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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"

4746 results found.

  1. GRB 250402A: Swift/UVOT Upper Limits
  2. GRB 250403A: REM NIR afterglow detection
  3. GRB 250403A: LCO optical counterpart detection
  4. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  5. GRB 250403A: JinShan optical observations
  6. GRB 250402A: EP-FXT afterglow detection
  7. Fermi GRB 250403A: Global MASTER-Net observations report
  8. GRB 250403A: GOTO optical counterpart follow-up observations
  9. GRB 250403A: GMG Optical Observation
  10. GRB 250403A: 1.6m Mephisto multi-band optical detection
  11. GRB 250403A: GOTO detection of the optical afterglow
  12. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  13. GRB 250402A: REM optical/NIR upper limits
  14. GRB 250402A: LCO optical counterpart detection
  15. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  16. GRB 250331E: SVOM/GRM observation
  17. GRB250331D: AbAO optical observations
  18. GRB 250328A: AbAO AS-32 Optical Observations
  19. GRB 250322B: GRBAlpha detection
  20. GRB 250331D: Swift-XRT observations
  21. GRB 250330B: SVOM/GRM observation of a short burst
  22. Fermi GRB 250331E: Global MASTER-Net observations report
  23. Fermi GRB 250331D: Global MASTER-Net observations report
  24. GRB 250330B: EIRSAT-1 GMOD Detection
  25. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  26. Fermi trigger No 765078057: Global MASTER-Net observations report
  27. Swift GRB 250331C: Global MASTER-Net observations report
  28. Swift GRB 250331B: Global MASTER-Net observations report
  29. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  30. GRB 250331C: Enhanced Swift-XRT position
  31. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  32. GRB 250320C : SVOM detection of a burst through offline search
  33. Fermi-LAT gamma-ray observations of IceCube-250330A
  34. SVOM/sb25033102 is a false trigger
  35. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  36. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  37. GRB 250331C: Prompt enhanced Swift-XRT position
  38. GRB 250331C: Swift detection of a burst
  39. GRB 250330A: SVOM/VT optical upper limit
  40. GRB 250331A: MAXI/GSC detection
  41. SVOM/sb25033102: SVOM detection of an X-ray transient
  42. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  43. Fermi GRB 250330B: Global MASTER-Net observations report
  44. Fermi GRB 250330A: Global MASTER-Net observations report
  45. GRB 250328A: 1.6m Mephisto optical observations
  46. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  47. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  48. IceCube Alert 250330.35: Global MASTER-Net observations report
  49. Swift GRB250330.26: Global MASTER-Net observations report
  50. GRB 250329B: SVOM/C-GFT optical upper limit
  51. GRB 250327B: VLA detection
  52. GRB 250329B: SVOM/VT optical upper limit
  53. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  54. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  55. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  56. GRB 250329B: GWAC-F50A optical upper limit
  57. GRB 250329B: SVOM detection of a faint transient
  58. GRB 250329A: Fading optical counterpart detection by LCO.
  59. GRB 250328A: SVOM/C-GFT optical upper limit
  60. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  61. GRB 250329A: SVOM detection of a burst
  62. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  63. GRB 250327B: J-band observations with WINTER
  64. GRB 250327B: MASTER detection of OT rebrightening
  65. GRB 250327B: LCO optical counterpart detection
  66. GRB 250328A: GWAC-F50A optical upper limit
  67. GRB 250328A: SVOM detection of a burst
  68. FRB 20250316A: FTW optical observations
  69. GRB 250327B: CrAO and SAO RAS Optical Observations
  70. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  71. GRB 250327B: further optical observations by LCOGT
  72. EP250315a: Pan-STARRS r and i-band imaging and photometry
  73. GRB 250327b: Liverpool Telescope optical observations
  74. GRB 250327A: SVOM/VT upper limits on the XRT position
  75. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  76. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  77. GRB 250327B: Las Cumbres optical counterpart detection
  78. GRB 250327B: 1.6m Mephisto optical observations
  79. GRB 250327B: GOTO optical counterpart detection
  80. GRB 250327B: SVOM detection of a burst
  81. GRB 250327A: J-band observations with WINTER
  82. GRB 250327A: SVOM/VT optical candidate
  83. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  84. Fermi GRB 250327A: Global MASTER-Net observations report
  85. Swift GRB 250327A: Global MASTER-Net observations report
  86. GRB 250327A: DDOTI Optical Observations
  87. GRB 250327A: COLIBRÍ optical upper limit
  88. Fermi trigger No 764700395: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  90. EP250321a: Mondy AZT-33IK Continued Optical Observations
  91. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  92. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  93. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  94. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  95. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  96. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  97. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  98. EP250321a: TNOT Observation of Optical Counterpart
  99. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  100. GRB 250322A: Gemini-North redshift of candidate host galaxy

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