The Astrophysical Journal Letters最新文献

{"title":"The Gravitational-wave Background Null Hypothesis: Characterizing Noise in Millisecond Pulsar Arrival Times with the Parkes Pulsar Timing Array","authors":"D. Reardon, A. Zic, R. Shannon, Valentina Di Marco, G. Hobbs, Agastya Kapur, M. Lower, R. Mandow, H. Middleton, M. T. Miles, Axl F. Rogers, Jacob Askew, M. Bailes, N. Bhat, A. Cameron, M. Kerr, Atharva Kulkarni, R. Manchester, R. Nathan, C. Russell, S. Osłowski, Xingjiang Zhu","doi":"10.3847/2041-8213/acdd03","DOIUrl":"https://doi.org/10.3847/2041-8213/acdd03","url":null,"abstract":"The noise in millisecond pulsar (MSP) timing data can include contributions from observing instruments, the interstellar medium, the solar wind, solar system ephemeris errors, and the pulsars themselves. The noise environment must be accurately characterized in order to form the null hypothesis from which signal models can be compared, including the signature induced by nanohertz-frequency gravitational waves (GWs). Here we describe the noise models developed for each of the MSPs in the Parkes Pulsar Timing Array (PPTA) third data release, which have been used as the basis of a search for the isotropic stochastic GW background. We model pulsar spin noise, dispersion measure variations, scattering variations, events in the pulsar magnetospheres, solar wind variability, and instrumental effects. We also search for new timing model parameters and detected Shapiro delays in PSR J0614−3329 and PSR J1902−5105. The noise and timing models are validated by testing the normalized and whitened timing residuals for Gaussianity and residual correlations with time. We demonstrate that the choice of noise models significantly affects the inferred properties of a common-spectrum process. Using our detailed models, the recovered common-spectrum noise in the PPTA is consistent with a power law with a spectral index of γ = 13/3, the value predicted for a stochastic GW background from a population of supermassive black hole binaries driven solely by GW emission.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124366814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NANOGrav 15 yr Data Set: Constraints on Supermassive Black Hole Binaries from the Gravitational-wave Background","authors":"G. Agazie, A. Anumarlapudi, A. Archibald, P. Baker, B. B'ecsy, L. Blecha, Alexander Bonilla, A. Brazier, P. Brook, S. Burke-Spolaor, R. Burnette, R. Case, J. A. Casey-Clyde, M. Charisi, S. Chatterjee, K. Chatziioannou, B. Cheeseboro, Siyuan Chen, T. Cohen, J. Cordes, N. Cornish, F. Crawford, H. Cromartie, K. Crowter, C. Cutler, D. D’Orazio, M. DeCesar, D. DeGan, P. Demorest, Heling Deng, T. Dolch, B. Drachler, E. Ferrara, W. Fiore, E. Fonseca, G. Freedman, E. Gardiner, N. Garver-Daniels, P. Gentile, K. A. Gersbach, J. Glaser, D. Good, K. Gultekin, J. Hazboun, S. Hourihane, K. Islo, R. Jennings, A. Johnson, Megan L. Jones, A. Kaiser, D. Kaplan, L. Kelley, M. Kerr, J. Key, N. Laal, M. Lam, W. Lamb, T. Lazio, N. Lewandowska, T. Littenberg, Tianyu Liu, Jing Luo, R. Lynch, Chung-Pei Ma, D. Madison, A. McEwen, J. McKee, M. Mclaughlin, N. McMann, B. W. Meyers, P. Meyers, C. Mingarelli, A. Mitridate, P. Natarajan, C. Ng, D. Nice, S. Ocker, K. Olum, T. Pennucci, B. Perera, P. Petrov, N. Pol, H. Radovan, S. Ransom,","doi":"10.3847/2041-8213/ace18b","DOIUrl":"https://doi.org/10.3847/2041-8213/ace18b","url":null,"abstract":"The NANOGrav 15 yr data set shows evidence for the presence of a low-frequency gravitational-wave background (GWB). While many physical processes can source such low-frequency gravitational waves, here we analyze the signal as coming from a population of supermassive black hole (SMBH) binaries distributed throughout the Universe. We show that astrophysically motivated models of SMBH binary populations are able to reproduce both the amplitude and shape of the observed low-frequency gravitational-wave spectrum. While multiple model variations are able to reproduce the GWB spectrum at our current measurement precision, our results highlight the importance of accurately modeling binary evolution for producing realistic GWB spectra. Additionally, while reasonable parameters are able to reproduce the 15 yr observations, the implied GWB amplitude necessitates either a large number of parameters to be at the edges of expected values or a small number of parameters to be notably different from standard expectations. While we are not yet able to definitively establish the origin of the inferred GWB signal, the consistency of the signal with astrophysical expectations offers a tantalizing prospect for confirming that SMBH binaries are able to form, reach subparsec separations, and eventually coalesce. As the significance grows over time, higher-order features of the GWB spectrum will definitively determine the nature of the GWB and allow for novel constraints on SMBH populations.