Wyniki wyszukiwania - BazTech

1

Photocenter Shift Effect in Double Stars of Gaia DR2 Database

López Oriona A., Ling J. F., Sánchez Sellero C.

Acta Astronomica

|

2020

|

Vol. 70, No. 1

19--32

EN

In order to check the performance of the Gaia satellite when detecting double stars, we attempted to discover a photocenter shift affecting Gaia's second data release (Gaia DR2). We analyzed data of bona-fide double stars from "Double and Multiple System Annex" catalog and matched them with the Gaia DR2 catalog. We tried to derive a relationship between measurements of visual magnitude and signs of binarity based on parallaxes and proper motions. A comprehensive study of parallaxes indicates the presence of the photocenter shift effect. Due to the proper motion two-dimensional nature, we conducted only a simply study which implies that a real photocenter shift may affect double stars appearing in the Gaia DR2 catalog as single sources.

2

System of Long-Period Comets as Indicator of the Large Planetary Body on the Periphery of the Solar System

Guliyev A. S., Guliyev R. A.

Acta Astronomica

|

2019

|

Vol. 69, No. 2

177--203

EN

We study some particular aspects of the hypothesis about the existence of a highly inclined massive celestial body at a distance of 250-400 au. The analysis covers 1249 long-period comets (LPCs) observed up to 2017, having q and Q greater than 0.1 au and 30 au respectively. A plane or planes around which the concentration of perihelia occurs have been searched. The search for such planes has been carried out for groups of LPCs, separated by clusters in T (discovery date), e, q, H (absolute magnitude), Q, 1/aori ("original" a), etc. In almost all cases two types of planes or zones have been detected: the first one is very close to the ecliptic, the other one has the parameters: ip=86°, Ωp=271°. According to the tested hypothesis there is a massive perturber at a distance of 250-400 au from the Sun. We show that the number of aphelia and distant nodes of long-period comet orbits within this interval (250-400 au) significantly exceeds the expected value. The distributions of Q and distant comet nodes may signal the presence of a massive perturber near 300 au. We have estimated that the most probable orbital elements of the hypothetical planet are a=339±34 au, e=0.16±0.02, ω=57°±15°, Ω=272.°7±3°, i=86°±2°. To test the stability of such an orbit as well as its influence on other planets, a model of solar system that includes only the Jovian planets and the putative perturber was integrated for 1 billion years, assuming that the mass of the highly inclined perturber is about 10 Earth masses.

3

Predicted Microlensing Events by Nearby Very-Low-Mass Objects: Pan-STARRS DR1 vs. Gaia DR2

Nielsen M. B., Bramich D. M.

Acta Astronomica

|

2018

|

Vol. 68, No. 4

351--370

EN

Microlensing events can be used to directly measure the masses of single field stars to a precision of ≈1–10%. The majority of direct mass measurements for stellar and sub-stellar objects typically only come from observations of binary systems. Hence microlensing provides an important channel for direct mass measurements of single stars. The Gaia satellite has observed ≈1.7 billion objects, and analysis of the second data release has recently yielded numerous event predictions for the next few decades. However, the Gaia catalog is incomplete for nearby very-low-mass objects such as brown dwarfs for which mass measurements are most crucial. We employ a catalog of very-low-mass objects from Pan-STARRS data release 1 (PDR1) as potential lens stars, and we use the objects from Gaia data release 2 (GDR2) as potential source stars. We then search for future microlensing events up to the year 2070. The Pan-STARRS1 objects are first cross-matched with GDR2 to remove any that are present in both catalogs. This leaves a sample of 1718 possible lenses. We fit MIST isochrones to the Pan-STARRS1, AllWISE and 2MASS photometry to estimate their masses. We then compute their paths on the sky, along with the paths of the GDR2 source objects, until the year 2070, and search for potential microlensing events. Source-lens pairs that will produce a microlensing signal with an astrometric amplitude of greater than 0.131 mas, or a photometric amplitude of greater than 0.4 mmag, are retained.

4

An Almanac of Predicted Microlensing Events for the 21st Century

Bramich D. M., Nielsen M. B.

