Abstract
We report on the discovery of the companion star to the millisecond pulsar PSR J1835−3259B in the Galactic globular cluster NGC 6652. Taking advantage of deep photometric archival ...observations acquired through the Hubble Space Telescope in near-UV and optical bands, we identified a bright and blue object at a position compatible with that of the radio pulsar. The companion is located along the helium-core white dwarf cooling sequence, and the comparison with binary evolution models provides a mass of 0.17 ± 0.02
M
⊙
, a surface temperature of 11,500 ± 1900 K, and a very young cooling age of only 200 ± 100 Myr. The mass and the age of the companion are compatible with a progenitor star of about 0.87
M
⊙
, which started transferring mass to the primary during its evolution along the subgiant branch and stopped during the early red giant branch phase. Combining together the pulsar mass function and the companion mass, we found that this system is observed at an almost edge-on orbit and hosts a neutron star with a mass of 1.44 ± 0.06
M
⊙
, thus suggesting a highly nonconservative mass accretion phase. The young age of the WD companion is consistent with the scenario of a powerful, relatively young MSP indicated by the earlier detection of gamma-rays from this system.
Relativistic Spin Precession in the Double Pulsar Breton, Rene P.; Kaspi, Victoria M.; Kramer, Michael ...
Science (American Association for the Advancement of Science),
07/2008, Volume:
321, Issue:
5885
Journal Article
Peer reviewed
The double pulsar PSR J0737-3039A/B consists of two neutron stars in a highly relativistic orbit that displays a roughly 30-second eclipse when pulsar A passes behind pulsar B. Describing this ...eclipse of pulsar A as due to absorption occurring in the magnetosphere of pulsar B, we successfully used a simple geometric model to characterize the observed changing eclipse morphology and to measure the relativistic precession of pulsar B's spin axis around the total orbital angular momentum. This provides a test of general relativity and alternative theories of gravity in the strong-field regime. Our measured relativistic spin precession rate of$4.77_{-0^{{{}^\circ}}.65}^{\circ +0^{{{}^\circ}}.66}$per year (68% confidence level) is consistent with that predicted by general relativity within an uncertainty of 13%.
We report the discovery of PSR J1646−4545, a 431 ms isolated pulsar, in the direction of the young massive cluster Westerlund 1. The pulsar was found in data taken between the years 2005 and 2010 ...with the “Murriyang” Parkes radio telescope in Australia. Thanks to the numerous detections of the pulsar, we were able to derive a phase-connected timing solution spanning the whole data set. This allowed us to precisely locate the pulsar at the border of the cluster and to measure its spin-down rate. The latter implies a characteristic age of ∼25 Myr, about twice as large as the estimated age of Westerlund 1. The age of PSR J1646−4545, together with its dispersion measure of ∼1029 pc cm−3, more than twice the value predicted by the two main galactic electron density models for Westerlund 1, makes the association of the pulsar with the cluster highly unlikely. We also report on ramifications from the presence of a magnetar in Westerlund 1 and the apparent lack of ordinary radio pulsars.
Abstract
The origin of fast radio bursts (FRBs), bright millisecond radio transients, is still somewhat of a mystery. Several theoretical models expect that the FRB accompanies an optical afterglow ...(e.g., Totani et al., 2013, PASJ, 65, L12; Kashiyama 2013, ApJ, 776, L39). In order to investigate the origin of FRBs, we perform gri-band follow-up observations of FRB 151230 (estimated $z$ ≲ 0.8) with Subaru/Hyper Suprime-Cam at 8, 11, and 14 days after discovery. The follow-up observation reaches a 50% completeness magnitude of 26.5 mag for point sources, which is the deepest optical follow-up of FRBs to-date. We find 13 counterpart candidates with variabilities during the observation. We investigate their properties with multi-color and multi-wavelength observations and archival catalogs. Two candidates are excluded by the non-detection of FRB 151230 in the other radio feed horns that operated simultaneously to the detection, as well as the inconsistency between the photometric redshift and that derived from the dispersion measure of FRB 151230. Eight further candidates are consistent with optical variability seen in active galactic nuclei (AGNs). Two more candidates are well fitted with transient templates (Type IIn supernovae), and the final candidate is poorly fitted with all of our transient templates and is located off-center of an extended source. It can only be reproduced with rapid transients with a faint peak and rapid decline, and the probability of chance coincidence is ∼3.6%. We also find that none of our candidates are consistent with Type Ia supernovae, which rules out the association of Type Ia supernovae to FRB 151230 at $z$ ≤ 0.6 and limits the dispersion measure of the host galaxy to ≲300 pc cm−3 in a Type Ia supernova scenario.
