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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"

20960 results found.

  1. EP250404a: Mephisto multi-band optical detection
  2. EP250321A: J band upper limit by SYSU 80cm telescope
  3. EP250404a: Nanshan/HMT optical counterpart detection
  4. GRB 250402A: Mondy optical observations
  5. EP250402a: Optical upper limit with Kinder observations
  6. GRB 250403A: REM NIR afterglow detection
  7. GRB 250403A: LCO optical counterpart detection
  8. GRB 250403A: JinShan optical observations
  9. GRB 250403A: Optical counterpart detection by LCO.
  10. EP250402a: EP-FXT follow-up observations
  11. GRB 250403A: Swift-XRT observations
  12. GRB 250322A: 10 GHz VLA radio upper limits
  13. Fermi GRB 250403A: Global MASTER-Net observations report
  14. GRB 250403A: GOTO optical counterpart follow-up observations
  15. GRB 250402A: NUTTelA-TAO Early Optical Limits
  16. GRB 250403A: 1.6m Mephisto multi-band optical detection
  17. GRB 250403A: SVOM/C-GFT optical observations
  18. GRB 250403A: GOTO detection of the optical afterglow
  19. GRB 250402A: Swift-XRT observations
  20. GRB 250225B: VLT host galaxy redshift z = 0.950
  21. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  22. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  23. GRB 250402A: REM optical/NIR upper limits
  24. GRB 250402A: LCO optical counterpart detection
  25. GRB 250402A: refined SVOM/MXT data analysis
  26. EP250402a: Einstein Probe detection of a fast X-ray transient
  27. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  28. GRB 250314A: ALMA detection
  29. GRB 250329B: Swift/UVOT Upper Limit
  30. GRB 250329A: Swift/UVOT Upper Limit
  31. GRB 250327B: Swift/UVOT Detection
  32. GRB 250327A: Swift/UVOT Upper Limits
  33. GRB 250327B: Kilonova-Catcher Observations
  34. GRB250331D: AbAO optical observations
  35. GRB 250331C: Swift/UVOT Upper Limits
  36. GRB 250331B: Swift/UVOT Upper Limits
  37. GRB 250328A: AbAO AS-32 Optical Observations
  38. GRB 250219A: NOT candidate host galaxy detection
  39. GRB 250331D: Swift-XRT observations
  40. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  41. Fermi GRB 250331E: Global MASTER-Net observations report
  42. Fermi GRB 250331D: Global MASTER-Net observations report
  43. Fermi trigger No 765078057: Global MASTER-Net observations report
  44. GRB 250331D: Swift ToO observations
  45. Swift GRB 250331C: Global MASTER-Net observations report
  46. Swift GRB 250331B: Global MASTER-Net observations report
  47. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  48. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  49. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  50. GRB 250330A: VLT/FORS2 Afterglow Detection
  51. GRB20250327B: 45th Parallel Observatory upper limit
  52. GRB 250328A: Swift/UVOT Detection
  53. Fermi-LAT gamma-ray observations of IceCube-250330A
  54. GRB 250330A: SVOM/VT optical upper limit
  55. GRB 250314A: VLA detection
  56. Fermi GRB 250330B: Global MASTER-Net observations report
  57. Fermi GRB 250330A: Global MASTER-Net observations report
  58. GRB 250330A: BOOTES-7 early optical upper limit
  59. GRB 250330A: Swift/UVOT Upper Limits
  60. GRB 250330A: Swift-XRT afterglow detection
  61. GRB 250328A: 1.6m Mephisto optical observations
  62. IceCube Alert 250330.35: Global MASTER-Net observations report
  63. GRB 250330A: VLT/FORS2 Optical Observations
  64. Swift GRB250330.26: Global MASTER-Net observations report
  65. GRB 250329B: SVOM/C-GFT optical upper limit
  66. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  67. GRB 250327B: ALMA detection
  68. GRB 250327B: VLA detection
  69. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  70. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  71. GRB250329A: REM optical afterglow detection
  72. GRB 250329B: GWAC-F50A optical upper limit
  73. GRB 250328A: SVOM/VT optical observation
  74. GRB 250329A: Fading optical counterpart detection by LCO.
  75. GRB 250328A: SVOM/C-GFT optical upper limit
  76. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  77. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  78. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  79. GRB 250327B: J-band observations with WINTER
  80. GRB 250327B: LCO optical counterpart detection
  81. GRB 250328A: GWAC-F50A optical upper limit
  82. FRB 20250316A: FTW optical observations
  83. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  84. GRB 250327B: CrAO and SAO RAS Optical Observations
  85. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  86. GRB 250327B: further optical observations by LCOGT
  87. GRB 250327b: Liverpool Telescope optical observations
  88. GRB 250327A: SVOM/VT upper limits on the XRT position
  89. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  90. GRB 250327B: 1.6m Mephisto optical observations
  91. GRB 250327B: GOTO optical counterpart detection
  92. GRB 250327B: SAO RAS optical candidate
  93. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  94. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  95. GRB 250327A: J-band observations with WINTER
  96. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  97. Fermi GRB 250327A: Global MASTER-Net observations report
  98. Swift GRB 250327A: Global MASTER-Net observations report
  99. GRB 250327A: DDOTI Optical Observations
  100. GRB 250327A: COLIBRÍ optical upper limit

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