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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"

21321 results found.

  1. GRB 251013D: Swift ToO observations
  2. GRB 251014A: DDOTI Upper Limit
  3. GRB 251013C NUTTelA-TAO / BSTI Early Measurements
  4. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  5. GRB 251013C: Asiago optical observations
  6. GRB 251013C: ABObservatory optical observations
  7. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  8. GRB 251011A: Swift/BAT-GUANO arcminute localization of a burst
  9. GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
  10. GRB 251013C: ALMA detection
  11. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  12. GRB 251013C: DDOTI detection of the optical afterglow
  13. GRB 251013C: SLKT optical afterglow photometry
  14. Swift GRB 251014A: Global MASTER-Net observations report
  15. Fermi trigger No 782044789: Global MASTER-Net observations report
  16. Fermi GRB 251013C: Global MASTER-Net observations report
  17. Fermi GRB 251013B: Global MASTER-Net observations report
  18. Fermi GRB 251013D: Global MASTER-Net observations report
  19. GRB 251013C: Swift-XRT counterpart detection
  20. GRB 251013C: GOTO optical afterglow detection
  21. GRB 251013C: SAO RAS optical observations
  22. GRB 251013C: LCO optical afterglow detection
  23. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  24. GRB 251013C: LAST detection of optical counterpart
  25. GRB 251003A: Mondy optical upper limit
  26. Fermi GRB 251013A: Global MASTER-Net observations report
  27. GRB 251011B inspection: MASTER orphan GRB detection
  28. GRB 251011B: Swift/UVOT Upper Limits
  29. Fermi GRB 251011A: Global MASTER-Net observations report
  30. GRB 251011B : MASTER optical observations
  31. GRB 251007B: Swift/UVOT Upper Limits
  32. GRB251007A: Swift/UVOT Detection
  33. GRB 251007B - SVOM/ECLAIRs refined analysis
  34. EP251006a: Global MASTER-Net observations report
  35. GRB 251002A - SVOM/ECLAIRs refined analysis
  36. IceCube Alert 251008A: Global MASTER-Net observations report
  37. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  38. GRB 251007B: SVOM/VT optical candidate
  39. GRB 251007A: NOT optical observations
  40. GRB 251007A: SVOM/C-GFT optical observations
  41. GRB 251005C: PRIME J-band upper limit
  42. Swift GRB 251007B: Global MASTER-Net observations report
  43. GRB 251007B: SVOM/C-GFT upper limit
  44. Swift GRB 251007A: Global MASTER-Net observations report
  45. GRB 251007B: SVOM detection of a faint burst
  46. GRB 250702B/EP250702a: JWST/NIRCam Observations
  47. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  48. GRB 251006B/EP251006a: SVOM/VT optical candidate
  49. Fermi GRB 251006B: Global MASTER-Net observations report
  50. GRB 251005C: COLIBRÍ optical observations
  51. Fermi GRB 251006A: Global MASTER-Net observations report
  52. GRB 251005C: VLT/X-shooter Imaging
  53. GRB 251003A: LAST optical observations
  54. GRB 251002A: LAST optical observations
  55. GRB 251005C: Swift/UVOT Upper Limits
  56. Swift GRB 251005A: Global MASTER-Net observations report
  57. GRB 251005C: GOTO optical upper limits
  58. Fermi trigger No 781367244: Global MASTER-Net observations report
  59. GRB 251002A: Mondy/AZT-33IK optical observations
  60. EP251003a: Einstein Probe detection of an X-ray transient
  61. GRB 251003A: J-band detection with WINTER
  62. GRB 251002A: NIR observations with WINTER
  63. Fermi GBM Sub-Threshold Detection of GRB 250910A
  64. GRB 251001B: NIR observations with WINTER
  65. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  66. GRB 251003A: Swift/UVOT Upper Limits
  67. GRB 251002A: Swift/UVOT detection
  68. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  69. GRB 251003A: COLIBRÍ photometric redshift
  70. GRB 251003A: GOTO detection of the optical counterpart
  71. GRB 251002A: GOTO detection of optical counterpart
  72. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  73. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  74. GRB 251003A: Kilonova-Catcher optical afterglow detection
  75. GRB 251002A: Swift-XRT afterglow detection
  76. GRB 251001B: AbAO optical upper limit
  77. GRB 251002A: Kilonova-Catcher optical afterglow detection
  78. GRB 251002A: AbAO optical observations
  79. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  81. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  82. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  83. GRB 251003A: LCOGT Optical Detection
  84. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  85. GRB 251003A: 1.5m OSN afterglow candidate
  86. Swift GRB251003A: Global MASTER-Net observations report
  87. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  88. GRB 251002A: SAO RAS optical observations
  89. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  90. GRB 251002A: LCO optical observation
  91. Fermi GRB 251002A: Global MASTER-Net observations report
  92. GRB 251001B: Swift/UVOT Detection
  93. GRB 251001B: COLIBRÍ optical observations
  94. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  95. GRB 251001B: NOT optical observations
  96. Swift GRB 251001B: Global MASTER-Net observations report
  97. GRB 251001B: Further GOTO observations of optical counterpart.
  98. GRB 251001B: LCOGT Optical Observations
  99. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  100. GRB 251001B: GOTO optical counterpart detection

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