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114114608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NANOGrav 15 yr Data Set: Observations and Timing of 68 Millisecond Pulsars","authors":"G. Agazie, Md F. Alam, A. Anumarlapudi, A. Archibald, Z. Arzoumanian, P. Baker, L. Blecha, Victoria Bonidie, A. Brazier, P. Brook, S. Burke-Spolaor, B. B'ecsy, Christopher Chapman, M. Charisi, S. Chatterjee, T. Cohen, J. Cordes, N. Cornish, F. Crawford, H. Cromartie, K. Crowter, M. DeCesar, P. Demorest, T. Dolch, B. Drachler, E. Ferrara, W. Fiore, E. Fonseca, G. Freedman, N. Garver-Daniels, P. Gentile, J. Glaser, D. Good, K. Gultekin, J. Hazboun, R. Jennings, Cody Jessup, A. Johnson, Megan L. Jones, A. Kaiser, D. Kaplan, L. Kelley, M. Kerr, J. Key, A. Kuske, N. Laal, M. Lam, W. Lamb, T. Lazio, N. Lewandowska, Ye Lin, Tianyu Liu, D. Lorimer, Jing Luo, R. Lynch, Chung-Pei Ma, D. Madison, Kaleb Maraccini, A. McEwen, J. McKee, Maura A. McLaughlin, N. McMann, B. W. Meyers, C. Mingarelli, A. Mitridate, C. Ng, D. Nice, S. Ocker, K. Olum, Elisa Panciu, T. Pennucci, B. Perera, N. Pol, H. Radovan, S. Ransom, P. Ray, J. Romano, Laura Salo, S. C. Sardesai, C. Schmiedekamp, A. Schmiedekamp, K. Schmitz, B. Shapiro-Albe","doi":"10.3847/2041-8213/acda9a","DOIUrl":"https://doi.org/10.3847/2041-8213/acda9a","url":null,"abstract":"We present observations and timing analyses of 68 millisecond pulsars (MSPs) comprising the 15 yr data set of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). NANOGrav is a pulsar timing array (PTA) experiment that is sensitive to low-frequency gravitational waves (GWs). This is NANOGrav’s fifth public data release, including both “narrowband” and “wideband” time-of-arrival (TOA) measurements and corresponding pulsar timing models. We have added 21 MSPs and extended our timing baselines by 3 yr, now spanning nearly 16 yr for some of our sources. The data were collected using the Arecibo Observatory, the Green Bank Telescope, and the Very Large Array between frequencies of 327 MHz and 3 GHz, with most sources observed approximately monthly. A number of notable methodological and procedural changes were made compared to our previous data sets. These improve the overall quality of the TOA data set and are part of the transition to new pulsar timing and PTA analysis software packages. For the first time, our data products are accompanied by a full suite of software to reproduce data reduction, analysis, and results. Our timing models include a variety of newly detected astrometric and binary pulsar parameters, including several significant improvements to pulsar mass constraints. We find that the time series of 23 pulsars contain detectable levels of red noise, 10 of which are new measurements. In this data set, we find evidence for a stochastic GW background.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120834101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NANOGrav 15 yr Data Set: Search for Signals from New Physics","authors":"A. Afzal, G. Agazie, A. Anumarlapudi, A. Archibald, Z. Arzoumanian, P. Baker, B. B'ecsy, J. Blanco-Pillado, L. Blecha, K. Boddy, A. Brazier, P. Brook, S. Burke-Spolaor, R. Burnette, R. Case, M. Charisi, S. Chatterjee, K. Chatziioannou, B. Cheeseboro, Siyuan Chen, T. Cohen, J. Cordes, N. Cornish, F. Crawford, H. Cromartie, K. Crowter, C. Cutler, M. DeCesar, D. DeGan, P. Demorest, Heling Deng, T. Dolch, B. Drachler, Richard von Eckardstein, E. Ferrara, W. Fiore, E. Fonseca, G. Freedman, N. Garver-Daniels, P. Gentile, K. A. Gersbach, J. Glaser, D. Good, Lydia Guertin, K. Gultekin, J. Hazboun, S. Hourihane, K. Islo, R. Jennings, A. Johnson, Megan L. Jones, A. Kaiser, D. Kaplan, L. Kelley, M. Kerr, J. Key, N. Laal, M. Lam, W. Lamb, T. Lazio, Vincent S. H. Lee, N. Lewandowska, Rafael R. Lino dos Santos, T. Littenberg, Tianyu Liu, D. Lorimer, Jing Luo, R. Lynch, Chung-Pei Ma, D. Madison, A. McEwen, J. McKee, M. Mclaughlin, N. McMann, B. W. Meyers, P. Meyers, C. Mingarelli, A. Mitridate, J. Nay, P. Natarajan, C. ","doi":"10.3847/2041-8213/acdc91","DOIUrl":"https://doi.org/10.3847/2041-8213/acdc91","url":null,"abstract":"The 