The images here are made using different X-ray colors, all extracted using MAXI/GSC data, for a subset of XRBs representative of major classes of XRBs.
For best viewing experience, please expand the web browser to accomodate four figures.
We compare the ability of different X-ray colors to distinguish classes of X-ray binaries as well as the spectral states of black hole binaries when using CCI diagrams, in different X-ray colors.
The axes of the plots are hard color (HC), soft color (SC) and relative intensity (RelInt).
Source Name
Compact Object
Companion Mass
Source Class
Cyg X-1
Black Hole
High
HMBH
LMC X-1
Black Hole
High
HMBH
LMC X-3
Black Hole
High
HMBH
GX 339-4
Black Hole
Low
LMBH
GRS 1915+105
Black Hole
Low
LMBH
H1743-32
Black Hole
Low
LMBH
4U 1630-472
Black Hole
Low
LMBH
Cyg X-2
Neutron Star
Low
Z source
GX 17+2
Neutron Star
Low
Z source
GX 5-1
Neutron Star
Low
Z source
Sco X-1
Neutron Star
Low
Z source
GX 9+9
Neutron Star
Low
Atoll source
GX 9+1
Neutron Star
Low
Atoll source
Aql X-1
Neutron Star
Low
Atoll source
4U 1608-52
Neutron Star
Low
Atoll source
Cen X-3
Neutron Star
High
HM pulsar
Vela X-1
Neutron Star
High
HM pulsar
SMC X-1
Neutron Star
High
HM pulsar
4U 1538-52 X-3
Neutron Star
High
HM pulsar
4U 1626-67
Neutron Star
Low
LM pulsar
4U 1822-37
Neutron Star
Low
LM pulsar
Her X-1
Neutron Star
Low
LM pulsar
Label
Energy bands used (in keV)
Soft Color (SC)
Hard Color (HC)
CR1
2-3;3-5;5-12
(3-5)/(2-3)
(5-12)/(2-3)
CR2
2-3; 3-5; 5-8
(3-5)/(2-3)
(5-8)/(2-3)
CR3
2.4-4; 4-7.3; 7.3-9.8; 9.8-18.2
(4-7.3)/(2.4-4)
(9.8-18.2)/(7.3-9.8)
CR4
2.2-3.6; 3.6-5; 5-8.6; 8.6-18
(3.6-5)/(2.2-3.6)
(8.6-18)/(5-8.6)
CR5
2-7; 7-12; 12-18
(7-12)/(2-7)
(12-18)/(2-7)
CR6
2-7; 7-12; 12-15; 15-18
(7-12)/(2-7)
(15-18)/(12-15)
CR7
2-5; 5-8; 8-18
(5-8)/(2-5)
(8-18)/(2-5)
CR8
2-5; 5-8; 8-13; 13-18
(5-8)/(2-5)
(13-18)/(8-13)
CR9
2.4-5; 5-8; 8-18.2
(5-8)/(2.4-5)
(8-18.2)/(2.4-5)
CR10
2.2-5; 5-8; 8-18
(5-8)/(2.4-5)
(8-18)/(2.4-5)
Figure 1:Color-Color-Intensity diagrams of Cyg X-1 (a): Using RXTE/ASM data in the bands provided by the ASM Team. 13 years of data are plotted as one day averages. (b): Using MAXI/GSC data extracted in colors closest to that of the ASM (CR1). 8 years of data are plotted as one day averages. The coordinates SC and HC are as defined in Table 2; the coordinate RelInt is the sum of the counts in all energy bands divided by the average of the top 1% of the counts for each source. The CCI plots show consistent patterns in both instruments.
Figure 2: Color-Color-Intensity plots using MAXI/GSC data extracted in four of the X-ray colors listed in Table 2: CR1 (red), CR2 (blue), CR3 (magenta) and CR4 (green). The average error bar is plotted as a purple cross on each plot. (a): Cyg X-1, a HMBH. While the location of the points in each color are slightly offset from each other, the soft and hard state are separated in each color. (b): LMC X-1, a HMBH. Only soft state is detected by MAXI. (c): GX339-4, a LMBH. Data includes the soft state, hard state and intermediate state. The soft state is not traced by CR3 and CR4. (d): GRS 1915+105, a LMBH showing the intermediate spectral state in all four colors.
Figure 3: As in Figure 2 for: (a) GX17+2, a LMXB non-pulsing Z source (b) GX 9+1, a LMXB non-pulsing Atoll source; (c) Cen X-3, a HMXB pulsar; (d) 4U 1626-67, a LMXB pulsar. While slightly offset from each other the full phase space occupied by each source is captured by each color.
Figure 4: Color-Color-Intensity plots using MAXI/GSC data extracted in four of the X-ray colors listed in Table 2 for the HMBHs in black, and the LMBHs in green. (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. LMBHs are separated from HMBHs by all four colors. CR1 and CR2 capture the soft states whereas CR3 and CR4 do not.
