1,378 research outputs found
FloorBroekgaarden/MRR_Project: ApJ accepted paper version
No full textVersion of the Github code that was used for making all results and plots in the ApJ accepted version of this paper
The code archived here reproduces all plots and results from the paper "Signatures of mass ratio reversal in gravitational waves from merging binary black holes" by Floor Broekgaarden, Simon Stevenson and Eric Thrane (ApJ 2022). See https://ui.adsabs.harvard.edu/abs/2022arXiv220501693B/abstract
This repository reproduces all results amd plots from the paper. Please email Floor Broekgaarden (see email on GitHub) for any questions.
Data
The data required to make the majority of figures can be downloaded at: https://doi.org/10.5281/zenodo.5651073
Floor Broekgaarden (2021) BHBH simulations from: Impact of Massive Binary Star and Cosmic Evolution on Gravitational Wave Observations II: Double Compact Object Mergers (Version 1) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.5651073
The original GitHub lives: https://github.com/FloorBroekgaarden/MRR_Projec
The nature of the X-ray transient MAXI J0556−332
No full textPhase-resolved spectroscopy of the newly discovered X-ray transient MAXIJ0556-332 has revealed the presence of narrow emission lines in the Bowen region that most likely arise on the surface of the mass donor star in this low-mass X-ray binary. A period search of the radial velocities of these lines provides two candidate orbital periods (16.43 ± 0.12 and 9.754 ± 0.048h), which differ from any potential X-ray periods reported. Assuming that MAXIJ0556-332 is a relatively high-inclination system that harbours a precessing accretion disc in order to explain its X-ray properties, it is only possible to obtain a consistent set of system parameters for the longer period. These assumptions imply a mass ratio of q≃ 0.45, a radial velocity semi-amplitude of the secondary of K 2≃ 190kms -1 and a compact object mass of the order of the canonical neutron star mass, making a black hole nature for MAXIJ0556-332 unlikely. We also report the presence of strong Niii emission lines in the spectrum, thereby inferring a high N/O abundance. Finally, we note that the strength of all emission lines shows a continuing decay over the ≃1 month of our observations
The 2dF Galaxy Redshift Survey: the amplitudes of fluctuations in the 2dFGRS and the CMB, and implications for galaxy biasing
No full textWe compare the amplitudes of fluctuations probed by the 2dF Galaxy Redshift Survey (2dFGRS) and by the latest measurements of the cosmic microwave background (CMB) anisotropies. By combining the 2dFGRS and CMB data, we find the linear-theory rms mass fluctuations in 8 h (-1) Mpc spheres to be sigma (8m) =0.73+/-0.05 (after marginalization over the matter density parameter Omega(m) and three other free parameters). This normalization is lower than the COBE normalization and previous estimates from cluster abundance, but it is in agreement with some revised cluster abundance determinations. We also estimate the scale-independent bias parameter of present-epoch L (s) =1.9L * APM-selected galaxies to be b (L (s) ,z =0)=1.10+/-0.08 on comoving scales of 0.02<k <0.15 h Mpc(-1). If luminosity segregation operates on these scales, L * galaxies would be almost unbiased, b (L (*) , z =0)approximate to0.96. These results are derived by assuming a flat LambdaCDM Universe, and by marginalizing over other free parameters and fixing the spectral index n =1 and the optical depth due to reionization tau =0. We also study the best-fitting pair (Omega(m) , b ), and the robustness of the results to varying n and tau . Various modelling corrections can each change the resulting b by 5-15 per cent. The results are compared with other independent measurements from the 2dFGRS itself, and from the Sloan Digital Sky Survey (SDSS), cluster abundance and cosmic shear
From star‐forming spirals to passive spheroids: integral field spectroscopy of E+A galaxies
No full textWe present three‐dimensional spectroscopy of 11 E+A galaxies at z = 0.06–0.12. These galaxies were selected for their strong Hδ absorption but weak (or non‐existent) [O ii ] λ3727 and Hα emission. This selection suggests that a recent burst of star formation was triggered but subsequently abruptly ended. We probe the spatial and spectral properties of both the young (≲1 Gyr) and old (≳few Gyr) stellar populations. Using the Hδ equivalent widths we estimate that the burst masses must have been at least 10 per cent by mass ( M burst ≳ 10 10 M ⊙ ), which is also consistent with the star formation history inferred from the broad‐band spectral energy distributions. On average the A stars cover ∼33 per cent of the galaxy image, extending over 2–15 kpc 2 , indicating that the characteristic E+A signature is a property of the galaxy as a whole and not due to a heterogeneous mixture of populations. In approximately half of the sample, we find that the A stars, nebular emission and continuum emission are not co‐located, suggesting that the newest stars are forming in a different place than those that formed ≲1 Gyr ago, and that recent star formation has occurred in regions distinct from the oldest stellar populations. At least 10 of the galaxies (91 per cent) have dynamics that class them as ‘fast rotators’ with magnitudes, v /σ, λ R and bulge‐to‐total (B/T) ratio comparable to local, representative ellipticals and S0s. We also find a correlation between the spatial extent of the A stars and the dynamical state of the galaxy such that the fastest rotators tend to have the most compact A star populations, providing new constraints on models that aim to explain the transformation of later type galaxies into early types. Finally, we show that there are no obvious differences between the line extents and kinematics of E+A galaxies detected in the radio (active galactic nucleus, AGN) compared to non‐radio sources, suggesting that AGN feedback does not play a dramatic role in defining their properties, and/or that its effects are short.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90164/1/j.1365-2966.2011.20082.x.pd
