S. Readhead1, M. A. Stevenson1, O. G. King1, R. Reeves1, E. Angelakis2, L. Fuhrmann2, J. A. Zensus2, S. E. Healey3, R. W. Romani3, M. S. Shaw3, K. Grainge4, G. B. Taylor5, G. Cotter6
1California Institute of Technology, 2Max-Planck-Institut-für-Radioastronomie, Germany, 3Stanford University, 4University of Cambridge, United Kingdom, 5University of New Mexico, 6University of Oxford, United Kingdom.
Since 2007, the Owens Valley Radio Observatory (OVRO) 40 meter telescope has been engaged in an intensive fast-cadence gamma-ray blazar monitoring program, observing about 1500 objects twice per week. Using our intrinsic modulation index method and careful likelihood analyses, we find that gamma-ray loud objects associated with Fermi 1LAC sources in our sample demonstrate radio variability amplitudes significantly larger than do gamma-ray quiet objects. We also find significant differences in variability amplitude between flat spectrum radio quasars and BL Lacertae objects within our sample as well as possible evidence for cosmological evolution of variability amplitude.
Physical Significance Of The Time Lags In Radio/gamma-ray Cross-correlations For Fermi-gst Blazars On The Ovro 40m Blazar Monitoring Program
Walter Max-Moerbeck1, J. L. Richards1, V. Pavlidou1, T. J. Pearson1, A. C. S. Readhead1, M. A. Stevenson1, O. King1, R. Reeves1, E. Angelakis2, L. Fuhrmann2, J. A. Zensus2, S. E. Healey3, R. W. Romani3, M. S. Shaw3, K. Gainge4, G. B. Taylor5, G. Cotter6
1California Institute of Technology, 2Max-Planck-Institut für Radioastronomie, Germany, 3Stanford University, 4University of Cambridge, United Kingdom, 5University of New Mexico, 6University of Oxford, United Kingdom.
The OVRO 40 m telescope has been monitoring ~1500 blazars since 2007. The sources are observed twice per week at 15 GHz. The sample contains all CGRaBS sources and the gamma-ray blazars detected by Fermi which are visible from OVRO. The availability of a large sample of sources with good cadence at radio and gamma-ray offers the opportunity to test the suggestion of correlated variability between these two bands. A Monte Carlo method to assess the physical significance of the cross-correlations taking into account the properties of the light curves and the uneven sampling is presented. Application to an early data set shows that in most cases the cross-correlations are not significant and that longer time duration light curves are required.
Testing the Radiative-Driving Hypothesis of Quasar Outflows
Michele A. Stark1, R. Ganguly1, S. C. Gallagher2, R. Gibson3, M. S. Brotherton4
1University of Michigan - Flint, 2University of Western Ontario, Canada, 3University of Washington, 4University of Wyoming.
Outflows are seen prominently in the UV spectra of Broad Absorption Line (BAL) QSOs. Models of radiatively-driven outflows predict that the velocity should scale with UV luminosity. Observations show that the UV luminosity only provides a cap to the velocity. One explanation is that the X-ray absorbing gas in an individual quasar provides a shield that improves its radiative-driving efficiency. That is, quasars with thick shields can accelerate gas to higher velocity. X-ray observations of BALQSOs support this in the sense that BALQSOs with more soft X-ray absorption tend to have higher velocity outflows. But there is much scatter in this trend, making the underlying physics difficult to extract. To combat this, we conducted an experiment using exploratory Chandra-ACIS observations of 12 carefully-selected z=1.7-2.0 BALQSOs. These BALQSOs were chosen to have very narrow ranges in (1) UV luminosity, (2) UV spectral shape, and (3) absorption velocity width. Within this otherwise uniform sample, the outflow velocities range from 4500km/s to 18000km/s, a factor of four. All objects are detected in the full band (0.5-8keV), with count rates in the range (0.5-5)e-3 cps, and have hardness ratios in the range -0.6 to 0.3. We compare the X-ray brightnesses and spectral shapes of our sample with those of more diverse samples of BALQSOs.
We gratefully acknowledge support through Chandra grant GO9-0120X.
