1,247 research outputs found

    A List of the Mayflies (Ephemeroptera) in the Michigan State University Entomology Museum

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    Excerpt: A fairly extensive collection of Epl~emeroptera representing 35 genera, 1 12 determined species and subspecies is preserved in alcohol in the Entomology Museum at Michigan State University, East Lansing, Michigan 48823. Although most of the specimens were collected in Michigan, the collection also contains representatives of many of the common species found in New England and neighboring Canada. A small portion of the collection is not Northeast in origin. This list is designed to aid those interested in the fauna of the Northeast and Great Lakes regions, especially if they need specimens for study. I have included the states or provinces in which specimens were collected, as well as the numbers of individuals; more complete collecting data may be obtained from the author or the museum. Many new state records occur in the collection, and some of these records extend the known range significantly

    A New Species of Thraulodes from New Mexico (Ephemeroptera: Leptophlebiidae)

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    While working on the Ephemeroptera collection in the Entomology Museum at Michigan State University, the author came upon a single specimen of Thraulodes which appeared to be a new species. Although it is only in fair condition (the preserving fluid having dissipated under field conditions), the colors are well preserved and very distinctive. The specimen was sent to Dr. Jay R. Traver, University of Massachusetts, who confirmed suspicions that the specimen was new. I have been informed by Dr. Traver that she and Dr. George F. Edmunds Jr. are presently engaged in a revisionary study of the genus for North and South America, and it should be in press shortly

    IC 751: a new changing-look AGN discovered by NuSTAR

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    We present the results of five NuSTAR observations of the type 2 active galactic nucleus (AGN) in IC 751, three of which were performed simultaneously with XMM-Newton or Swift/XRT. We find that the nuclear X-ray source underwent a clear transition from a Compton-thick (N H≃2×1024 cm−2N_{\rm\,H}\simeq 2\times 10^{24}\rm\,cm^{-2}) to a Compton-thin (N H≃4×1023 cm−2N_{\rm\,H}\simeq 4\times 10^{23}\rm\,cm^{-2}) state on timescales of ≲3\lesssim 3 months, which makes IC 751 the first changing-look AGN discovered by NuSTAR. Changes of the line-of-sight column density at a ∼2σ\sim2\sigma level are also found on a time-scale of ∼48\sim 48 hours (ΔN H∼1023 cm−2\Delta N_{\rm\,H}\sim 10^{23}\rm\,cm^{-2}). From the lack of spectral variability on timescales of ∼100\sim 100 ks we infer that the varying absorber is located beyond the emission-weighted average radius of the broad-line region, and could therefore be related either to the external part of the broad-line region or a clumpy molecular torus. By adopting a physical torus X-ray spectral model, we are able to disentangle the column density of the non-varying absorber (N H∼3.8×1023 cm−2N_{\rm\,H}\sim 3.8\times 10^{23}\rm\,cm^{-2}) from that of the varying clouds [N H∼(1−150)×1022 cm−2N_{\rm\,H}\sim(1-150)\times10^{22}\rm\,cm^{-2}], and to constrain that of the material responsible for the reprocessed X-ray radiation (N H∼6×1024 cm−2N_{\rm\,H} \sim 6 \times 10^{24}\rm\,cm^{-2}). We find evidence of significant intrinsic X-ray variability, with the flux varying by a factor of five on timescales of a few months in the 2-10 and 10-50 keV band.Comment: Accepted for publication in ApJ, 11 pages, 6 figure

    Extended X-ray emission in the IC 2497 - Hanny's Voorwerp system: energy injection in the gas around a fading AGN

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    We present deep Chandra X-ray observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp and hosting a fading AGN. We find extended soft X-ray emission from hot gas around the low intrinsic luminosity (unobscured) AGN (Lbol∼1042−1044L_{\rm bol} \sim 10^{42}-10^{44} erg s−1^{-1}). The temperature structure in the hot gas suggests the presence of a bubble or cavity around the fading AGN (\mbox{E_{\rm bub}} \sim 10^{54} - 10^{55} erg). A possible scenario is that this bubble is inflated by the fading AGN, which after changing accretion state is now in a kinetic mode. Other possibilities are that the bubble has been inflated by the past luminous quasar (Lbol∼1046L_{\rm bol} \sim 10^{46} erg s−1^{-1}), or that the temperature gradient is an indication of a shock front from a superwind driven by the AGN. We discuss the possible scenarios and the implications for the AGN-host galaxy interaction, as well as an analogy between AGN and X-ray binaries lifecycles. We conclude that the AGN could inject mechanical energy into the host galaxy at the end of its lifecycle, and thus provide a source for mechanical feedback, in a similar way as observed for X-ray binaries.Comment: 9 pages, 5 figures, accepted for publication in MNRA

    Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers

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    We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 1011^{11} M⊙M_\odot that already have optical AGN signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (NH≲1.1×1022N_H \lesssim 1.1 \times 10^{22} cm−2^{-2}) X-ray nuclei are relatively common (8/12), but the detections are too faint (<40< 40 counts per nucleus; f2−10keV≲1.2×10−13f_{2-10 keV} \lesssim 1.2 \times 10^{-13} erg s−1^{-1} cm−2^{-2}) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGN in these mergers are rare (0-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.Comment: 8 pages, including 5 figures and 1 table. Accepted by Ap

    A Hard Look at NGC 5347: Revealing a Nearby Compton-thick AGN

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    Current measurements show that the observed fraction of Compton-thick (CT) active galactic nuclei (AGN) is smaller than the expected values needed to explain the cosmic X-ray background. Prior fits to the X-ray spectrum of the nearby Seyfert-2 galaxy NGC 5347 (z = 0.00792, D = 35.5 Mpc ) have alternately suggested a CT and Compton-thin source. Combining archival data from Suzaku, Chandra, and—most importantly—new data from NuSTAR, ... See full text for complete abstrac

    The relationship between adverse childhood experiences, coping using sex, and adult sexual coercion in non-incarcerated, community-based females

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    Adverse childhood experiences have been associated with negative outcomes in adulthood, including sexual offending. Using a cross-sectional design, we investigated whether self-reported adverse childhood experiences related to the perpetration of coercive sexual acts among 250 females recruited from the community. Furthermore, we examined whether sexualised coping mediated any potential relationship between childhood experiences and sexual coercion. A Spearman’s rank order correlation revealed no relationship between adverse childhood experiences and sexual coercion. However, adverse childhood experiences were significantly correlated with sexualised coping, which in turn was correlated with sexual coercion. Additionally, there was a significant but small indirect effect of adverse childhood experiences on sexual coercion through sexualised coping. Findings may help researchers to better understand the causal relationship between childhood experiences, sexual coping, and sexual coercion in females

    The 2-79 keV X-ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton and Chandra: a Fully Compton-Thick AGN

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    The Circinus galaxy is one of the nearest obscured AGN, making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18% of the nuclear flux in the Fe line region, but becomes comparable to the nuclear emission above 30 keV. The new analysis no longer supports a prominent transmitted AGN component in the observed band. We find that the nuclear spectrum is consistent with Compton-scattering by an optically-thick torus, where the intrinsic spectrum is a powerlaw of photon index Γ=2.2−2.4\Gamma = 2.2-2.4, the torus has an equatorial column density of NH=(6−10)×1024N_{\rm H} = (6-10)\times10^{24}cm−2^{-2} and the intrinsic AGN 2−102-10 keV luminosity is (2.3−5.1)×1042(2.3-5.1)\times 10^{42} erg/s. These values place Circinus along the same relations as unobscured AGN in accretion rate-vs-Γ\Gamma and LXL_X-vs-LIRL_{IR} phase space. NuSTAR's high sensitivity and low background allow us to study the short time-scale variability of Circinus at X-ray energies above 10 keV for the first time. The lack of detected variability favors a Compton-thick absorber, in line with the the spectral fitting results.Comment: Accepted for publication in Ap

    The nature of the torus in the heavily obscured AGN Markarian 3: an X-ray study

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    In this paper we report the results of an X-ray monitoring campaign on the heavily obscured Seyfert galaxy Markarian 3 carried out between the fall of 2014 and the spring of 2015 with NuSTAR, Suzaku and XMM-Newton. The hard X-ray spectrum of Markarian 3 is variable on all the time scales probed by our campaign, down to a few days. The observed continuum variability is due to an intrinsically variable primary continuum seen in transmission through a large, but still Compton-thin column density (N_H~0.8-1.1×\times1024^{24} cm−2^{-2}). If arranged in a spherical-toroidal geometry, the Compton scattering matter has an opening angle ~66 degrees and is seen at a grazing angle through its upper rim (inclination angle ~70 degrees). We report a possible occultation event during the 2014 campaign. If the torus is constituted by a system of clouds sharing the same column density, this event allows us to constrain their number (17±\pm5) and individual column density, [~(4.9±\pm1.5)×\times1022^{22} cm−2^{-2}]. The comparison of IR and X-ray spectroscopic results with state-of-the art "torus" models suggests that at least two thirds of the X-ray obscuring gas volume might be located within the dust sublimation radius. We report also the discovery of an ionized absorber, characterised by variable resonant absorption lines due to He- and H-like iron. This discovery lends support to the idea that moderate column density absorbers could be due to clouds evaporated at the outer surface of the torus, possibly accelerated by the radiation pressure due to the central AGN emission leaking through the patchy absorber.Comment: Accepted for publication in MNRAS, 17 pages, 11 figures, 5 table
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