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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

16000 results found.

  1. GRB 260421B: 3.6m DOT optical observation
  2. EP260416a: ZTSh R band observations
  3. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  4. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  5. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  6. GRB 260421B: SVOM/GRM observation
  7. GRB 260421B: EP-FXT follow-up observation
  8. GRB 260421B: J-band upper limit with WINTER
  9. GRB 260421B: LCO optical counterpart detection
  10. GRB 260421B: SVOM/VT optical observations
  11. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  12. GRB 260310A: Late-time Chandra X-ray Detection
  13. EP260416a: 1.3m DFOT optical observation
  14. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  15. GRB 260421B: BOOTES-7 early optical afterglow detection
  16. GRB 260421B: LCO optical afterglow confirmation
  17. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  18. GRB 260421B: TRT optical counterpart detection
  19. GRB 260412A: LCOGT Optical Upper Limits
  20. EP260416a: Optical follow-up observations with Kinder
  21. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  22. EP-WXT trigger 01709260303: KAIT optical observations
  23. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  24. GRB 260417A: SVOM/GRM observation
  25. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  26. EP260417a: GROWTH-India Telescope optical upper limit
  27. EP260417b: GROWTH-India Telescope optical upper limit
  28. EP260416a: Ondrejov D50 optical detection
  29. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  30. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  31. EP260416a: GMG Optical Observation
  32. EP260416a: LCO observations confirm end of flaring phase
  33. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  34. EP260417a: TRT optical counterpart detection
  35. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP-WXT trigger 01709259586: KAIT optical observations
  37. EP260416a: KAIT optical upper limit
  38. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  39. EP260416a: WFST optical observations and rebrightening
  40. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  41. EP260416a: SVOM/VT optical observation
  42. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  43. EP260416a: COLIBRÍ optical counterpart candidate
  44. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  45. GOTO26djh/AT2026jpw : MASTER OT observation
  46. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  47. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  48. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  49. EP260321a: CMO SAI J,K observations
  50. EP260321a: SVOM/VT optical observations and color changes around peak
  51. GRB 260411B: Fermi-LAT detection
  52. GRB 260412A: SVOM detection of a long burst
  53. GRB 260411B: COLIBRÍ optical observations
  54. GRB 260411B: Ondrejov D50 optical afterglow detection
  55. GRB260411B: 3.6m DOT optical observation
  56. GRB 260411A: SVOM/GRM observation
  57. GRB 260411B: SVOM/GRM observation of a long burst
  58. GRB 260411B: Fermi GBM Detection
  59. GRB 260411B: GOTO optical counterpart candidate
  60. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  61. GRB 260410A: COLIBRÍ optical upper limit
  62. EP-WXT01709259790: Optical Upper limits with kinder observations
  63. EP-WXT01709259790: Xinglong optical upper limit
  64. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  65. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  66. EP260409a: SVOM/VT optical upper limits
  67. EP260409a: COLIBRÍ optical upper limits
  68. GRB 260310A / AT2026fgk: X-ray rebrightening
  69. EP260402a / GRB 260402A: Mephisto optical upper limits
  70. EP-WXT01709259586: Xinglong optical upper limit
  71. EP260403a: Mephisto optical upper limits
  72. EP260402a/GRB 260402A: Xinglong optical upper limit
  73. EP260321a: Upper limits from VLA radio observations
  74. EP260321a: uGMRT observations
  75. EP260405a: GMOS-N optical upper limits
  76. EP260405a: SVOM/VT optical upper limits
  77. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  78. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  79. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  80. GRB 260330B: SVOM/VT further optical observation
  81. EP260403a: LCO optical observations of the counterpart
  82. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  83. EP260403a: LCO optical counterpart detection
  84. EP260403a: COLIBRÍ optical counterpart candidate
  85. GRB 260330B: SVOM/VT optical candidate
  86. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  87. EP260324A / AT 2026hir: COLIBRÍ optical observations
  88. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  89. GRB 260402A: WINTER J-band upper limit
  90. GRB260402A: GROWTH-India Telescope optical upper limit
  91. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  92. GRB 260401A: SVOM/GRM observation
  93. GRB 260402A: Kilonova-Catcher optical upper limit
  94. GRB 260402A: MASTER optical observations
  95. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. EP260329b: Mondy and Assy-Turgen optical upper limits
  97. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  98. EP260321a :Xinglong optical observations
  99. EP260327a: Xinglong optical upper limit
  100. EP260329b: GOTO detection of optical counterpart

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