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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"

31727 results found.

  1. GRB 241029A: Swift-XRT observations
  2. GRB 241029A: Fermi GBM Observation
  3. GRB 241029A: AKO Optical Afterglow Detection
  4. GRB 241029A: GOTO optical afterglow detection
  5. EP241021a: continued SOAR observations confirm optical rebrightening
  6. GRB 241029A: MASTER early optical counterpart detection
  7. GRB 241029A: Xinglong-2.16m optical afterglow confirmation
  8. GRB 241029A: Mephisto observations
  9. EP 241026b: LBT possible optical counterpart (brightening source)
  10. GRB 241029A: TRT optical afterglow candidate detection
  11. GRB 241029A: Swift ToO observations
  12. GRB 241029A: SVOM/GRM observation
  13. GRB 241029A : Detection and localization of a bright long GRB by SVOM/ECLAIRs
  14. GRB 240821A: Keck/LRIS spectroscopic observations
  15. EP241021a: Gemini-South detection of optical rebrightening
  16. GRB 241026A: the 100th GRB detected by GRBAlpha
  17. GRB 241026A: TNOT optical counterpart detection
  18. Konus-Wind detection of GRB 241025A
  19. GRB 241025A (EP241025a): Optical afterglow observations with the Tsinghua-Nanshan Optical Telescope
  20. GRB 241026A: LBT redshift confirmation
  21. GRB 241026A: GECAM detection
  22. GRB 241025A: further SAO RAS optical observations
  23. GRB 241026A: BTA and Zeiss-1000 optical observations
  24. GRB 241026A: SVOM/GRM observation
  25. EP241026B: GROWTH-India Telescope optical upper limit
  26. GRB 241025A: Swift/UVOT Detection
  27. GRB 241026A: GROWTH-India Telescope optical observations
  28. GRB 241026A Fermi GBM Analysis
  29. GRB 241026A: BTA redshift identification of z = 2.79
  30. GRB 241026A: J-band observations with WINTER
  31. GRB 241025A: SAO RAS optical observations
  32. GRB 241026A: Las Cumbres optical detection
  33. GRB 241025A: Mondy optical observations
  34. EP241021a: SOAR observations of the optical counterpart
  35. EP241021a: further SAO RAS optical observations
  36. EP241026a (GRB 241026A): EP on-board trigger and follow-up observation
  37. EP 241026b: LBT optical observations
  38. EP241021a: e-MERLIN radio observation
  39. EP EP241026b: Global MASTER-Net observations report
  40. GRB 241026A: KAIT optical observations
  41. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  42. GRB 241026A: SAO RAS observations of possible optical afterglow
  43. Fermi GRB 241026A: Global MASTER-Net observations report
  44. GRB241025A: 1.3m DFOT optical afterglow detection
  45. EP241021a: optical follow-up observations with Xinglong Observatory
  46. ​GRB 241025A: optical photometry from Konkoly
  47. GRB 241025A: GROWTH-India Telescope optical observations
  48. GRB 241025A: COLIBRÍ Detection of the Afterglow
  49. GRB 241025C: Fermi GBM Detection
  50. GRB 241025A: Fermi GBM Observation
  51. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  52. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  53. EP241021a: Optical and NIR observations of counterpart with the Fraunhofer Telescope at Wendelstein Observatory
  54. EP 241021a: Swift-XRT observations
  55. EP241021a: optical follow-up observations with the Liverpool Telescope
  56. Fermi GRB 241025A: Global MASTER-Net observations report
  57. Swift GRB 241025A: Global MASTER-Net observations report
  58. EP241025a (GRB 241025A): EP observations update
  59. GRB 241025A : SVOM/VT optical afterglow observations
  60. EP 241021A: Swift ToO observations
  61. EP241021a: Liverpool Telescope optical follow-up observations
  62. GRB 241001A: JWST spectroscopic identification of a supernova counterpart
  63. GRB 241025A: NOT spectroscopic redshift of z = 4.20
  64. GRB 241025A: DDOTI Afterglow detection
  65. EP241025a (GRB 241025A): EP on-board trigger and autonomous follow-up observation
  66. GRB 241025A: SVOM/GRM observation
  67. GRB 241025A: TRT optical afterglow observation
  68. Fermi GRB 241024B: Global MASTER-Net observations report
  69. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  70. GRB 241001A: ATCA radio observations
  71. EP241021a: No Detection in Fermi-GBM Observation
  72. GRB 241010A: VIRT Optical Upper Limit
  73. EP241021a: VLT/FORS2 redshift z = 0.75
  74. EP241021a: SAO RAS optical observations
  75. EP241021a: KAIT optical observations
  76. EP241021a: EP-FXT follow-up observation update
  77. IPN triangulation of GRB 241021A (long)
  78. EP241021a: Optical counterpart observations with the Liverpool Telescope
  79. EP241021a: 1.3m DFOT Optical observations
  80. EP241021a: GSP detects optical candidate counterpart
  81. EP241021a: Optical upper limits with Kinder observations
  82. EP241021a: TRT optical observations
  83. GRB 241018A: SVOM/C-GFT optical observations
  84. EP241021a: NOT likely optical counterpart
  85. EP EP241021a: Global MASTER-Net observations report
  86. GRB241017A: 1.3m DFOT optical upper limit
  87. GRB 241018A: 1.3m DFOT Optical upper limit
  88. GRB 241018A: EP-FXT afterglow detection
  89. EP241021a: GOTO optical upper limits
  90. Konus-Wind detection of GRB 241018A
  91. GRB 241018A: SVOM/GRM observation
  92. GRB 241018A/sb24101802: Mephisto optical upper limit
  93. GRB 241017A/sb24101702: Mephisto optical upper limit
  94. GRB 241018A: Mondy optical upper limit
  95. GRB 241018A: SVOM/VT further analysis and counterpart confirmed
  96. GRB 241018A: GROWTH-India telescope optical upper limit
  97. GRB241018A: XingLong Optical Upper Limit
  98. GRB 241018A: REM optical/NIR upper limits
  99. GRB 241018A: NOT optical observations
  100. GRB 241017A: SVOM/VT follow-up and optical upper limit

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