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) shows positive evidence for the presence of a low-frequency gravitational-wave (GW) background. In this paper, we investigate potential cosmological interpretations of this signal, specifically cosmic inflation, scalar-induced GWs, first-order phase transitions, cosmic strings, and domain walls. We find that, with the exception of stable cosmic strings of field theory origin, all these models can reproduce the observed signal. When compared to the standard interpretation in terms of inspiraling supermassive black hole binaries (SMBHBs), many cosmological models seem to provide a better fit resulting in Bayes factors in the range from 10 to 100. However, these results strongly depend on modeling assumptions about the cosmic SMBHB population and, at this stage, should not be regarded as evidence for new physics. Furthermore, we identify excluded parameter regions where the predicted GW signal from cosmological sources significantly exceeds the NANOGrav signal. These parameter constraints are independent of the origin of the NANOGrav signal and illustrate how pulsar timing data provide a new way to constrain the parameter space of these models. Finally, we search for deterministic signals produced by models of ultralight dark matter (ULDM) and dark matter substructures in the Milky Way. We find no evidence for either of these signals and thus report updated constraints on these models. In the case of ULDM, these constraints outperform torsion balance and atomic clock constraints for ULDM coupled to electrons, muons, or gluons.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129052175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Search for an Isotropic Gravitational-wave Background with the Parkes Pulsar Timing Array","authors":"D. Reardon, A. Zic, R. Shannon, G. Hobbs, M. Bailes, Valentina Di Marco, Agastya Kapur, Axl F. Rogers, E. Thrane, Jacob Askew, N. Bhat, A. Cameron, M. Curyło, W. Coles, S. Dai, B. Goncharov, M. Kerr, Atharva Kulkarni, Y. Levin, M. Lower, R. Manchester, R. Mandow, M. T. Miles, R. Nathan, S. Osłowski, C. Russell, R. Spiewak, Songbo Zhang, Xingjiang Zhu","doi":"10.3847/2041-8213/acdd02","DOIUrl":"https://doi.org/10.3847/2041-8213/acdd02","url":null,"abstract":"Pulsar timing arrays aim to detect nanohertz-frequency gravitational waves (GWs). A background of GWs modulates pulsar arrival times and manifests as a stochastic process, common to all pulsars, with a signature spatial correlation. Here we describe a search for an isotropic stochastic gravitational-wave background (GWB) using observations of 30 millisecond pulsars from the third data release of the Parkes Pulsar Timing Array (PPTA), which spans 18 yr. Using current Bayesian inference techniques we recover and characterize a common-spectrum noise process. Represented as a strain spectrum hc=A(f/1yr−1)α , we measure A=3.1−0.9+1.3×10−15 and α = −0.45 ± 0.20, respectively (median and 68% credible interval). For a spectral index of α = −2/3, corresponding to an isotropic background of GWs radiated by inspiraling supermassive black hole binaries, we recover an amplitude of A=2.04−0.22+0.25×10−15 . However, we demonstrate that the apparent signal strength is time-dependent, as the first half of our data set can be used to place an upper limit on A that is in tension with the inferred common-spectrum amplitude using the complete data set. We search for spatial correlations in the observations by hierarchically analyzing individual pulsar pairs, which also allows for significance validation through randomizing pulsar positions on the sky. For a process with α = −2/3, we measure spatial correlations consistent with a GWB, with an estimated false-alarm probability of p ≲ 0.02 (approx. 2σ). The long timing baselines of the PPTA and the access to southern pulsars will continue to play an important role in the International Pulsar Timing Array.