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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"

28284 results found.

  1. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  2. GRB 250329B: Swift/UVOT Upper Limit
  3. GRB 250329A: Swift/UVOT Upper Limit
  4. GRB 250327B: Swift/UVOT Detection
  5. GRB 250327A: Swift/UVOT Upper Limits
  6. GRB 250331E: SVOM/GRM observation
  7. GRB 250327B: Kilonova-Catcher Observations
  8. GRB250331D: AbAO optical observations
  9. GRB 250331D: Fermi GBM observation
  10. GRB 250331C: Swift/UVOT Upper Limits
  11. GRB 250331B: Swift/UVOT Upper Limits
  12. GRB 250328A: AbAO AS-32 Optical Observations
  13. GRB 250219A: NOT candidate host galaxy detection
  14. GRB 250331D: Swift-XRT observations
  15. GRB 250331C: Swift-XRT refined Analysis
  16. GRB 250331B: Swift-XRT refined Analysis
  17. GRB 250331B: Swift-XRT refined Analysis
  18. GRB 250322B possible detection by the AstroSat Satellite
  19. GRB 250330B: SVOM/GRM observation of a short burst
  20. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  21. GRB 250330B: EIRSAT-1 GMOD Detection
  22. GRB 250327A Swift-BAT refined analysis
  23. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  24. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  25. Swift GRB 250331C: Global MASTER-Net observations report
  26. Swift GRB 250331B: Global MASTER-Net observations report
  27. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  28. GRB 250331C: Enhanced Swift-XRT position
  29. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  30. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  31. GRB 250331B: Enhanced Swift-XRT position
  32. GRB 250320C : SVOM detection of a burst through offline search
  33. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  34. GRB 250330A: VLT/FORS2 Afterglow Detection
  35. GRB20250327B: 45th Parallel Observatory upper limit
  36. GRB 250328A: Swift/UVOT Detection
  37. GRB 250328A: Swift-XRT refined Analysis
  38. Fermi-LAT gamma-ray observations of IceCube-250330A
  39. SVOM/sb25033102 is a false trigger
  40. GRB 250330A: Fermi GBM Observation
  41. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  42. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  43. GRB 250331C: Swift detection of a burst
  44. GRB 250331B: Swift detection of a burst
  45. GRB 250331A: MAXI/GSC detection
  46. SVOM/sb25033102: SVOM detection of an X-ray transient
  47. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  48. GRB 250330A: Swift/UVOT Upper Limits
  49. GRB 250330A: Swift-XRT afterglow detection
  50. GRB 250328A: 1.6m Mephisto optical observations
  51. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  52. GRB 250330A: VLT/FORS2 Optical Observations
  53. GRB 250329B: Swift-XRT afterglow detection
  54. GRB 250330A: Swift detection of a burst
  55. GRB 250329B: SVOM/C-GFT optical upper limit
  56. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  57. GRB 250329B: SVOM/VT optical upper limit
  58. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  59. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  60. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  61. GRB250329A: REM optical afterglow detection
  62. GRB 250329A: Swift-XRT afterglow detection
  63. GRB 250328A: SVOM/VT optical observation
  64. GRB 250329A: Fading optical counterpart detection by LCO.
  65. GRB 250328A: SVOM/C-GFT optical upper limit
  66. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  67. GRB 250329A: SVOM/VT optical counterpart confirmation
  68. GRB 250329A: SVOM detection of a burst
  69. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  70. GRB 250327B: J-band observations with WINTER
  71. GRB 250327B: LCO optical counterpart detection
  72. GRB 250328A: SVOM detection of a burst
  73. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  74. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  75. GRB 250327B: CrAO and SAO RAS Optical Observations
  76. GRB 250327b: Liverpool Telescope optical observations
  77. GRB 250322A: GRANDMA/TNOT optical upper limits
  78. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  79. GRB 250327A: SVOM/VT upper limits on the XRT position
  80. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  81. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  82. GRB 250327B: Las Cumbres optical counterpart detection
  83. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  84. GRB 250327B: 1.6m Mephisto optical observations
  85. GRB 250327A: Swift-XRT refined Analysis
  86. GRB 250327B: SVOM/VT optically bright counterpart
  87. GRB 250327B: SAO RAS optical candidate
  88. GRB 250327B: SVOM detection of a burst
  89. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  90. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  91. GRB 250327A: J-band observations with WINTER
  92. GRB 250327A: SVOM/VT optical candidate
  93. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  94. GRB 250327A: DDOTI Optical Observations
  95. GRB 250327A: COLIBRÍ optical upper limit
  96. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  97. IPN triangulation of GRB 250322B
  98. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  99. EP250321a: Mondy AZT-33IK Continued Optical Observations
  100. Swift follow-up observations of FRB250316A and EP J120944.2+585060

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