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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"

19195 results found.

  1. GRB 250818B: Keck redshift of the optical afterglow
  2. GRB 250818A: Swift/UVOT Upper Limits
  3. GRB 250818A: Enhanced Swift-XRT position
  4. GRB 250818A: Fermi GBM Observation
  5. GRB 250818B: SVOM/VT optical observation
  6. GRB 250814A: Further GRAWITA TNG NIR observations
  7. GRB 250818B: Swift-XRT afterglow detection
  8. GRB 250818A: Swift detection of a burst
  9. sb25081602: Swift-XRT observations
  10. GRB 250814A: Swift-BAT refined analysis
  11. GRB 250814A: Further COLIBRÍ optical upper limit
  12. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  13. GRB 250814A: GRAWITA TNG NIR observations
  14. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  15. GRB250814A: TRT optical upper limits
  16. GRB 250814C: SVOM/GRM observation of a short burst
  17. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  18. GRB 250813B: SVOM/GRM observation
  19. GRB 250814A: P200/WIRC observations of the afterglow candidate
  20. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  21. GRB 250814A: KAIT optical upper limit
  22. GRB 250814A: Swift-XRT refined Analysis
  23. GRB 240814A: Fermi GBM Observation
  24. GRB 250814A: Possible afterglow candidate from P200/WIRC
  25. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  26. Swift GRB250814.32: Global MASTER-Net observations report
  27. GRB 250814A: J-band upper limit from WINTER
  28. GRB 250813B: SVOM/VT optical observations
  29. GRB 250814A: COLIBRÍ optical upper limit
  30. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  31. GRB 250814A: DDOTI Optical Upper Limit
  32. GRB 250813B: Swift-XRT afterglow detection
  33. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  34. EP250812a: NOT, NTT, and GS observations
  35. GRB 250812A: Swift/UVOT Detection
  36. EP250812a: SVOM/VT optical counterpart
  37. GRB 250812A: Swift ToO observations
  38. GRB 250807B: Swift-BAT refined analysis
  39. EP 250812a: GOTO optical upper limit
  40. GRB 250812A: Kilonova-Catcher optical afterglow detection
  41. EP250812a: Swift-XRT counterpart detection
  42. GRB 250812A: SVOM/VT optical afterglow confirmation
  43. GRB 250812A: Swift-XRT afterglow detection
  44. GRB 250809A: Swift-BAT refined analysis
  45. GRB 250807A: Swift-BAT refined analysis
  46. GRB 250809A: Swift/UVOT Detection
  47. Corrected Swift-XRT Refined Analysis of GRB 250809A
  48. GRB 250809A: Swift-XRT refined Analysis
  49. GRB 250807B: SVOM/VT optical observation
  50. GRB 250809A: LCOGT Optical Upper Limits
  51. GRB 250702B: Chandra X-ray Detection
  52. GRB 250808A: VLT X-shooter candidate counterpart
  53. GRB 250809A: Prompt enhanced Swift-XRT position
  54. GRB 250809A: Swift detection of a gamma ray burst
  55. GRB 250808A: Swift-XRT candidate counterpart detection
  56. GRB 250807A: SVOM/VT optical continued observation
  57. Konus-Wind detection of GRB 250807A
  58. GRB 250807B: Swift/UVOT Detection
  59. GRB 250807B: Kilonova-Catcher optical afterglow detection
  60. GRB 250807A: Swift/UVOT Detection
  61. GRB 250807A: Swift-XRT refined Analysis
  62. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  63. GRB 250806A: SVOM/MXT refined analysis
  64. GRB 250806A: SVOM/ECLAIRs refined analysis
  65. GRB 250807A: SVOM/GRM observation
  66. Swift GRB250807.45: Global MASTER-Net observations report
  67. GRB 250807A: AstroSat CZTI detection of bright long burst
  68. GRB 250807B: Swift-XRT refined Analysis
  69. GRB 250807B: NTT optical observations
  70. GRB 250807A: SVOM/VT optical observation
  71. GRB 250807B: Enhanced Swift-XRT position
  72. Swift GRB250807.65: Global MASTER-Net observations report
  73. GRB 250807A: Enhanced Swift-XRT position
  74. GRB 250807B: Swift detection of a burst with an optical counterpart.
  75. GRB 250805A: Kilonova-Catcher optical upper limits
  76. GRB 250805A: Swift/UVOT Upper Limits
  77. GRB 250806A: Swift/UVOT U-band detection
  78. GRB 250807A: Swift detection of a burst with an optical counterpart
  79. GRB 250806A: EP-FXT observation
  80. EP#01709198415/EP250806a: Swift-XRT observations
  81. GRB 250805A: Swift-BAT refined analysis
  82. GRB 250806A: KAIT optical upper limit
  83. GRB 250806A: SVOM/VT refined analysis
  84. GRB 250806A: Swift-XRT counterpart detection
  85. GRB 250805A: SVOM/VT optical counterpart
  86. GRB 250805A: ESO/VLT observations
  87. GRB 250805A: Swift-XRT refined Analysis
  88. GRB 250804B: Swift-XRT observations
  89. GRB 250805A: Enhanced Swift-XRT position
  90. GRB 250805A: TRT optical upper limits
  91. GRB 250805A: Swift-XRT observations
  92. GRB 250805A: Swift detection of a burst
  93. Swift GRB250805.26: Global MASTER-Net observations report
  94. GRB 250804B: Tiled Swift observations
  95. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  96. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  97. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  98. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  99. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  100. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO

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