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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"

5514 results found.

  1. Fermi-LAT gamma-ray observations of IceCube-250330A
  2. SVOM/sb25033102 is a false trigger
  3. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  4. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  5. GRB 250331C: Prompt enhanced Swift-XRT position
  6. GRB 250331C: Swift detection of a burst
  7. GRB 250330A: SVOM/VT optical upper limit
  8. GRB 250331A: MAXI/GSC detection
  9. SVOM/sb25033102: SVOM detection of an X-ray transient
  10. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  11. Fermi GRB 250330B: Global MASTER-Net observations report
  12. Fermi GRB 250330A: Global MASTER-Net observations report
  13. GRB 250328A: 1.6m Mephisto optical observations
  14. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  15. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  16. IceCube Alert 250330.35: Global MASTER-Net observations report
  17. Swift GRB250330.26: Global MASTER-Net observations report
  18. GRB 250329B: SVOM/C-GFT optical upper limit
  19. GRB 250327B: VLA detection
  20. GRB 250329B: SVOM/VT optical upper limit
  21. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  22. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  23. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  24. GRB 250329B: GWAC-F50A optical upper limit
  25. GRB 250329B: SVOM detection of a faint transient
  26. GRB 250329A: Fading optical counterpart detection by LCO.
  27. GRB 250328A: SVOM/C-GFT optical upper limit
  28. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  29. GRB 250329A: SVOM detection of a burst
  30. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  31. GRB 250327B: J-band observations with WINTER
  32. GRB 250327B: MASTER detection of OT rebrightening
  33. GRB 250327B: LCO optical counterpart detection
  34. GRB 250328A: GWAC-F50A optical upper limit
  35. GRB 250328A: SVOM detection of a burst
  36. FRB 20250316A: FTW optical observations
  37. GRB 250327B: CrAO and SAO RAS Optical Observations
  38. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  39. GRB 250327B: further optical observations by LCOGT
  40. EP250315a: Pan-STARRS r and i-band imaging and photometry
  41. GRB 250327b: Liverpool Telescope optical observations
  42. GRB 250327A: SVOM/VT upper limits on the XRT position
  43. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  44. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  45. GRB 250327B: Las Cumbres optical counterpart detection
  46. GRB 250327B: 1.6m Mephisto optical observations
  47. GRB 250327B: GOTO optical counterpart detection
  48. GRB 250327B: SVOM detection of a burst
  49. GRB 250327A: J-band observations with WINTER
  50. GRB 250327A: SVOM/VT optical candidate
  51. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  52. Fermi GRB 250327A: Global MASTER-Net observations report
  53. Swift GRB 250327A: Global MASTER-Net observations report
  54. GRB 250327A: DDOTI Optical Observations
  55. GRB 250327A: COLIBRÍ optical upper limit
  56. Fermi trigger No 764700395: Global MASTER-Net observations report
  57. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  58. EP250321a: Mondy AZT-33IK Continued Optical Observations
  59. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  60. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  61. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  62. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  63. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  64. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  65. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  66. EP250321a: TNOT Observation of Optical Counterpart
  67. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  68. GRB 250322A: Gemini-North redshift of candidate host galaxy
  69. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  70. SVOM/sb25032302: SVOM detection of a long X-ray transient
  71. GRB 250322A: AstroSat CZTI detection of a short burst
  72. GRB 250322B: AstroSat CZTI detection of a bright long burst
  73. GRB 250322A: Gemini-South optical observations
  74. FRB 250316A: DDOTI Continued Optical Observations
  75. GRB 250322A: NOT optical upper limits
  76. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  77. GRB 250322A: MASTER optical observation
  78. EP250321a: Liverpool Telescope optical follow-up
  79. EP250321a: Mondy AZT-33IK Optical Observations
  80. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  81. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  82. EP250321A: COLIBRÍ Continuing Optical Observations
  83. GRB 250312A: GECAM-A detection
  84. EP250321a: WFST optical observations
  85. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  86. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  87. EP250321a: Xinglong 216 decaying optical observations
  88. GRB 250321A: Swift-BAT refined analysis
  89. GRB 250321B: SVOM detection of a sub-threshold transient event
  90. EP250321a: SVOM/VT optical observation
  91. EP 250321A: Optical counterpart detection by LCO.
  92. GRB 250320B: SVOM/GRM observation of a long burst
  93. EP250321a: LCO optical counterpart detection
  94. EP250321A: COLIBRÍ Optical Observations
  95. GRB 250320B: AstroSat CZTI detection
  96. Fermi GRB 250320B: Global MASTER-Net observations report
  97. EP250321a: BOOTES-5/JGT optical afterglow detection
  98. EP250321a: Global MASTER-Net observations report
  99. Swift GRB 250321A: Global MASTER-Net observations report
  100. Fermi GRB 250321A: Global MASTER-Net observations report

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