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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"

15554 results found.

  1. EP260227a: Liverpool Telescope optical observations
  2. EP260227a: LCOGT Optical Observations
  3. EP260227a: Thai National Telescope observations
  4. EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
  5. EP260227a: Liverpool Telescope observations
  6. EP260227a: COLIBRÍ optical observations
  7. EP260227a: NOT optical observations
  8. GRB 260225A: SVOM/VT optical continued observations and upper limit
  9. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  10. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  11. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  12. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  13. EP260214a: VLT/FORS2 optical observations
  14. GRB 260225A: WINTER J-band upper limit
  15. GRB 260226A: COLIBRÍ optical upper limits
  16. GRB 260226A: LCOGT Optical Upper Limit
  17. GRB 260226A : GROWTH-India Telescope optical observations
  18. GRB 260226A: LAST optical upper limit
  19. EP260224a: LCO optical upper limits
  20. GRB260225A: SVOM/ECLAIRs refined position
  21. GRB 260225A: EP-FXT follow-up observation
  22. GRB 260225A: SVOM/VT optical observation
  23. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  24. GRB 260225A: SVOM/VT optical upper limits
  25. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  26. EP260223a: Xinglong optical upper limit
  27. EP260213a: Mephisto optical upper limits
  28. sb26021801: SVOM/VT optical upper limits
  29. GRB 260223A: COLIBRÍ optical afterglow decay confirmation
  30. EP260223a: COLIBRÍ optical upper limits
  31. GRB 260223A: SVOM/VT optical observation
  32. GRB 260223A: SVOM/GRM observation
  33. GRB 260223A: COLIBRÍ further optical observations and a brightening
  34. EP260221a: Optical upper limit with Kinder observations
  35. GRB 260223A: COLIBRÍ optical observations
  36. GRB 260223A: DDOTI Optical Candidate
  37. EP260221a: COLIBRÍ optical counterpart candidate
  38. EP260221a: EP-FXT follow-up observation
  39. EP-WXT01709258519: Xinglong optical upper limit
  40. EP260221a: Xinglong optical upper limit
  41. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  42. EP260221a: GOTO optical upper limit
  43. EP260221a: COLIBRÍ optical upper limit
  44. SVOM alert sb26021801: LCO optical upper limit
  45. SVOM alert sb26021801: LAST optical upper limit
  46. sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. sb26021801: SVOM detection of a long faint X-ray transient
  48. EP-WXT 01709258455: NOT optical upper limits
  49. EP260214b: Mondy optical observations
  50. EP260214b: 1.3m DFOT optical upper limit
  51. EP260210a: Mondy optical upper limits
  52. GRB 260208A: AbAO and Terskol optical upper limits
  53. GRB 260208A: continued Mondy optical observations
  54. EP260214b: Liverpool Telescope optical observations
  55. EP260214b: Optical upper limit with Kinder observations
  56. EP260214a: Optical upper limits with Kinder observations
  57. EP260214b: EP-FXT follow-up observation
  58. EP260214b: DDOTI Optical Detection
  59. EP260214b: GROWTH-India Telescope optical upper limit
  60. EP260214b: SVOM/VT optical observation
  61. EP260214a: NOT optical upper limits
  62. EP260214a: COLIBRÍ optical upper limits
  63. EP260214b: OHP/T120 optical observations
  64. EP260214b: LCO optical counterpart detection
  65. EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
  66. GRB 260211A: SVOM/VT optical counterpart
  67. EP260214b: COLIBRÍ optical observations
  68. EP260214a: SVOM/VT optical upper limits
  69. EP260214b: NOT optical counterpart detection
  70. EP260213a: Liverpool Telescope optical upper limits
  71. EP260213a: COLIBRÍ optical upper limits
  72. EP260213a: Optical upper limits with Kinder observations
  73. EP260213a: SVOM/VT optical upper limit
  74. EP260213a: Mondy R-band optical upper limit
  75. EP260213a: NUTTelA-TAO Early Optical Limits
  76. EP/WXT 01709258378: NOT optical upper limits
  77. GRB 260212A: SVOM/GRM observation of a long burst
  78. GRB 260211A: SVOM/VT optical observation
  79. GRB 260211A: GOTO optical upper limit
  80. GRB 260211A: LAST optical upper limit
  81. GRB 260210A: SVOM/GRM observation
  82. GRB 260211A: LCO optical upper limits
  83. GRB260131A/B: 3.6m DOT Optical Observations
  84. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  85. GRB 260211A: SVOM detection of a burst
  86. EP260209a: COLIBRÍ optical upper limit
  87. EP260209a: LCO optical upper limits
  88. GRB 260208A: LCO detection of the optical counterpart
  89. EP260210a: Optical upper limits with Kinder observations
  90. EP260210a: SVOM/VT optical upper limit
  91. EP260210a: COLIBRÍ optical upper limit
  92. GRB 260208C: SVOM/GRM observation
  93. GRB 260204A: Swift-XRT afterglow detection
  94. GRB260208A: Liverpool Telescope optical follow-up observations
  95. GRB 260208A: NuSTAR detection of prompt emission
  96. GRB 260131A/B: continued Mondy optical observations
  97. GRB 260208B: COLIBRÍ optical observations
  98. GRB 260208A: Mondy optical observations (duplicate submission)
  99. GRB 260208A: Mondy optical observations
  100. GRB 260208A: 1.3m DFOT optical detection

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