2000ApJ...541..734A


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.21CEST04:26:34

2000ApJ...541..734A - Astrophys. J., 541, 734-766 (2000/October-1)

The MACHO project: microlensing optical depth toward the Galactic Bulge from difference image analysis.

ALCOCK C., ALLSMAN R.A., ALVES D.R., AXELROD T.S., BECKER A.C., BENNETT D.P., COOK K.H., DRAKE A.J., FREEMAN K.C., GEHA M., GRIEST K., LEHNER M.J., MARSHALL S.L., MINNITI D., NELSON C.A., PETERSON B.A., POPOWSKI P., PRATT M.R., QUINN P.J., STUBBS C.W., SUTHERLAND W., TOMANEY A.B., VANDEHEI T. and WELCH D.L.

Abstract (from CDS):

We present the microlensing optical depth toward the Galactic bulge based on the detection of 99 events found in our Difference Image Analysis (DIA) survey. This analysis encompasses 3 yr of data, covering ∼17 million stars in ∼4 deg2, to a source-star baseline magnitude limit of V=23. The DIA technique improves the quality of photometry in crowded fields, and allows us to detect more microlensing events with faint source stars. We find that this method increases the number of detection events by 85% compared with the standard analysis technique. DIA light curves of the events are presented, and the microlensing fit parameters are given. The total microlensing optical depth is estimated to be τtotal=2.43+0.39–0.38x10–6, averaged over eight fields centered at l=2°.68 and b=-3°.35. For the bulge component, we find τbulge=3.23+0.52–0.50x10–6, assuming a 25% stellar contribution from disk sources. These optical depths are in good agreement with the past determinations of the MACHO and OGLE groups, and are higher than predicted by contemporary Galactic models. We show that our observed event timescale distribution is consistent with the distribution expected from normal mass stars, if we adopt the Scalo stellar mass function as our lens mass function. However, we note that since there is still disagreement about the exact form of the stellar mass function, there is uncertainty in this conclusion. Based on our event timescale distribution, we find no evidence for the existence of a large population of brown dwarfs in the direction of the Galactic bulge.

Abstract Copyright:

Journal keyword(s): Cosmology: Dark Matter - Galaxy: Structure - Cosmology: Gravitational Lensing - Stars: Low-Mass, Brown Dwarfs

Nomenclature: Table 4, col(1): MACHO YY-BLG-dNN, MACHO YY-BLG-sNN N=38+7. Table 4, col(2): DIA FFF.NNNNN.NNNN N=83.

Errata: Erratum vol. 557, p. 1035 (2001)

