المؤلفون: Martinez, J. G., Stovall, K., Freire, P. C. C., Deneva, J. S., Tauris, T. M., Ridolfi, A., Wex, N., Jenet, F. A., McLaughlin, M. A., Bagchi, M.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics, General Relativity and Quantum Cosmology

الوصف: In this work, we report the discovery and characterization of PSR J1411+2551, a new binary pulsar discovered in the Arecibo 327 MHz Drift Pulsar Survey. Our timing observations of the radio pulsar in the system span a period of about 2.5 years. This timing campaign allowed a precise measurement of its spin period (62.4 ms) and its derivative (9.6 $\pm$ 0.7) $\times 10^{-20}\, \rm s\, s^{-1}$; from these, we derive a characteristic age of $\sim 10\,$Gyr and a surface magnetic field strength of 2.5 $\times 10^{9}$ G. These numbers indicate that this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. The system has an eccentric ($e\, = \, 0.17$) 2.61 day orbit. This eccentricity allows a highly significant measurement of the rate of advance of periastron, $\dot{\omega} = 0.07686 \pm 0.00046 ^{\circ}~{\rm yr}^{-1}$. Assuming general relativity accurately models the orbital motion, this implies a total system mass M = $2.538 \pm 0.022 M_{\odot}$. The minimum companion mass is $0.92\, M_{\odot}$ and the maximum pulsar mass is $1.62\, M_{\odot}$. The large companion mass and the orbital eccentricity suggest that PSR J1411+2551 is a double neutron star system; the lightest known to date including the DNS merger GW 170817. Furthermore, the relatively low orbital eccentricity and small proper motion limits suggest that the second supernova had a relatively small associated kick; this and the low system mass suggest that it was an ultra-stripped supernova.
Comment: Accepted for publication in APJ letters

الوصول الحر: http://arxiv.org/abs/1711.09804Test

المؤلفون: Mereghetti, S., Kuiper, L., Tiengo, A., Hessels, J., Hermsen, W., Stovall, K., Possenti, A., Rankin, J., Esposito, P., Turolla, R., Mitra, D., Wright, G., Stappers, B., Horneffer, A., Oslowski, S., Serylak, M., Griessmeier, J. -M., Rigoselli, M.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: New simultaneous X-ray and radio observations of the archetypal mode-switching pulsar PSR B0943+10 have been carried out with XMM-Newton and the LOFAR, LWA and Arecibo radio telescopes in November 2014. They allowed us to better constrain the X-ray spectral and variability properties of this pulsar and to detect, for the first time, the X-ray pulsations also during the X-ray-fainter mode. The combined timing and spectral analysis indicates that unpulsed non-thermal emission, likely of magnetospheric origin, and pulsed thermal emission from a small polar cap are present during both radio modes and vary in a correlated way.
Comment: 4 pages, 1 figure, 1 table - To appear in the proceedings of "IAUS 337: Pulsar Astrophysics - The Next 50 Years" eds: P. Weltevrede, B.B.P. Perera, L. Levin Preston & S. Sanidas

الوصول الحر: http://arxiv.org/abs/1711.04477Test

المؤلفون: Bécsy, B., Cornish, N., Meyers, P., Kelley, L., Agazie, G., Anumarlapudi, A., Archibald, A., Arzoumanian, Z., Baker, P., Blecha, L., Brazier, A., Brook, P., Burke-Spolaor, S., Casey-Clyde, J., Charisi, M., Chatterjee, S., Chatziioannou, K., Cohen, T., Cordes, J., Crawford, F., Cromartie, H., Crowter, K., DeCesar, M., Demorest, P., Dolch, T., Ferrara, E., Fiore, W., Fonseca, E., Freedman, G., Garver-Daniels, N., Gentile, P., Glaser, J., Good, D., Gültekin, K., Hazboun, J., Hourihane, S., Jennings, R., Johnson, A., Jones, M., Kaiser, A., Kaplan, D., Kerr, M., Key, J., Laal, N., Lam, M., Lamb, W., Lazio, T., Lewandowska, N., Littenberg, T., Liu, T., Lorimer, D., Luo, J., Lynch, R., Ma, C., Madison, D., McEwen, A., McKee, J., McLaughlin, M., McMann, N., Meyers, B., Mingarelli, C., Mitridate, A., Ng, C., Nice, D., Ocker, S., Olum, K., Pennucci, T., Perera, B., Pol, N., Radovan, H., Ransom, S., Ray, P., Romano, J., Sardesai, S., Schmiedekamp, A., Schmiedekamp, C., Schmitz, K., Shapiro-Albert, B., Siemens, X., Simon, J., Siwek, M., Fiscella, S., Stairs, I., Stinebring, D., Stovall, K., Susobhanan, A., Swiggum, J., Taylor, S., Turner, J., Unal, C., Vallisneri, M., van Haasteren, R., Vigeland, S., Wahl, H., Witt, C., Young, O.