Dust-enshrouded AGN: Implications for cosmological backgrounds
No full textThe goal of this thesis is to develop an obscured AGN model for the X-ray background (XRB), and then to test the model via its predictions for the intensity of the cosmic background in the far infra-red, and by searching for obscured nuclei in individual X-ray sources in the near infra-red. A model invoking populations of obscured QSOs with a flat distribution of absorbing columns is found to give a good fit to the X-ray source counts and to the XRB spectrum. The model also accommodates the recent detection of a population of narrow-line X-ray galaxies, identifying them as low-luminosity obscured AGN. We investigate the selection effects present in optical QSO samples, and find that absorption in both the X-ray and optical wavebands combine to produce the tight observed X-ray/optical correlation, while still allowing a wide range of intrinsic column densities. X-ray sources with no obvious optical counterparts are predicted by this model, with a frequency in agreement with the numbers of these 'blank field' sources found in deep ROSAT surveys. We predict that in forthcoming AXAF surveys, ~ 50 per cent of the sources detected will be optically blank and lie at z (^>))(_~) 1. Obscured QSOs are estimated to outnumber unobscured QSOs by a factor of at least four to one. At longer wavelengths, we make a conservative prediction that obscured QSOs can account for approximately ten per cent of the sub-mm number counts and the far infra-red background, which is a modest, but non-negligible fraction. We then make observations to determine the extent of dust reddening in X-ray galaxies and QSOs, in the light of predictions of our obscured QSO model. We present K-band imaging of ROSAT and ASCA X-ray luminous galaxies and blank field sources. A trend is observed between the hardness of the X-ray spectra and the occurrence of red, unresolved counterparts, consistent with an obscured QSO origin for the X-ray emission. Near infra-red spectroscopy of X-ray luminous galaxies is then presented, searching for broad Pa(_a) emission lines. A broad line is possibly detected in one of six galaxies observed, which would indicate AGN activity. From far infra-red ISO photometry of X-ray galaxies and QSOs, we detect emission at ~ lOOμm from six narrow- line galaxies at low redshift, and from a Type 2 QSO at higher redshift. For at least two of the low redshift galaxies, there is clear proof of AGN activity on the grounds of X-ray variability and near infra-red spectroscopy. This, together with the 100μm detections, forms conclusive proof of the presence of dust-enshrouded AGN in at least some X-ray galaxies, supporting the obscured QSO explanation for the cosmic X-ray background
Correlated X-ray/ultraviolet/optical variability in the very low mass AGN NGC 4395
No full textWe report the results of a 1-yr Swift X-ray/ultraviolet (UV)/optical programme monitoring the dwarf Seyfert nucleus in NGC4395 in 2008-2009. The UV/optical flux from the nucleus was found to vary dramatically over the monitoring period, with a similar pattern of variation in each of the observed UV/optical bands (spanning 1900-5500 Å). In particular, the luminosity of NGC4395 in the 1900 Å band changed by more than a factor of 8 over the monitoring period. The fractional variability was smaller in the UV/optical bands than that seen in the X-rays, with the X-ray/optical ratio increasing with increasing flux. Pseudo-instantaneous flux measurements in the X-ray and each UV/optical band were well correlated, with cross-correlation coefficients of ≥0.7, significant at 99.9per cent confidence. Archival Swift observations from 2006 sample the intra-day X-ray/optical variability on NGC4395. These archival data show a very strong correlation between the X-ray and b bands, with a cross-correlation coefficient of 0.84 (significant at >99per cent confidence). The peak in the cross-correlation function is marginally resolved and asymmetric, suggesting that X-rays lead the b band, but by ≤1h. In response to recent (2011 August) very high X-ray flux levels from NGC4395 we triggered Swift target of opportunity observations, which sample the intra-hour X-ray/UV variability. These observations indicate, albeit with large uncertainties, a lag of the 1900 Å band behind the X-ray flux of ∼400s. The tight correlation between the X-ray and UV/optical lightcurves, together with the constraints we place on the lag time-scale, is consistent with the UV/optical variability of NGC4395 being primarily due to reprocessing of X-ray photons by the accretion disc