Toward a Prescription for Feedback from Quasar Outflows
Rajib Ganguly1, M. Bourjaily1, J. Munsell1, M. S. Brotherton2, A. Bhattacharjee2, J. Runnoe2, J. C. Charlton3, M. Eracleous3
1Univ. of Michigan-Flint, 2Univ. of Wyoming, 3The Pennsylvania State University.
Models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, distance, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 14000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) estimates of the quasar black hole mass. To this, we are adding photometry from GALEX, 2MASS, and ROSAT in an effort to characterize more fully the quasar SEDs. ROSAT photometry provides estimates of the level of soft X-ray absorption, which helps regulate the velocity of outflows. GALEX photometry samples the extreme ultraviolet range where several high ionization species, that may be present in the outflows, absorb light. 2MASS photometry samples the rest-frame optical, where the effects of absorption and dust reddening are minimal, yield better estimates of the bolometric luminosity (hence, Eddington ratio). In this poster, we will present preliminary measurements of the amount of absorption in the soft X-ray and extreme ultraviolet bands as a function of both outflow properties and quasar physical properties.
This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the Astrophysics Data Analysis Program.
Recent Star-formation in Post-Starburst Quasars
Shonda Townsend1, R. Ganguly1, A. Strom2, S. Cales3, M. S. Brotherton3
1University of Michigan - Flint, 2University of Arizona, 3University of Wyoming.
Post-Starburst Quasars (PSQ, alternatively Q+As) show simultaneously the spectrum of a massive A-type stellar population and a quasar. The prototype PSQ, UNJ1025-0040, shows a UV excess over the quasar spectrum, indicating more recent star-formation (Brotherton et al 2002). To gauge the frequency and distribution of these younger stellar populations in PSQs, we have collected GALEX (GR45) and 2MASS photometry for 409 objects. The objects are catalog 609 spectroscopically-selected PSQs from Brotherton et al. (2010) that uses similar criteria as Zabludoff et al. (1996) for post-starburst galaxies (PSG, E+A). For comparison, we have compiled two samples: (1) 16,000 quasars that is matched in redshift (0.01-0.7) and Sloan-u magnitude (16.1-21.2), which is blueward of the Balmer edge and provides the least contamination from the massive stellar population; and (2) 500 PSGs from Goto et al. (2007). 389 (55) PSQs show an NUV (FUV) excess over the expected UV flux if the underlying quasar were ``normal.’’ 126 (460) objects show an NUV (FUV) decrement. The observed NUV to u-band flux ratio of the median PSQ rises from ~1 at z=0.01 to 2.5 at z=0.4, while the same for the median QSO remains at ~1. The observed FUV to u-band flux ratio of the median QSO rises slightly from ~0.6 to ~0.8 over the redshift range 0.05-0.2, whereas the median PSQ is nearly a factor of three lower. The disparity between the median PSQ and QSO suggests the presence of young stars that add in NUV light, but not FUV light. To quantify the youth and mass of this putative population, we will present preliminary efforts to model PSQs using two simple stellar populations, an underlying quasar, and dust reddening. We acknowledge funding from GALEX through grant NNX10AC63G.
Parsec-Scale Localization of the Quasar SDSS J1536+0441A, a Candidate Binary Black Hole System
J. M. Wrobel1, A. Laor2
1NRAO, 2Technion, Israel.
The radio-quiet quasar (RQQ) SDSS J1536+0441A shows two broad-line emission systems, recently interpreted as a binary black hole (BBH) system with a subparsec separation; as a double-peaked emitter (DPE); or as both types of systems. The NRAO VLBA was used to search for 8.4 GHz emission from SDSS J1536+0441A, focusing on the localization region for the broad-line emission, of area 5400 mas2 (0.15 kpc2). One source was detected, with a diameter of less than 1.63 mas (8.5 pc) and a brightness temperature Tb > 1.2 x 107 K. New NRAO VLA photometry at 22.5 GHz, and earlier photometry at 8.5 GHz, gives a rising spectral slope of alpha = 0.35+/-0.08. The slope implies an optically thick synchrotron source, with a radius of about 0.04 pc, and thus Tb ~ 4.8 x 1010 K. The implied radio sphere at the rest frequency 31.2 GHz has a radius of 800 gravitational radii, just below the size of the broad line region in this object. Observations at higher frequencies with the EVLA and ALMA can probe whether or not the radio sphere is as compact as expected from the coronal framework for the radio emission of RQQs. The NRAO is a facility of the NSF operated under cooperative agreement by AUI.