المصدر: The Astrophysical Journal

الوصف: Analysis of pulsar timing data have provided evidence for a stochastic gravitational wave background in the nHz frequency band. The most plausible source of such a background is the superposition of signals from millions of supermassive black hole binaries. The standard statistical techniques used to search for such a background and assess its significance make several simplifying assumptions, namely: i) Gaussianity; ii) isotropy; and most often iii) a power-law spectrum. However, a stochastic background from a finite collection of binaries does not exactly satisfy any of these assumptions. To understand the effect of these assumptions, we test standard analysis techniques on a large collection of realistic simulated datasets. The dataset length, observing schedule, and noise levels were chosen to emulate the NANOGrav 15-year dataset. Simulated signals from millions of binaries drawn from models based on the Illustris cosmological hydrodynamical simulation were added to the data. We find that the standard statistical methods perform remarkably well on these simulated datasets, despite their fundamental assumptions not being strictly met. They are able to achieve a confident detection of the background. However, even for a fixed set of astrophysical parameters, different realizations of the universe result in a large variance in the significance and recovered parameters of the background. We also find that the presence of loud individual binaries can bias the spectral recovery of the background if we do not account for them.

وصف الملف: application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/arxiv/2309.04443; http://hdl.handle.net/21.11116/0000-000E-3C61-2Test; http://hdl.handle.net/21.11116/0000-000E-3C63-0Test; http://hdl.handle.net/21.11116/0000-000E-3C64-FTest

الإتاحة: https://doi.org/10.3847/1538-4357/ad09e4Test
http://hdl.handle.net/21.11116/0000-000E-3C61-2Test
http://hdl.handle.net/21.11116/0000-000E-3C63-0Test
http://hdl.handle.net/21.11116/0000-000E-3C64-FTest

المؤلفون: Agazie, G., Anumarlapudi, A., Archibald, A., Arzoumanian, Z., Baker, P., Bécsy, B., Blecha, L., Brazier, A., Brook, P., Burke-Spolaor, S., Case, R., Casey-Clyde, J., Charisi, M., Chatterjee, S., Cohen, T., Cordes, J., Cornish, N., Crawford, F., Cromartie, H., Crowter, K., DeCesar, M., Demorest, P., Digman, M., Dolch, T., Drachler, B., Ferrara, E., Fiore, W., Fonseca, E., Freedman, G., Garver-Daniels, N., Gentile, P., Glaser, J., Good, D., Gültekin, K., Hazboun, J., Hourihane, S., Jennings, R., Johnson, A., Jones, M., Kaiser, A., Kaplan, D., Kelley, L., Kerr, M., Key, J., Laal, N., Lam, M., Lamb, W., Lazio, T., Lewandowska, N., Liu, T., Lorimer, D., Luo, J., Lynch, R., Ma, C., Madison, D., McEwen, A., McKee, J., McLaughlin, M., McMann, N., Meyers, B., Meyers, P., Mingarelli, C., mitridate, a., natarajan, p., Ng, C., Nice, D., Ocker, S., Olum, K., Pennucci, T., Perera, B., Petrov, P., Pol, N., Radovan, H., Ransom, S., Ray, P., Romano, J., Sardesai, S., Schmiedekamp, A., Schmiedekamp, C., Schmitz, K., Shapiro-Albert, B., Siemens, X., Simon, J., Siwek, M., Stairs, I., Stinebring, D., Stovall, K., Susobhanan, A., Swiggum, J., Taylor, J., Taylor, S., Turner, J., Unal, C., Vallisneri, M., van Haasteren, R., Vigeland, S., Wahl, H., Witt, C., Young, O.

المصدر: Astrophysical Journal Letters

الوصف: Evidence for a low-frequency stochastic gravitational wave background has recently been reported based on analyses of pulsar timing array data. The most likely source of such a background is a population of supermassive black hole binaries, the loudest of which may be individually detected in these datasets. Here we present the search for individual supermassive black hole binaries in the NANOGrav 15-year dataset. We introduce several new techniques, which enhance the efficiency and modeling accuracy of the analysis. The search uncovered weak evidence for two candidate signals, one with a gravitational-wave frequency of $\sim$4 nHz, and another at $\sim$170 nHz. The significance of the low-frequency candidate was greatly diminished when Hellings-Downs correlations were included in the background model. The high-frequency candidate was discounted due to the lack of a plausible host galaxy, the unlikely astrophysical prior odds of finding such a source, and since most of its support comes from a single pulsar with a commensurate binary period. Finding no compelling evidence for signals from individual binary systems, we place upper limits on the strain amplitude of gravitational waves emitted by such systems.

