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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"

28075 results found.

  1. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  2. GRB 250329A: VLT/X-shooter redshift z = 2.921
  3. GRB 250329A: SVOM detection of a burst
  4. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  5. GRB 250327B: MASTER detection of OT rebrightening
  6. GRB 250327B: LCO optical counterpart detection
  7. GRB 250328A: SVOM detection of a burst
  8. GRB 250327B: CrAO and SAO RAS Optical Observations
  9. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  10. EP250315a: Pan-STARRS r and i-band imaging and photometry
  11. GRB 250327b: Liverpool Telescope optical observations
  12. GRB 250322A: GRANDMA/TNOT optical upper limits
  13. GRB 250327A: SVOM/VT upper limits on the XRT position
  14. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  15. GRB 250327B: Las Cumbres optical counterpart detection
  16. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  17. GRB 250327B: 1.6m Mephisto optical observations
  18. GRB 250327B: NOT spectroscopic redshift z = 3.035
  19. GRB 250327A: Swift-XRT refined Analysis
  20. GRB 250327B: GOTO optical counterpart detection
  21. GRB 250327B: SVOM detection of a burst
  22. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  23. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  24. GRB 250327A: DDOTI Optical Observations
  25. GRB 250327A: Swift detection of a burst
  26. GRB 250327A: Fermi GBM Final Real-time Localization
  27. Konus-Wind detection of GRB 250322A (short)
  28. IPN triangulation of GRB 250322B
  29. EP250321a: Mondy AZT-33IK Continued Optical Observations
  30. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  31. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  32. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  33. GRB 250322A: further NOT optical observations
  34. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  35. GRB 250322A: Swift/UVOT Upper Limits
  36. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  37. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  38. GRB 250321B: Swift-XRT observations
  39. GRB 250322A: Swift-XRT refined Analysis
  40. EP250321a: TNOT Observation of Optical Counterpart
  41. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  42. GRB 250322A: Gemini-North redshift of candidate host galaxy
  43. SVOM/sb25032302: SVOM detection of a long X-ray transient
  44. GRB 250322A: AstroSat CZTI detection of a short burst
  45. GRB 250322B: AstroSat CZTI detection of a bright long burst
  46. GRB250322A: STEP/T80S optical limits
  47. GRB 250322A: Gemini-South optical observations
  48. GRB 250322A: VLT optical observations
  49. GRB 250322A: VLT near-infrared observations
  50. GRB 250322A: NOT optical upper limits
  51. GRB 250322A: Enhanced Swift-XRT position
  52. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  53. EP250321a: Liverpool Telescope optical follow-up
  54. EP250321a: Mondy AZT-33IK Optical Observations
  55. GRB 250322A: Swift detection of a short burst
  56. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  57. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP250321a: KAIT optical observations
  59. GRB 250225B: GECAM-A detection
  60. GRB 250312A: GECAM-A detection
  61. GRB 250321B: Swift ToO observations
  62. EP250321a: WFST optical observations
  63. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  64. GRB 250321C: Fermi GBM Final Real-time Localization
  65. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  66. GRB 250321A: Swift-XRT refined Analysis
  67. GRB 250320B: Fermi-LAT detection
  68. GRB 250321B: SVOM detection of a sub-threshold transient event
  69. EP 250321A: Optical counterpart detection by LCO.
  70. GRB 250321A: Swift/UVOT Upper Limits
  71. EP250321a: LCO optical counterpart detection
  72. EP250321a: Swift-XRT detection of an X-ray source
  73. EP250321a: VLT/X-shooter redshift z = 4.368
  74. GRB 250320B: AstroSat CZTI detection
  75. EP250321a: REM optical/NIR afterglow detection
  76. EP250321a: BOOTES-5/JGT optical afterglow detection
  77. EP250321a: TRT optical counterpart detection
  78. EP250321a: Einstein Probe detection of an X-ray transient
  79. GRB 250321A: GOTO optical upper limits
  80. GRB 250321A: Swift-XRT localisation
  81. GRB 250314A: Keck/NIRC2 J-band upper limit
  82. EP250226a/GRB 250226A: KAIT optical observations
  83. GRB 250321A: Swift detection of a burst
  84. GRB 250321A: Fermi GBM Final Real-time Localization
  85. GRB 250320B: Fermi GBM Final Real-time Localization
  86. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  87. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  88. GRB 250320A: Fermi GBM Final Real-time Localization
  89. GRB 250313A: GRBAlpha detection
  90. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  91. GRB 250319B: Fermi GBM Final Localization
  92. GRB 250319A: Fermi GBM Final Localization
  93. GRB 250317D: EIRSAT-1 GMOD Detection
  94. EP250302a: VLA observations
  95. GRB 250317B: OHP/T193 continued follow-up
  96. GRB 250309B/AT2025dws: further ATCA observations
  97. GRB 250317B: Mondy AZT-33IK Optical Observations
  98. GRB 250317C: AstroSat CZTI detection
  99. GRB 250317B: NOT optical observations suggest an optical plateau phase
  100. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44

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