Announcements
High-Resolution spectroscopy
IGRINS-2 is operated in a single, high-resolution spectroscopic mode. This mode provides full wavelength coverage between 1.49-1.80 μm (H-band) and between 1.96-2.46 μm (K-band) region at a spectral resolution of R~45,000. These two spectroscopic channels, composed of two separate detectors (H and K bands), are being obtained simultaneously.
Spectral range and resolution
IGRINS-2 makes use of a silicon immersion grating as the main disperser and two VPH gratings as cross-dispersers. The resulting resolving power is R~45,000.
Figure 1: One dimentional H (left) and K (right) band spectra of a point source. IGRINS-2 provides simultaneous wavelength coverage over the 1.49-1.80 μm (H-band) and 1.96-2.46 μm (K-band) ranges.
Figure 2: Resolving power of IGRINS-2 for the H (blue) and K (red) bands, measured from the OH sky emssion lines.
The coverages of the different orders in which the light is dispersed are provided below.
| H-band spectral format | |||||||||
| Order no. | Wavelength (nm) | Free spectral range | Order separation | ||||||
| blaze | min | max | nm | deg. | mm | mm | pix | arcsec | |
| 122 | 1474.85 | 1468.81 | 1480.90 | 12.089 | 2.828 | 6.25 | 1.077 | 59.8 | 11.77 |
| 121 | 1486.58 | 1480.44 | 1492.72 | 12.286 | 2.851 | 6.30 | 1.097 | 61.0 | 11.95 |
| 120 | 1498.50 | 1492.26 | 1504.75 | 12.488 | 2.875 | 6.36 | 1.118 | 62.1 | 12.12 |
| 119 | 1510.63 | 1504.29 | 1516.98 | 12.694 | 2.899 | 6.41 | 1.140 | 63.3 | 12.30 |
| 118 | 1522.97 | 1516.52 | 1529.42 | 12.907 | 2.924 | 6.46 | 1.162 | 64.6 | 12.49 |
| 117 | 1535.52 | 1528.96 | 1542.09 | 13.124 | 2.949 | 6.52 | 1.186 | 65.9 | 12.68 |
| 116 | 1548.30 | 1541.62 | 1554.97 | 13.347 | 2.974 | 6.57 | 1.211 | 67.3 | 12.88 |
| 115 | 1561.30 | 1554.51 | 1568.09 | 13.576 | 3.000 | 6.63 | 1.237 | 68.7 | 13.09 |
| 114 | 1574.53 | 1567.62 | 1581.43 | 13.812 | 3.026 | 6.69 | 1.264 | 70.2 | 13.31 |
| 113 | 1588.00 | 1580.97 | 1595.03 | 14.053 | 3.053 | 6.75 | 1.292 | 71.8 | 13.53 |
| 112 | 1601.71 | 1594.56 | 1608.86 | 14.301 | 3.080 | 6.81 | 1.322 | 73.5 | 13.76 |
| 111 | 1615.68 | 1608.40 | 1622.96 | 14.556 | 3.108 | 6.87 | 1.354 | 75.2 | 14.00 |
| 110 | 1629.90 | 1622.49 | 1637.31 | 14.817 | 3.136 | 6.93 | 1.387 | 77.1 | 14.25 |
| 109 | 1644.39 | 1636.85 | 1651.93 | 15.086 | 3.165 | 7.00 | 1.422 | 79.0 | 14.50 |
| 108 | 1659.15 | 1651.47 | 1666.83 | 15.363 | 3.194 | 7.06 | 1.459 | 81.1 | 14.77 |
| 107 | 1674.19 | 1666.37 | 1682.02 | 15.647 | 3.224 | 7.13 | 1.498 | 83.2 | 15.05 |
| 106 | 1689.52 | 1681.55 | 1697.49 | 15.939 | 3.255 | 7.20 | 1.540 | 85.5 | 15.35 |
| 105 | 1705.15 | 1697.03 | 1713.27 | 16.240 | 3.286 | 7.27 | 1.584 | 88.0 | 15.65 |
| 104 | 1721.08 | 1712.80 | 1729.35 | 16.549 | 3.317 | 7.34 | 1.631 | 90.6 | 15.97 |
| 103 | 1737.32 | 1728.89 | 1745.76 | 16.867 | 3.349 | 7.41 | 1.682 | 93.4 | 16.31 |
