Evidence for Nonlinear X-ray Variability from the Broad-line Radio Galaxy 3C 390.3

We present analysis of the light curve from the ROSAT HRI monitoring observations of the broad-line radio galaxy 3C 390.3. Observed every three days for about 9 months, this is the first well sampled X-ray light curve on these time scales. The flares and quiescent periods in the light curve suggest that the variability is nonlinear, and a statistical test yields a detection with >6 sigma confidence. The structure function has a steep slope ~0.7, while the periodogram is much steeper with a slope ~2.6, with the difference partially due to a linear trend in the data. The non-stationary character of the light curve could be evidence that the variability power spectrum has not turned over to low frequencies, or it could be an essential part of the nonlinear process. Evidence for X-ray reprocessing suggests that the X-ray emission is not from the compact radio jet, and the reduced variability before and after flares suggests there cannot be two components contributing to the X-ray short term variability. Thus, these results cannot be explained easily by simple models for AGN variability, including shot noise which may be associated with flares in disk-corona models or active regions on a rotating disk, because in those models the events are independent and the variability is therefore linear. The character of the variability is similar to that seen in Cygnus X-1, which has been explained by a reservoir or self-organized criticality model. Inherently nonlinear, this model can reproduce the reduced variability before and after large flares and the steep PDS seen generally from AGN. The 3C 390.3 light curve presented here is the first support for such models to explain AGN variability on intermediate time scales from a few days to months.Comment: 10 pages using (AASTeX) aaspp4.sty and 3 Postscript figures. Astrophysical Journal Letters, in pres

The Ursinus Weekly, April 30, 1928

Haverford track team buries Ursinus squad under 101 1/2- 33 1/2 score • Dr. Holmes addresses joint service on patriotism • Ursinus to be scene of county play festival • Junior festivities reign supreme in weekend of dance and drama • Ursinus relay team finishes third at Penn • Shepherd Whitman chosen commencement orator • Grizzly nine home for two games this week • Penn man lectures on preparation of serums • Dinner opening event of busy junior program • All net matches washed out; Temple here Wednesday • Juniors entertain with delightful tea dance • Trophy for court victor in girls\u27 tournament • Debate cancelled • Ursinus seniors to take Carnegie Foundation exam • W.S.G.A. installs new officers • H. - P. group • Represents Ursinus at football meeting • Friday afternoon time set for inter-class meethttps://digitalcommons.ursinus.edu/weekly/2215/thumbnail.jp

The Ursinus Weekly, November 5, 1928

Chapel speakers address students in week of intellectual attainment • Dr. Omwake host to guests at dinner and luncheon • Bears win 6-0 as Muhlenberg falls before superior playing of grizzlies • Non-partisan political rally held last Tuesday • Many events scheduled for coming week-end • The Patsy to be given again by senior class • Newspaper conference held at Haverford, Saturday • Pep dance falls flat as students leave for home • Ursinus lassies bow to Swarthmore maids 9-4 • Grizzlies face Drexel in last home appearance • Women\u27s dorm drive • F. & M. drops baseball as a varsity sport • Candle lighting service held by YWCA • Seniors trim frosh in inter-class hockey game • Dr. Wellburn addresses weekly YMCA meetinghttps://digitalcommons.ursinus.edu/weekly/2163/thumbnail.jp

The Ursinus Weekly, January 7, 1929

Rev. Lentz delivers annual Christmas religious address • Important meeting of literary group, Thursday • Montgomery County dance starts off new year • Bears trim Lafayette 30-27: Grizzlies overcome Leopards\u27 early lead to finish out in front • Christmas dinners mark final event of old year • 1929 Ruby rapidly nearing completion • Grizzlies have two court games this week • Ursinus Debating Club • Rev. Tomkins to talk to joint YM-YWCA • Swarthmore party to observe eclipse • College bulletin released • New order of service • Kermit Black picked on coach Harman\u27s eleven • Takes trip to Florida during Xmas holidays • Football men hold banquet at athletic club • Alumnus writes poem read at Wilson dinner • Y.W.C.A. Xmas party • Mail boxes erected • Choir Xmas concert • Debating issue of Weekly sent to schools • Many colleges in midst of building campaigns • Here is the quiz; test your knowledgehttps://digitalcommons.ursinus.edu/weekly/2171/thumbnail.jp

The Ursinus Weekly, February 18, 1929

Academic exercises of Founders\u27 Day mark sixtieth anniversary • Frosh prove ability as good entertainers • Rev. Asher R. Kepler \u2798 gives monthly lecture • Glee Club on extended trip in coal regions • Entertainment concludes Founders\u27 Day program • Men\u27s negative team wins initial debate • Ursinus loses to Temple and F. & M. in contests played last week • Speeches and good eats feature family dinner • Girls defeat Beaver in exciting game • Girls lose dual debate to Cedar Crest women • Muhlenberg defeats grizzly cubs 19-16 • Rev. Elliott to speak at YM-YW week of prayer • American legion to present annual show • Lorelei dance this Saturday evening • Frosh elect officers for coming semester • Ursinus plays Swarthmore and Delaware this week • Junior class to give movie for 1930 Ruby • Girls install new hall presidents • Booklet on history of Ursinus College issued • Women\u27s Debating Club • Directors order plans for science building • Men\u27s Debating Clubhttps://digitalcommons.ursinus.edu/weekly/2175/thumbnail.jp

