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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"

21791 results found.

  1. GRB 251007B: Swift/UVOT Upper Limits
  2. GRB251007A: Swift/UVOT Detection
  3. GRB 251007B - SVOM/ECLAIRs refined analysis
  4. EP251006a: Global MASTER-Net observations report
  5. GRB 251002A - SVOM/ECLAIRs refined analysis
  6. IceCube Alert 251008A: Global MASTER-Net observations report
  7. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  8. GRB 251007B: SVOM/VT optical candidate
  9. GRB 251007A: NOT optical observations
  10. GRB 251007A: SVOM/C-GFT optical observations
  11. GRB 251005C: PRIME J-band upper limit
  12. Swift GRB 251007B: Global MASTER-Net observations report
  13. GRB 251007B: SVOM/C-GFT upper limit
  14. Swift GRB 251007A: Global MASTER-Net observations report
  15. GRB 251007B: SVOM detection of a faint burst
  16. GRB 250702B/EP250702a: JWST/NIRCam Observations
  17. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  18. GRB 251006B/EP251006a: SVOM/VT optical candidate
  19. Fermi GRB 251006B: Global MASTER-Net observations report
  20. GRB 251005C: COLIBRÍ optical observations
  21. Fermi GRB 251006A: Global MASTER-Net observations report
  22. GRB 251005C: VLT/X-shooter Imaging
  23. GRB 251003A: LAST optical observations
  24. GRB 251002A: LAST optical observations
  25. GRB 251005C: Swift/UVOT Upper Limits
  26. Swift GRB 251005A: Global MASTER-Net observations report
  27. GRB 251005C: GOTO optical upper limits
  28. Fermi trigger No 781367244: Global MASTER-Net observations report
  29. GRB 251002A: Mondy/AZT-33IK optical observations
  30. EP251003a: Einstein Probe detection of an X-ray transient
  31. GRB 251003A: J-band detection with WINTER
  32. GRB 251002A: NIR observations with WINTER
  33. Fermi GBM Sub-Threshold Detection of GRB 250910A
  34. GRB 251001B: NIR observations with WINTER
  35. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  36. GRB 251003A: Swift/UVOT Upper Limits
  37. GRB 251002A: Swift/UVOT detection
  38. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  39. GRB 251003A: COLIBRÍ photometric redshift
  40. GRB 251003A: GOTO detection of the optical counterpart
  41. GRB 251002A: GOTO detection of optical counterpart
  42. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  43. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  44. GRB 251003A: Kilonova-Catcher optical afterglow detection
  45. GRB 251002A: Swift-XRT afterglow detection
  46. GRB 251001B: AbAO optical upper limit
  47. GRB 251002A: Kilonova-Catcher optical afterglow detection
  48. GRB 251002A: AbAO optical observations
  49. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  50. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  51. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  52. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  53. GRB 251003A: LCOGT Optical Detection
  54. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  55. GRB 251003A: 1.5m OSN afterglow candidate
  56. Swift GRB251003A: Global MASTER-Net observations report
  57. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  58. GRB 251002A: SAO RAS optical observations
  59. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  60. GRB 251002A: LCO optical observation
  61. Fermi GRB 251002A: Global MASTER-Net observations report
  62. GRB 251001B: Swift/UVOT Detection
  63. GRB 251001B: COLIBRÍ optical observations
  64. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  65. GRB 251001B: NOT optical observations
  66. Swift GRB 251001B: Global MASTER-Net observations report
  67. GRB 251001B: Further GOTO observations of optical counterpart.
  68. GRB 251001B: LCOGT Optical Observations
  69. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  70. GRB 251001B: GOTO optical counterpart detection
  71. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  72. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  73. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  74. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  75. GRB 250925A: MAO/AZT-22 optical observations
  76. Fermi GRB 250929A: Global MASTER-Net observations report
  77. GRB 250925A: Mondy I-band optical observations
  78. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  79. Fermi trigger No 780609036: Global MASTER-Net observations report
  80. IceCube Alert 250926.52: Global MASTER-Net observations report
  81. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  82. GRB 250925A: Swift/UVOT Upper Limits
  83. GRB 250925A: Mondy and AbAO optical observations
  84. GRB 250925A: COLIBRÍ photometric redshift
  85. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  86. GRB 250925A: JinShan optical observations
  87. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  88. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  89. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  90. Fermi GRB 250926A: Global MASTER-Net observations report
  91. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  92. GRB250925A: Liverpool Telescope optical observations
  93. GRB 250925A: NOT optical afterglow candidate
  94. GRB 250925A: Leavitt Observatory optical upper limit
  95. Swift GRB 250925A: Global MASTER-Net observations report
  96. GRB 250924A: 1.6m Mephisto optical upper limits
  97. GRB 250924A: SAO RAS optical observations
  98. GRB 250924A: NOT optical observations
  99. GRB 250924A: Swift/UVOT Detection
  100. GRB 250924A: J-band detection with WINTER

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