scholarly journals Evidence for the Galactic Bar from the Two Color Photometry of the Bulge Red Clump Stars

1996 ◽  
Vol 169 ◽  
pp. 103-109
Author(s):  
K. Z. Stanek ◽  
M. Mateo ◽  
A. Udalski ◽  
M. Szymański ◽  
J. Kałużny ◽  
...  
Keyword(s):  
Data Base ◽  
Gravitational Lensing ◽  
Galactic Bulge ◽  
Gravitational Microlensing ◽  
Huge Data ◽  
Red Clump

The Optical Gravitational Lensing Experiment (OGLE, Udalski et al. 1994a; Paczynski et al. 1994b – these proceedings; and references therein) is an extensive photometric search for the rare cases of gravitational microlensing of Galactic bulge stars by foreground objects. It provides a huge data base (Szymański & Udalski 1993), from which color-magnitude diagrams have been compiled (Udalski et al. 1993, 1994b). Here we discuss the use a of well-defined population of bulge red clump stars to investigate the presence of the bar in our Galaxy. The results of our earlier studies are described by Stanek et al. (1994).

scholarly journals Modelling the Galactic Bar using Red Clump Stars

1996 ◽  
Vol 157 ◽  
pp. 545-548 ◽  
Author(s):  
K. Z. Stanek ◽  
M. Mateo ◽  
A. Udalski ◽  
M. Szymański ◽  
J. Kałuzny ◽  
...  
Keyword(s):  
Line Of Sight ◽  
Galactic Bulge ◽  
Preliminary Results ◽  
Gravitational Microlensing ◽  
Luminosity Functions ◽  
Red Clump ◽  
Additional Constraints ◽  
Galactic Longitude

AbstractThe color-magnitude diagrams of ~ 1 × 106 stars obtained for 19 fields towards the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump stars. We found that the distributions of the extinction-adjusted apparent magnitudes of red clump stars in fields lying at ι = ±5° in galactic longitude differ by ∼ 0.4 mag. A plausible explanation of this observed difference in the luminosity distribution is that the Galactic bulge is a triaxial structure, or a bar, which is inclined to the line of sight by no more than 45°. The part of the bar at the positive galactic longitude is closer to us. Work is now under way to model the Galactic bar by fitting the observed luminosity functions in the red clump region for various fields. Preliminary results indicate that the angle of the inclination of the bar to the line of sight can be as small as ∼ 20°. Gravitational microlensing can provide us with additional constraints on the structure of the Galactic bar.

scholarly journals Non-parametric density reconstruction of the Galactic bulge area using red clump stars in the VVV survey

2020 ◽  
Vol 499 (2) ◽  
pp. 1937-1947
Author(s):  
Dylan Paterson ◽  
Brendan Coleman ◽  
Chris Gordon
Keyword(s):  
Parametric Method ◽  
Major Axis ◽  
Galactic Bulge ◽  
Buckling Instability ◽  
Giant Stars ◽  
Red Clump ◽  
Red Giant ◽  
High Resolution Reconstruction ◽  
Spiral Arm ◽  
Non Parametric

ABSTRACT Studies of the red clump giant population in the inner Milky Way suggest the Galactic bulge/bar has a boxy/peanut/X-shaped structure as predicted by its formation via a disc buckling instability. We used a non-parametric method of estimating the Galactic bulge morphology that is based on maximum entropy regularization. This enabled us to extract the 3D distribution of the red giant stars in the bulge from deep photometric catalogues of the VISTA Variables in the Via Lactea survey. Our high-resolution reconstruction confirms the well-known boxy/peanut/X-shaped structure of the bulge. We also find spiral arm structures that extend to around 3 kpc in front of and behind the bulge and are on different sides of the bulge major axis. We show that the detection of these structures is robust to the uncertainties in the luminosity function.

