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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').
Advanced Search

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.

Advanced Search Examples (click to copy):

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

18182 results found.

  1. GRB 260818B: Further EP-FXT observation
  2. GRB 260818B: VLT optical and nIR observations
  3. GRB 260818B: TNG NIR observations
  4. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  5. GRB 260818B: 6 GHz VLA observations
  6. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  7. GRB 260808B: SAO RAS observations of the optical rebrightening
  8. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  9. GRB 260822A: EP/FXT follow-up observations
  10. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  11. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  12. EP260822a: EP-FXT non-detection and upper limit
  13. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  14. EP260822a: Einstein Probe detection of a fast X-ray transient
  15. GRB 260822A: LCO optical upper limits
  16. The EP-WXT trigger 01709287395 is likely a flaring star
  17. GRB 260822A: GROWTH-India Telescope Upper Limits
  18. GRB 260818B: VLA radio observations
  19. GRB 260818B: SVOM/C-GFT optical upper limit
  20. The EP-WXT trigger 01709286204 is likely a flaring star
  21. EP detected a brightening of LMXB 1ES 1735-26.9
  22. GRB 260818B: EP-FXT follow-up observation
  23. GRB 260818A: J-band observations with WINTER
  24. GRB 260818B: NOT optical upper limits
  25. GRB 260810A: SVOM/GRM observation
  26. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB260818A: EP-FXT follow-up observation
  28. GRB 260818B: LCO optical upper limits
  29. EP260806a: SAO RAS multicolor optical observations
  30. GRB 260818A: LCO optical upper limits
  31. EP260812a: AbAO optical upper limit
  32. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  33. EP260806a: NUTTELA-TAO optical observations
  34. The EP-WXT trigger 01709281429 is likely a flaring star
  35. EP260812a: AZT-22 optical upper limit
  36. EP260806a: WFST optical observations
  37. The EP-WXT trigger 01709280562 is likely a flaring star
  38. EP260812b: Optical upper limit with Kinder
  39. The EP-WXT trigger 01709279838 is likely a flaring star
  40. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  41. GRB 260808B: Liverpool Telescope further optical observations
  42. EP260812a: NOT and Liverpool Telescope upper limits:
  43. EP260812b: Liverpool Telescope observations
  44. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  45. EP260812a: SVOM/C-GFT optical upper limit
  46. EP260812b: COLIBRÍ optical observations
  47. EP260812b: SVOM/VT optical observation
  48. GRB 260808A: SVOM/GRM observation
  49. EP260812b: Einstein Probe detection of an X-ray transient
  50. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  51. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  52. EP260812a: Einstein Probe detection of an X-ray transient
  53. GRB 260809A: SAO RAS optical observations
  54. GRB 260808B: SAO RAS optical observations
  55. EP260806a: MAO/AZT-22 optical observations
  56. GRB260808B: MAO/AZT-22 optical observations
  57. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  58. GRB 260809A: J-band upper limit with WINTER
  59. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  60. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  61. The EP-WXT trigger 01709278015 is likely a flaring star
  62. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  63. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  64. GRB 260809A: NOT optical observations
  65. GRB260809A: MAO/AZT-22 optical observations
  66. GRB260809A: OHP/T193 optical observations
  67. EP260809a: J-band upper limit with WINTER
  68. GRB 260808B: J-band upper limit with WINTER
  69. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  70. GRB 260809A: SVOM detection of a faint burst
  71. GRB 260808B: Liverpool Telescope optical observations
  72. GRB 260808B: NOT optical observations
  73. GRB 260808B: LCO optical observations
  74. EP260809a: COLIBRÍ optical observations
  75. EP260809a: LCO optical observation
  76. EP260809a: OHP/T193 optical observations
  77. GRB260808B: OHP/T193 optical observations
  78. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  79. EP260809a: Einstein Probe detection of an X-ray transient
  80. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  81. GRB 260808B: SVOM/VT optical candidate from VHF data
  82. GRB 260808B: SVOM detection of a faint burst
  83. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. EP260806a: COLIBRÍ optical observations
  85. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  86. EP260806a: SVOM/VT optical observation
  87. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  88. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  89. EP260806a: LCO likely optical counterpart
  90. EP260806a: Einstein Probe detection of an X-ray transient
  91. SN 2026stf / GRB 260708A: ATLAS forced photometry
  92. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  93. GRB 260802A: SVOM/VT optical upper limits from VHF data
  94. GRB 260802A: LCO optical upper limits
  95. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. The EP-WXT trigger 01709277420 is likely a flaring star
  97. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  98. EP260731a: COLIBRÍ optical upper limit
  99. EP260731a: NOT optical upper limit
  100. EP260731a: Einstein Probe detection of an X-ray transient

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