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Ingram A.,University of Amsterdam | Motta S.,European Space Astronomy Center
Monthly Notices of the Royal Astronomical Society | Year: 2014

The relativistic precession model (RPM) can be used to obtain a precise measurement of the mass and spin of a black hole when the appropriate set of quasi-periodic oscillations is detected in the power-density spectrum of an accreting black hole. However, in previous studies, the solution of the RPM equations could be obtained only through numerical methods at a price of an intensive computational effort. Here, we demonstrate that the RPM system of equations can be solved analytically, drastically reducing the computational load, now limited to the Monte Carlo simulation necessary to estimate the uncertainties. The analytical method not only provides an easy solution to the RPM system when three oscillations are detected, but in all the cases where the detection of two simultaneous oscillations is coupled with an independent mass measurement. We also present a computationally inexpensive method to place limits on the black hole mass and spin when only two oscillations are observed. © 2014 The Authors. Source

Agundez M.,CSIC - Institute of Materials Science | Cernicharo J.,CSIC - Institute of Materials Science | Decin L.,University of Amsterdam | Decin L.,Catholic University of Leuven | And 2 more authors.
Astrophysical Journal Letters | Year: 2014

Phosphine (PH3) was tentatively identified a few years ago in the carbon star envelopes IRC +10216 and CRL 2688 from observations of an emission line at 266.9 GHz attributable to the J = 1-0 rotational transition. We report the detection of the J = 2-1 rotational transition of PH3 in IRC +10216 using the HIFI instrument on board Herschel, which definitively confirms the identification of PH3. Radiative transfer calculations indicate that infrared pumping in excited vibrational states plays an important role in the excitation of PH3 in the envelope of IRC +10216, and that the observed lines are consistent with phosphine being formed anywhere between the star and 100 R* from the star, with an abundance of 10-8 relative to H2. The detection of PH3 challenges chemical models, none of which offer a satisfactory formation scenario. Although PH 3 holds just 2% of the total available phosphorus in IRC +10216, it is, together with HCP, one of the major gas phase carriers of phosphorus in the inner circumstellar layers, suggesting that it could also be an important phosphorus species in other astronomical environments. This is the first unambiguous detection of PH3 outside the solar system, and is a further step toward a better understanding of the chemistry of phosphorus in space. © 2014. The American Astronomical Society. All rights reserved. Source

Motta S.E.,European Space Astronomy Center | Belloni T.M.,National institute for astrophysics | Stella L.,National institute for astrophysics | Munoz-Darias T.,University of Southampton | Fender R.,University of Southampton
Monthly Notices of the Royal Astronomical Society | Year: 2014

We present a systematic analysis of the fast time variability properties of the transient black hole binary GRO J1655-40, based on the complete set of Rossi X-ray Timing Explorer observations.We demonstrate that the frequencies of the quasi-periodic oscillations and of the broad-band noise components and their variations match accurately the strong field general relativistic frequencies of particle motion in the close vicinity of the innermost stable circular orbit, as predicted by the relativistic precession model.We obtain high-precision measurements of the black hole mass [M = (5.31 ± 0.07)M⊙, consistent with the value from optical/NIR observations] and spin (a = 0.290 ± 0.003), through the sole use of X-ray timing. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

Sanchez Contreras C.,CSIC - National Institute of Aerospace Technology | Sanchez Contreras C.,European Space Astronomy Center | Sahai R.,Jet Propulsion Laboratory
Astrophysical Journal, Supplement Series | Year: 2012

We have performed interferometric observations of the 12CO(J= 1-0) emission in a sample of 27 objects spanning different evolutionary stages from the late asymptotic giant branch (late-AGB), through the post-AGB (pAGB) phase, and to the planetary nebula (PN) stage, but dominated by pAGB objects and young PNs (≥81%). In this paper (the first in a series) we present our maps and main nebular properties derived for the whole sample. Observations were performed with the Caltech Millimeter Array at the Owens Valley Radio Observatory. The angular resolution obtained in our survey ranges between 23 and 107. The 13CO and C 18O (J= 1-0) transitions as well as the 2.6mm continuum emission have also been observed in several objects. The detection statistics in the 12CO, 13CO, C 18O transitions and 2.6mm continuum are 89%, 83%, 0%, and 37%, respectively. We report first detections of 12CO(J= 1-0) emission in 13 targets and confirm emission from several previous marginal detections. The molecular envelope probed by 12CO(J= 1-0) emission is extended for 18 (out of 24) sources; envelope asymmetries and/or velocity gradients are found in most extended objects. Our data have been used to derive accurate target coordinates and systemic velocities and to characterize the envelope size, morphology, and kinematics. We also provide an estimate of the total molecular mass and the fraction of it contained in fast flows, lower limits to the linear momentum and to the isotopic 12C/ 13C ratio, as well as the AGB mass-loss rate and timescale for sources with extended CO emission. © 2012. The American Astronomical Society. All rights reserved.. Source

Dobrotka A.,Slovak University of Technology in Bratislava | Ness J.-U.,European Space Astronomy Center
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present timing analyses of eight X-ray light curves and one optical/UV light curve of the nova V4743 Sgr (2002) taken by Chandra and XMM-Newton on the following days after outburst: 50 (early hard emission phase), 180, 196, 302, 371, 526 [super soft source (SSS) phase], and 742 and 1286 (quiescent emission phase). We have studied the multifrequency nature and time evolution of the dominant peak at ∼0.75 mHz using the standard Lomb-Scargle method and a 2D sine fitting method. We found a double structure of the peak and its overtone for days 180 and 196. The two frequencies were closer together on day 196, suggesting that the difference between the two peaks is gradually decreasing. For the later observations, only a single frequency can be detected, which is likely due to the exposure times being shorter than the beat period between the two peaks, especially if they are moving closer together. The observations on days 742 and 1286 are long enough to detect two frequencies with the difference found for day 196, but we confidently find only a single frequency. We found significant changes in the oscillation frequency and amplitude. We have derived blackbody temperatures from the SSS spectra, and the evolution of changes in frequency and blackbody temperature suggests that the 0.75-mHz peak was modulated by pulsations. Later, after nuclear burning had ceased, the signal stabilized at a single frequency, although the X-ray frequency differs from the optical/UV frequency obtained consistently from the Optical Monitor onboard XMM-Newton and from ground-based observations. We believe that the late frequency is the white dwarf rotation and that the ratio of spin/orbit period strongly supports that the system is an intermediate polar. © 2010 The Authors. Journal compilation © 2010 RAS. Source

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