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125567554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NANOGrav 15 yr Data Set: Detector Characterization and Noise Budget","authors":"G. Agazie, A. Anumarlapudi, A. Archibald, Z. Arzoumanian, P. Baker, B. Bécsy, L. Blecha, A. Brazier, P. Brook, S. Burke-Spolaor, M. Charisi, S. Chatterjee, T. Cohen, J. Cordes, N. Cornish, F. Crawford, H. Cromartie, K. Crowter, M. DeCesar, P. Demorest, T. Dolch, B. Drachler, E. Ferrara, W. Fiore, E. Fonseca, G. Freedman, N. Garver-Daniels, P. Gentile, J. Glaser, D. Good, Lydia Guertin, K. Gültekin, J. Hazboun, R. Jennings, A. Johnson, Megan L. Jones, A. Kaiser, D. Kaplan, L. Kelley, M. Kerr, J. Key, N. Laal, M. Lam, W. Lamb, T. Joseph W. Lazio, N. Lewandowska, Tingting Liu, D. Lorimer, Jing Luo, R. Lynch, Chung-Pei Ma, D. Madison, A. McEwen, J. McKee, M. Mclaughlin, N. McMann, B. W. Meyers, C. Mingarelli, A. Mitridate, C. Ng, D. Nice, S. Ocker, K. Olum, T. Pennucci, B. Perera, N. Pol, H. Radovan, S. Ransom, P. Ray, J. Romano, S. C. Sardesai, A. Schmiedekamp, C. Schmiedekamp, K. Schmitz, B. Shapiro-Albert, X. Siemens, J. Simon, M. Siwek, I. Stairs, D. Stinebring, K. Stovall, A. Susobhanan, J. Swiggum, S. T","doi":"10.3847/2041-8213/acda88","DOIUrl":"https://doi.org/10.3847/2041-8213/acda88","url":null,"abstract":"Pulsar timing arrays (PTAs) are galactic-scale gravitational wave (GW) detectors. Each individual arm, composed of a millisecond pulsar, a radio telescope, and a kiloparsecs-long path, differs in its properties but, in aggregate, can be used to extract low-frequency GW signals. We present a noise and sensitivity analysis to accompany the NANOGrav 15 yr data release and associated papers, along with an in-depth introduction to PTA noise models. As a first step in our analysis, we characterize each individual pulsar data set with three types of white-noise parameters and two red-noise parameters. These parameters, along with the timing model and, particularly, a piecewise-constant model for the time-variable dispersion measure, determine the sensitivity curve over the low-frequency GW band we are searching. We tabulate information for all of the pulsars in this data release and present some representative sensitivity curves. We then combine the individual pulsar sensitivities using a signal-to-noise ratio statistic to calculate the global sensitivity of the PTA to a stochastic background of GWs, obtaining a minimum noise characteristic strain of 7 × 10−15 at 5 nHz. A power-law-integrated analysis shows rough agreement with the amplitudes recovered in NANOGrav’s 15 yr GW background analysis. While our phenomenological noise model does not model all known physical effects explicitly, it provides an accurate characterization of the noise in the data while preserving sensitivity to multiple classes of GW signals.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122318125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NANOGrav 15 yr Data Set: Bayesian Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries","authors":"G. Agazie, A. Anumarlapudi, A. Archibald, Z. Arzoumanian, P. Baker, B. B'ecsy, L. Blecha, A. Brazier, P. Brook, S. Burke-Spolaor, R. Case, J. A. Casey-Clyde, M. Charisi, S. Chatterjee, T. Cohen, J. Cordes, N. Cornish, F. Crawford, H. Cromartie, K. Crowter, M. DeCesar, P. Demorest, Matthew C. Digman, T. Dolch, B. Drachler, E. Ferrara, W. Fiore, E. Fonseca, Gabriel Freedman, N. Garver-Daniels, P. Gentile, J. Glaser, D. Good, K. Gultekin, J. Hazboun, S. Hourihane, R. Jennings, A. Johnson, Megan L. Jones, A. Kaiser, D. Kaplan, L. Kelley, M. Kerr, J. Key, N. Laal, M. Lam, W. Lamb, T. Lazio, N. Lewandowska, Tingting Liu, D. Lorimer, Jingshu Luo, R. Lynch, Chung-Pei Ma, D. Madison, A. McEwen, J. McKee, M. Mclaughlin, N. McMann, B. W. Meyers, P. Meyers, C. Mingarelli, A. Mitridate, P. Natarajan, C. Ng, D. Nice, S. Ocker, K. Olum, T. Pennucci, B. Perera, P. Petrov, N. Pol, H. Radovan, S. Ransom, P. Ray, Jo√£o Romano, S. C. Sardesai, A. Schmiedekamp, C. Schmiedekamp, K. Schmitz, B. Shapiro-Albert, X. Siemens, J. Si","doi":"10.3847/2041-8213/ace18a","DOIUrl":"https://doi.org/10.3847/2041-8213/ace18a","url":null,"abstract":"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 data sets. Here we present the search for individual supermassive black hole binaries in the NANOGrav 15 yr data set. 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 ∼4 nHz, and another at ∼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. At our most sensitive frequency of 6 nHz, we place a sky-averaged 95% upper limit of 8 × 10−15 on the strain amplitude. We also calculate an exclusion volume and a corresponding effective radius, within which we can rule out the presence of black hole binaries emitting at a given frequency.