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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"

6520 results found.

  1. GRB 250327A: Swift/UVOT Upper Limits
  2. GRB 250331D: Fermi GBM observation
  3. GRB 250331D: Swift-XRT observations
  4. GRB 250331C: Swift-XRT refined Analysis
  5. GRB 250331B: Swift-XRT refined Analysis
  6. GRB 250331B: Swift-XRT refined Analysis
  7. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  8. Konus-Wind detection of GRB 250327B
  9. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  10. GRB 250328A: Swift-XRT refined Analysis
  11. Fermi-LAT gamma-ray observations of IceCube-250330A
  12. GRB 250330A: Fermi GBM Observation
  13. GRB 250331C: Prompt enhanced Swift-XRT position
  14. GRB 250330A: Swift-XRT afterglow detection
  15. GRB 250330A: Prompt Swift-XRT position
  16. GRB 250329B: Swift-XRT afterglow detection
  17. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  18. GRB 250329A: Swift-XRT afterglow detection
  19. GRB 250329A: Fading optical counterpart detection by LCO.
  20. GRB 250327B: LCO optical counterpart detection
  21. GRB 250327B: CrAO and SAO RAS Optical Observations
  22. GRB 250327B: further optical observations by LCOGT
  23. GRB 250327A: SVOM/VT upper limits on the XRT position
  24. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  25. GRB 250327A: Swift-XRT refined Analysis
  26. GRB 250327B: SVOM detection of a burst
  27. GRB 250327A: Fermi GBM observation
  28. Konus-Wind detection of GRB 250322A (short)
  29. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  30. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  31. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  32. GRB 250321B: Swift-XRT observations
  33. GRB 250322A: Swift-XRT refined Analysis
  34. GRB 250322A: NOT optical upper limits
  35. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  36. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  37. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 250320B: Fermi GBM Observation
  39. GRB 250321A: Swift-XRT refined Analysis
  40. GRB 250320B: Fermi-LAT detection
  41. EP250321a: Kinder optical follow-up observations
  42. EP250321a: Swift-XRT detection of an X-ray source
  43. EP250321a: TRT optical counterpart detection
  44. GRB 250321A: Swift-XRT localisation
  45. GRB 250321A: Fermi GBM Observation
  46. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  47. GRB 250317B: NOT optical observations suggest an optical plateau phase
  48. GRB 250317B: Swift-XRT observations
  49. GRB 250316A: Swift/UVOT Upper Limits
  50. EP 250317B: Fading optical counterpart detection by LCO
  51. GRB 250316A: Swift-XRT afterglow detection
  52. GRB 250317B: LCO detection of the fading optical afterglow
  53. GRB 250316A: Fermi GBM Observation
  54. GRB 250316A: Swift-XRT observations
  55. GRB 250314A: Swift/UVOT Upper Limits
  56. GRB 250314A: SVOM/VT upper limit
  57. GRB 250313A: Fermi GBM Detection
  58. GRB 250312B: Fermi GBM Observation
  59. GRB 250313A: Swift-XRT observations
  60. GRB 250313A: Fermi-LAT detection
  61. EP250302a: Chandra X-ray Detection
  62. GRB 250312A: Swift-XRT refined Analysis
  63. GRB 250226B: Fermi GBM Observation
  64. GRB 250302A: Fermi GBM Observation
  65. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  66. GRB 250223B: Fermi GBM Observation
  67. GRB 250311A: Swift-XRT observations
  68. GRB 250228A: Fermi GBM Observation
  69. GRB 250309B / AT2025dws: further SAO RAS optical observations
  70. Konus-Wind detection of GRB 250309B
  71. GRB 250309B: Swift-XRT refined Analysis
  72. GRB 250309B / IceCube-250309A: GECAM-B observations
  73. GRB 250309B / AT2025dws: SAO RAS optical observations
  74. GRB 250309B: Fermi GBM Observation
  75. Fermi GRB 250309A: Global MASTER-Net observations report
  76. Fermi-LAT gamma-ray observations of IceCube-250309A
  77. EP250308a: Einstein Probe detection of an X-ray transient
  78. EP250308a: NOT optical upper limit
  79. Fermi trigger No 762963055: Global MASTER-Net observations report
  80. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  81. EP250302a: Optical Observations at CrAO and SAO RAS
  82. EP250302A: 1.3m DFOT optical afterglow detection
  83. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  84. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  85. EP250304a: Swift-XRT detection of a fading X-ray source
  86. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  87. EP250302a: SAO RAS optical observations
  88. EP250302a: Kinder optical follow-up observations
  89. EP250302a: NUTTelA-TAO Early Measurments
  90. EP250302a: Swift-XRT observations of a fading X-ray source
  91. EP250228a: Optical observations with Kinder and Swift/UVOT
  92. Konus-Wind detection of GRB 250226A
  93. EP250227a: TRT optical upper limit
  94. GRB 250225B: VLT/HAWKI near-infrared observations
  95. EP250227a: Optical upper limits with Kinder observations
  96. GRB 250226A: Fermi GBM Observation
  97. EP250225a: EP-FXT follow-up observation
  98. GRB 250226A / EP250226a: LCO detection of the afterglow
  99. EP250225a: TRT optical upper limits
  100. EP250226a/GRB 250226A: 1.6m Mephisto observations

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