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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"

12058 results found.

  1. EP250223A: Upper limits from Fermi-GBM Observations
  2. EP250227a: TRT optical upper limit
  3. GRB 250225B: VLT/HAWKI near-infrared observations
  4. EP250227a: Optical upper limits with Kinder observations
  5. EP250225a: EP-FXT follow-up observation
  6. EP250223a: J band upper limit by SYSU 80cm telescope
  7. EP250228a: Global MASTER-Net observations report
  8. GRB 250205A / EP250205A: further radio observations with the VLA
  9. EP250225a: TRT optical upper limits
  10. EP250226a/GRB 250226A: 1.6m Mephisto observations
  11. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  12. Fermi GRB 250226B: Global MASTER-Net observations report
  13. GRB 250221A: ATCA Detections and Upper Limits
  14. GRB 250225B: REM NIR upper limits
  15. Konus-Wind detection of GRB 250225B
  16. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  17. EP250226a: Global MASTER-Net observations report
  18. Swift GRB 250225B: Global MASTER-Net observations report
  19. Fermi GRB 250226A: Global MASTER-Net observations report
  20. Fermi trigger No 762205158: Global MASTER-Net observations report
  21. EP250225a: Global MASTER-Net observations report
  22. EP250225a: GSP optical upper limit
  23. Fermi GRB 250225A: Global MASTER-Net observations report
  24. EP250215A: J band upper limit by SYSU 80cm telescope
  25. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  26. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  27. GRB 250207a: ATCA Radio Upper Limits
  28. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  29. EP250223a: REM NIR upper limit
  30. EP250223a: 1.6m Mephisto and 50cm array observations
  31. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  32. EP250223a: Global MASTER-Net observations report
  33. Fermi GRB 250223A: Global MASTER-Net observations report
  34. Fermi trigger No 762020305: Global MASTER-Net observations report
  35. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  36. EP250220a: FTW optical and NIR observations and upper limits
  37. EP250220a: EP-FXT follow-up observations
  38. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  39. Fermi trigger No 761805304: Global MASTER-Net observations report
  40. GRB 250221A: 1.6m Mephisto optical detection
  41. GRB 250221A: AKO Optical Upper Limit
  42. GRB 250221A: Swift/UVOT Detection
  43. EP250220a: Liverpool Telescope upper limits
  44. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  45. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  46. EP250220a: 1.6m Mephisto observations
  47. EP250220a: Liverpool Telescope optical upper limits
  48. EP250220a: Optical upper limit with Kinder observations
  49. Swift GRB250221.15: Global MASTER-Net OT detection
  50. Swift GRB250221.15: Global MASTER-Net observations report
  51. EP250220a: Xinglong optical upper limit
  52. EP250220a: Global MASTER-Net observations report
  53. GRB 250219A: Swift/UVOT Upper Limits
  54. GRB 250219A: OHP/T193 optical upper limit
  55. GRB 250219A: 1.6m Mephisto optical upper limits
  56. GRB 250219A: Swift-XRT observations
  57. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  58. GRB 250217C: Swift-XRT observations
  59. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  60. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  61. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  62. GRB 250213A: Swift-XRT observations
  63. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  64. Fermi GRB 250217C: Global MASTER-Net observations report
  65. IceCube-Cascade 250215A: Upper limits from a search for additional neutrino events in IceCube
  66. Fermi GRB 250217A: Global MASTER-Net observations report
  67. GRANDMA/OPD observations of GRB250215A
  68. Fermi GRB 250216A: Global MASTER-Net observations report
  69. EP250212a: FTW optical and NIR upper limits
  70. GRB 250215A: Swift/UVOT Upper Limits
  71. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  72. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  73. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  74. EP250215a: Global MASTER-Net observations report
  75. Fermi GRB 250215A: Global MASTER-Net observations report
  76. Fermi trigger No 761206993: Global MASTER-Net observations report
  77. EP250207b: Xinglong optical upper limit
  78. Fermi GRB 250214A: Global MASTER-Net observations report
  79. EP250212a: Xinglong optical upper limit
  80. EP250212a: Global MASTER-Net observations report
  81. GRB 250205A: VIRT Optical Upper Limit
  82. GRB 250205A: Leavitt Observatory optical upper limit
  83. EP250207b: VLA radio upper limits
  84. EP250212a: Liverpool Telescope optical upper limits
  85. EP250212a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  86. GRB250101A: Radio upper limits from GMRT observations
  87. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  88. Fermi GRB 250212A: Global MASTER-Net observations report
  89. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  90. Fermi trigger No 760945500: Global MASTER-Net observations report
  91. Integral GRB250211.89: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  93. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  94. Konus-Wind detection of GRB 250206A
  95. EP250207b: Global MASTER-Net observations report
  96. GRB 241128A: VIRT Optical Upper Limit
  97. EP250207A: Upper limits from Fermi-GBM Observations
  98. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  99. Fermi GRB 250210A: Global MASTER-Net observations report
  100. LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations

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