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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"

11049 results found.

  1. IPN triangulation of GRB 250222A
  2. GRB 250226A: GRANDMA Optical Observations
  3. Fermi GRB 250302A: Global MASTER-Net observations report
  4. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 250302A: Fermi GBM Final Real-time Localization
  6. GRB 250228A: Fermi GBM Final Localization
  7. Konus-Wind detection of GRB 250226A
  8. GRB 250225B: EIRSAT-1 GMOD Detection
  9. GRB 250226A: KAO Optical Upper Limit
  10. GRB 250226A: AbAO AS-32 Optical Upper Limit
  11. EP250223A: Upper limits from Fermi-GBM Observations
  12. GRB 250226A: Fermi GBM Observation
  13. GRB 250226A / EP250226a: LCO detection of the afterglow
  14. GRB 250205A / EP250205A: further radio observations with the VLA
  15. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  16. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  17. GRB 250225B: INTEGRAL SPI-ACS detection
  18. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  19. EP250226a / GRB 250226A: SVOM/VT optical observations
  20. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  21. EP250226a/GRB 250226A: 1.6m Mephisto observations
  22. EP250226a/GRB 250226A: Kinder optical follow-up observations
  23. Fermi GRB 250226B: Global MASTER-Net observations report
  24. GRB 250226B: Fermi GBM Final Real-time Localization
  25. GRB 250225B: Fermi GBM Observation
  26. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  27. GRB 250225B: SVOM/GRM observation of a long burst
  28. GRB 250226A: GECAM-B detection
  29. GRB 250214A: SVOM/GRM observation
  30. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  31. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  32. EP250226a / GRB 250226A: TRT optical counterpart observation
  33. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  34. Fermi GRB 250226A: Global MASTER-Net observations report
  35. Fermi trigger No 762205158: Global MASTER-Net observations report
  36. GRB 250226A: Fermi GBM Final Real-time Localization
  37. Fermi GRB 250225A: Global MASTER-Net observations report
  38. GRB 250223C: SVOM/GRM observation of a long burst
  39. EP250215A: J band upper limit by SYSU 80cm telescope
  40. GRB 250225A: Fermi GBM Final Real-time Localization
  41. GRB 250207a: ATCA Radio Upper Limits
  42. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  43. GRB 250119B: VZLUSAT-2 detection
  44. GRB 250223C: Fermi GBM Final Real-time Localization
  45. GRB 250202B: VZLUSAT-2 detection
  46. GRB 250210A: VZLUSAT-2 detection
  47. GRB 250206A: VZLUSAT-2 detection
  48. GRB 250223B: Fermi GBM Final Localization
  49. Fermi GRB 250223A: Global MASTER-Net observations report
  50. Fermi trigger No 762020305: Global MASTER-Net observations report
  51. GRB 250223A: Fermi GBM Final Real-time Localization
  52. Fermi trigger No 761805304: Global MASTER-Net observations report
  53. Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
  54. Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
  55. GRB 250220B: Fermi GBM Final Real-time Localization
  56. Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
  57. GRB 250220A: Fermi GBM Final Real-time Localization
  58. Konus-Wind detection of GRB 250217C (short)
  59. Konus-Wind detection of GRB 250215A / EP250215a
  60. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  61. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  62. GRB 250217C: SVOM/GRM observation
  63. GRB 250217C: Fermi GBM Observation
  64. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  65. IPN triangulation of GRB 250217C (short)
  66. GRB 250216A: AstroSat CZTI detection
  67. GRB 250217C: AstroSat CZTI detection of a short burst
  68. Fermi GRB 250217C: Global MASTER-Net observations report
  69. GRB 250217C: Fermi GBM Final Real-time Localization
  70. Fermi GRB 250217A: Global MASTER-Net observations report
  71. GRANDMA/OPD observations of GRB250215A
  72. GRB 250217B: Fermi GBM Final Real-time Localization
  73. GRB 250217A: Fermi GBM Final Real-time Localization
  74. Fermi GRB 250216A: Global MASTER-Net observations report
  75. GRB 250215A / EP250215a: LCO detection of the afterglow
  76. GRB 250216A: Fermi GBM Final Real-time Localization
  77. GRB 250215A: Swift/UVOT Upper Limits
  78. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  79. EP250215a / GRB 250215A : GTC redshift z = 4.61
  80. GRB 250215A: Fermi GBM Observation
  81. EP250215a / GRB 250215A : NOT optical observations
  82. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  83. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  84. GRB 250215A: Swift-XRT refined Analysis
  85. GRB 250215A: SVOM/GRM observation
  86. EP250215a / GRB 250215A: AstroSat CZTI detection
  87. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  88. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  89. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  90. Fermi GRB 250215A: Global MASTER-Net observations report
  91. GRB 250215A: Fermi GBM Final Real-time Localization
  92. Fermi trigger No 761206993: Global MASTER-Net observations report
  93. Fermi Gamma-ray Burst Monitor trigger 761206993/250214266 is not a GRB
  94. Fermi GRB 250214A: Global MASTER-Net observations report
  95. GRB 250214A: Fermi GBM Final Real-time Localization
  96. GRB 250210A: GRBAlpha detection
  97. Fermi GRB 250212A: Global MASTER-Net observations report
  98. Fermi trigger No 760945500: Global MASTER-Net observations report
  99. GRB 250212A: Fermi GBM Final Real-time Localization
  100. GRB 250207A: Fermi GBM Observation

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