6,757 research outputs found
Near-Infrared Photometric Study of the Old Open Cluster Trumpler 5
We present JHK near-infrared photometric study for the old open cluster (OC)
Trumpler 5 (Tr 5), based on the 2MASS data. From the color-magnitude diagrams
of Tr 5, we have located the position of the red giant clump (RGC) stars, and
used the mean magnitude of the RGC stars in K-band to estimate the distance to
Tr 5, d = 3.1 +/- 0.1 kpc ((m-M)_0 = 12.46 +/- 0.04). From fitting the
theoretical isochrones of Padova group, we have estimated the reddening,
metallicity, and age : E(B-V) = 0.64 +/- 0.05, [Fe/H] = -0.4 +/- 0.1 dex, and t
=2.8 +/- 0.2 Gyr (log t=9.45 +/- 0.04), respectively. These parameters
generally agree well with those obtained from the previous studies on Tr 5 and
confirms that this cluster is an old OC with metallicity being metal-poorer
than solar abundance, located in the anti-Galactic center region.Comment: JKAS (J. of the Korean Astron. Soc.) in press (2009 Dec issue), page
numbers will be change
Physical Parameters of the Old Open Cluster Trumpler 5
We present a study of the old open cluster Trumpler 5 (Tr 5), based on the
CDS archival data. From the color-magnitude diagrams of Tr 5, we have found the
positions of main-sequence turn-off (MSTO) and red giant clump (RGC) stars.
Using the mean magnitude of the RGC stars, we have estimated the reddening
toward Tr 5, E(B-V) = 0.60 +/- 0.10. Using the stars common in two data sets
and the theoretical isochrones of Padova group, we have estimated the distance
modulus V_0-M_V=12.64 +/- 0.20 (d = 3.4 +/- 0.3 kpc), the metallicity [Fe/H] =
-0.30 +/- 0.10, and the age of 2.4 +/- 0.2 Gyr (log t=9.38). These metallicity
and distance values are consistent with the relation between the metallicity
and the Galactocentric distance of other old open clusters, for which we obtain
the slope of Delta_[Fe/H]/R_gc= -0.064 +/- 0.010 dex/kpc.Comment: 9 pages(AASLaTeX), 8 Postscript figures, Accepted for publication in
the Journal of the Korean Astronomical Society, 2003 March issu
UBVI CCD Photometry of the Old Open Cluster NGC 1193
We present UBVI photometry of the old open cluster NGC 1193. Color-magnitude
diagrams (CMDs) of this cluster show a well defined main sequence and a sparse
red giant branch. For the inner region of r<50 arcsec, three blue straggler
candidates are newly found in addition to the objects Kaluzny (1988) already
found. The color-color diagrams show that the reddening value toward NGC 1193
is E(B-V) =0.19 +/- 0.04. From the ultraviolet excess measurement, we derived
the metallicity to be [Fe/H]=-0.45 +/- 0.12. A distance modulus of (m-M)_0
=13.3 +/- 0.15 is obtained from zero age main sequence fitting with the
empirically calibrated Hyades isochrone of Pinsonneault et al. (2004). CMD
comparison with the Padova isochrones by Bertelli et al. (1994) gives an age of
log t =9.7 +/- 0.1.Comment: JKAS (J. of the Korean Astron. Soc.) in press (Dec 2008 issue
Physiological Antioxidative Network of the Bilirubin System in Aging and Age-Related Diseases
Oxidative stress is detrimental to life process and is particularly responsible for aging and age-related diseases. Thus, most organisms are well equipped with a spectrum of biological defense mechanisms against oxidative stress. The major efficient antioxidative mechanism is the glutathione system, operating a redox cycling mechanism for glutathione utilization, which consists of glutathione and its peroxidase and reductase. However, this system is mainly effective for hydrophilic oxidants, while lipophilic oxidants require another scavenging system. Since many age-related pathological conditions are related to lipid peroxidation, especially in association with the aging process, the physiological role of the scavenging system for lipophilic oxidants should be considered. In this regard, the biliverdin to bilirubin conversion pathway, via biliverdin reductase (BVR), is suggested to be another major protective mechanism that scavenges lipophilic oxidants because of the lipophilic nature of bilirubin. The efficiency of this bilirubin system might be potentiated by operation of the intertwined bicyclic systems of the suggested redox metabolic cycle of biliverdin and bilirubin and the interactive control cycle of BVR and heme oxygenase. In order to combat oxidative stress, both antioxidative systems against hydrophilic and lipophilic oxidants are required to work cooperatively. In this regard, the roles of the bilirubin system in aging and age-related diseases are reassessed in this review, and their interacting networks are evaluated
A Near-Infrared Study of the Highly-Obscured Active Star-Forming Region W51B
We present wide-field JHKs-band photometric observations of the three compact
HII regions G48.9-0.3, G49.0-0.3, and G49.2-0.3 in the active star-forming
region W51B. The star clusters inside the three compact HII regions show the
excess number of stars in the J-Ks histograms compared with reference fields.
While the mean color excess ratio E(J-H)/E(H-Ks) of the three compact HII
regions are similar to ~ 2.07, the visual extinctions toward them are somewhat
different: ~ 17 mag for G48.9-0.3 and G49.0-0.3; ~ 23 mag for G49.2-0.3. Based
on their sizes and brightnesses, we suggest that the age of each compact HII
region is =< 2 Myr. The inferred total stellar mass, ~ 1.4 x 10^4 M_sun, of
W51B makes it one of the most active star forming regions in the Galaxy with
the star formation efficiency of ~ 10 %.Comment: 12 pages, 10 eps figures, uses jkas.st
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