وصف الملف: application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/arxiv/2306.16222; http://hdl.handle.net/21.11116/0000-000D-D69E-0Test; http://hdl.handle.net/21.11116/0000-000D-D6A0-CTest; http://hdl.handle.net/21.11116/0000-000D-D6A1-BTest

الإتاحة: https://doi.org/10.3847/2041-8213/ace18aTest
http://hdl.handle.net/21.11116/0000-000D-D69E-0Test
http://hdl.handle.net/21.11116/0000-000D-D6A0-CTest
http://hdl.handle.net/21.11116/0000-000D-D6A1-BTest

المؤلفون: Agazie, G., Anumarlapudi, A., Archibald, A., Arzoumanian, Z., Baker, P., Becsy, B., Blecha, L., Brazier, A., Brook, P., Burke-Spolaor, S., Burnette, R., Case, R., Charisi, M., Chatterjee, S., Chatziioannou, K., Cheeseboro, B., Chen, S., Cohen, T., Cordes, J., Cornish, N., Crawford, F., Cromartie, H., Crowter, K., Cutler, C., DeCesar, M., DeGan, D., Demorest, P., Deng, H., Dolch, T., Drachler, B., Ellis, J., Ferrara, E., Fiore, W., Fonseca, E., Freedman, G., Garver-Daniels, N., Gentile, P., Gersbach, K., Glaser, J., Good, D., Gultekin, K., Hazboun, J., Hourihane, S., Islo, K., Jennings, R., Johnson, A., Jones, M., Kaiser, A., Kaplan, D., Kelley, L., Kerr, M., Key, J., Klein, T., Laal, N., Lam, M., Lamb, W., Lazio, T., Lewandowska, N., Littenberg, T., Liu, T., Lommen, A., Lorimer, D., Luo, J., Lynch, R., Ma, C., Madison, D., Mattson, M., McEwen, A., McKee, J., McLaughlin, M., McMann, N., Meyers, B., Meyers, P., Mingarelli, C., Mitridate, A., Natarajan, P., Ng, C., Nice, D., Ocker, S., Olum, K., Pennucci, T., Perera, B., Petrov, P., Pol, N., Radovan, H., Ransom, S., Ray, P., Romano, J., Sardesai, S., Schmiedekamp, A., Schmiedekamp, C., Schmitz, K., Schult, L., Shapiro-Albert, B., Siemens, X., Simon, J., Siwek, M., Stairs, I., Stinebring, D., Stovall, K., Sun, J., Susobhanan, A., Swiggum, J., Taylor, J., Taylor, S., Turner, J., Unal, C., Vallisneri, M., van Haasteren, R., Vigeland, S., Wahl, H., Wang, Q., Witt, C., Young, O.

المساهمون: The NANOGrav Collaboration

المصدر: he Astrophysical Journal Letters

الوصف: We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15-year pulsar-timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings-Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law-spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of $10^{14}$, and this same model is favored over an uncorrelated common power-law-spectrum model with Bayes factors of 200-1000, depending on spectral modeling choices. We have built a statistical background distribution for these latter Bayes factors using a method that removes inter-pulsar correlations from our data set, finding $p = 10^{-3}$ (approx. $3\sigma$) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of inter-pulsar correlations yields $p = 5 \times 10^{-5} - 1.9 \times 10^{-4}$ (approx. $3.5 - 4\sigma$). Assuming a fiducial $f^{-2/3}$ characteristic-strain spectrum, as appropriate for an ensemble of binary supermassive black-hole inspirals, the strain amplitude is $2.4^{+0.7}_{-0.6} \times 10^{-15}$ (median + 90% credible interval) at a reference frequency of 1/(1 yr). The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black-hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings-Downs correlations points to the gravitational-wave origin of this signal.

