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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"

26037 results found.

  1. GRB 260924A: COLIBRÍ optical observations
  2. GRB 260924A: Second-epoch J-band upper limit from the SYSU 80 cm infrared telescope
  3. GRB 260925A: J-band upper limit by SYSU 80cm infrared telescope
  4. GRB 260925A: Swift-XRT refined Analysis
  5. Swift Trigger 1513439 is probably not a GRB
  6. GRB 260925A: Swift/UVOT Upper Limits
  7. Konus-Wind detection of GRB 260924A
  8. GRB 260922A: Glowbug gamma-ray detection
  9. GRB 260925A: Enhanced Swift-XRT position
  10. GRB 260925A: COLIBRÍ optical upper limits
  11. GRB 260925A: FRAM-Auger optical limit
  12. GRB 260924A: Ondrejov D50 optical afterglow detection
  13. GRB 260924A: SVOM/GRM observation
  14. GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
  15. GRB 260925A: Swift detection of a burst
  16. GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
  17. GRB 260924A: Swift/UVOT Detection
  18. GRB 260924A: Swift-BAT refined analysis
  19. GRB 260924A: NuSTAR detection of prompt emission
  20. GRB 260924A: Swift/UVOT Upper Limits
  21. GRB 260924A: Swift-XRT refined Analysis
  22. Konus-Wind detection of GRB 260922A
  23. GRB 260922A: NuSTAR detection of prompt emission
  24. GRB 260921A: NuSTAR detection of prompt emission
  25. GRB 260921A: SVOM/GRM observation
  26. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  27. GRB 260924A: Fermi GRB Observation
  28. Konus-Wind detection of GRB 260921A (possible merger-origin)
  29. GRB 260924A: Fermi-LAT detection of a bright burst
  30. GRB 260924A: AstroSat CZTI detection
  31. GRB 260924A: NOT optical counterpart confirmation
  32. GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
  33. GRB 260922A: CALET Gamma-Ray Burst Monitor detection
  34. GRB 260924A: Enhanced Swift-XRT position
  35. GRB 260924A: Swift detection of a burst
  36. Trigger_21914: Swift ToO observations
  37. GRB 260922A: Ondrejov D50 optical limit
  38. ATCA observations of GRB 260909A
  39. GRB 260922A: Swift-BAT refined analysis
  40. EP260920a: VLT/HAWK-I near-infrared counterpart confirmation
  41. GRB 260922A: Swift/UVOT Upper Limits
  42. GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
  43. GRB 260922A: COLIBRÍ optical upper limits
  44. GRB 260922A: Swift-XRT refined Analysis
  45. GRB 260922A: Enhanced Swift-XRT position
  46. Fermi-LAT Gamma-ray Observations of IceCube-260805A
  47. GRB 260922A: SVOM/C-GFT optical upper limit
  48. GRB 260922A: Swift detection of a burst
  49. GRB 260921A: AstroSat CZTI detection
  50. GRB 260921A: Swift-BAT refined analysis
  51. GRB 260921A: Fermi GBM Observation
  52. EP260920b: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  53. Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
  54. Swift GRB 260921A: Global MASTER-Net observations report
  55. GRB 260921A: Swift detection of a burst
  56. EP260920b: VLT/X-shooter spectroscopic redshift z = 3.582
  57. GRB 260915A: VLT optical and near-infrared upper limits
  58. GRB 260915A: Swift-XRT afterglow detection
  59. GRB 260914A: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  60. GRB 260909A: NOEMA detection
  61. GRB 260909A: Swift-XRT observations
  62. GRB 260915A: Swift ToO observations
  63. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  64. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  65. GRB 260914A: SVOM/VT optical observation from VHF data
  66. GRB 260818A: Continued ATCA observations
  67. GRB 260909A: Swift ToO observations
  68. GRB 260903A: Swift-XRT observations
  69. GRB 260909A: OHP/T193 z-band upper limit
  70. EP260806a: NOEMA detection
  71. EP260623a: NOEMA detections
  72. GRB 260909A: Mondy optical observations and afterglow candidate
  73. GRB 260903A: Swift ToO observations
  74. GRB 260903A: OHP/T193 optical afterglow detection
  75. GRB 260903A: NOT optical observations and afterglow fading
  76. GRB 260818A: ATCA detection of a candidate radio counterpart
  77. NuSTAR 260828: a 1100s hard X-ray transient
  78. GRB 260818B: 6 GHz VLA observations
  79. GRB 260807A: EP-FXT follow-up observations
  80. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  81. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  82. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  83. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  84. GRB 260808B: SVOM/VT optical re-brightening at day 3
  85. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  86. GRB 260809A: NOT optical observations
  87. GRB260809A: MAO/AZT-22 optical observations
  88. GRB260809A: OHP/T193 optical observations
  89. GRB 260808B: NOT optical observations
  90. GRB260808B: OHP/T193 optical observations
  91. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  92. GRB 260808B: SVOM/VT optical afterglow confirmation
  93. SN 2026stf / GRB 260708A: ATLAS forced photometry
  94. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  95. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  96. EP260623a: KAIT optical observations
  97. GRB 260708A: GRANDMA Optical Observations
  98. GRB 260708A: Kilonova-Catcher optical afterglow detection
  99. Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
  100. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B

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