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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"

15985 results found.

  1. GRB 260903A: OHP/T193 optical afterglow detection
  2. GRB 260903A: NOT optical observations and afterglow fading
  3. NuSTAR Transient 260828: SOAR Optical Upper Limits
  4. SVOM GRB260903A: Global MASTER-Net observations report
  5. GRB 260903A: LCO optical observations
  6. GRB 260903A: SVOM/VT optical candidate
  7. GRB 260903A: Retraction of optical counterpart of GCN 45501
  8. GRB 260903A: LCO optical counterpart detection
  9. GRB 260903A: SVOM detection of a soft faint burst
  10. EP260901a: SVOM/VT optical upper limits
  11. GRB 260829A: SVOM/GRM observation
  12. EP260901a: Global MASTER-Net observations report
  13. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  14. GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
  15. NuSTAR Transient 260828: LCO Optical Upper Limits
  16. GRB 260831B: LCO optical upper limits
  17. EP260830a: Global MASTER-Net observations report
  18. GRB 260827A: SVOM/GRM observation
  19. EP260727a: ATCA 10 GHz detection
  20. GRB 260825A: SVOM/GRM observation of a long burst
  21. GRB 260818B: Further EP-FXT observation
  22. GRB 260818B: VLT optical and nIR observations
  23. MAXI GRB260827.40: Global MASTER-Net observations report
  24. GRB 260818B: 6 GHz VLA observations
  25. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  26. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  27. GRB 260808B: SAO RAS observations of the optical rebrightening
  28. EP260822a: Global MASTER-Net observations report
  29. EP Alert 260820.31: Global MASTER-Net observations report
  30. GRB 260822A: SVOM/VT optical upper limits
  31. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  32. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  33. GRB 260822A: GOTO optical counterpart detection
  34. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  35. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  36. GRB 260822A: LCO optical upper limits
  37. GRB 260822A: GROWTH-India Telescope Upper Limits
  38. GRB 260822A: GOTO optical upper limit
  39. GRB 260818B: SVOM/C-GFT optical upper limit
  40. GRB 260818B: SVOM/GRM observation
  41. GRB 260818B: NOT optical upper limits
  42. GRB 260810A: SVOM/GRM observation
  43. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  44. GRB 260818B: LCO optical upper limits
  45. GRB 260818B: SVOM detection of a short burst
  46. EP260806a: SAO RAS multicolor optical observations
  47. GRB 260818A: LCO optical upper limits
  48. EP260812a: AbAO optical upper limit
  49. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. EP260806a: NUTTELA-TAO optical observations
  51. EP260812a: AZT-22 optical upper limit
  52. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  53. EP260806a: WFST optical observations
  54. EP260812b: Optical upper limit with Kinder
  55. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  56. GRB 260808B: Liverpool Telescope further optical observations
  57. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  58. EP260812a: NOT and Liverpool Telescope upper limits:
  59. EP260812b: Liverpool Telescope observations
  60. EP260812b: GOTO detection of the optical counterpart
  61. EP260812a: SVOM/C-GFT optical upper limit
  62. EP260812b: COLIBRÍ optical observations
  63. EP260812b: SVOM/VT optical observation
  64. GRB 260808A: SVOM/GRM observation
  65. EP260812b: Einstein Probe detection of an X-ray transient
  66. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  67. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  68. GRB 260809A: SAO RAS optical observations
  69. GRB 260808B: SAO RAS optical observations
  70. GRB 260808B: SVOM/VT optical re-brightening at day 3
  71. EP260806a: MAO/AZT-22 optical observations
  72. GRB260808B: MAO/AZT-22 optical observations
  73. GRB 260809A: J-band upper limit with WINTER
  74. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  75. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  76. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  77. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  78. GRB 260809A: NOT optical observations
  79. GRB260809A: MAO/AZT-22 optical observations
  80. GRB260809A: OHP/T193 optical observations
  81. GRB 260809A: SVOM/VT optical counterpart
  82. EP260809a: J-band upper limit with WINTER
  83. GRB 260808B: J-band upper limit with WINTER
  84. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  85. GRB 260808B: Liverpool Telescope optical observations
  86. GRB 260808B: NOT optical observations
  87. GRB 260808B: LCO optical observations
  88. EP260809a: COLIBRÍ optical observations
  89. EP260809a: LCO optical observation
  90. EP260809a: OHP/T193 optical observations
  91. GRB260808B: OHP/T193 optical observations
  92. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  93. GRB 260808B: SVOM/VT optical afterglow confirmation
  94. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  95. GRB 260808B: SVOM/VT optical candidate from VHF data
  96. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  97. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. GRB 260807A: SVOM possible detection of a faint burst
  99. EP260806a: COLIBRÍ optical observations
  100. EP260806a: SVOM/VT optical observation

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