Galaxy-scale Clouds Of Ionized Gas Around Agn - History And Obscuration
Drew Chojnowski1, W. C. Keel2
1Texas Christian University, 2University of Alabama.
Motivated by the discovery of Hanny's Voorwerp, a 45-kpc highly-ionized cloud near the spiral galaxy IC 2497, and accompanying evidence for strong variability of its AGN over 105 year scales, members of the Galaxy Zoo project have carried out surveys for similar (albeit smaller) ionized clouds around galaxies both with and without spectroscopic AGN. The color-composite SDSS images detect strong [OIII] in the g band at low z, allowing a useful color search of Galaxy Zoo targets. In addition, a targeted search was made of over 16,000 spectroscopic AGN and candidates. We used SDSS data to produce crude [OIII] images of the top candidates, and obtained long-slit optical spectra from KPNO and Lick for 30 of the most promising. Roughly half of the spectra showed extended [OIII]λ5007 emission, some exceeding 30 kpc in radial extent. Of the 16 extended clouds we identified, 11 lie in strongly interacting or merging systems, probably because these events leave cold gas out of the plane to be ionized. Most nuclei of extended cloud hosts are type 2 Seyferts. We consider the energy budgets, between ionizing luminosity required for the most distant line emission and the FIR output of the nucleus, to see whether any suggest strong variability rather than obscuration. Several galaxies have such strong mismatches that obscuration alone becomes implausible as an explanation for the strong ionizing continuum, and are candidates for fading events similar to that in IC 2497 and Hanny's Voorwerp. This project was funded by the National Science Foundation Research Experiences for Undergraduates (REU) program through grant NSF AST-1004872.
The History And Environment Of A Faded Quasar: HST Observations Of Hanny's Voorwerp And IC 2497
William C. Keel1, C. Lintott2, K. Schawinski3, V. Bennert4, D. Thomas5, A. Manning1, S. D. Chojnowski6, H. van Arkel7, S. Lynn8, Galaxy Zoo team
1Univ. of Alabama, 2Adler Planetarium, 3Yale Univ., 4UCSB, 5Univ. of Portsmouth, United Kingdom, 6Texas Christian Univ., 7CITAVERDE College, Netherlands, 8Oxford Univ., United Kingdom.
Perhaps the signature discovery of the Galaxy Zoo citizen-science project has been Hanny's Voorwerp, high-ionization cloud extending 45 kpc from the spiral galaxy IC 2497. It must be ionized by a luminous AGN, either deeply obscured or having dimmed dramatically within 200,000 years. We explore this system using HST imaging and spectroscopy. The disk of IC 2497 is warped, with complex dust absorption near the nucleus; the near-IR peak coincides closely with the VLBI core marking the AGN. STIS spectra show the AGN as a low-luminosity LINER, with ionization parameter log U= -3.5, matching its weak X-ray emission. The nucleus is accompanied by an expanding loop of ionized gas ∼ 500 pc in diameter, opposite Hanny's Voorwerp. The loop's Doppler span 300 km/s implies kinematic age < 700,000 years. We find no high-ionization gas near the core, further evidence that the AGN is seen at a low radiative output (perhaps now dominated by kinetic energy). [O III] and Hα +[N II] ACS images show fine structure in Hanny's Voorwerp, including limb-brightened sections suggesting modest interaction with a galactic outflow. We identify small regions ionized by recent star formation, unlike the AGN ionization of the overall cloud. These H II regions contain blue continuum objects, consistent with young stellar populations; these occur where projected closest to IC 2497, perhaps meaning that the star formation was triggered by compression from an outflow. The ionization-sensitive [O III]/Hα ratio shows broad bands across the object, and no discernible pattern with emission-line structures or near the prominent ";hole"; in the ionized gas. These results fit with our picture of an ionization echo from an AGN whose ionizing luminosity has dropped by a factor >100 within the last 200,000 years. Such rapid fluctuations in luminosity could alter our understanding of AGN demographics. Supported by NASA/STScI.
