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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"

21952 results found.

  1. GRB 250331D: Swift-XRT observations
  2. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  3. Fermi GRB 250331E: Global MASTER-Net observations report
  4. Fermi GRB 250331D: Global MASTER-Net observations report
  5. Fermi trigger No 765078057: Global MASTER-Net observations report
  6. GRB 250331D: Swift ToO observations
  7. Swift GRB 250331C: Global MASTER-Net observations report
  8. Swift GRB 250331B: Global MASTER-Net observations report
  9. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  10. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  11. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  12. GRB 250330A: VLT/FORS2 Afterglow Detection
  13. GRB20250327B: 45th Parallel Observatory upper limit
  14. GRB 250328A: Swift/UVOT Detection
  15. Fermi-LAT gamma-ray observations of IceCube-250330A
  16. GRB 250330A: SVOM/VT optical upper limit
  17. GRB 250314A: VLA detection
  18. Fermi GRB 250330B: Global MASTER-Net observations report
  19. Fermi GRB 250330A: Global MASTER-Net observations report
  20. GRB 250330A: BOOTES-7 early optical upper limit
  21. GRB 250330A: Swift/UVOT Upper Limits
  22. GRB 250330A: Swift-XRT afterglow detection
  23. GRB 250328A: 1.6m Mephisto optical observations
  24. IceCube Alert 250330.35: Global MASTER-Net observations report
  25. GRB 250330A: VLT/FORS2 Optical Observations
  26. Swift GRB250330.26: Global MASTER-Net observations report
  27. GRB 250329B: SVOM/C-GFT optical upper limit
  28. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  29. GRB 250327B: ALMA detection
  30. GRB 250327B: VLA detection
  31. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  32. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  33. GRB250329A: REM optical afterglow detection
  34. GRB 250329B: GWAC-F50A optical upper limit
  35. GRB 250328A: SVOM/VT optical observation
  36. GRB 250329A: Fading optical counterpart detection by LCO.
  37. GRB 250328A: SVOM/C-GFT optical upper limit
  38. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  39. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  40. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  41. GRB 250327B: J-band observations with WINTER
  42. GRB 250327B: LCO optical counterpart detection
  43. GRB 250328A: GWAC-F50A optical upper limit
  44. FRB 20250316A: FTW optical observations
  45. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  46. GRB 250327B: CrAO and SAO RAS Optical Observations
  47. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  48. GRB 250327B: further optical observations by LCOGT
  49. GRB 250327b: Liverpool Telescope optical observations
  50. GRB 250327A: SVOM/VT upper limits on the XRT position
  51. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  52. GRB 250327B: 1.6m Mephisto optical observations
  53. GRB 250327B: GOTO optical counterpart detection
  54. GRB 250327B: SAO RAS optical candidate
  55. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  56. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  57. GRB 250327A: J-band observations with WINTER
  58. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  59. Fermi GRB 250327A: Global MASTER-Net observations report
  60. Swift GRB 250327A: Global MASTER-Net observations report
  61. GRB 250327A: DDOTI Optical Observations
  62. GRB 250327A: COLIBRÍ optical upper limit
  63. Fermi trigger No 764700395: Global MASTER-Net observations report
  64. EP250321a: Mondy AZT-33IK Continued Optical Observations
  65. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  66. GRB 250322A: third epoch of NOT optical observations
  67. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  68. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  69. GRB 250322A: further NOT optical observations
  70. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  71. GRB 250322A: Swift/UVOT Upper Limits
  72. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  73. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  74. GRB 250321B: Swift-XRT observations
  75. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  76. GRB 250322A: Gemini-North redshift of candidate host galaxy
  77. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  78. GRB250322A: STEP/T80S optical limits
  79. GRB 250322A: Gemini-South optical observations
  80. GRB 250322A: VLT optical observations
  81. GRB 250322A: VLT near-infrared observations
  82. FRB 250316A: DDOTI Continued Optical Observations
  83. GRB 250322A: NOT optical upper limits
  84. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  85. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  86. GRB 250322A: MASTER optical observation
  87. EP250321a: Liverpool Telescope optical follow-up
  88. EP250321a: Mondy AZT-33IK Optical Observations
  89. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  90. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP250321a: KAIT optical observations
  92. EP250321A: COLIBRÍ Continuing Optical Observations
  93. GRB 250321B: Swift ToO observations
  94. EP250321a: WFST optical observations
  95. EP250321a: Xinglong 216 decaying optical observations
  96. EP250321a: SVOM/VT optical observation
  97. EP 250321A: Optical counterpart detection by LCO.
  98. EP250321a: Kinder optical follow-up observations
  99. GRB 250321A: Swift/UVOT Upper Limits
  100. EP250321a: LCO optical counterpart detection

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