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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"

36143 results found.

  1. GRB 250329B: GWAC-F50A optical upper limit
  2. GRB 250329B: SVOM detection of a faint transient
  3. GRB 250329A: Swift-XRT afterglow detection
  4. GRB 250328A: SVOM/VT optical observation
  5. GRB 250329A: Fading optical counterpart detection by LCO.
  6. GRB 250328A: SVOM/C-GFT optical upper limit
  7. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  8. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  9. GRB 250329A: VLT/X-shooter redshift z = 2.921
  10. GRB 250329A: SVOM/VT optical counterpart confirmation
  11. GRB 250329A: SVOM detection of a burst
  12. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  13. GRB 250327B: J-band observations with WINTER
  14. GRB 250327B: MASTER detection of OT rebrightening
  15. GRB 250327B: LCO optical counterpart detection
  16. GRB 250328A: GWAC-F50A optical upper limit
  17. GRB 250328A: SVOM detection of a burst
  18. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  19. GRB 250327B: CrAO and SAO RAS Optical Observations
  20. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  21. GRB 250327B: further optical observations by LCOGT
  22. GRB 250327b: Liverpool Telescope optical observations
  23. GRB 250322A: GRANDMA/TNOT optical upper limits
  24. GRB 250327A: SVOM/VT upper limits on the XRT position
  25. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  26. GRB 250327B: Las Cumbres optical counterpart detection
  27. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  28. GRB 250327B: 1.6m Mephisto optical observations
  29. GRB 250327B: NOT spectroscopic redshift z = 3.035
  30. GRB 250327A: Swift-XRT refined Analysis
  31. GRB 250327B: GOTO optical counterpart detection
  32. GRB 250327B: SVOM/VT optically bright counterpart
  33. GRB 250327B: SAO RAS optical candidate
  34. GRB 250327B: SVOM detection of a burst
  35. GRB 250327A: J-band observations with WINTER
  36. GRB 250327A: SVOM/VT optical candidate
  37. GRB 250327A: Fermi GBM observation
  38. Fermi GRB 250327A: Global MASTER-Net observations report
  39. Swift GRB 250327A: Global MASTER-Net observations report
  40. GRB 250327A: DDOTI Optical Observations
  41. GRB 250327A: COLIBRÍ optical upper limit
  42. GRB 250327A: Swift detection of a burst
  43. GRB 250327A: Fermi GBM Final Real-time Localization
  44. Konus-Wind detection of GRB 250322A (short)
  45. IPN triangulation of GRB 250322B
  46. EP250321a: Mondy AZT-33IK Continued Optical Observations
  47. GRB 250322A: third epoch of NOT optical observations
  48. GRB 250322A: Swift-BAT refined analysis
  49. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  50. GRB 250322A: further NOT optical observations
  51. GRB 250322A: Swift/UVOT Upper Limits
  52. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  53. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  54. GRB 250321B: Swift-XRT observations
  55. GRB 250322A: Swift-XRT refined Analysis
  56. GRB 250322A: Gemini-North redshift of candidate host galaxy
  57. GRB 250322A: AstroSat CZTI detection of a short burst
  58. GRB 250322B: AstroSat CZTI detection of a bright long burst
  59. GRB250322A: STEP/T80S optical limits
  60. GRB 250322A: Gemini-South optical observations
  61. GRB 250322A: VLT optical observations
  62. GRB 250322A: VLT near-infrared observations
  63. GRB 250322A: NOT optical upper limits
  64. GRB 250322A: Enhanced Swift-XRT position
  65. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  66. GRB 250322A: MASTER optical observation
  67. EP250321a: Mondy AZT-33IK Optical Observations
  68. GRB 250322A: Swift detection of a short burst
  69. EP250321a: KAIT optical observations
  70. GRB 250225B: GECAM-A detection
  71. GRB 250312A: GECAM-A detection
  72. GRB 250321B: Swift ToO observations
  73. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  74. GRB 250321C: Fermi GBM Final Real-time Localization
  75. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  76. GRB 250320B: Fermi GBM Observation
  77. GRB 250321A: Swift-BAT refined analysis
  78. GRB 250321A: Swift-XRT refined Analysis
  79. GRB 250320B: Fermi-LAT detection
  80. GRB 250321B: SVOM detection of a sub-threshold transient event
  81. EP 250321A: Optical counterpart detection by LCO.
  82. GRB 250321A: Swift/UVOT Upper Limits
  83. GRB 250320B: SVOM/GRM observation of a long burst
  84. GRB 250320B: AstroSat CZTI detection
  85. Fermi GRB 250320B: Global MASTER-Net observations report
  86. Swift GRB 250321A: Global MASTER-Net observations report
  87. Fermi GRB 250321A: Global MASTER-Net observations report
  88. GRB 250321A: GOTO optical upper limits
  89. GRB 250321A: Swift-XRT localisation
  90. GRB 250314A: Keck/NIRC2 J-band upper limit
  91. EP250226a/GRB 250226A: KAIT optical observations
  92. GRB 250321A: Fermi GBM Observation
  93. GRB 250321A: Swift detection of a burst
  94. GRB 250321A: Fermi GBM Final Real-time Localization
  95. GRB 250320B: Fermi GBM Final Real-time Localization
  96. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  97. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  98. GRB 250320A: Fermi GBM Final Real-time Localization
  99. Fermi GRB 250319B: Global MASTER-Net observations report
  100. GRB 250313A: GRBAlpha detection

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