وصف الملف: application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/arxiv/2306.16213; http://hdl.handle.net/21.11116/0000-000D-B1C3-ETest; http://hdl.handle.net/21.11116/0000-000D-B1C5-CTest; http://hdl.handle.net/21.11116/0000-000D-BBEB-8Test

الإتاحة: https://doi.org/10.3847/2041-8213/acdac6Test
http://hdl.handle.net/21.11116/0000-000D-B1C3-ETest
http://hdl.handle.net/21.11116/0000-000D-B1C5-CTest
http://hdl.handle.net/21.11116/0000-000D-BBEB-8Test

المؤلفون: Law, C. J., Abruzzo, M. W., Bassa, C. G., Bower, G. C., Burke-Spolaor, S., Butler, B. J., Cantwell, T., Carey, S. H., Chatterjee, S., Cordes, J. M., Demorest, P., Dowell, J., Fender, R., Gourdji, K., Grainge, K., Hessels, J. W. T., Hickish, J., Kaspi, V. M., Lazio, T. J. W., McLaughlin, M. A., Michilli, D., Mooley, K., Perrott, Y. C., Ransom, S. M., Razavi-Ghods, N., Rupen, M., Scaife, A., Scott, P., Scholz, P., Seymour, A., Spitler, L. G., Stovall, K., Tendulkar, S. P., Titterington, D., Wharton, R. S., Williams, P. K. G.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We present results of the coordinated observing campaign that made the first subarcsecond localization of a Fast Radio Burst, FRB 121102. During this campaign, we made the first simultaneous detection of an FRB burst by multiple telescopes: the VLA at 3 GHz and the Arecibo Observatory at 1.4 GHz. Of the nine bursts detected by the Very Large Array at 3 GHz, four had simultaneous observing coverage at other observatories. We use multi-observatory constraints and modeling of bursts seen only at 3 GHz to confirm earlier results showing that burst spectra are not well modeled by a power law. We find that burst spectra are characterized by a ~500 MHz envelope and apparent radio energy as high as $10^{40}$ erg. We measure significant changes in the apparent dispersion between bursts that can be attributed to frequency-dependent profiles or some other intrinsic burst structure that adds a systematic error to the estimate of DM by up to 1%. We use FRB 121102 as a prototype of the FRB class to estimate a volumetric birth rate of FRB sources $R_{FRB} \approx 5x10^{-5}/N_r$ Mpc$^{-3}$ yr$^{-1}$, where $N_r$ is the number of bursts per source over its lifetime. This rate is broadly consistent with models of FRBs from young pulsars or magnetars born in superluminous supernovae or long gamma-ray bursts, if the typical FRB repeats on the order of thousands of times during its lifetime.
Comment: 17 pages, 7 figures. Submitted to AAS Journals

الوصول الحر: http://arxiv.org/abs/1705.07553Test

المؤلفون: Chawla, P., Kaspi, V. M., Josephy, A., Rajwade, K. M., Lorimer, D. R., Archibald, A. M., DeCesar, M. E., Hessels, J. W. T., Kaplan, D. L., Karako-Argaman, C., Kondratiev, V. I., Levin, L., Lynch, R. S., McLaughlin, M. A., Ransom, S. M., Roberts, M. S. E., Stairs, I. H., Stovall, K., Swiggum, J. K., van Leeuwen, J.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We report on a search for Fast Radio Bursts (FRBs) with the Green Bank Northern Celestial Cap (GBNCC) Pulsar Survey at 350 MHz. Pointings amounting to a total on-sky time of 61 days were searched to a DM of 3000 pc cm$^{-3}$ while the rest (23 days; 29% of the total time) were searched to a DM of 500 pc cm$^{-3}$. No FRBs were detected in the pointings observed through May 2016. We estimate a 95% confidence upper limit on the FRB rate of $3.6\times 10^3$ FRBs sky$^{-1}$ day$^{-1}$ above a peak flux density of 0.63 Jy at 350 MHz for an intrinsic pulse width of 5 ms. We place constraints on the spectral index $\alpha$ by running simulations for different astrophysical scenarios and cumulative flux density distributions. The non-detection with GBNCC is consistent with the 1.4-GHz rate reported for the Parkes surveys for $\alpha > +0.35 $ in the absence of scattering and free-free absorption and $\alpha > -0.3$ in the presence of scattering, for a Euclidean flux distribution. The constraints imply that FRBs exhibit either a flat spectrum or a spectral turnover at frequencies above 400 MHz. These constraints also allow estimation of the number of bursts that can be detected with current and upcoming surveys. We predict that CHIME may detect anywhere from several to $\sim$50 FRBs a day (depending on model assumptions), making it well suited for interesting constraints on spectral index, the log $N$-log $S$ slope and pulse profile evolution across its bandwidth (400-800 MHz).
Comment: 18 pages, 10 figures, Accepted for publication in ApJ