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117071160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Periodic Radio Emission from the T8 Dwarf WISE J062309.94–045624.6","authors":"Kovi Rose, J. Pritchard, T. Murphy, M. Caleb, D. Dobie, L. Driessen, S. Duchesne, D. Kaplan, E. Lenc, Ziteng Wang","doi":"10.3847/2041-8213/ace188","DOIUrl":"https://doi.org/10.3847/2041-8213/ace188","url":null,"abstract":"We present the detection of rotationally modulated, circularly polarized radio emission from the T8 brown dwarf WISE J062309.94−045624.6 between 0.9 and 2.0 GHz. We detected this high-proper-motion ultracool dwarf with the Australian SKA Pathfinder in 1.36 GHz imaging data from the Rapid ASKAP Continuum Survey. We observed WISE J062309.94−045624.6 to have a time and frequency averaged Stokes I flux density of 4.17 ± 0.41 mJy beam−1, with an absolute circular polarization fraction of 66.3% ± 9.0%, and calculated a specific radio luminosity of L ν ∼ 1014.8 erg s−1 Hz−1. In follow-up observations with the Australian Telescope Compact Array and MeerKAT we identified a multipeaked pulse structure, used dynamic spectra to place a lower limit of B > 0.71 kG on the dwarf’s magnetic field, and measured a P = 1.912 ± 0.005 hr periodicity, which we concluded to be due to rotational modulation. The luminosity and period we measured are comparable to those of other ultracool dwarfs observed at radio wavelengths. This implies that future megahertz to gigahertz surveys, with increased cadence and improved sensitivity, are likely to detect similar or later-type dwarfs. Our detection of WISE J062309.94−045624.6 makes this dwarf the coolest and latest-type star observed to produce radio emission.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132025073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temporal Variation of the Rotation in the Solar Transition Region","authors":"Xiaojuan Zhang, L. Deng, Y. Fei, Chun Li, X. Tian","doi":"10.3847/2041-8213/acd9a3","DOIUrl":"https://doi.org/10.3847/2041-8213/acd9a3","url":null,"abstract":"The temporal variations of solar rotation in the photosphere, chromosphere, and corona have been widely investigated, whereas the rotation of the solar transition region is rarely studied. Here, we perform a primary study about the long-term variation of the rotation in the transition region using Lyα irradiance from 1947 February 14 to 2023 February 20. Correlation techniques are used, and the main results are as follows. (1) The sidereal rotation period of the solar transition region varies between 22.24 and 31.49 days, and the mean sidereal rotation period is 25.50 days for the studied time interval 1947–2022. (2) The rotation period of the transition region exhibits a clear downward trend during 1947–2022, which might be caused by the reduced heliospheric pressure and the weaker solar global magnetic fields. (3) Significant periodic signal of the quasi-Schwabe cycle is found in the rotation periods of the transition region. (4) The cross-correlation between the rotation periods of the solar transition region and sunspot activity corroborates a strong correlation with the Schwabe cycle. Possible mechanisms responsible for these results are discussed.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126683700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining Dark Energy from the Local Group Dynamics","authors":"D. Benisty, A. Davis, N. W. Evans","doi":"10.3847/2041-8213/ace90b","DOIUrl":"https://doi.org/10.3847/2041-8213/ace90b","url":null,"abstract":"This Letter develops a method to constrain the cosmological constant Λ from binary galaxies, focusing on the Milky Way and Andromeda galaxies. We provide an analytical solution to the two-body problem with Λ and show that the ratio between the Keplerian period and TΛ=2π/(cΛ)≈63.2Gyr controls the importance of effects from the cosmological constant. The Andromeda–Milky Way orbit has a period of ∼17 Gyr, and so dark energy has to be taken into account. Using the current best mass estimates of the Milky Way and Andromeda galaxies, we find the cosmological constant value has an upper bound that is 5.44 times the value obtained by Planck. With future astrometric measurements, the bound on the cosmological constant can be reduced to 1.67±0.79ΛPL . Our results offer the prospects of constraints on Λ over very different scales than previously. The Local Group provides also a completely novel platform to test alternative theories of gravity. We illustrate this by deriving bounds on scalar-tensor theories of gravity over megaparsec scales.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134163610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}