Mauri J. Valtonen

A massive binary black-hole system in OJ 287 and a test of general relativity

Tests of Einstein’s general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Newton’s theory. Binary pulsars provide a means of probing the strong gravitational field around a neutron star, but strong-field effects may be best tested in systems containing black holes. Here we report such a test in a close binary system of two candidate black holes in the quasar OJ 287. This quasar shows quasi-periodic optical outbursts at 12-year intervals, with two outburst peaks per interval. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity. The observations confirm the binary nature of the system and also provide evidence for the loss of orbital energy in agreement (within 10 per cent) with the emission of gravitational waves from the system. In the absence of gravitational wave emission the outburst would have happened 20 days later.

Predicting the Next Outbursts of OJ 287 in 2006-2010

In its nearly regular cycle of outbursts the quasar OJ 287 is due for another outburst season in 2006-2010. The prediction for the exact timing depends on the adopted model. In the precessing binary model of Lehto and Valtonen the timing depends on the time delay between the impact on the primary disk and the time when the impacted gas becomes optically thin. The time delay in turn depends on the properties of the accretion disk, the accretion rate, and the viscosity parameter α, which are not exactly known. We study the flexibility in timing provided by the uncertainties. In order to fix the model, two methods are used: the wobble of the jet, induced by the secondary, and the timing of the 1956 outburst, which has not been previously used. As a result, rather definite dates for the outbursts are obtained, which are different from a straightforward extrapolation of the past light curve. A new optical light curve with many new historical as well as recent points of observation have been put together and has been analyzed in order to reach these conclusions. Also, the high-frequency radio observations are found to agree with the jet wobble picture.

A Numerical Simulation of the Brightness Variations of OJ 287

A numerical simulation of the binary black hole model of the blazar OJ 287 is presented. In this model, the observed major outbursts are identified with the pericenter passages of the secondary black hole, and the superflares are identified with its disk crossings. In the simulation, a disk of particles interacting with the black holes is used to generate the light curve. The simulation reproduces satisfactorily the observed light curve of OJ 287 and predicted the outbursts in 1995-1996 with high accuracy.

On the redshift-apparent size diagram of double radio sources

We review the data on the angular sizes of double radio sources. A list of 540 Fanaroff-Riley type II double sources is collected from literature, and it is used for a critical discussion of previous work based on smaller samples. We find that results from all previous samples agree well with each other and with our new sample, if the discussion is limited only to well-defined two-sided (classical) doubles. Different results which have appeared in literature are traced to different sample definitions of double radio sources. In addition, we find that the behavior of high radio power quasars and radio galaxies is different from low radio power radio galaxies which, if unnoticed, leads to contradicting conclusions

Testing the 1995 Binary Black Hole Model of OJ287

In 1995, a binary black hole model was proposed for the quasar OJ287, where the smaller secondary black hole impacts the accretion disk of the primary black hole twice during its 12 yr orbit and causes a double peak of optical outbursts. The model predicted four major outbursts and one minor outburst during the period 1996-2010. All five have now been observed. In this paper, we ask how accurate the predictions were. We use the latest optical observations from Tuorla Observatory and the KVA telescope at La Palma together with previously published data to construct a light curve for this period. We average the data in 0.04 yr bins, and subtract the observed flux from the 1995 model flux at each bin. We find that the residuals are small: they are well described by random noise of amplitude 1.4 mJy. This level is small compared with the amplitudes of the major outbursts, 5-7 mJy. Ignoring the noise, the binary model explains the optical data remarkably well.

New Orbit Solutions for the Precessing Binary Black Hole Model of OJ 287

We derive new solutions for the binary black hole model of OJ 287, using the 2005 November outburst as one of the fixed points. Previous models have used the 1994 September outburst, which is in many ways ill defined and leads to considerable uncertainty in the orbit. In addition, the inherent asymmetry in the double outburst structure, due to the vantage point of the observer lying to one side of the accretion disk, has been included in the models for the first time. The disk bending is calculated using a million-particle disk as a model for the accretion disk. In addition, allowance is made for the possibility of different values of disk thickness. The parameters of the system to be determined are the orbital period, fixed by the separation of the 1947.30 and 1983.00 outbursts; the orientation of the major axis of the orbit at a given time, fixed by the 1972.99 outburst; the time delay factor, which is a function of the disk thickness, fixed by the 2005.82 outburst; and the precession rate of the binary, fixed by the 1913.02 outburst. A unique solution is found for both the case of gravitational radiation and that of no gravitational radiation. The 2007 September outburst begins 2007 September 9-16 in the former models and 2007 October 8 in the latter model. The 3 week difference will be easily resolved in future observations, and thus the emission of gravitational radiation can be indirectly measured.

