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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45501 results found.

  1. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  2. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  3. GRB 250322A: MASTER optical observation
  4. EP250321a: Liverpool Telescope optical follow-up
  5. EP250321a: Mondy AZT-33IK Optical Observations
  6. GRB 250322A: Swift detection of a short burst
  7. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  8. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  9. EP250321a: KAIT optical observations
  10. EP250321A: COLIBRÍ Continuing Optical Observations
  11. GRB 250225B: GECAM-A detection
  12. GRB 250312A: GECAM-A detection
  13. GRB 250321B: Swift ToO observations
  14. EP250321a: WFST optical observations
  15. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  16. GRB 250321C: Fermi GBM Final Real-time Localization
  17. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  18. GRB 250320B: Fermi GBM Observation
  19. EP250321a: Xinglong 216 decaying optical observations
  20. GRB 250321A: Swift-BAT refined analysis
  21. GRB 250321A: Swift-XRT refined Analysis
  22. GRB 250320B: Fermi-LAT detection
  23. GRB 250321B: SVOM detection of a sub-threshold transient event
  24. EP250321a: SVOM/VT optical observation
  25. EP 250321A: Optical counterpart detection by LCO.
  26. EP250321a: Kinder optical follow-up observations
  27. GRB 250321A: Swift/UVOT Upper Limits
  28. GRB 250320B: SVOM/GRM observation of a long burst
  29. EP250321a: LCO optical counterpart detection
  30. EP250321a: Swift-XRT detection of an X-ray source
  31. EP250321A: COLIBRÍ Optical Observations
  32. EP250321a: VLT/X-shooter redshift z = 4.368
  33. GRB 250320B: AstroSat CZTI detection
  34. EP250321a: REM optical/NIR afterglow detection
  35. Fermi GRB 250320B: Global MASTER-Net observations report
  36. EP250321a: BOOTES-5/JGT optical afterglow detection
  37. EP250321a: TRT optical counterpart detection
  38. EP250321a: Global MASTER-Net observations report
  39. Swift GRB 250321A: Global MASTER-Net observations report
  40. Fermi GRB 250321A: Global MASTER-Net observations report
  41. EP250321a: Einstein Probe detection of an X-ray transient
  42. GRB 250321A: GOTO optical upper limits
  43. GRB 250321A: Swift-XRT localisation
  44. GRB 250314A: Keck/NIRC2 J-band upper limit
  45. EP250226a/GRB 250226A: KAIT optical observations
  46. GRB 250321A: Fermi GBM Observation
  47. GRB 250321A: Swift detection of a burst
  48. GRB 250321A: Fermi GBM Final Real-time Localization
  49. GRB 250320B: Fermi GBM Final Real-time Localization
  50. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  51. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  52. GRB 250320A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 250319B: Global MASTER-Net observations report
  54. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  55. GRB 250313A: GRBAlpha detection
  56. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  57. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  58. GRB 250319B: Fermi GBM Final Localization
  59. GRB 250319A: Fermi GBM Final Localization
  60. GRB 250317D: EIRSAT-1 GMOD Detection
  61. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  62. GRB 250314A: ATCA radio upper limits
  63. EP250302a: VLA observations
  64. GRB 250317B: OHP/T193 continued follow-up
  65. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  66. GRB 250317C: SVOM/GRM observation of a long burst
  67. GRB 250317B: Leavitt Observatory optical upper limit
  68. GRB 250309B/AT2025dws: further ATCA observations
  69. GRB 250317B: Mondy AZT-33IK Optical Observations
  70. GRB 250317C: AstroSat CZTI detection
  71. GRB 250317B: NOT optical observations suggest an optical plateau phase
  72. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  73. GRB 250317C: GECAM-B detection
  74. GRB 250317B: OHP/T193 optical observations
  75. Fermi trigger No 763933627: Global MASTER-Net observations report
  76. GRB250312A: Swift/UVOT Upper Limits
  77. GRB 250317B: REM optical/NIR observations
  78. GRB 250317B: Swift-XRT observations
  79. GRB 250316A: Swift/UVOT Upper Limits
  80. GRB 250314A: REM optical/NIR upper limits
  81. GRB 250316A: AbAO AS-32 Optical Upper Limit
  82. EP 250317B: Fading optical counterpart detection by LCO
  83. GRB 250316A: Swift-XRT afterglow detection
  84. GRB 250317B: LCO detection of the fading optical afterglow
  85. GRB 250317B: refined SVOM/MXT analysis
  86. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  87. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  88. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  89. GRB 250317B: SVOM detection of a burst
  90. GRB 250316A: Fermi GBM Observation
  91. GRB 250316A: Swift-XRT observations
  92. Fermi trigger No 763862734: Global MASTER-Net observations report
  93. GRB 250317A: Fermi GBM Final Real-time Localization
  94. Fermi GRB 250316A: Global MASTER-Net observations report
  95. GRB 250314A: SVOM/GRM analysis
  96. GRB 250316A: Swift ToO observations
  97. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  98. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  99. The EP-WXT trigger 01709132801 is likely a flaring star
  100. GRB 250316A: Fermi GBM Final Real-time Localization

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