Astrophys.J.561:337-345,2001 We used a set of archived HST/WFPC2 images to probe the stellar population in
the core of the nearby Galactic Globular Cluster (GGC) 47 Tuc. From the
ultraviolet (UV) ...Color Magnitude Diagrams (CMDs) obtained for ~4,000 stars
detected within the Planetary Camera (PC) field of view we have pinpointed a
number of interesting objects:
(i) 43 blue stragglers stars (BSSs) including 20 new candidates;
(ii) 12 bright (young) cooling white dwarfs (WDs) at the extreme blue region
of the UV-CMD; (iii) a large population of UV-excess (UVE) stars, lying between
the BSS and the WD sequences. The WD candidates identified here define a clean
pattern in the CMD, which define the WD cooling sequence. Moreover, both the
location on the UV-CMDs and the number of WDs are in excellent agreement with
the theoretical expectations. The UVE stars discovered here represent the
largest population of anomalous blue objects ever observed in a globular
cluster -- if the existence of such a large population is confirmed, we have
finally found the long-searched population of interacting binaries predicted by
the theory. Finally, we have investigated the feasibility of the optical
identification of the companions of the binary X-ray sources recently detected
by CHANDRA and of binary millisecond pulsars (MSPs) residing in the core of 47
Tuc. Unfortunately, the extreme faintness expected for the MSP companions
together with the huge stellar crowding in the cluster center prevent
statistically reliable identifications based only on positional coincidences.
We report on the proper motion measurement of the proposed optical counterpart of the X-ray/radio pulsar PSR 1929+10. Using images obtained with the HST/STIS (average epoch 2001.73) we computed a ...yearly displacement of +97 +/- 1 mas yr^{-1} in RA and +46 +/- 1 mas yr^{-1} in Dec since the epoch (1994.52) of the original HST/FOC detection. Both the magnitude and direction of the optical proper motion components are found to be fully consistent with the most recent VLBA radio measurements. This result provides an unambiguous confirmation of the pulsar optical identification. In addition, we have used the combined STIS/FOC datasets to derive information on the pulsar spectrum, which seems characterized by a power law component, apparently unrelated to the X-ray emission.
We used a set of archived HST/WFPC2 images to probe the stellar population in the core of the nearby Galactic Globular Cluster (GGC) 47 Tuc. From the ultraviolet (UV) Color Magnitude Diagrams (CMDs) ...obtained for ~4,000 stars detected within the Planetary Camera (PC) field of view we have pinpointed a number of interesting objects: (i) 43 blue stragglers stars (BSSs) including 20 new candidates; (ii) 12 bright (young) cooling white dwarfs (WDs) at the extreme blue region of the UV-CMD; (iii) a large population of UV-excess (UVE) stars, lying between the BSS and the WD sequences. The WD candidates identified here define a clean pattern in the CMD, which define the WD cooling sequence. Moreover, both the location on the UV-CMDs and the number of WDs are in excellent agreement with the theoretical expectations. The UVE stars discovered here represent the largest population of anomalous blue objects ever observed in a globular cluster -- if the existence of such a large population is confirmed, we have finally found the long-searched population of interacting binaries predicted by the theory. Finally, we have investigated the feasibility of the optical identification of the companions of the binary X-ray sources recently detected by CHANDRA and of binary millisecond pulsars (MSPs) residing in the core of 47 Tuc. Unfortunately, the extreme faintness expected for the MSP companions together with the huge stellar crowding in the cluster center prevent statistically reliable identifications based only on positional coincidences.
Most counterparts of the identified low-latitude gamma -ray sources are isolated neutron stars (INSs). Since INSs are characterized by an extremely high value of f sub(X)/f sub(opt), a systematic ...X-ray/optical coverage of the fields of unidentified low-latitude gamma -ray sources is the best way to unveil INS counterparts of unidentified sources. Since the low-latitude sources are heavily affected by the interstellar absorption in both the X-ray and optical bands, we decided to apply the above strategy to two middle-latitude EGRET sources, which could belong to a local galactic population: 3EG J0616-3310 and 3EG J1249-8330. Here we report on the global X-ray characterization of about 300 objects, on their candidate optical counterparts and on the preliminary results of their identification.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Galactic population of Open Clusters provides an insight into star formation in the Galaxy. The open cluster catalogue by Dias et al. Astron. Astrophys. 389, 871 (2002) is a rich source of data, ...including kinematic information. This large sample made it possible to carry out a systematic analysis of 481 open cluster orbits, using parameters based on orbit eccentricity and separation from the Galactic plane. These two parameters may be indicative of origin, and we find them to be correlated. We also find them to be correlated with metallicity, another parameter suggested elsewhere to be a marker for origin in that high values of any of these two parameters generally indicate a low metallicity (Fe/H Solar<−0.2dex). The resulting analysis points to four open clusters in the catalogue being of extra-Galactic origin by impact of high velocity cloud on the disk: Berkeley21, 32, 99, and Melotte66, with a possible further four due to this origin (NGC2158, 2420, 7789, IC1311). A further three may be due to Galactic globular cluster impact on the disk i.e of internal Galactic origin (NGC6791, 1817, and 7044).
Multi-messenger astrophysics is becoming a major avenue to explore the Universe, with the potential to span a vast range of redshifts. The growing synergies between different probes is opening new ...frontiers, which promise profound insights into several aspects of fundamental physics and cosmology. In this context, THESEUS will play a central role during the 2030s in detecting and localizing the electromagnetic counterparts of gravitational wave and neutrino sources that the unprecedented sensitivity of next generation detectors will discover at much higher rates than the present. Here, we review the most important target signals from multi-messenger sources that THESEUS will be able to detect and characterize, discussing detection rate expectations and scientific impact.
The intra-arterial administration of fibrinolytics in a massive embolism to the renal artery of a solitary functioning kidney determined quick normalization of the severe renal failure and ...hypertension.
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