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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"

183 results found.

  1. EP260806a: NUTTELA-TAO optical observations
  2. EP260806a: MAO/AZT-22 optical observations
  3. GRB260808B: MAO/AZT-22 optical observations
  4. GRB260809A: MAO/AZT-22 optical observations
  5. EP260727a: NUTTELA-TAO Early Optical Limits
  6. GRB 260727A: Kilonova-Catcher optical upper limit
  7. GRB 260718A: LCO optical upper limits
  8. GRB 260718A : GRANDMA and KNC upper limits
  9. GRB 260708A: GRANDMA Optical Observations
  10. GRB 260706A : GRANDMA Upper limits
  11. GRB 260708A: Kilonova-Catcher optical afterglow detection
  12. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  13. GRB 260619A: Kilonova-Catcher optical upper limit
  14. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  15. GRB 260610B / AT2026owq: GRANDMA optical observations
  16. GRB 260604C: GRANDMA further observations
  17. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  18. GRB 260604C: GRANDMA observations
  19. GRB 260604C: Kilonova-Catcher optical afterglow detection
  20. GRB 260603A: Kilonova-Catcher optical upper limit
  21. GRB 260421B: radio detection with the VLA
  22. GRB 260421B: Kilonova-Catcher optical afterglow detection
  23. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  24. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  25. GRB 260402A: Kilonova-Catcher optical upper limit
  26. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  27. EP260213a: NUTTelA-TAO Early Optical Limits
  28. GRB 251222A: radio detection with the VLA
  29. GRB 260109C: Kilonova-Catcher optical upper limit
  30. GRB 251230A: GRANDMA/TAROT Early Detection
  31. GRB 251222A: NUTTelA-TAO Early Measurements
  32. GRB 251205A: Kilonova-Catcher optical afterglow detection
  33. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  34. GRB 251201B: Kilonova-Catcher optical afterglow detection
  35. GRB 251126A: Kilonova-Catcher optical afterglow detection
  36. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  37. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  38. GRB 251106A: Kilonova-Catcher optical upper limit
  39. GRB 251103A: Kilonova-Catcher optical afterglow detection
  40. GRB 251025B: Kilonova-Catcher optical afterglow detection
  41. GRB 251013C: Kilonova-Catcher optical afterglow detection
  42. GRB 251003A: Kilonova-Catcher optical afterglow detection
  43. GRB 251002A: Kilonova-Catcher optical afterglow detection
  44. GRB 250924A: Kilonova-Catcher optical afterglow detection
  45. GRB 250920C: Kilonova-Catcher optical afterglow detection
  46. GRB 250821A: Kilonova-Catcher optical upper limits
  47. GRB 250818B: Kilonova-Catcher optical afterglow detection
  48. GRB 250812A: Kilonova-Catcher optical afterglow detection
  49. GRB 250807B: Kilonova-Catcher optical afterglow detection
  50. GRB 250805A: Kilonova-Catcher optical upper limits
  51. GRB 250806A: Kilonova-Catcher optical upper limits
  52. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  53. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  54. GRB 250704A: GRANDMA observations
  55. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  56. GRB 250702F: GRANDMA observations
  57. GRB 250702F: Kilonova-Catcher optical afterglow detection
  58. GRB 250615A: Kilonova-Catcher optical upper limits
  59. GRB 250617B: Kilonova-Catcher optical afterglow detection
  60. GRB 250424A: Kilonova-Catcher optical afterglow detection
  61. GRB 250327B: Kilonova-Catcher Observations
  62. GRB 250322A: GRANDMA/TNOT optical upper limits
  63. GRB 250226A: GRANDMA Optical Observations
  64. GRB 250221A: GRANDMA/TAROT Detection
  65. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  66. GRANDMA/OPD observations of GRB250215A
  67. GRB 250129A: GRANDMA Continued Afterglow Detection
  68. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  69. GRB 250129A: COLIBRÍ Optical Observations
  70. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  71. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  72. GRB 241217A / EP241217B: GRANDMA/T1MPicduMidi optical upperlimits
  73. GRB 241217A: GRANDMA/TAROT optical upperlimits
  74. GRB 241209B: GRANDMA/TRT upper limit
  75. GRB 241209D: COLIBRÍ detection of the afterglow
  76. GRB 241209A: COLIBRÍ Optical Upper Limit
  77. GRB 241209A: GRANDMA/TAROT upper limit
  78. GRB 241128A : RAPAS follow-up observations
  79. GRB 241113B : RAPAS follow-up observation
  80. LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
  81. GRB 241128A: GRANDMA and Kilonova-Catcher Optical Afterglow Detections and Upperlimits
  82. LIGO/Virgo S241127aj: GRANDMA/FRAM-CTA-N Observations
  83. GRB 241127A: GRANDMA and Kilonova-Catcher optical afterglow detections
  84. LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on Optical Counterparts to Two of the Swift/XRT Sources
  85. LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on a Optical Counterpart at the BAT Position
  86. GRB 241108A: Further COLIBRÍ Upper Limits on the Optical Counterpart
  87. GRB 241108A: COLIBRÍ Upper Limits on the Optical Counterpart
  88. GRB241030B: GRANDMA/TAROT Upper Limit
  89. GRB 241025A: GRANDMA and Kilonova-Catcher optical afterglow detections and upperlimits
  90. GRB 241006A: VIRT Optical Upper Limit
  91. GRB 241009A: GRANDMA optical upper limits
  92. GRB 241006A: GRANDMA optical upper limits
  93. GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits
  94. GRB 240828B: GRANDMA Optical Upper Limit
  95. GRB240824A: GRANDMA/TAROT-TCA Upper Limit
  96. GRB 240821A: Colibri Optical Upper Limit
  97. GRB 240821A: GMG Optical Upper Limit
  98. GRB 240821A: GRANDMA/LesMakes-T60 Upper Limit
  99. GRB 240809A : RAPAS follow-up observations
  100. EP240801a: GRANDMA and Kilonova-Catcher optical observations

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