الوصول الحر: http://arxiv.org/abs/1701.07457Test

المؤلفون: Jones, M. L., McLaughlin, M. A., Lam, M. T., Cordes, J. M., Levin, L., Chatterjee, S., Arzoumanian, Z., Crowter, K., Demorest, P. B., Dolch, T., Ellis, J. A., Ferdman, R. D., Fonseca, E., Gonzalez, M. E., Jones, G., Lazio, T. J. W., Nice, D. J., Pennucci, T. T., Ransom, S. M., Stinebring, D. R., Stairs, I. H., Stovall, K., Swiggum, J. K., Zhu, W. W.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: We analyze dispersion measure (DM) variations of 37 millisecond pulsars in the 9-year NANOGrav data release and constrain the sources of these variations. Variations are significant for nearly all pulsars, with characteristic timescales comparable to or even shorter than the average spacing between observations. Five pulsars have periodic annual variations, 14 pulsars have monotonically increasing or decreasing trends, and 13 pulsars show both effects. Several pulsars show correlations between DM excesses and lines of sight that pass close to the Sun. Mapping of the DM variations as a function of the pulsar trajectory can identify localized ISM features and, in one case, an upper limit to the size of the dispersing region of 13.2 AU. Finally, five pulsars show very nearly quadratic structure functions, which could be indicative of an underlying Kolmogorov medium. Four pulsars show roughly Kolmogorov structure functions and another four show structure functions less steep than Kolmogorov. One pulsar has too large an uncertainty to allow comparisons. We discuss explanations for apparent departures from a Kolmogorov-like spectrum, and show that the presence of other trends in the data is the most likely cause.
Comment: 20 pages, 13 figures, submitted to ApJ

الوصول الحر: http://arxiv.org/abs/1612.03187Test

المؤلفون: Taylor, G. B., Stovall, K., McCrackan, M., McLaughlin, M. A., Miller, R., Karako-Argaman, C., Dowell, J., Schinzel, F. K.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Rotating Radio Transients (RRATs) are a subclass of pulsars first identified in 2006 that are detected only in searches for single pulses and not through their time averaged emission. Here, we present the results of observations of 19 RRATs using the first station of the Long Wavelength Array (LWA1) at frequencies between 30 MHz and 88 MHz. The RRATs observed here were first detected in higher frequency pulsar surveys. Of the 19 RRATs observed, 2 sources were detected and their dispersion measures, periods, pulse profiles, and flux densities are reported and compared to previous higher frequency measurements. We find a low detection rate (11%), which could be a combination of the lower sensitivity of LWA1 compared to the higher frequency telescopes, and the result of scattering by the interstellar medium or a spectral turnover.
Comment: 10 pages, 6 figures, accepted to the Astrophysical Journal

الوصول الحر: http://arxiv.org/abs/1610.04270Test

المؤلفون: Lam, M. T., Cordes, J. M., Chatterjee, S., Arzoumanian, Z., Crowter, K., Demorest, P. B., Dolch, T., Ellis, J. A., Ferdman, R. D., Fonseca, E., Gonzalez, M. E., Jones, G., Jones, M. L., Levin, L., Madison, D. R., McLaughlin, M. A., Nice, D. J., Pennucci, T. T., Ransom, S. M., Shannon, R. M., Siemens, X., Stairs, I. H., Stovall, K., Swiggum, J. K., Zhu, W. W.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics

الوصف: Gravitational wave astronomy using a pulsar timing array requires high-quality millisecond pulsars, correctable interstellar propagation delays, and high-precision measurements of pulse times of arrival. Here we identify noise in timing residuals that exceeds that predicted for arrival time estimation for millisecond pulsars observed by the North American Nanohertz Observatory for Gravitational Waves. We characterize the excess noise using variance and structure function analyses. We find that 26 out of 37 pulsars show inconsistencies with a white-noise-only model based on the short timescale analysis of each pulsar and we demonstrate that the excess noise has a red power spectrum for 15 pulsars. We also decompose the excess noise into chromatic (radio-frequency-dependent) and achromatic components. Associating the achromatic red-noise component with spin noise and including additional power-spectrum-based estimates from the literature, we estimate a scaling law in terms of spin parameters (frequency and frequency derivative) and data-span length and compare it to the scaling law of Shannon \& Cordes (2010). We briefly discuss our results in terms of detection of gravitational waves at nanohertz frequencies.
Comment: 20 pages, 16 figures, to be published in ApJ

الوصول الحر: http://arxiv.org/abs/1610.01731Test