Acta Astronomica

|

2018

|

Vol. 68, No. 3

183--203

EN

Using Gaia data release 2 (GDR2), we present an almanac of 2509 predicted microlensing events, caused by 2130 unique lens stars, that will peak between July 25, 2026 and the end of the century. This work extends and completes a thorough search for future microlensing events initiated by Bramich and Nielsen using GDR2. The almanac includes 161 lenses that will cause at least two microlensing events each. A few highlights are presented and discussed, including: (i) an astrometric microlensing event with a peak amplitude of ≈9.7 mas, (ii) an event that will probe the planetary system of a lens with three known planets, and (iii) an event (resolvable from space) where the blend of the lens and the minor source image will brighten by a detectable amount (≈2 mmag) due to the appearance of the minor source image. All of the predicted microlensing events in the almanac will exhibit astrometric signals that are detectable by observing facilities with an angular resolution and astrometric precision similar to, or better than, that of the Hubble Space Telescope (e.g., NIRCam on the James Webb Space Telescope), although the events with the most extreme source-to-lens contrast ratios may be challenging. Ground-based telescopes of at least 1 m in diameter can be used to observe many of the events that are also expected to exhibit a photometric signal.

5

The Optical Gravitational Lensing Experiment. The Catalog of Stellar Proper Motions toward the Magellanic Clouds

Poleski R., Soszyński I., Udalski A., Szymański M. K., Kubiak M., Pietrzyński G., Wyrzykowski Ł., Ulaczyk K.

Acta Astronomica

|

2012

|

Vol. 62, No. 1

1-22

EN

We present a catalog of over 6.2 million stars with measured proper motions. All these stars are observed in the direction of the Magellanic Clouds within the brightness range 12

6

The Optical Gravitational Lensing Experiment. Gaia South Ecliptic Pole Field as Seen by OGLE-IV

Soszyński I., Udalski A., Poleski R., Kozłowski S., Wyrzykowski Ł., Pietrukowicz P., Szymański M. K., Kubiak M., Pietrzyński G., Ulaczyk K., Skowron J.

Acta Astronomica

|

2012

|

Vol. 62, No. 3

219--245

EN

We present a comprehensive analysis of the Gaia South Ecliptic Pole (GSEP) field, 5.3 square degrees area around the South Ecliptic Pole on the outskirts of the LMC, based on the data collected during the fourth phase of the Optical Gravitational Lensing Experiment, OGLE-IV. The GSEP field will be observed during the commissioning phase of the ESA Gaia space mission for testing and calibrating the Gaia instruments. We provide the photometric maps of the GSEP region containing the mean VI photometry of all detected stellar objects and their equatorial coordinates. We show the quality and completeness of the OGLE-IV photometry and color-magnitude diagrams of this region. We conducted an extensive search for variable stars in the GSEP field leading to the discovery of 6789 variable stars. In this sample we found 132 classical Cepheids, 686 RR Lyr type stars, 2819 long-period, and 1377 eclipsing variables. Several objects deserving special attention were also selected, including a new classical Cepheid in a binary eclipsing system. To provide empirical data for the Gaia Science Alert system we also conducted a search for optical transients. We discovered two firm type Ia supernovae and nine additional supernova candidates. To facilitate future Gaia supernovae detections we prepared a list of more than 1900 galaxies to redshift about 0.1 located in the GSEP field. Finally, we present the results of astrometric study of the GSEP field. With the 26 months time base of the presented here OGLE-IV data, proper motions of stars could be detected with the accuracy reaching 2 mas/yr. Astrometry allowed to distinguish galactic foreground variable stars detected in the GSEP field from LMC objects and to discover about 50 high proper motion stars (proper motion ≥ 100 mas/yr). Among them three new nearby white dwarfs were found. All data presented in this paper are available to the astronomical community from the OGLE Internet archive.

7

A Proper Motion Study of the Globular Clusters M4, M12, M22, NGC 3201, NGC 6362 and NGC 6752

Zloczewski K., Kaluzny J., Rozyczka M., Krzeminski W., Mazur B., Thompson I. B.

Acta Astronomica

|

2012

|

Vol. 62, No. 4

357--375

EN

We derive relative proper motions of stars in the fields of globular clusters M4, M12, M22, NGC 3201, NGC 6362 and NGC 6752 based on a uniform data set collected between 1997 and 2008. We assign a membership class for each star with a measured proper motion and show that these membership classes can be successfully used to eliminate field stars from color-magnitude diagrams of the clusters. They also allow for the efficient selection of rare objects such as blue/yellow/red stragglers and stars from the asymptotic giant branch. Tables with proper motions and photometry of over 87 000 stars are made publicly available via the Internet.