Simbad objects: 86

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Number of rows : 86

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11051 1
2 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9556 1
3 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14988 1
4 MACHO 95-BLG-10 Lev 17 58 16.1 -29 32 11     18.9     ~ 6 0
5 MACHO 97-BLG-d9 Lev 17 58 28.69 -29 29 11.5           ~ 1 0
6 MACHO 96-BLG-21 Lev 17 58 43.15 -29 00 30.0           ~ 3 0
7 MACHO 95-BLG-1 Lev 17 59 00.7 -28 36 58     19.0     ~ 3 0
8 MACHO 97-BLG-d7 Lev 17 59 02.71 -29 03 02.5           ~ 1 0
9 MACHO 97-BLG-4 Lev 17 59 04.71 -30 07 06.5           ~ 2 0
10 MACHO 95-BLG-d16 Lev 17 59 18.58 -29 47 49.4           ~ 1 0
11 MACHO 96-BLG-s10 Lev 17 59 25.01 -28 46 32.9           ~ 2 0
12 MACHO 96-BLG-d13 Lev 17 59 34.95 -29 30 04.2           ~ 1 0
13 MACHO 97-BLG-8 Lev 17 59 35.35 -30 08 48.1           ~ 2 0
14 MACHO 96-BLG-d12 Lev 17 59 37.67 -30 00 53.1           ~ 1 0
15 MACHO 96-BLG-20 Lev 17 59 40.59 -28 47 24.9           ~ 3 0
16 OGLE BUL-SC21 45456 Lev 17 59 53.4 -29 09 08           ~ 7 0
17 MACHO 97-BLG-16 Lev 17 59 56.37 -29 56 37.5           ~ 2 0
18 MACHO 96-BLG-d11 Lev 18 00 01.63 -29 52 19.7           ~ 1 0
19 MACHO 96-BLG-10 Lev 18 00 02.01 -28 45 17.6           ~ 3 0
20 MACHO 95-BLG-4 Lev 18 00 03.41 -29 11 04.3     18.1     ~ 4 0
21 MACHO 95-BLG-23 Lev 18 00 03.61 -28 39 14.8           ~ 2 0
22 MACHO 97-BLG-26 Lev 18 00 06.94 -29 38 06.0           ~ 7 0
23 MACHO 96-BLG-d9 Lev 18 00 26.34 -29 17 36.1           ~ 1 0
24 MACHO 95-BLG-s13 Lev 18 00 28.87 -29 09 34.9           ~ 2 0
25 MACHO 97-BLG-d8 Lev 18 00 32.48 -28 53 22.7           ~ 1 0
26 MACHO 95-BLG-d14 Lev 18 00 34.56 -28 47 06.5           ~ 1 0
27 MACHO 95-BLG-d17 Lev 18 00 42.46 -30 06 37.2           ~ 1 0
28 MACHO 95-BLG-d15 Lev 18 00 46.72 -28 46 45.0           ~ 1 0
29 MACHO 96-BLG-8 Lev 18 00 58.17 -29 49 50.5           ~ 3 0
30 MACHO 96-BLG-d8 Lev 18 01 04.67 -29 17 31.1           ~ 1 0
31 MACHO 95-BLG-d12 Lev 18 01 15.47 -29 18 06.6           ~ 1 0
32 MACHO 97-BLG-d6 Lev 18 01 35.64 -29 08 39.3           ~ 1 0
33 MACHO 95-BLG-d19 Lev 18 01 41.23 -29 37 23.2           ~ 2 0
34 MACHO 119.19444.2055 Lev 18 01 45.6 -29 49 47           ~ 18 0
35 MACHO 95-BLG-39 Lev 18 02 04.76 -29 43 15.6           ~ 2 0
36 MACHO 119.19571.1616 Lev 18 02 07.62 -30 01 12.7           ~ 2 0
37 MACHO 95-BLG-d18 Lev 18 02 22.70 -29 50 35.2           ~ 1 0
38 MACHO 95-BLG-3 Lev 18 02 37.52 -29 39 35.9     18.7     ~ 6 0
39 MACHO 95-BLG-d20 Lev 18 03 07.84 -29 40 09.7           ~ 1 0
40 MACHO 97-BLG-18 Lev 18 03 15.26 -28 00 13.9           ~ 4 0
41 MACHO 97-BLG-d11 Lev 18 03 33.85 -29 53 30.0           ~ 1 0
42 MACHO 96-BLG-12 Lev 18 03 53.20 -27 57 35.7           G2III 10 0
43 MACHO 96-BLG-26 Lev 18 03 53.97 -27 33 30.5           ~ 3 0
