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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"

16760 results found.

  1. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  2. GRB 250814A: Swift/UVOT Upper Limits
  3. GRB 250813B: Swift/UVOT Upper Limit
  4. IPN triangulation of GRB 250816A (short)
  5. IPN triangulation of GRB 250814C (short)
  6. IPN triangulation of GRB 250804B (short)
  7. GRB 250818B: Kilonova-Catcher optical afterglow detection
  8. GRB 250818B: Swift/UVOT Detection
  9. GRB 250818B: SAO RAS optical observations
  10. GRB 250818B: EP-FXT counterpart detection
  11. GRB 250818B: KAIT optical observations
  12. GRB 250818A: Swift/UVOT Upper Limits
  13. GRB 250818A: Enhanced Swift-XRT position
  14. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  15. GRB 250814A: Further GRAWITA TNG NIR observations
  16. GRB 250818A: Swift detection of a burst
  17. GRB 250816A: SVOM/GRM observation of a short burst
  18. GRB 250813B: Liverpool Telescope optical upper limits
  19. GRB 250814A: Further COLIBRÍ optical upper limit
  20. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  21. GRB 250814A: GRAWITA TNG NIR observations
  22. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  23. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  24. GRB250814A: TRT optical upper limits
  25. GRB 250814B: SVOM/GRM observation
  26. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  27. GRB 250814A: P200/WIRC observations of the afterglow candidate
  28. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  29. GRB 250814A: KAIT optical upper limit
  30. GRB 250814A: Swift-XRT refined Analysis
  31. GRB 250814A: Possible afterglow candidate from P200/WIRC
  32. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  33. GRB 250814A: J-band upper limit from WINTER
  34. GRB 250813B: NOT observations of the optical afterglow
  35. GRB 250814A: COLIBRÍ optical upper limit
  36. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  37. GRB 250814A: DDOTI Optical Upper Limit
  38. GRB 250813B: EP-FXT counterpart detection
  39. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  40. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  42. GRB 250813B: SVOM detection of a bright long burst
  43. EP250812a: Nickel optical upper limit
  44. EP250812a: NOT, NTT, and GS observations
  45. GRB 250812A: Swift/UVOT Detection
  46. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  47. EP250812a: Liverpool Telescope upper limits
  48. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  49. GRB 250812A: EP-FXT counterpart detection
  50. EP 250812a: GOTO optical upper limit
  51. GRB 250812A: Kilonova-Catcher optical afterglow detection
  52. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. EP250812a: Einstein Probe detection of an X-ray transient
  54. GRB 250812A: Swift-XRT afterglow detection
  55. GRB 250812A: TRT likely optical counterpart detection
  56. GRB 250809A: Swift/UVOT Detection
  57. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  58. GRB 250809A: Swift-XRT refined Analysis
  59. EP250807a: EP-FXT follow-up observation upper limit
  60. GRB 250809A: LCOGT Optical Upper Limits
  61. GRB 250808A: VLT X-shooter candidate counterpart
  62. GRB 250809A: Swift detection of a gamma ray burst
  63. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 250808A: Fermi GBM Observation
  65. GRB 250807B: Swift/UVOT Detection
  66. GRB 250807B: Kilonova-Catcher optical afterglow detection
  67. GRB 250807A: Swift/UVOT Detection
  68. EP250807a: NTT z-band optical upper limit
  69. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  70. GRB 250807A: SVOM/GRM observation
  71. GRB 250807B: Swift-XRT refined Analysis
  72. EP250807a: EP-WXT detection of a fast X-ray transient
  73. EP 250807.979: GOTO optical upper limit
  74. EP250807a: COLIBRÍ optical upper limit
  75. GRB 250807B: Enhanced Swift-XRT position
  76. GRB 250807A: Enhanced Swift-XRT position
  77. GRB 250807B: Swift detection of a burst with an optical counterpart.
  78. GRB 250805A: Kilonova-Catcher optical upper limits
  79. GRB 250805A: Swift/UVOT Upper Limits
  80. GRB 250806A: Swift/UVOT U-band detection
  81. EP250806a: Liverpool telescope optical upper limit
  82. GRB 250807A: Swift detection of a burst with an optical counterpart
  83. GRB 250806A: EP-FXT observation
  84. EP250802a: EP-FXT follow-up observation
  85. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP250806a: SVOM /VT optical candidate
  87. GRB 250806A: J-band upper limit from WINTER
  88. GRB 250806A: KAIT optical upper limit
  89. GRB 250806A: SVOM/VT refined analysis
  90. EP250806a: COLIBRÍ optical upper limit
  91. GRB 250806A: Kilonova-Catcher optical upper limits
  92. EP250806a: Einstein Probe detection of an X-ray transient
  93. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 250806A: SVOM/VT optical upper limit
  95. GRB 250806A: SVOM detection of a soft burst
  96. GRB 250805A: SVOM/VT optical counterpart
  97. GRB 250805A: Enhanced Swift-XRT position
  98. GRB 250804C: AstroSat CZTI detection of a long burst
  99. GRB 250805A: TRT optical upper limits
  100. GRB 250805A: Swift-XRT observations

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