An enigmatic pointlike feature within the HD 169142 transitional disk
No full textMagAO was constructed with NSF MRI, TSIP, and ATI awards.We report the detection of a faint pointlike feature possibly related to ongoing planet-formation in the disk of the transition disk star HD 169142. The pointlike feature has a Delta-mag(L) ∼ 6.4, at a separation of ∼ 0" .11 and PA ∼ 0º. Given its lack of an H or KS counterpart despite its relative brightness, this candidate cannot be explained by purely photospheric emission and must be a disk feature heated by an as yet unknown source. Its extremely red colors make it highly unlikely to be a background object, but future multi-wavelength followup is necessary for confirmation and characterization of this feature.Peer reviewe
Generation of quasi-periodic waves and flows in the solar atmosphere by oscillatory reconnection
No full textWe investigate the long-term evolution of an initially buoyant magnetic flux tube emerging into a gravitationally stratified coronal hole environment and report on the resulting oscillations and outflows. We perform 2.5-dimensional nonlinear numerical simulations, generalizing the models of McLaughlin et al. and Murray et al. We find that the physical mechanism of oscillatory reconnection naturally generates quasi-periodic vertical outflows, with a transverse/swaying aspect. The vertical outflows consist of both a periodic aspect and evidence of a positively directed flow. The speed of the vertical outflow (20-60 km/s) is comparable to those reported in the observational literature. We also perform a parametric study varying the magnetic strength of the buoyant flux tube and find a range of associated periodicities: 1.75-3.5 minutes. Thus, the mechanism of oscillatory reconnection may provide a physical explanation to some of the high-speed, quasi-periodic, transverse outflows/jets recently reported by a multitude of authors and instruments
Detection of the irradiated donor in the LMXBs 4U 1636-536 (=V801 Ara) and 4U 1735-444 (=V926 Sco)
No full textPhase-resolved VLT spectroscopy of the bursting low-mass X-ray binaries 4U 1636-536/V801 Ara and 4U 1735-444/V926 Sco is presented. Doppler images of the N iiiλ4640 Bowen transition reveal compact spots which we attribute to fluorescent emission from the donor star and enable us to define a new set of spectroscopic ephemerides. We measure Kem= 277 ± 22 and 226 ± 22 km s−1 from the N iii spots in V801 Ara and V926 Sco, respectively, which represent strict lower limits to the radial velocity semi-amplitude of the donor stars. Our new ephemerides provide confirmation that light-curve maxima in V801 Ara and likely V926 Sco occur at superior conjunction of the donor star and hence photometric modulation is caused by the visibility of the X-ray heated donor. The velocities of He iiλ4686 and the broad Bowen blend are strongly modulated with the orbital period, with phasing supporting emission dominated by the disc bulge. In addition, a reanalysis of burst oscillations in V801 Ara, using our spectroscopic T0, leads to K1= 90–113 km s−1. We also estimate the K-corrections for all possible disc flaring angles and present the first dynamical constraints on the masses of these X-ray bursters. These are K2= 360 ± 74 km s−1, f(M) = 0.76 ± 0.47 M⊙ and q= 0.21–0.34 for V801 Ara and K2= 298 ± 83 km s−1, f(M) = 0.53 ± 0.44 M⊙ and q= 0.05–0.41 for V926 Sco. Disc flaring angles α≥ 12° and q≃ 0.26–0.34 are favoured for V801 Ara whereas the lack of K1 constraint for V926 Sco prevents tight constraints on this system. Although both binaries seem to have intermediate inclinations, the larger equivalent width of the narrow N iii line in V801 Ara at phase 0.5 relative to phase 0 suggests that it has the higher inclination of the two
ALMA and Herschel observations of the prototype dusty and polluted white dwarf G29-38
No full textJF gratefully acknowledges the support of the STFC via an Ernest Rutherford Fellowship. AB acknowledges the support of the ANR-2010 BLAN-0505-01 (EXOZODI). MCW and OP are grateful for the support of the European Union through ERC grant number 279973.ALMA Cycle 0 and Herschel PACS observations are reported for the prototype, nearest, and brightest example of a dusty and polluted white dwarf, G29-38. These long-wavelength programmes attempted to detect an outlying, parent population of bodies at 1–100 au, from which originates the disrupted planetesimal debris that is observed within 0.01 au and which exhibits LIR/L* = 0.039. No associated emission sources were detected in any of the data down to LIR/L* ∼ 10−4, generally ruling out cold dust masses greater than 1024–1025 g for reasonable grain sizes and properties in orbital regions corresponding to evolved versions of both asteroid and Kuiper belt analogues. Overall, these null detections are consistent with models of long-term collisional evolution in planetesimal discs, and the source regions for the disrupted parent bodies at stars like G29-38 may only be salient in exceptional circumstances, such as a recent instability. A larger sample of polluted white dwarfs, targeted with the full ALMA array, has the potential to unambiguously identify the parent source(s) of their planetary debris.Peer reviewe
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