8

The Optical Gravitational Lensing Experiment. High Proper Motion Stars in the OGLE-III Data for Magellanic Clouds Fields

Poleski R., Soszyński I., Udalski A., Szymański M. K., Kubiak M., Pietrzyński G., Wyrzykowski Ł., Ulaczyk K.

Acta Astronomica

|

2011

|

Vol. 61, No. 3

199--216

EN

We present the results of a search for High Proper Motion (HPM) stars, i.e., the ones with μ>100 mas/yr, in the direction to the Magellanic Clouds. This sky area was not examined in detail as the high stellar density hampers efforts in performing high-quality astrometry. Altogether 549 HPM stars were found with median uncertainties of proper motions per coordinate equal to 0.5 mas/yr. The fastest HPM star has the proper motion of 722.19±0.74 mas/yr. For the majority of objects (70%) parallaxes were also measured. The highest value found is π=91.3±1.6 mas. The parallaxes were used to estimate absolute magnitudes which enriched with color information show that 21 of HPM stars are white dwarfs. Other 23 candidate white dwarfs were selected of HPM stars with no measurable parallaxes using color-magnitude diagram. The search for common proper motion binaries revealed 27 such pairs in the catalog. The completeness of the catalog is estimated to be >80% and it is slightly higher than for previous catalogs in the direction to the Magellanic Clouds.

9

Polish astro-geodetic geoid - final results

Rogowski J. B., Barlik M., Bogusz J., Hefty J., Kłęk M., Kujawa L.

Reports on Geodesy

|

2006

|

z. 1/76

119-128

10

Zastosowanie elementów astrometrii do wyznaczania kąta padania promieni słonecznych na przegrody budowlane

Respondek Z.

Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo

|

2002

|

Z. 9 (154)

89-96

11

The Optical Gravitational Lensing Experiment. Catalog of High Proper Motion Stars Towards the Magellanic Clouds

Soszyński I., Żebruń K., Udalski A., Woźniak P. R., Szymański M., Kubiak M., Pietrzyński G., Szewczyk O., Wyrzykowski Ł.

Acta Astronomica

|

2002

|

Vol. 52, No. 2

129--142

EN

We present a Catalog of high proper motion (HPM) stars detected in the foreground of central parts of the Magellanic Clouds. The Catalog contains 2161 objects in the 4.5 square degree area towards the LMC, and 892 HPM stars in the 2.4 square degree area towards the SMC. The Catalog is based on observations collected during four years of the OGLE-II microlensing survey. The Difference Image Analysis (DIA) of the images provided candidate HPM stars with proper motion as small as 4 mas/yr. These appeared as pseudo-variables, and were all measured astrometrically on all CCD images, providing typically about 400 data points per star. The reference frame was defined by the majority of background stars, most of them members of the Magellanic Clouds. The reflex motion due to solar velocity with respect to the local standards of rest is clearly seen. The largest proper motion in our sample is 363 mas/yr. Parallaxes were measured with errors smaller than 20% for several stars.

12

Stellar Kinematics Near the Galactic Center - Possible Test for a Binary Black Hole

Jaroszyński M.

Acta Astronomica

|

2000

|

Vol. 50, No. 1

67--78

EN

We consider consequences of the presence of a binary black hole system in the center of our Galaxy. We show that the existence of such a system with total mass ≈2.6×106 Msolar and semimajor axis ≈0.001 pc is not excluded on theoretical grounds and it may have characteristic evolution time of a few billions years. We simulate astrometric measurements of proper motion of stars in the vicinity of the black hole system and check whether such observations are sufficient to discover the binary nature of the central mass. We show that such findings require astrometric accuracy about ten times higher than presently available; the Keck Interferometer, will be able to place stringent observational limits on the presence of a black hole binary in the Galactic center.

13

Identification and Astrometry of Variable Stars in M3

Bakos G. Á., Benkö J. M., Jurcsik J.

Acta Astronomica

|

2000

|

Vol. 50, No. 2

221--248

EN

The space distribution of orbital poles for 252 visual binaries is analyzed to check a possible tendency towards parallelism. It is confirmed that orbital planes do not show any trend to be parallel to the Galactic plane. No strong evidence is found for a preferential orientation of the orbital planes for subgroups of binaries with similar periods and eccentricities. Asymmetry in the distribution of orbital poles is seen only for a subgroup of 19 binaries lying closer than 10 pc. Small differences in the distribution of orbital poles are also detected for subgroups with different location on HR diagram.