Calibrators at 610 MHz

Based on our criteria for a calibrator ( Flux density $>$ 0.75 Jy, flat $uv$-distance plot and no secondary source greater than 10% of the calibrator), we identified 102 sources which could be used as GMRT calibrators at 610MHz. These are presented in Table 4.1, List 1 as Class A calibrators.

To increase the number of calibrators and give the astronomer a larger choice, we have also defined a list of Class B calibrators where we have relaxed the limit on the secondary sources in the field allowing it to be as high as 25%. While the class B calibrators will be inferior to the Class A, they could be used with some care in the situation demanded. There are 9 source in this category which are listed in Table 4.2, List 2 as Class B calibrators.

• Class A - List 1 : The table 4.1 lists the sources as GMRT calibrators for which, the flux density (both peak as well as integrated) is greater than 0.75 Jy, $uv$-distance plots are flat & the secondary source is less than 10% the flux density of the source.

• Class B - List 2 : Considering the another criteria of flux density of the secondary source to be greater than 10% and less than 25% of the primary source, the table 4.2 lists the sources as GMRT calibrators for which, the flux density (both peak as well as integrated) is greater than 0.75 Jy, $uv$-distance plots are flat & the secondary source is less than 25% the flux density of the source.

Table 4.1: (Class A - List 1) : Identified Calibrators for GMRT at 610 MHz (Flux Density of Secondary Source is $<$ 10% of that of Primary Source.)

(Class A - List 1) : Identified Calibrators for GMRT at 610 MHz (Flux Density of Secondary Source is $<$ 10% of that of Primary Source.)

Sr.	Source	Flux	Sr.	Source	Flux	Sr.	Source	Flux
No.	Name	Density	No.	Name	Density	No.	Name	Density
	(J2000)	(Jy.)		(J2000)	(Jy.)		(J2000)	(Jy.)
1.	0022+002	3.62	26.	0447-220	4.21	51.	1154-350	8.82
2.	0024-420	1.19	27.	0453-281	3.09	52.	1219+484	0.76
3.	0029+349	1.92	28.	0459+024	1.09	53.	1227+365	1.77
4.	0059+001	3.66	29.	0503+020	1.20	54.	1248-199	7.77
5.	0102+584	1.19	30.	0530+135	1.43	55.	1313+675	4.55
6.	0119+321	3.69	31.	0541-056	1.29	56.	1323-448	4.29
7.	0136+478	1.23	32.	0604+442	1.43	57.	1330+251	11.9
8.	0155-408	2.66	33.	0607-085	2.58	58.	1347+122	8.12
9.	0204-170	0.99	34.	0609-157	2.75	59.	1351-148	1.48
10.	0217+738	2.24	35.	0632+103	2.80	60.	1400+621	6.93
11.	0237+288	2.03	36.	0713+438	1.50	61.	1432-180	1.18
12.	0238+166	1.25	37.	0735-175	3.01	62.	1435+760	2.05
13.	0240-231	5.27	38.	0739+016	2.15	63.	1445+099	2.48
14.	0321+123	2.40	39.	0741+312	1.44	64.	1448-163	1.82
15.	0323+055	5.17	40.	0745+101	1.83	65.	1545+478	0.85
16.	0329+279	1.33	41.	0828-375	1.41	66.	1602+334	2.94
17.	0336+323	2.46	42.	0837-198	8.95	67.	1609+266	4.40
18.	0403+260	0.82	43.	0842+185	1.16	68.	1613+342	4.41
19.	0410+769	7.89	44.	0854+201	1.16	69.	1629+679	1.40
20.	0414+343	2.09	45.	0943-083	4.10	70.	1635+381	3.00
21.	0423-013	2.00	46.	1035+564	1.95	71.	1653+397	1.82
22.	0424+020	1.40	47.	1107-448	1.85	72.	1743-038	0.90
23.	0432+416	13.8	48.	1120+143	3.76	73.	1800+784	1.76
24.	0438+488	2.34	49.	1130-148	5.77	74.	1845+401	1.21
25.	0440-435	6.65	50.	1150-003	3.85	75.	1923-210	1.68

Table 4.1: (Class A - List 1) : Identified Calibrators for GMRT at 610 MHz (Flux Density of Secondary Source is $<$ 10% of that of Primary Source.)

Continued... (Class A - List 1) : Identified Calibrators for GMRT at 610 MHz (Flux Density of Secondary Source is $<$ 10% of that of Primary Source.)

Sr.	Source	Flux	Sr.	Source	Flux	Sr.	Source	Flux
No.	Name	Density	No.	Name	Density	No.	Name	Density
	(J2000)	(Jy.)		(J2000)	(Jy.)		(J2000)	(Jy.)
76.	1924+334	6.10	85.	2035+109	1.27	94.	2202+422	2.35
77.	1925+211	1.08	86.	2035+189	2.42	95.	2212+018	4.42
78.	1944+548	1.84	87.	2050+314	0.83	96.	2214-385	2.90
79.	2007-445	0.99	88.	2052+365	4.87	97.	2236+284	0.82
80.	2011-067	2.15	89.	2101-423	1.09	98.	2246-121	1.76
81.	2015+371	1.47	90.	2130+050	4.60	99.	2254+247	2.64
82.	2022+616	1.61	91.	2136+006	1.53	100.	2314-449	3.20
83.	2023+544	1.01	92.	2139+143	1.03	101.	2344+824	5.67
84.	2025+337	0.87	93.	2148+069	3.43	102.	2355+498	2.91

Table 4.2: (Class B - List 2) : Identified Calibrators for GMRT at 610 MHz (Flux Density of Secondary Source is $>$ 10% and $<$ 25% of that of Primary Source.)

Sr.	Source	Flux	Sr.	Source	Flux	Sr.	Source	Flux
No.	Name	Density	No.	Name	Density	No.	Name	Density
	(J2000)	(Jy.)		(J2000)	(Jy.)		(J2000)	(Jy.)
1.	0334-401	0.76	4.	1316-336	1.23	7.	1751-253	0.75
2.	0614+607	1.53	5.	1513+236	2.34	8.	1937-399	0.79
3.	1111+199	1.13	6.	1751+096	0.75	9.	2005+778	0.84