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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

23464 results found.

  1. GRB 250331C: Swift detection of a burst
  2. GRB 250331B: Swift detection of a burst
  3. GRB 250330A: SVOM/VT optical upper limit
  4. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  5. GRB 250330A: Swift/UVOT Upper Limits
  6. GRB 250330A: Swift-XRT afterglow detection
  7. GRB 250328A: 1.6m Mephisto optical observations
  8. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  9. GRB 250330A: VLT/FORS2 Optical Observations
  10. GRB 250329B: Swift-XRT afterglow detection
  11. GRB 250330A: Swift detection of a burst
  12. GRB 250329B: SVOM/C-GFT optical upper limit
  13. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  14. GRB 250329B: SVOM/VT optical upper limit
  15. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  16. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  17. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  18. GRB250329A: REM optical afterglow detection
  19. GRB 250329B: GWAC-F50A optical upper limit
  20. GRB 250329A: Swift-XRT afterglow detection
  21. GRB 250328A: SVOM/VT optical observation
  22. GRB 250329A: Fading optical counterpart detection by LCO.
  23. GRB 250328A: SVOM/C-GFT optical upper limit
  24. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  25. GRB 250329A: SVOM/VT optical counterpart confirmation
  26. GRB 250329A: SVOM detection of a burst
  27. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  28. GRB 250327B: J-band observations with WINTER
  29. GRB 250327B: LCO optical counterpart detection
  30. GRB 250328A: GWAC-F50A optical upper limit
  31. FRB 20250316A: FTW optical observations
  32. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  33. GRB 250327B: CrAO and SAO RAS Optical Observations
  34. EP250315a: Pan-STARRS r and i-band imaging and photometry
  35. GRB 250327b: Liverpool Telescope optical observations
  36. GRB 250322A: GRANDMA/TNOT optical upper limits
  37. GRB 250327A: SVOM/VT upper limits on the XRT position
  38. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  39. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  40. GRB 250327B: Las Cumbres optical counterpart detection
  41. GRB 250327B: 1.6m Mephisto optical observations
  42. GRB 250327B: SVOM/VT optically bright counterpart
  43. GRB 250327B: SAO RAS optical candidate
  44. GRB 250327B: SVOM detection of a burst
  45. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  46. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  47. GRB 250327A: J-band observations with WINTER
  48. GRB 250327A: SVOM/VT optical candidate
  49. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  50. GRB 250327A: DDOTI Optical Observations
  51. GRB 250327A: COLIBRÍ optical upper limit
  52. GRB 250327A: Swift detection of a burst
  53. Fermi trigger No 764700395: Global MASTER-Net observations report
  54. Konus-Wind detection of GRB 250322A (short)
  55. IPN triangulation of GRB 250322B
  56. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  57. EP250321a: Mondy AZT-33IK Continued Optical Observations
  58. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  59. GRB 250322A: third epoch of NOT optical observations
  60. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  61. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  62. GRB 250322A: further NOT optical observations
  63. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  64. GRB 250322A: Swift/UVOT Upper Limits
  65. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  66. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  67. GRB 250321B: Swift-XRT observations
  68. EP250321a: TNOT Observation of Optical Counterpart
  69. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  70. GRB 250322B: AstroSat CZTI detection of a bright long burst
  71. GRB250322A: STEP/T80S optical limits
  72. GRB 250322A: Gemini-South optical observations
  73. GRB 250322A: VLT optical observations
  74. GRB 250322A: VLT near-infrared observations
  75. FRB 250316A: DDOTI Continued Optical Observations
  76. GRB 250322A: NOT optical upper limits
  77. GRB 250322A: Enhanced Swift-XRT position
  78. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  79. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  80. EP250321a: Liverpool Telescope optical follow-up
  81. EP250321a: Mondy AZT-33IK Optical Observations
  82. GRB 250322A: Swift detection of a short burst
  83. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  84. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  85. EP250321A: COLIBRÍ Continuing Optical Observations
  86. EP250321a: WFST optical observations
  87. EP250321a: Xinglong 216 decaying optical observations
  88. GRB 250321A: Swift-XRT refined Analysis
  89. EP 250321A: Optical counterpart detection by LCO.
  90. EP250321a: Kinder optical follow-up observations
  91. GRB 250321A: Swift/UVOT Upper Limits
  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. EP250321a: REM optical/NIR afterglow detection
  97. EP250321a: TRT optical counterpart detection
  98. EP250321a: Einstein Probe detection of an X-ray transient
  99. GRB 250321A: GOTO optical upper limits
  100. GRB 250314A: Keck/NIRC2 J-band upper limit

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