| 102 | 1753.89 | 1745.29 | 1762.49 | 17.195 | 3.382 | 7.48 | 1.735 | 96.4 | 16.66 |
| 101 | 1770.79 | 1762.03 | 1779.56 | 17.533 | 3.416 | 7.55 | 1.793 | 99.6 | 17.03 |
| 100 | 1788.03 | 1779.09 | 1796.97 | 17.880 | 3.450 | 7.63 | 1.855 | 103.1 | 17.42 |
| 99 | 1805.63 | 1796.51 | 1814.75 | 18.239 | 3.485 | 7.71 | 1.922 | 106.8 | 17.83 |
| 98 | 1823.59 | 1814.28 | 1832.89 | 18.608 | 3.520 | 7.79 | 1.995 | 110.8 | 18.26 |
| K-band spectral format | |||||||||
| Order no. | Wavelength (nm) | Free spectral range | Order separation | ||||||
| blaze | min | max | nm | deg. | mm | mm | pix | arcsec | |
| 92 | 1939.65 | 1929.11 | 1950.19 | 21.083 | 3.750 | 8.29 | 1.129 | 62.7 | 12.06 |
| 91 | 1960.50 | 1949.73 | 1971.27 | 21.544 | 3.791 | 8.39 | 1.156 | 64.2 | 12.30 |
| 90 | 1981.81 | 1970.80 | 1992.82 | 22.020 | 3.833 | 8.48 | 1.183 | 65.7 | 12.55 |
| 89 | 2003.62 | 1992.36 | 2014.87 | 22.513 | 3.876 | 8.57 | 1.212 | 67.3 | 12.81 |
| 88 | 2025.92 | 2014.41 | 2037.43 | 23.022 | 3.920 | 8.67 | 1.242 | 69.0 | 13.07 |
| 87 | 2048.74 | 2036.96 | 2060.51 | 23.549 | 3.965 | 8.77 | 1.274 | 70.8 | 13.35 |
| 86 | 2072.09 | 2060.05 | 2084.14 | 24.094 | 4.011 | 8.88 | 1.307 | 72.6 | 13.64 |
| 85 | 2096.01 | 2083.68 | 2108.34 | 24.659 | 4.059 | 8.98 | 1.342 | 74.6 | 13.95 |
| 84 | 2120.49 | 2107.87 | 2133.11 | 25.244 | 4.107 | 9.09 | 1.379 | 76.6 | 14.26 |
| 83 | 2145.57 | 2132.65 | 2158.50 | 25.850 | 4.156 | 9.20 | 1.418 | 78.8 | 14.60 |
| 82 | 2171.27 | 2158.03 | 2184.51 | 26.479 | 4.207 | 9.31 | 1.460 | 81.1 | 14.94 |
| 81 | 2197.61 | 2184.05 | 2211.18 | 27.131 | 4.259 | 9.42 | 1.504 | 83.5 | 15.30 |
| 80 | 2224.62 | 2210.71 | 2238.52 | 27.808 | 4.312 | 9.54 | 1.551 | 86.1 | 15.68 |
| 79 | 2252.31 | 2238.05 | 2266.56 | 28.510 | 4.367 | 9.66 | 1.600 | 88.9 | 16.08 |
| 78 | 2280.72 | 2266.10 | 2295.34 | 29.240 | 4.423 | 9.79 | 1.653 | 91.9 | 16.50 |
| 77 | 2309.87 | 2294.87 | 2324.87 | 29.998 | 4.480 | 9.92 | 1.710 | 95.0 | 16.94 |
| 76 | 2339.80 | 2324.40 | 2355.19 | 30.787 | 4.539 | 10.05 | 1.771 | 98.4 | 17.41 |
| 75 | 2370.53 | 2354.72 | 2386.33 | 31.607 | 4.600 | 10.18 | 1.836 | 102.0 | 17.90 |
| 74 | 2402.10 | 2385.86 | 2418.33 | 32.461 | 4.662 | 10.32 | 1.907 | 105.9 | 18.42 |
| 73 | 2434.53 | 2417.86 | 2451.21 | 33.350 | 4.726 | 10.46 | 1.983 | 110.2 | 18.97 |
| 72 | 2467.88 | 2450.74 | 2485.02 | 34.276 | 4.791 | 10.61 | 2.066 | 114.8 | 19.56 |
| 71 | 2502.17 | 2484.55 | 2519.79 | 35.242 | 4.859 | 10.76 | 2.156 | 119.8 | 20.18 |
Sensitivity
The final evaluation of the instrument performance is in the process of being completed. However, the following table provides preliminary estimates for the signal-to-noise ratio for 3,600s (6x600s) integration on a point source in the 70%-ile image quality, 50%-ile cloud cover (clear).
| K-band magnitude | S/N (H-band) | S/N (K-band) |
| 11 | 380 | 300 |
| 12 | 240 | 190 |
| 13 | 150 | 115 |
| 14 | 90 | 70 |
| 15 | 50 | 40 |
| 16 | 30 | 17 |