The Ursinus Weekly, June 4, 1928

Tennis squad closes successful season by trouncing Drexel, 5-1 • Summary of baseball season credits bears with 6 wins, 4 losses • Willard Moyer first in recent Carnegie exams • Seniors hold banquet at Spring Mountain House • Girls\u27 tennis team trims Lebanon Valley lassies, 5-1 • John F. W. Stock given music scholarship • Review of track season; records for local field • Dr. Omwake commencement speaker at Elizabethtown • Men\u27s student council elects new officers • Regular Memorial Day services in chapel • Frosh trim Norristown High School to maintain clean slate • Junior oratoricals Friday • Commencement calendar • Ursinus College to be site of summer conventionshttps://digitalcommons.ursinus.edu/weekly/2220/thumbnail.jp

The Ursinus Weekly, October 8, 1928

Debating association holds annual meeting Saturday in Harrisburg • Large crowd at first home game watches Haverford trip bears 8-0 • Weekly to conduct straw vote in Bomberger Hall • Band reorganizes with Snyder-Ferguson, leaders • Large crowd attends hop after Haverford game • Frosh lose to National Farm School lads, 6-0 • Student council to hold first dance next Saturday • Chautauqua begins • A family monument • Dates announced for first group meetings • Math group organizes • Sophs elect officers • Franklin & Marshall next grid foe to face Ursinus • Professor Stock donates piano for college use • Seniors beat juniors in inter-class hockey matchhttps://digitalcommons.ursinus.edu/weekly/2159/thumbnail.jp

Simultaneous Ultraviolet and X-ray Observations of the Seyfert Galaxy NGC 4151. II. Physical Conditions in the UV Absorbers

We present a detailed analysis of the intrinsic absorption in the Seyfert 1 galaxy NGC 4151 using UV spectra from the HST/STIS and FUSE, obtained 2002 May as part of a set of contemporaneous observations that included Chandra/HETGS spectra. In our analysis of the Chandra spectra, we determined that the soft X-ray absorber was the source of the saturated UV lines of O VI, C IV, and N V associated with the absorption feature at a radial velocity of ~ -500 km/sec, which we referred to as component D+E. In the present work, we have derived tighter constrains on the the line-of-sight covering factors, densities, and radial distances of the absorbers. We find that the Equivalent Widths (EWs) of the low-ionization lines associated with D+E varied over the period from 1999 July to 2002 May. The drop in the EWs of these lines between 2001 April and 2002 May are suggestive of bulk motion of gas out of our line-of-sight. If these lines from these two epochs arose in the same sub-component, the transverse velocity of the gas is ~ 2100 km/sec. Transverse velocities of this order are consistent with an origin in a rotating disk, at the roughly radial distance we derived for D+E.Comment: 51 pages, including 12 figures. Accepted for publication in ApJ Supplement

STIS Echelle Observations of the Seyfert Galaxy NGC 4151: Physical Conditions in the Ultraviolet Absorbers

We have examined the physical conditions in intrinsic UV-absorbing gas in the Seyfert galaxy NGC 4151, using echelle spectra obtained with the Space Telescope Imaging Spectrograph (STIS). We confirm the presence of the kinematic components detected in earlier GHRS observations as well as a new broad absorption feature at a radial velocity of -1680 km/s. The UV continuum of NGC 4151 decreased by a factor of 4 over the previous two years, and we argue the changes in the column density of the low ionization absorption lines associated with the broad component at -490 km/s reflect the decrease in the ionizing flux. Most of the strong absorption lines (e.g., N V, C IV, Si IV) from this component are saturated, but show substantial residual flux in their cores, indicating that the absorber does not fully cover the source of emission. Our interpretation is that the unocculted light is due to scattering by free electrons from an extended region, which reflects continuum, emission lines, and absorption lines. We have been able to constrain the densities for the kinematic components based on absorption lines from metastable states of C III and Fe II, and/or the ratios of ground and fine structure lines of O I,C II, and Si II. We have generated a set of photoionization models which match the ionic column densities for each component during the present low flux state and those seen in previous high flux states with the GHRS and STIS, confirming that the absorbers are photoionized and respond to the changes in the continuum flux. We have been able to map the relative radial positions of the absorbers, and find that the gas decreases in density with distance. None of the UV absorbers is of sufficiently large column density or high enough ionization state to account for the X-ray absorption.Comment: 46 pages (Latex), 14 figures (postscript), plus a landscape table (Latex), to appear in the Astrophysical Journa