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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"

24375 results found.

  1. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  2. GRB 250330A: Fermi GBM Final Localization
  3. IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
  4. IceCube Alert 250330.35: Global MASTER-Net observations report
  5. GRB 250330A: Prompt Swift-XRT position
  6. GRB 250329B: Swift-XRT afterglow detection
  7. GRB 250330A: Swift detection of a burst
  8. Swift GRB250330.26: Global MASTER-Net observations report
  9. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  10. GRB 250329B: SVOM/C-GFT optical upper limit
  11. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  12. GRB 250329B: SVOM/VT optical upper limit
  13. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  14. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  15. GRB250329A: REM optical afterglow detection
  16. GRB 250329B: GWAC-F50A optical upper limit
  17. GRB 250329B: SVOM detection of a faint transient
  18. GRB 250328A: SVOM/VT optical observation
  19. GRB 250329A: VLT/X-shooter redshift z = 2.921
  20. GRB 250329A: SVOM/VT optical counterpart confirmation
  21. GRB 250329A: SVOM detection of a burst
  22. GRB 250327B: MASTER detection of OT rebrightening
  23. GRB 250327B: LCO optical counterpart detection
  24. GRB 250328A: GWAC-F50A optical upper limit
  25. GRB 250328A: SVOM detection of a burst
  26. FRB 20250316A: FTW optical observations
  27. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  28. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  29. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  30. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  31. GRB 250327B: 1.6m Mephisto optical observations
  32. GRB 250327B: GOTO optical counterpart detection
  33. GRB 250327B: SVOM/VT optically bright counterpart
  34. GRB 250327B: SVOM detection of a burst
  35. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  36. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  37. GRB 250327A: J-band observations with WINTER
  38. GRB 250327A: SVOM/VT optical candidate
  39. GRB 250327A: Fermi GBM observation
  40. Fermi GRB 250327A: Global MASTER-Net observations report
  41. Swift GRB 250327A: Global MASTER-Net observations report
  42. GRB 250327A: COLIBRÍ optical upper limit
  43. GRB 250327A: Fermi GBM Final Real-time Localization
  44. Fermi trigger No 764700395: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  46. Konus-Wind detection of GRB 250322A (short)
  47. IPN triangulation of GRB 250322B
  48. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  49. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  50. GRB 250322A: third epoch of NOT optical observations
  51. GRB 250322A: Swift-BAT refined analysis
  52. The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
  53. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  54. GRB 250322A: further NOT optical observations
  55. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  56. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  57. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  58. EP250321a: TNOT Observation of Optical Counterpart
  59. GRB 250322A: Gemini-North redshift of candidate host galaxy
  60. SVOM/sb25032302: SVOM detection of a long X-ray transient
  61. GRB 250322A: Gemini-South optical observations
  62. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  63. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  64. GRB 250322A: MASTER optical observation
  65. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  66. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  68. GRB 250321C: Fermi GBM Final Real-time Localization
  69. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  70. GRB 250320B: Fermi GBM Observation
  71. EP250321a: Xinglong 216 decaying optical observations
  72. GRB 250321A: Swift-BAT refined analysis
  73. GRB 250320B: Fermi-LAT detection
  74. GRB 250321B: SVOM detection of a sub-threshold transient event
  75. EP250321a: SVOM/VT optical observation
  76. EP250321A: COLIBRÍ Optical Observations
  77. EP250321a: VLT/X-shooter redshift z = 4.368
  78. EP250321a: REM optical/NIR afterglow detection
  79. Fermi GRB 250320B: Global MASTER-Net observations report
  80. EP250321a: Global MASTER-Net observations report
  81. Swift GRB 250321A: Global MASTER-Net observations report
  82. Fermi GRB 250321A: Global MASTER-Net observations report
  83. EP250226a/GRB 250226A: KAIT optical observations
  84. GRB 250321A: Fermi GBM Observation
  85. GRB 250321A: Swift detection of a burst
  86. GRB 250321A: Fermi GBM Final Real-time Localization
  87. GRB 250320B: Fermi GBM Final Real-time Localization
  88. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  89. GRB 250320A: Fermi GBM Final Real-time Localization
  90. Fermi GRB 250319B: Global MASTER-Net observations report
  91. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  92. GRB 250313A: GRBAlpha detection
  93. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  94. GRB 250319B: Fermi GBM Final Localization
  95. GRB 250319A: Fermi GBM Final Localization
  96. GRB 250317D: EIRSAT-1 GMOD Detection
  97. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  98. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  99. GRB 250317B: Leavitt Observatory optical upper limit
  100. GRB 250317C: GECAM-B detection

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