scholarly journals Two new free-floating or wide-orbit planets from microlensing

2019 ◽  
Vol 622 ◽  
pp. A201 ◽  
Author(s):  
Przemek Mróz ◽  
Andrzej Udalski ◽  
David P. Bennett ◽  
Yoon-Hyun Ryu ◽  
Takahiro Sumi ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Milky Way ◽  
Planet Formation ◽  
Physical Mechanism ◽  
Galactic Disk ◽  
Galactic Bulge ◽  
Brown Dwarf ◽  
Low Mass ◽  
Rule Out

Planet formation theories predict the existence of free-floating planets that have been ejected from their parent systems. Although they emit little or no light, they can be detected during gravitational microlensing events. Microlensing events caused by rogue planets are characterized by very short timescales tE (typically below two days) and small angular Einstein radii θE (up to several μas). Here we present the discovery and characterization of two ultra-short microlensing events identified in data from the Optical Gravitational Lensing Experiment (OGLE) survey, which may have been caused by free-floating or wide-orbit planets. OGLE-2012-BLG-1323 is one of the shortest events discovered thus far (tE = 0.155 ± 0.005 d, θE = 2.37 ± 0.10μas) and was caused by an Earth-mass object in the Galactic disk or a Neptune-mass planet in the Galactic bulge. OGLE-2017-BLG-0560 (tE = 0.905 ± 0.005 d, θE = 38.7 ± 1.6μas) was caused by a Jupiter-mass planet in the Galactic disk or a brown dwarf in the bulge. We rule out stellar companions up to a distance of 6.0 and 3.9 au, respectively. We suggest that the lensing objects, whether located on very wide orbits or free-floating, may originate from the same physical mechanism. Although the sample of ultrashort microlensing events is small, these detections are consistent with low-mass wide-orbit or unbound planets being more common than stars in the Milky Way.

scholarly journals Candidate Hypervelocity Red Clump Stars in the Galactic Bulge Found Using the VVV and Gaia Surveys

2019 ◽  
Vol 887 (2) ◽  
pp. L39
Author(s):  
Alonso Luna ◽  
Dante Minniti ◽  
Javier Alonso-García
Keyword(s):  
Galactic Bulge ◽  
Red Clump

New VIRAC proper motion maps show signature of galactic boxy/peanut bulge

2019 ◽  
Vol 14 (S353) ◽  
pp. 29-30
Author(s):  
Jonathan P. Clarke ◽  
Christopher Wegg ◽  
Ortwin Gerhard ◽  
Leigh C. Smith ◽  
Phil W. Lucas ◽  
...  
Keyword(s):  
Proper Motion ◽  
Dynamical Model ◽  
Line Of Sight ◽  
Selection Function ◽  
Kinematic Structure ◽  
Proper Motions ◽  
Galactic Bulge ◽  
Bulge Region ◽  
Pattern Speed ◽  
Red Clump

AbstractWe have derived absolute proper motions of stars in the Galactic bulge region combining the VVV InfraRed Astrometric Catalogue (VIRAC) and Gaia. We use the proper motions to study the kinematic structure of the bulge both integrated along the line-of-sight and in magnitude intervals using red clump stars as standard candles. In parallel we compare to a made-to-measure barred dynamical model, folding in the VIRAC selection function, to understand and interpret the structures that we observe. The barred dynamical model, which contains a boxy/peanut bulge, and has a pattern speed of 37.5 kms−1 kpc−1, is able to reproduce all structures impressively well.

scholarly journals Recent developments in gravitational microlensing and the latest MACHO results: Microlensing towards the galactic bulge

1995 ◽  
Author(s):  
D. P. Bennett ◽  
C. Alcock ◽  
R. A. Allsman ◽  
T. S. Axelrod ◽  
K. H. Cook ◽  
...  
Keyword(s):  
Galactic Bulge ◽  
Gravitational Microlensing ◽  
Recent Developments

Probable gravitational microlensing toward the galactic bulge

1995 ◽  
Vol 445 ◽  
pp. 133 ◽  
Author(s):  
C. Alcock ◽  
R. A. Allsman ◽  
T. S. Axelrod ◽  
D. P. Bennett ◽  
K. H. Cook ◽  
...  
Keyword(s):  
Galactic Bulge ◽  
Gravitational Microlensing
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