ar X iv : a st ro - p h / 02 10 36 7 v 2 3 M ar 2 00 3 1 The Optical Gravitational Lensing Experiment . Is Interstellar Extinction Toward the Galactic Center
ثبت نشده
چکیده
Photometry of the Galactic bulge, collected during the OGLE-II microlensing search, indicates high and non-uniform interstellar extinction toward the observed fields. We use the mean I-band magnitude and V −I color of red clump stars as a tracer of interstellar extinction toward four small regions of the Galactic bulge with highly variable reddening. Similar test is performed for the most reddened region observed in the LMC. We find that the slope of the location of red clump stars in the color-magnitude diagrams (CMDs) in the Galactic bulge is significantly smaller than the slope of the reddening line following the standard extinction law (R V = 3.1) for approximations of the extinction curve by both Cardelli, Clayton and Mathis (1989, CCM89) and Fitzpatrick (1999, F99). The differences are much larger for the CCM89 approximation which, on the other hand, indicates the same slopes for the control field in the LMC, contrary to the F99 approximation. We discuss possible systematic effects that could cause the observed discrepancy. Anomalous extinction toward the Galactic bulge seems to be the most natural explanation. Our data indicate that, generally, the ratio of the total to selective absorption, R VI , is much smaller toward the Galactic bulge than the value corresponding to the standard extinction curve (R V = 3.1). However, R VI varies from one line-of-sight to another. Our results explain why the red clump and RR Lyr stars in the Baade's window dereddened with standard value of R VI are redder compared to those of the local population.
منابع مشابه
ar X iv : a st ro - p h / 02 10 36 7 v 1 1 6 O ct 2 00 2 1 The Optical Gravitational Lensing Experiment . Is Interstellar Extinction Toward the Galactic
Photometry of the Galactic bulge, collected during the OGLE-II microlensing search, indicates high and non-uniform interstellar extinction toward the observed fields. We use the mean I-band magnitude and V −I color of red clump stars as a tracer of interstellar extinction toward four small regions of the Galactic bulge with highly variable reddening. Similar test is performed for the most redde...
متن کاملar X iv : a st ro - p h / 05 02 36 3 v 3 2 7 M ay 2 00 5 Microlensing optical depth toward the Galactic Bulge using bright sources from OGLE - II
We present a measurement of the microlensing optical depth toward the Galactic Bulge based on 4 years of OGLE-II survey. We consider only bright sources in the extended Red Clump Giant (RCG) region of the Color-Magnitude
متن کاملar X iv : a st ro - p h / 05 02 36 3 v 2 1 9 M ay 2 00 5 Microlensing optical depth toward the Galactic Bulge using bright sources from OGLE - II
We present a measurement of the microlensing optical depth toward the Galactic Bulge based on 4 years of OGLE-II survey. We consider only bright sources in the extended Red Clump Giant (RCG) region of the Color-Magnitude
متن کاملar X iv : a st ro - p h / 05 02 36 3 v 4 3 1 A ug 2 00 5 Microlensing optical depth toward the Galactic Bulge using bright sources from OGLE - II
We present a measurement of the microlensing optical depth toward the Galactic Bulge based on 4 years of the OGLE-II survey. We consider only bright sources in the extended Red Clump Giant (RCG) region of the Color
متن کاملar X iv : a st ro - p h / 93 04 02 5 v 1 2 8 A pr 1 99 3 Lensing of invisible stars by brown dwarfs
To detect brown dwarfs in the dark galactic halo through gravitational lensing, experiments follow the luminosity of millions of stars to observe a few lensing events per year. The luminosity of a star too faint to be continuously followed can be temporarily increased above the detection limit by a lensing. The detection of these invisible stars would increase the number of events by a factor 2...
متن کامل