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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"

27400 results found.

  1. IceCube-250708A: No Candidates from WINTER
  2. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  3. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  4. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  5. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  6. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  7. EP250704a/GRB 250704B: 10 GHz VLA detection
  8. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  9. IceCube-250706A: No Candidates from WINTER
  10. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  11. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  12. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  13. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  14. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  15. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  16. EP250704a/GRB250704B : HCT optical and NIR upper limits
  17. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  18. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  19. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  20. GRB 250702F: radio detection with the VLA
  21. IceCube-250706A: EP-FXT follow-up observations
  22. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  23. GRB 250706B/C: Fermi-LAT detection
  24. IceCube-250706A: Global MASTER-Net observations report
  25. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  26. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  27. GRB 250706B: Swift/UVOT Detection
  28. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  29. GRB 250702F: GRANDMA observations
  30. GRB 250706A: Swift-XRT refined Analysis
  31. GRB 250706B: refined SVOM/MXT data analysis
  32. GRB 250706A: Swift/UVOT Upper Limits
  33. GRB 250706B: REM optical observations
  34. GRB 250706A: REM optical/NIR observations
  35. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  36. IceCube-250416A: DDOTI Optical Upper Limit
  37. IceCube-250706A: COLIBRÍ optical upper limits
  38. GRB 250706A: JinShan optical upper limits
  39. GRB 250706A: SAO RAS optical observations
  40. EP250704A: NOWT Detection
  41. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  42. GRB250706B: Swift-XRT counterpart detection
  43. GRB 250706B: iTelescope optical observations
  44. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  45. GRB 250706B: SVOM/VT optical observation
  46. GRB 250706B: TRT bright optical counterpart detection
  47. GRB 250706A: GROWTH-India Telescope optical upper limit
  48. GRB 250706B: SVOM detection of a long burst
  49. GRB 250706A: Swift detection of a burst
  50. GRB 250704B: Swift-XRT refined Analysis
  51. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  52. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  53. GRB 250703A: EIRSAT-1 GMOD Detection
  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. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  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: refined analysis of the EP-WXT and FXT follow-up observations
  71. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  72. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  73. EP250704a / GRB250704B: Swift-XRT counterpart detection
  74. GRB 250704A: Swift-XRT afterglow detection
  75. EP250704a / GRB 250704B - REM observations
  76. GRB 250702F: GROWTH-India Telescope optical observations
  77. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  78. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  79. EP250702a: WFST optical observations
  80. EP250704a: COLIBRÍ optical counterpart candidate
  81. EP250704a: Einstein Probe detection of an X-ray transient
  82. GRB 250704A: REM detection of the optical afterglow
  83. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  84. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  85. GRB 250704A: SVOM detection of a burst
  86. GRB 250702F: Swift/UVOT Detection
  87. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  88. GRB 250702F: Swift-XRT refined Analysis
  89. GRB 250702F: Fermi GBM Observation
  90. GRB 250702F: Leavitt Observatory optical observations
  91. GRB 250702F: AKO Optical Afterglow Detection
  92. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  93. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  94. GRB 250702F: Skynet Optical Observations
  95. GRB 250424A: VIRT Optical Upper Limit
  96. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  97. GRB 250702F: TRT Optical Observation
  98. GRB 250703A: DDOTI Optical Upper Limit
  99. GRB 250702F: REM optical afterglow detection
  100. EP250702a: Global MASTER-Net observations report

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