1,041 research outputs found
The mass function of GX 339-4 from spectroscopic observations of its donor star
We obtained 16 VLT/X-shooter observations of GX 339-4 in quiescence in the
period May - September 2016 and detected absorption lines from the donor star
in its NIR spectrum. This allows us to measure the radial velocity curve and
projected rotational velocity of the donor for the first time. We confirm the
1.76 day orbital period and we find that = km s,
km s and km s. From
these values we compute a mass function , a
factor lower than previously reported, and a mass ratio . We confirm the donor is a K-type star and estimate that it contributes
of the light in the - and H-band. We constrain the binary
inclination to and the black hole mass to
. GX 339-4 may therefore be the
first black hole to fall in the 'mass-gap' of .Comment: 11 pages, 7 figures, accepted for publication in Ap
From SN 2010da to NGC 300 ULX-1: Ten Years of Observations of an Unusual High Mass X-Ray Binary in NGC 300
In May 2010, an intermediate luminosity optical transient was discovered in the nearby galaxy NGC 300 by a South African amateur astronomer. In the decade since its discovery, multi-wavelength observations of the misnamed “SN 2010da” have continually reshaped our understanding of this high mass X-ray binary system. In this review, we present an overview of the multi-wavelength observations and attempt to understand the 2010 transient event, and later, the reclassification of this system as NGC 300 ULX-1: a red supergiant + neutron star ultraluminous X-ray source
Averaging of time-periodic dissipation potentials in rate-independent processes
We study the existence and well-posedness of rate-independent systems (or hysteresis operators) with a dissipation potential that oscillates in time with period ε. In particular, for the case of quadratic energies in a Hilbert space, we study the averaging limit ε → 0 and show that the effective dissipation potential is given by the minimum of all friction thresholds in one period, more precisely as the intersection of all the characteristic domains. We show that the rates of the process do not converge weakly, hence our analysis uses the notion of energetic solutions and relies on a detailed estimates to obtain a suitable equi-continuity of the solutions in the limit ε → 0
Towards a computational model for stimulation of the Pedunculopontine nucleus
The pedunculopontine nucleus (PPN) has recently been suggested as a new therapeutic target for deep brain stimulation (DBS) in patients suffering from Parkinson's disease, particularly those with severe gait and postural impairment [1]. Stimulation at this site is typically delivered at low frequencies in contrast to the high frequency stimulation required for therapeutic benefit in the subthalamic nucleus (STN) [1]. Despite real therapeutic successes, the fundamental physiological mechanisms underlying the effect of DBS are still not understood. A hypothesis is that DBS masks the pathological synchronized firing patterns of the basal ganglia that characterize the Parkinsonian state with a regularized firing pattern. It remains unclear why stimulation of PPN should be applied with low frequency in contrast to the high frequency stimulation of STN. To get a better understanding of PPN stimulation we construct a computational model for the PPN Type I neurons in a network
Quiescent NIR and optical counterparts to candidate black hole X-ray binaries
We present near-infrared and optical imaging of fifteen candidate black hole
X-ray binaries. In addition to quiescent observations for all sources, we also
observed two of these sources (IGR J17451-3022 and XTE J1818-245) in outburst.
We detect the quiescent counterpart for twelve out of fifteen sources, and for
the remaining three we report limiting magnitudes. The magnitudes of the
detected counterparts range between = 17.59 and = 22.29 mag. We
provide (limits on) the absolute magnitudes and finding charts of all sources.
Of these twelve detections in quiescence, seven represent the first quiescent
reported values (for MAXI J1543-564, XTE J1726-476, IGR J17451-3022, XTE
J1818-245, MAXI J1828-249, MAXI J1836-194, Swift J1910.2-0546) and two
detections show fainter counterparts to XTE J1752-223 and XTE J2012+381 than
previously reported. We used theoretical arguments and observed trends, for
instance between the outburst and quiescent X-ray luminosity and orbital period
to derive an expected trend between and of
. Comparing this to observations we
find a different behaviour. We discuss possible explanations for this result.Comment: 18 pages, 6 figures. Accepted for publication in MNRA
Characterisation of a candidate dual AGN
We present Chandra and optical observations of a candidate dual AGN
discovered serendipitously while searching for recoiling black holes via a
cross-correlation between the serendipitous XMM source catalog (2XMMi) and
SDSS-DR7 galaxies with a separation no larger than ten times the sum of their
Petrosian radii. The system has a stellar mass ratio M/M. One of the galaxies (Source 1) shows clear evidence for AGN activity in
the form of hard X-ray emission and optical emission-line diagnostics typical
of AGN ionisation. The nucleus of the other galaxy (Source 2) has a soft X-ray
spectrum, bluer colours, and optical emission line ratios dominated by stellar
photoionisation with a "composite" signature, which might indicate the presence
of a weak AGN. When plotted on a diagram with X-ray luminosity vs [OIII]
luminosity both nuclei fall within the locus defined by local Seyfert galaxies.
From the optical spectrum we estimate the electron densities finding n e cm and n e cm. From a 2D
decomposition of the surface brightness distribution we infer that both
galaxies host rotationally supported bulges (Sersic index ). While the
active nature of Source 1 can be established with confidence, whether the
nucleus of Source 2 is active remains a matter of debate. Evidence that a faint
AGN might reside in its nucleus is, however, tantalising.Comment: 16 pages, 9 figures. Accepted for publication on MNRAS. Comments
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Searching for the Donor Stars of ULX Pulsars
We report on our search for the optical counterparts of two ultraluminous
X-ray pulsars with known orbital periods, M82 X-2 and NGC 5907 X-1, in new and
archival HST observations, in an effort to characterize the donor stars in
these systems. We detect five near-infrared sources consistent with the
position of M82 X-2 that are too bright to be single stars. We also detect
seven sources in the WFC3/UVIS F336W image whose photometry matches that of
10-15 M stars turning off the main sequence. Such stars have densities
consistent with the properties of the donor star of M82 X-2 as inferred from
X-ray timing analysis, although it is also possible that the donor is a lower
mass star below our detection limit or that there is a significant contribution
from the accretion disc to the optical emission. We detect three candidate
counterparts to NGC 5907 X-1 in the near-infrared. All of these are too bright
to be the donor star of the ULX, which based on its orbital period is a red
giant. The high background at the location of NGC 5907 X-1 precludes us from
detecting this expected donor star. The recently discovered NGC 5907 ULX-2 also
falls within the field of view of the near-infrared imaging; we detect four
sources in the error circle, with photometry that matches AGB stars. The star
suggested to be the counterpart of NGC 5907 ULX-2 by Pintore et al. (2018)
falls outside our 2- error circle.Comment: 10 pages, 3 figures, accepted for publication in Ap
Topologies and measures on the space of functions of bounded variation taking values in a Banach or metric space
We study functions of bounded variation with values in a Banach or in a metric space. In finite dimensions, there are three well-known topologies; we argue that in infinite dimensions there is a natural fourth topology. We provide some insight into the structure of these four topologies. In particular, we study the meaning of convergence, duality and regularity for these topologies and provide some useful compactness criteria, also related to the classical Aubin–Lions theorem. After this we study the Bore
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