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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"

32506 results found.

  1. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  2. GRB 250314A: ALMA detection
  3. GRB 250329B: Swift/UVOT Upper Limit
  4. GRB 250329A: Swift/UVOT Upper Limit
  5. GRB 250327B: Swift/UVOT Detection
  6. GRB 250327A: Swift/UVOT Upper Limits
  7. GRB 250331E: SVOM/GRM observation
  8. GRB 250327B: Kilonova-Catcher Observations
  9. GRB250331D: AbAO optical observations
  10. GRB 250331D: Fermi GBM observation
  11. GRB 250331C: Swift/UVOT Upper Limits
  12. GRB 250331B: Swift/UVOT Upper Limits
  13. GRB 250328A: AbAO AS-32 Optical Observations
  14. GRB 250219A: NOT candidate host galaxy detection
  15. GRB 250322B: GRBAlpha detection
  16. GRB 250330B: SVOM/GRM observation of a short burst
  17. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  18. Fermi GRB 250331E: Global MASTER-Net observations report
  19. Fermi GRB 250331D: Global MASTER-Net observations report
  20. GRB 250330B: EIRSAT-1 GMOD Detection
  21. GRB 250327A Swift-BAT refined analysis
  22. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  23. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  24. GRB 250331D: Swift ToO observations
  25. Swift GRB 250331C: Global MASTER-Net observations report
  26. Swift GRB 250331B: Global MASTER-Net observations report
  27. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  28. Konus-Wind detection of GRB 250327B
  29. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 250329B: Swift-XRT confirmation of fading
  31. GRB 250330A: VLT/FORS2 Afterglow Detection
  32. GRB20250327B: 45th Parallel Observatory upper limit
  33. GRB 250328A: Swift/UVOT Detection
  34. GRB 250328A: Swift-XRT refined Analysis
  35. Fermi-LAT gamma-ray observations of IceCube-250330A
  36. SVOM/sb25033102 is a false trigger
  37. GRB 250330A: Fermi GBM Observation
  38. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  39. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  40. GRB 250330A: SVOM/VT optical upper limit
  41. GRB 250314A: VLA detection
  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 250330A: BOOTES-7 early optical upper limit
  46. GRB 250330A: Swift/UVOT Upper Limits
  47. GRB 250328A: 1.6m Mephisto optical observations
  48. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  49. GRB 250330A: Fermi GBM Final Localization
  50. GRB 250330A: VLT/FORS2 Optical Observations
  51. GRB 250330A: Prompt Swift-XRT position
  52. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  53. GRB 250329B: SVOM/C-GFT optical upper limit
  54. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  55. GRB 250327B: ALMA detection
  56. GRB 250327B: VLA detection
  57. GRB 250329B: SVOM/VT optical upper limit
  58. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  59. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  60. GRB250329A: REM optical afterglow detection
  61. GRB 250329B: GWAC-F50A optical upper limit
  62. GRB 250329A: Swift-XRT afterglow detection
  63. GRB 250328A: SVOM/VT optical observation
  64. GRB 250329A: Fading optical counterpart detection by LCO.
  65. GRB 250328A: SVOM/C-GFT optical upper limit
  66. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  67. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  68. GRB 250329A: VLT/X-shooter redshift z = 2.921
  69. GRB 250329A: SVOM/VT optical counterpart confirmation
  70. GRB 250327B: J-band observations with WINTER
  71. GRB 250327B: MASTER detection of OT rebrightening
  72. GRB 250327B: LCO optical counterpart detection
  73. GRB 250328A: GWAC-F50A optical upper limit
  74. FRB 20250316A: FTW optical observations
  75. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  76. GRB 250327B: CrAO and SAO RAS Optical Observations
  77. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  78. GRB 250327B: further optical observations by LCOGT
  79. EP250315a: Pan-STARRS r and i-band imaging and photometry
  80. GRB 250327b: Liverpool Telescope optical observations
  81. GRB 250322A: GRANDMA/TNOT optical upper limits
  82. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  83. GRB 250327A: SVOM/VT upper limits on the XRT position
  84. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  85. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  86. GRB 250327B: Las Cumbres optical counterpart detection
  87. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  88. GRB 250327B: 1.6m Mephisto optical observations
  89. GRB 250327B: NOT spectroscopic redshift z = 3.035
  90. GRB 250327B: GOTO optical counterpart detection
  91. GRB 250327B: SVOM/VT optically bright counterpart
  92. GRB 250327B: SAO RAS optical candidate
  93. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  94. GRB 250327A: J-band observations with WINTER
  95. GRB 250327A: SVOM/VT optical candidate
  96. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  97. GRB 250327A: Fermi GBM observation
  98. Fermi GRB 250327A: Global MASTER-Net observations report
  99. Swift GRB 250327A: Global MASTER-Net observations report
  100. GRB 250327A: DDOTI Optical Observations

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