Twenty-Year Optical Variability of The Blazar PKS 1749+096: Exponential Outbursts?
Thomas J. Balonek1, M. T. Lam1, P. A. Patrick1, E. L. Scott1, A. J. Kaercher1, J. Rupert2, T. Taber2, P. Hegel3, Y. H. N. Tam4, A. Morin5, K. Levandowski6, E. L. Graber7, T. S. Quirk8
1Colgate Univ., 2Vassar Coll., 3Wesleyan Univ., 4Williams Coll., 5RPI, 6Wellesley Coll., 7Univ. Michigan, 8Siena Coll..
We present the twenty-year R-band optical variability light curve for the BL Lac type quasar PKS 1749+096. We investigate the characteristic timescales and intensity of outbursts and flares by fitting exponential profiles to the variations. PKS 1749+096 underwent strong optical outbursts during the summers of 2007 and 2008, reaching its brightest optical level in two decades, and exhibited an inactive period during summer 2009. We compare these two outbursts with lower amplitude well-sampled variations in 2000 through 2003. Observations were obtained as part of the intensive blazar variability monitoring program at the Colgate University Foggy Bottom Observatory (FBO). We gratefully acknowledge support for student research through an REU grant to the Keck Northeast Astronomy Consortium from the National Science Foundation, the NASA / New York Space Grant, and the Justus and Jayne Schlichting Student Research Fund at Colgate University.
Time Series Analysis of the Quasar PKS 1749+096
Michael T. Lam1, T. J. Balonek1
Multiple timescales of variability are observed in quasars at a variety of wavelengths, the nature of which is not fully understood. In 2007 and 2008, the quasar 1749+096 underwent two unprecedented optical outbursts, reaching a brightness never before seen in our twenty years of monitoring. Much lower level activity had been seen prior to these two outbursts. We present an analysis of the timescales of variability over the two regimes using a variety of statistical techniques. An IDL software package developed at Colgate University over the summer of 2010, the Quasar User Interface (QUI), provides effective computation of four time series functions for analyzing underlying trends present in generic, discretely sampled data sets. Using the Autocorrelation Function, Structure Function, and Power Spectrum, we are able to quickly identify possible variability timescales. QUI is also capable of computing the Cross-Correlation Function for comparing variability at different wavelengths. We apply these algorithms to 1749+096 and present our analysis of the timescales for this object. Funding for this project was received from Colgate University, the Justus and Jayne Schlichting Student Research Fund, and the NASA / New York Space Grant.
Feedback from radio-quiet quasars
Nadia L. Zakamska1, J. E. Greene2
1KIPAC/Stanford, 2UT Austin.
The correlations between properties of supermassive black holes and stellar spheroids in nearby galaxies strongly suggest that there is a physical connection between these two components, even though their masses and physical scales are vastly different. There is growing evidence that radio-loud active galactic nuclei exert a strong feedback on the gas in their host galaxies, providing a possible mechanism for such connection. However, as only a minority of active galaxies are radio-loud at any given time, the radio-loud feedback may only be a part of the explanation. Here we report the discovery of powerful outflows from radio-quiet quasars observed in the emission lines of the photo-ionized gas.
Optical Spectra of the Teacup AGN
Justin Gagne1, D. M. Crenshaw1, W. C. Keel2, T. C. Fischer1
1Georgia State University, 2University of Alabama.
We present optical spectra of the ";Teacup AGN";, at a redshift of 0.085, discovered in the Sloan Digital Sky Survey (SDSS). The spectra were obtained with the Lowell Observatory 1.8-m Perkins telescope. The SDSS image shows a ";handle"; of ionized gas extending out to 5'' (8 kpc) away from the nucleus of the galaxy. Our optical spectra reveal a myriad of emission lines resembling those from a typical Seyfert 2 galaxy. We use dereddened emission-line ratios to investigate the physical conditions in the gas and to estimate the luminosity of the hidden AGN.
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