44 MACHO 97-BLG-37 Lev 18 03 58.66 -29 58 48.8           ~ 4 0
45 MACHO 97-BLG-38 Lev 18 04 06.10 -27 48 26.9           ~ 3 0
46 MACHO 95-BLG-d11 Lev 18 04 06.15 -27 39 21.4           ~ 1 0
47 OGLE BUL-SC35 144974 * 18 04 09.68 -27 44 35.1   17.2       ~ 7 0
48 MACHO 97-BLG-d10 Lev 18 04 13.52 -30 09 25.9           ~ 1 0
49 MACHO 97-BLG-14 Lev 18 04 16.36 -30 07 23.2           ~ 2 0
50 MACHO 101.20650.1216 Lev 18 04 20.2 -27 24 45           ~ 6 0
51 MACHO 95-BLG-5 Lev 18 04 22.40 -26 53 15.8           ~ 2 0
52 MACHO 95-BLG-d10 Lev 18 04 25.12 -27 54 31.6           ~ 1 0
53 MACHO 96-BLG-1 Lev 18 04 26.19 -27 47 35.0           ~ 4 0
54 OGLE 15 Lev 18 04 37.3 -30 12 11           ~ 9 0
55 MACHO 97-BLG-2 Lev 18 04 50.73 -27 45 57.3           ~ 2 0
56 MACHO 97-BLG-42 Lev 18 04 56.56 -27 10 43.2           ~ 2 0
57 MACHO 96-BLG-d7 Lev 18 04 57.73 -27 33 18.3           ~ 1 0
58 MACHO 97-BLG-d5 Lev 18 05 02.68 -28 00 47.7           ~ 1 0
59 MACHO 96-BLG-14 Lev 18 05 15.39 -27 58 24.4           ~ 4 0
60 MACHO 96-BLG-d6 Lev 18 05 29.53 -27 54 00.6           ~ 1 0
61 MACHO 95-BLG-s9 Lev 18 05 34.46 -28 02 51.7           ~ 2 0
62 MACHO 95-BLG-d21 Lev 18 05 36.73 -28 32 41.5           ~ 1 0
63 MACHO 96-BLG-d2 Lev 18 05 38.12 -27 23 07.8           ~ 1 0
64 MACHO 97-BLG-s4 Lev 18 05 38.80 -27 08 29.5           ~ 2 0
65 MACHO 96-BLG-d17 Lev 18 05 40.51 -29 05 59.6           ~ 1 0
66 MACHO 96-BLG-d3 Lev 18 05 47.03 -27 08 54.8           ~ 1 0
67 MACHO 96-BLG-d4 Lev 18 05 47.75 -27 56 32.9           ~ 1 0
68 MACHO 96-BLG-d18 Lev 18 06 07.41 -28 47 25.5           ~ 1 0
69 MACHO 96-BLG-d5 Lev 18 06 09.00 -27 53 39.1           ~ 1 0
70 MACHO 95-BLG-15 Lev 18 06 28.79 -27 09 35.9           ~ 2 0
71 MACHO 96-BLG-31 Lev 18 06 42.39 -28 41 15.9           ~ 2 0
72 MACHO 95-BLG-s8 Lev 18 06 52.77 -27 23 19.8           ~ 2 0
73 MACHO 97-BLG-d12 Lev 18 06 52.95 -28 42 19.2           ~ 1 0
74 MACHO 95-BLG-d6 Lev 18 07 02.02 -27 32 40.2           ~ 1 0
75 MACHO 95-BLG-30 * 18 07 04.4 -27 22 06     16.21     M4III 39 0
76 MACHO 95-BLG-d22 Lev 18 07 11.15 -28 46 59.8           ~ 1 0
77 MACHO 95-BLG-18 Lev 18 07 20.7 -28 36 51     18.7     ~ 5 0
78 MACHO 95-BLG-d7 Lev 18 07 25.07 -27 24 41.1           ~ 1 0
79 MACHO 96-BLG-d15 Lev 18 07 32.70 -29 13 06.8           ~ 1 0
80 MACHO 96-BLG-s16 Lev 18 07 38.96 -28 57 11.8           ~ 2 0
81 MACHO 96-BLG-d14 Lev 18 08 24.14 -28 54 59.9           ~ 1 0
82 MACHO 97-BLG-s14 Lev 18 15 42.76 -25 41 01.9           ~ 2 0
83 MACHO 97-BLG-d15 Lev 18 16 51.10 -25 19 03.8           ~ 1 0
84 MACHO 95-BLG-22 Lev 18 17 14.80 -25 55 58.2           ~ 2 0
85 MACHO 97-BLG-d13 Lev 18 18 21.08 -25 56 37.1           ~ 2 0
86 NAME Galactic Bulge reg ~ ~           ~ 3457 0

    Equat.    Gal    SGal    Ecl

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2020.10.21-04:26:34

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