On the masses of OJ287 black holes

Two multifrequency campaigns were carried out on OJ287 in 2005: in April when it was in its pre-outburst state, and in November during the main 12 yr cycle outburst. The wavelength coverage was from radio to X-rays. In the optical-to-ultraviolet range, the differential spectrum between the observations has a bremsstrahlung spectral shape, consistent with gas at 3 × 10 5 K temperature. Our result supports the hydrogen column density of the OJ287 host galaxy of ∼9.3 × 10 20 cm −2 , the average value found by Ghosh & Soundararajaperumal. The 3 × 10 5 K bremsstrahlung radiation was predicted in the binary black hole model of OJ287, and it arises from a hot bubble of gas which is torn off the accretion disc by the impact of the secondary. As this radiation is not Doppler boosted, the brightness of the outburst provides an estimate for the mass of the secondary black hole, ∼1.4 × 10 8 M� . In order to estimate the mass of the primary black hole, we ask what is the minimum mass ratio in a binary system which allows the stability of the accretion disc. By using particle simulations, we find that the ratio is ∼1.3 × 10 2 . This makes the minimum mass of the primary ∼1.8 × 10 10 M� , in agreement with the mass determined from the orbit solution, 1.84 × 10 10 M � . With this mass value and the measured K magnitude of the bulge of the host galaxy of OJ287, the system lies almost exactly on the previously established correlation in the black hole mass versus K-magnitude diagram. It supports the extension of this correlation to brighter magnitudes and to more massive black holes than has been done previously.

NATURAL TRANSFER OF VIABLE MICROBES IN SPACE FROM PLANETS IN EXTRA-SOLAR SYSTEMS TO A PLANET IN OUR SOLAR SYSTEM AND VICE VERSA

We investigate whether it is possible that viable microbes could have been transported to the Earth from planets in extra-solar systems by means of natural vehicles such as ejecta expelled by comets or asteroid impacts on such planets. The probabilities of close encounters with other solar systems are taken into account as well as the limitations of bacterial survival times inside ejecta in space, caused by radiation and DNA decay. The conclusion is that no potentially DNA/RNA life-carrying ejecta from another solar system in the general Galactic star field landed on the Earth before life already existed on the Earth, even if the microbial survival time in space is as long as tens of millions of years. However, if the Sun formed initially as a part of a star cluster, as is commonly assumed, we cannot rule out the possibility of transfer of life from one of the sister systems to us. Likewise, there is a possibility that some extra-solar planets carry life that originated in our solar system. It will be of great interest to identify the members of the Suns birth cluster of stars and study them for evidence of planets and life on the planets. The former step may be accomplished by the GAIA mission, the latter step by the SIM and DARWIN missions. Therefore it may not be too long until we have experimental knowledge to answer the question of whether the natural transfer of life from one solar system to another has actually taken place.

Risks threatening viable transfer of microbes between bodies in our solar system

Abstract A fraction of the number of ejecta expelled from a planet by comet or asteroid impacts end up landing on another planet. If microorganisms were living in the ground before impact, they would be transported inside ejecta to the target planet. During that perilous trip, they would be subject to four main categories of threat to their survival: dynamical stress, excess temperature, radiation, chemical attack and vacuum. The effect of these, in the form of survival fractions as a function of time, as well as approximate numbers of arriving ejecta with viable flight times, have been investigated in a quantitative study we have made. The result shows that viable transfer from Mars to Earth and vice versa was highly probable during the first 0.5 Ga, and also probable, but with lower frequency, thereafter. Here we follow up with considerations about the consequences of the result regarding the question of whether the ancestor cell of all life on Earth must have originated on Earth, or whether it could have originated on Mars, its descendants thereafter moving to Earth. Some other possible consequences are also discussed.

A revised history of the local group and a generalized method of timing

Recent measurements suggest that the giant galaxies IC 342 and Maffei 1 are moving so rapidly for their distances that they were close to M31 only 4 billion years ago. If correct, the two-body approximation of Local Group Timing would not be valid. N-body simulations have been carried out to explore how the indicated configuration of four massive bodies might arise, and to study the implications for the mass of local dark matter and the age of the universe. Provided that the total systematic mass is close to 3 × 10 12 solar masses, the high speed of IC 342 and Maffei 1 and the turn around of the motion of M31 with respect to the Milky Way could be explained if IC 342 and Maffei 1 were each members of binaries which successively fell past M31, interacting with M31 strongly and ejecting one component