Figure 5: As in Figure 4 for HMBHs in black, and Z sources in blue (a) Using CR1; (b) Using CR3; (c) Using CR2; (d) Using CR4. HMBHs and Z sources are separated by all four colors. CR3 and CR4 do not capture the soft state of HMBHs.
Figure 6: As in Figure 4 for HMBHs in black, and Atoll sources in magenta (a) Using CR1; (b) Using CR3; (c) Using CR2; (d) Using CR4. All four colors separate HMBHs from Atoll sources. CR3 and CR4 do not capture the soft state of HMBHs
Figure 7: As in Figure 4 for LMBHs in green, and Z sources in blue (a) Using CR1; (b) Using CR3; (c) Using CR2; (d) Using CR4. All four colors separate LMBHs from Atoll sources. CR3 and CR4 do not capture the soft state of LMBHs.
Figure 8: As in Figure 4 for LMBHs in green, and Atoll sources in magenta (a) Using CR1; (b) Using CR3; (c) Using CR2; (d) Using CR4. All four colors separate LMBHs from Atoll sources. CR3 and CR4 do not capture the soft state of LMBHs.
Figure 9: As in Figure 4 for HMBHs in black, and HMXB pulsars in red. (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. All four colors separate HMBHs from HMXB Pulsars. CR3 and CR4 do not capture the soft state of HMBHs.
Figure 10: As in Figure 4 for HMBHs in black, and LMXB pulsars in yellow (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. All four colors separate HMBHs from LMXB pulsars. CR3 and CR4 do not capture the soft state of HMBHs.Figure 11: As in Figure 4 for LMBHs in green, and HMXB pulsars in red. (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. LMBHs and HMXB pulsars are separated. CR3 and CR4 do not capture the soft state of LMBHs. Figure 12: As in Figure 4 for LMBHs in green, and for LMXB pulsars in yellow (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. LMBHs and LMXB pulsars are separated. CR3 and CR4 do not capture the soft state of LMBHs.Figure 13: As in Figure 4 for Z sources in blue, and for Atoll sources in magenta. (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. None of the colors distinguish between Atoll and Z sources. Figure 14: As in Figure 4 for HMXB pulsars in red, and LMXB pulsars in yellow. (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. All four colors show some overlap between HMXB and LMXB pulsars.Figure 15: As in Figure 4 for Z sources in blue, Atoll sources in magenta, HMXB pulsars in red, and LMXB pulsars in yellow. (a) Using CR1; (b) Using CR2; (c) Using CR3; (d) Using CR4. Figure 16: Color-Color-Intensity plots using MAXI/GSC data of the HMBH Cyg X-1 extracted in each of the X-ray colors (a) CR5; (b) CR6; (c) CR7; and (d) CR8 as listed in Table 2. CR5 and CR7 are better at separating the hard and soft states.
Figure 17: Color-Color-Intensity plots using MAXI/GSC data of the LMBH GX 339-4 extracted in each of the X-ray colors (a) CR5; (b) CR6; (c) CR7; and (d) CR8 as listed in Table 2. Only CR7 suggests the possibility of three states in the system (soft, hard, and intermediate).
Figure 18: Color-Color-Intensity plots using MAXI/GSC data extracted in each of the X-ray colors (left to right panels): (a) CR9 for Cyg X-1; (b) CR10 for Cyg X-1 (c); CR9 for GX 339-4; and (d) CR10 for GX 339-4. Both colors separate hard and soft states and , where present, the intermediate state. Figure 19: Color-Color-Intensity plots using MAXI/GSC data extracted for all the XRBs plotted in Done & Gierlin ́ski (2003; their Fig. 8) using CR1-CR4. Our plots extend to the same HC and SC limits that they used and we use a similar color scheme BHs are in black, Z sources in red, Atoll sources in cyan, and Cir X–1 in blue. The average error bar is plotted as a purple cross in each plot. The region Done & Gierlin ́ski identify as inaccessible to NS is clearly isolated. In CCI space (when seen in 3 dimensions) colors CR1 and CR2 completely separate all BH systems from all systems containing NS. Cir X-1 has no overlap with BHs. Figure 20: Color-Color-Intensity plots using MAXI/GSC data with HMBHs in black, LMBHs in green, Z sources in blue, Atolls in magenta, LMXB pulsars in yellow, HMXB pulsars in red and GRS 1739-278 in orange. The data-points of GRS 1739-278 are separated from the Z sources, and both HMXB and LMXB pulsars, however they show some overlap with the low states of Atoll sources. They are located closer to LMBHs than to HMBHs, identifying it as a LMBH.
Figure 21: Color-Color-Intensity plots using MAXI/GSC data with HMBHs in black, LMBHs in green, Z sources in blue, Atolls in magenta, LMXB pulsars in yellow, HMXB pulsars in red and 4U 1957+115 in pink. The data-points of 4U 1957+115 are separated from the Atoll sources, and both HMXB and LMXB pulsars, however they show some overlap with Z sources. They show an overlap with both HMBHs and LMBHs in their high soft states.
