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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"

35431 results found.

  1. GRB 250327B: J-band observations with WINTER
  2. GRB 250327B: MASTER detection of OT rebrightening
  3. GRB 250327B: LCO optical counterpart detection
  4. GRB 250328A: GWAC-F50A optical upper limit
  5. GRB 250328A: SVOM detection of a burst
  6. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  7. GRB 250327B: CrAO and SAO RAS Optical Observations
  8. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  9. GRB 250327B: further optical observations by LCOGT
  10. GRB 250327b: Liverpool Telescope optical observations
  11. GRB 250322A: GRANDMA/TNOT optical upper limits
  12. GRB 250327A: SVOM/VT upper limits on the XRT position
  13. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  14. GRB 250327B: Las Cumbres optical counterpart detection
  15. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  16. GRB 250327B: 1.6m Mephisto optical observations
  17. GRB 250327B: NOT spectroscopic redshift z = 3.035
  18. GRB 250327A: Swift-XRT refined Analysis
  19. GRB 250327B: GOTO optical counterpart detection
  20. GRB 250327B: SVOM/VT optically bright counterpart
  21. GRB 250327B: SAO RAS optical candidate
  22. GRB 250327B: SVOM detection of a burst
  23. GRB 250327A: J-band observations with WINTER
  24. GRB 250327A: SVOM/VT optical candidate
  25. GRB 250327A: Fermi GBM observation
  26. Fermi GRB 250327A: Global MASTER-Net observations report
  27. Swift GRB 250327A: Global MASTER-Net observations report
  28. GRB 250327A: DDOTI Optical Observations
  29. GRB 250327A: COLIBRÍ optical upper limit
  30. GRB 250327A: Swift detection of a burst
  31. GRB 250327A: Fermi GBM Final Real-time Localization
  32. Konus-Wind detection of GRB 250322A (short)
  33. IPN triangulation of GRB 250322B
  34. EP250321a: Mondy AZT-33IK Continued Optical Observations
  35. GRB 250322A: third epoch of NOT optical observations
  36. GRB 250322A: Swift-BAT refined analysis
  37. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  38. GRB 250322A: further NOT optical observations
  39. GRB 250322A: Swift/UVOT Upper Limits
  40. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  41. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  42. GRB 250321B: Swift-XRT observations
  43. GRB 250322A: Swift-XRT refined Analysis
  44. GRB 250322A: Gemini-North redshift of candidate host galaxy
  45. GRB 250322A: AstroSat CZTI detection of a short burst
  46. GRB 250322B: AstroSat CZTI detection of a bright long burst
  47. GRB250322A: STEP/T80S optical limits
  48. GRB 250322A: Gemini-South optical observations
  49. GRB 250322A: VLT optical observations
  50. GRB 250322A: VLT near-infrared observations
  51. GRB 250322A: NOT optical upper limits
  52. GRB 250322A: Enhanced Swift-XRT position
  53. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  54. GRB 250322A: MASTER optical observation
  55. EP250321a: Mondy AZT-33IK Optical Observations
  56. GRB 250322A: Swift detection of a short burst
  57. EP250321a: KAIT optical observations
  58. GRB 250225B: GECAM-A detection
  59. GRB 250312A: GECAM-A detection
  60. GRB 250321B: Swift ToO observations
  61. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  62. GRB 250321C: Fermi GBM Final Real-time Localization
  63. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  64. GRB 250320B: Fermi GBM Observation
  65. GRB 250321A: Swift-BAT refined analysis
  66. GRB 250321A: Swift-XRT refined Analysis
  67. GRB 250320B: Fermi-LAT detection
  68. GRB 250321B: SVOM detection of a sub-threshold transient event
  69. EP 250321A: Optical counterpart detection by LCO.
  70. GRB 250321A: Swift/UVOT Upper Limits
  71. GRB 250320B: SVOM/GRM observation of a long burst
  72. GRB 250320B: AstroSat CZTI detection
  73. Fermi GRB 250320B: Global MASTER-Net observations report
  74. Swift GRB 250321A: Global MASTER-Net observations report
  75. Fermi GRB 250321A: Global MASTER-Net observations report
  76. GRB 250321A: GOTO optical upper limits
  77. GRB 250321A: Swift-XRT localisation
  78. GRB 250314A: Keck/NIRC2 J-band upper limit
  79. EP250226a/GRB 250226A: KAIT optical observations
  80. GRB 250321A: Fermi GBM Observation
  81. GRB 250321A: Swift detection of a burst
  82. GRB 250321A: Fermi GBM Final Real-time Localization
  83. GRB 250320B: Fermi GBM Final Real-time Localization
  84. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  85. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  86. GRB 250320A: Fermi GBM Final Real-time Localization
  87. Fermi GRB 250319B: Global MASTER-Net observations report
  88. GRB 250313A: GRBAlpha detection
  89. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  90. GRB 250319B: Fermi GBM Final Localization
  91. GRB 250319A: Fermi GBM Final Localization
  92. GRB 250317D: EIRSAT-1 GMOD Detection
  93. GRB 250314A: ATCA radio upper limits
  94. GRB 250317B: OHP/T193 continued follow-up
  95. GRB 250317C: SVOM/GRM observation of a long burst
  96. GRB 250317B: Leavitt Observatory optical upper limit
  97. GRB 250309B/AT2025dws: further ATCA observations
  98. GRB 250317B: Mondy AZT-33IK Optical Observations
  99. GRB 250317C: AstroSat CZTI detection
  100. GRB 250317B: NOT optical observations suggest an optical plateau phase

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