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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"

38258 results found.

  1. GRB 250327B: Las Cumbres optical counterpart detection
  2. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  3. GRB 250327B: 1.6m Mephisto optical observations
  4. GRB 250327B: NOT spectroscopic redshift z = 3.035
  5. GRB 250327A: Swift-XRT refined Analysis
  6. GRB 250327B: GOTO optical counterpart detection
  7. GRB 250327B: SVOM/VT optically bright counterpart
  8. GRB 250327B: SAO RAS optical candidate
  9. GRB 250327B: SVOM detection of a burst
  10. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  11. GRB 250327A: J-band observations with WINTER
  12. GRB 250327A: SVOM/VT optical candidate
  13. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  14. GRB 250327A: Fermi GBM observation
  15. Fermi GRB 250327A: Global MASTER-Net observations report
  16. Swift GRB 250327A: Global MASTER-Net observations report
  17. GRB 250327A: DDOTI Optical Observations
  18. GRB 250327A: COLIBRÍ optical upper limit
  19. GRB 250327A: Swift detection of a burst
  20. GRB 250327A: Fermi GBM Final Real-time Localization
  21. Fermi trigger No 764700395: Global MASTER-Net observations report
  22. Konus-Wind detection of GRB 250322A (short)
  23. IPN triangulation of GRB 250322B
  24. EP250321a: Mondy AZT-33IK Continued Optical Observations
  25. GRB 250322A: third epoch of NOT optical observations
  26. GRB 250322A: Swift-BAT refined analysis
  27. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  28. GRB 250322A: further NOT optical observations
  29. GRB 250322A: Swift/UVOT Upper Limits
  30. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  31. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  32. GRB 250321B: Swift-XRT observations
  33. GRB 250322A: Swift-XRT refined Analysis
  34. EP250321a: TNOT Observation of Optical Counterpart
  35. GRB 250322A: Gemini-North redshift of candidate host galaxy
  36. SVOM/sb25032302: SVOM detection of a long X-ray transient
  37. GRB 250322A: AstroSat CZTI detection of a short burst
  38. GRB 250322B: AstroSat CZTI detection of a bright long burst
  39. GRB 250322A: Gemini-South optical observations
  40. GRB 250322A: VLT optical observations
  41. GRB 250322A: VLT near-infrared observations
  42. GRB 250322A: NOT optical upper limits
  43. GRB 250322A: Enhanced Swift-XRT position
  44. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  45. GRB 250322A: MASTER optical observation
  46. EP250321a: Mondy AZT-33IK Optical Observations
  47. GRB 250322A: Swift detection of a short burst
  48. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  49. EP250321a: KAIT optical observations
  50. GRB 250225B: GECAM-A detection
  51. GRB 250312A: GECAM-A detection
  52. GRB 250321B: Swift ToO observations
  53. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  54. GRB 250321C: Fermi GBM Final Real-time Localization
  55. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  56. GRB 250320B: Fermi GBM Observation
  57. EP250321a: Xinglong 216 decaying optical observations
  58. GRB 250321A: Swift-BAT refined analysis
  59. GRB 250321A: Swift-XRT refined Analysis
  60. GRB 250320B: Fermi-LAT detection
  61. GRB 250321B: SVOM detection of a sub-threshold transient event
  62. EP 250321A: Optical counterpart detection by LCO.
  63. GRB 250321A: Swift/UVOT Upper Limits
  64. GRB 250320B: SVOM/GRM observation of a long burst
  65. EP250321a: LCO optical counterpart detection
  66. GRB 250320B: AstroSat CZTI detection
  67. EP250321a: REM optical/NIR afterglow detection
  68. Fermi GRB 250320B: Global MASTER-Net observations report
  69. EP250321a: TRT optical counterpart detection
  70. EP250321a: Global MASTER-Net observations report
  71. Swift GRB 250321A: Global MASTER-Net observations report
  72. Fermi GRB 250321A: Global MASTER-Net observations report
  73. GRB 250321A: GOTO optical upper limits
  74. GRB 250321A: Swift-XRT localisation
  75. GRB 250314A: Keck/NIRC2 J-band upper limit
  76. EP250226a/GRB 250226A: KAIT optical observations
  77. GRB 250321A: Fermi GBM Observation
  78. GRB 250321A: Swift detection of a burst
  79. GRB 250321A: Fermi GBM Final Real-time Localization
  80. GRB 250320B: Fermi GBM Final Real-time Localization
  81. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  82. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  83. GRB 250320A: Fermi GBM Final Real-time Localization
  84. Fermi GRB 250319B: Global MASTER-Net observations report
  85. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  86. GRB 250313A: GRBAlpha detection
  87. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  88. GRB 250319B: Fermi GBM Final Localization
  89. GRB 250319A: Fermi GBM Final Localization
  90. GRB 250317D: EIRSAT-1 GMOD Detection
  91. GRB 250314A: ATCA radio upper limits
  92. GRB 250317B: OHP/T193 continued follow-up
  93. GRB 250317C: SVOM/GRM observation of a long burst
  94. GRB 250317B: Leavitt Observatory optical upper limit
  95. GRB 250309B/AT2025dws: further ATCA observations
  96. GRB 250317B: Mondy AZT-33IK Optical Observations
  97. GRB 250317C: AstroSat CZTI detection
  98. GRB 250317B: NOT optical observations suggest an optical plateau phase
  99. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  100. GRB 250317C: GECAM-B detection

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