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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"

27391 results found.

  1. IceCube-250706A: No Candidates from WINTER
  2. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  3. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  4. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  5. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  6. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  7. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  8. EP250704a/GRB250704B : HCT optical and NIR upper limits
  9. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  10. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  11. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  12. GRB 250702F: radio detection with the VLA
  13. IceCube-250706A: EP-FXT follow-up observations
  14. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  15. GRB 250706B/C: Fermi-LAT detection
  16. IceCube-250706A: Global MASTER-Net observations report
  17. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  18. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  19. GRB 250706B: Swift/UVOT Detection
  20. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  21. GRB 250702F: GRANDMA observations
  22. GRB 250706A: Swift-XRT refined Analysis
  23. GRB 250706B: refined SVOM/MXT data analysis
  24. GRB 250706A: Swift/UVOT Upper Limits
  25. GRB 250706B: REM optical observations
  26. GRB 250706A: REM optical/NIR observations
  27. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  28. IceCube-250416A: DDOTI Optical Upper Limit
  29. IceCube-250706A: COLIBRÍ optical upper limits
  30. GRB 250706A: JinShan optical upper limits
  31. GRB 250706A: SAO RAS optical observations
  32. EP250704A: NOWT Detection
  33. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  34. GRB250706B: Swift-XRT counterpart detection
  35. GRB 250706B: iTelescope optical observations
  36. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  37. GRB 250706B: SVOM/VT optical observation
  38. GRB 250706B: TRT bright optical counterpart detection
  39. GRB 250706A: GROWTH-India Telescope optical upper limit
  40. GRB 250706B: SVOM detection of a long burst
  41. GRB 250706A: Swift detection of a burst
  42. GRB 250704B: Swift-XRT refined Analysis
  43. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  44. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  45. GRB 250703A: EIRSAT-1 GMOD Detection
  46. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  47. GRB 250704B: Swift/UVOT Upper Limits
  48. GRB 250704A: Swift/UVOT Detection
  49. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  50. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  51. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  52. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  53. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  54. EP250704a/GRB 250704B VLT/HAWK-I NIR afterglow detection
  55. GRB 250702F: Kilonova-Catcher optical afterglow detection
  56. GRB 250702F: Monte Agliale Observatory optical observations
  57. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  58. EP250704a / GRB 250704B: JinShan optical observations
  59. EP250704a / GRB 250704B: SAO RAS optical observations
  60. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  61. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  62. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  63. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  64. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  65. EP250704a / GRB250704B: Swift-XRT counterpart detection
  66. GRB 250704A: Swift-XRT afterglow detection
  67. EP250704a / GRB 250704B - REM observations
  68. GRB 250702F: GROWTH-India Telescope optical observations
  69. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  70. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  71. EP250702a: WFST optical observations
  72. EP250704a: COLIBRÍ optical counterpart candidate
  73. EP250704a: Einstein Probe detection of an X-ray transient
  74. GRB 250704A: REM detection of the optical afterglow
  75. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  76. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  77. GRB 250704A: SVOM detection of a burst
  78. GRB 250702F: Swift/UVOT Detection
  79. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  80. GRB 250702F: Swift-XRT refined Analysis
  81. GRB 250702F: Fermi GBM Observation
  82. GRB 250702F: Leavitt Observatory optical observations
  83. GRB 250702F: AKO Optical Afterglow Detection
  84. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  85. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  86. GRB 250702F: Skynet Optical Observations
  87. GRB 250424A: VIRT Optical Upper Limit
  88. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  89. GRB 250702F: TRT Optical Observation
  90. GRB 250703A: DDOTI Optical Upper Limit
  91. GRB 250702F: REM optical afterglow detection
  92. EP250702a: Global MASTER-Net observations report
  93. GRB 250702F: DDOTI Optical Observation
  94. GRB 250702F: COLIBRÍ Observations of the Afterglow
  95. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  96. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  97. GRB 250702F: Enhanced Swift-XRT position
  98. GRB 250702F: NOT observations of the optical afterglow
  99. GRB 250702F: Swift detection of a burst with an optical counterpart
  100. Fermi GBM Triggers 250702B, C, D and E are likely from the same source

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