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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"

21036 results found.

  1. GRB 250711A: DDOTI Optical Upper Limit
  2. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  3. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  4. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  5. GRB 250711A: SVOM/GRM observation
  6. EP250711a: NOT optical counterpart candidate
  7. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  8. Fermi GRB 250711A: Global MASTER-Net observations report
  9. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  10. GRB 250704A: GRANDMA observations
  11. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  12. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  13. IceCube-250708A: No Candidates from WINTER
  14. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  15. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  16. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  17. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  18. EP250704a/GRB 250704B: 10 GHz VLA detection
  19. IceCube-250706A: No Candidates from WINTER
  20. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  21. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  22. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  23. EP250704a/GRB250704B : HCT optical and NIR upper limits
  24. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  25. GRB 250702F: radio detection with the VLA
  26. GRB 250706B/C: Fermi-LAT detection
  27. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  28. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  29. GRB 250706B: Swift/UVOT Detection
  30. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  31. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  32. GRB 250702F: GRANDMA observations
  33. GRB 250706B: refined SVOM/MXT data analysis
  34. GRB 250706A: Swift/UVOT Upper Limits
  35. GRB 250706B: REM optical observations
  36. GRB 250706A: REM optical/NIR observations
  37. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  38. IceCube-250416A: DDOTI Optical Upper Limit
  39. IceCube-250706A: COLIBRÍ optical upper limits
  40. GRB 250706A: JinShan optical upper limits
  41. GRB 250706A: SAO RAS optical observations
  42. EP250704A: NOWT Detection
  43. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  44. GRB 250706B: iTelescope optical observations
  45. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  46. GRB 250706B: SVOM/VT optical observation
  47. GRB 250706B: TRT bright optical counterpart detection
  48. GRB 250706A: GROWTH-India Telescope optical upper limit
  49. GRB 250706B: SVOM detection of a long burst
  50. GRB 250706A: Swift detection of a burst
  51. GRB 250704B: Swift-XRT refined Analysis
  52. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  53. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  54. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  55. GRB 250704B: Swift/UVOT Upper Limits
  56. GRB 250704A: Swift/UVOT Detection
  57. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  58. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  59. IPN triangulation of GRB 250703A
  60. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  61. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  62. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  63. GRB 250702F: Kilonova-Catcher optical afterglow detection
  64. GRB 250702F: Monte Agliale Observatory optical observations
  65. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  66. EP250704a / GRB 250704B: JinShan optical observations
  67. EP250704a / GRB 250704B: SAO RAS optical observations
  68. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  69. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  70. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  71. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  72. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  73. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  74. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  75. EP250704a / GRB250704B: Swift-XRT counterpart detection
  76. GRB 250704A: Swift-XRT afterglow detection
  77. GRB 250702B / EP2050702a: FTW optical and NIR observations
  78. Konus-Wind detection of GRB 250702F
  79. EP250704a / GRB 250704B - REM observations
  80. GRB 250702F: GROWTH-India Telescope optical observations
  81. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  82. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  83. EP250702a: WFST optical observations
  84. EP250704a: COLIBRÍ optical counterpart candidate
  85. EP250704a: Einstein Probe detection of an X-ray transient
  86. GRB 250704A: REM detection of the optical afterglow
  87. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  88. GRB 250704A: SVOM detection of a burst
  89. GRB 250702F: Swift/UVOT Detection
  90. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  91. GRB 250702F: Leavitt Observatory optical observations
  92. GRB 250702F: AKO Optical Afterglow Detection
  93. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  94. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  95. GRB 250702F: Skynet Optical Observations
  96. GRB 250424A: VIRT Optical Upper Limit
  97. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  98. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  99. GRB 250702F: TRT Optical Observation
  100. GRB 250703A: DDOTI Optical Upper Limit

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