We explore the origin of the high Galactic latitude black hole X-ray binary XTE J1118+480 and in particular its birth location and the magnitude of the kick received by the black hole upon formation ...in the supernova explosion. Our analysis is constrained by the evolutionary state of the companion star, the observed limits on the orbital inclination, the Galactic position, and the peculiar velocity of the binary system. We constrain the age of the companion to the black hole using stellar evolution calculations between 2 and 5 Gyr, making an origin in a globular cluster unlikely. We therefore argue that the system was born in the Galactic disk, in which case the supernova must have propelled it in its current high-latitude orbit. Given the current estimates on its position in the sky, proper motion, and radial velocity, we back-trace the orbit of XTE J1118+480 in the Galactic potential to infer the peculiar velocity of the system at different disk crossings over the last 5 Gyr. Taking into account the uncertainties on the velocity components, we infer that the peculiar velocity required to change from a Galactic disk orbit to the currently observed orbit is 183 plus or minus 31 km s super(-1). The maximum velocity that the binary can acquire by symmetric supernova mass loss is about 100 km s super(-1), which is 2.7 sigma away from the mean of the peculiar velocity distribution. We therefore argue that an additional asymmetric kick velocity is required. By considering the orientation of the system relative to the plane of the sky, we derive a 95% probability for a nonnull component of the kick perpendicular to the orbital plane of the binary. The distribution of perpendicular velocities is skewed to lower velocities with an average of 93 super(+) sub(-) super(5) sub(6) super(5) sub(0) km s super(-1). These estimates are independent of the age of the system but depend quite sensitively on the kinematic parameters of the system. A better constraint on the asymmetric kick velocity requires an order-of-magnitude improvement in the measurement of the current space velocity of the system.
Theoretical models suggest that intermediate-mass black holes (IMBHs) may form and reside in the centers of globular clusters. IMBHs are still elusive to observations, but the accelerations of ...pulsars may bring along a unique fingerprint of their presence. In this work, we focus on the pulsars in the globular cluster M62. Using the new distance of M62 obtained from Gaia observations, we find that the measured pulsars' accelerations suggest a central excess of mass in the range 1200, 6000 M☉, corresponding to 0.2, 1% of the current total mass of the cluster. Our analysis cannot unambiguously discriminate between an IMBH or a system of stellar mass dark remnants of comparable total mass.
This book provides a comprehensive, authoritative and timely review of the astrophysical approach to the investigation of gravity theories. Particular attention is paid to strong-field tests of ...general relativity and alternative theories of gravity, performed using collapsed objects (neutron stars, black holes and white dwarfs) in relativistic binaries as laboratories. The book starts with an introduction which gives the background linking experimental gravity in cosmic laboratories to astrophysics and fundamental physics. Subsequent chapters cover observational and theoretical aspects of the following topics: from binaries as test-beds of gravity theories to binary pulsars as cosmic laboratories, from binary star evolution to the formation of relativistic binaries, from short gamma-ray bursts to low mass X-ray binaries, from stellar-mass black hole binaries to coalescing super-massive black holes in galaxy mergers. The book will be useful to researchers, PhD and graduate students in Astrophysics, Cosmology, Physics and Mathematics who are interested in relativistic astrophysics, experimental gravity and general relativity.
We present the discovery of the first X-ray counterpart to a Rotating RAdio Transient (RRAT) source. RRAT J1819-1458 is a relatively highly magnetized (B65 x 10 super(13) G) member of a new class of ...unusual pulsar-like objects discovered by their bursting activity at radio wavelengths. A Chandra observation of that position revealed a pointlike source, CXOU J181934.1-145804, with a soft spectrum well fit by an absorbed blackbody with N sub(H) = 7 super(+) sub(-) super(7) sub(4) x 10 super(21) cm super(-2), temperature kT = 0.12 c 0.04 keV, and an unabsorbed flux of 62 x 10 super(-12) ergs cm super(-2) s super(-1) between 0.5 and 8 keV. No optical or infrared (IR) counterparts are visible within 1" of our X-ray position. The positional coincidence, spectral properties, and lack of an optical/IR counterpart make it highly likely that CXOU J181934.1-145804 is a neutron star and is the same object as RRAT J1819-1458. The source showed no variability on any timescale from the pulse period of 4.26 s up to the 5 day window covered by the observations, although our limits (especially for pulsations) are not particularly constraining. The X-ray properties of CXOU J181934.1-145804, while not yet measured to high precision, are similar to those of comparably aged radio pulsars and are consistent with thermal emission from a cooling neutron star.
This paper surveys some of the astrophysical environments in which the effects of Lense-Thirring precession and, more generally, frame dragging are expected to be important. We concentrate on ...phenomena that can probe
in situ
the very strong gravitational field and single out Lense-Thirring precession in the close vicinity of accreting neutron stars and black holes: these are the fast quasi periodic oscillations in the X-ray flux of accreting compact objects. We emphasise that the expected magnitude of Lense-Thirring/frame dragging effects in the regions where these signals originate are large and thus their detection does not pose a challenge; rather it is the interpretation of these phenomena that needs to be corroborated through deeper studies. Relativistic precession in the spin axis of radio pulsars hosted in binary systems hosting another neutron star has also been measured. The remarkable properties of the double pulsar PSR J0737–3039 has opened a new perspective for testing the predictions of general relativity also in relation to the precession of spinning bodies.
Proteins employ the information stored in the genetic code and translated into their sequences to carry out well‐defined functions in the cellular environment. The possibility to encode for such ...functions is controlled by the balance between the amount of information supplied by the sequence and that left after that the protein has folded into its structure. We study the amount of information necessary to specify the protein structure, providing an estimate that keeps into account the thermodynamic properties of protein folding. We thus show that the information remaining in the protein sequence after encoding for its structure (the ‘information gap’) is very close to what needed to encode for its function and interactions. Then, by predicting the information gap directly from the protein sequence, we show that it may be possible to use these insights from information theory to discriminate between ordered and disordered proteins, to identify unknown functions, and to optimize artificially‐designed protein sequences.