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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"

24870 results found.

  1. GRB 250331B: Swift-XRT refined Analysis
  2. GRB 250331B: Swift-XRT refined Analysis
  3. GRB 250322B possible detection by the AstroSat Satellite
  4. GRB 250330B: SVOM/GRM observation of a short burst
  5. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  6. GRB 250330B: EIRSAT-1 GMOD Detection
  7. GRB 250327A Swift-BAT refined analysis
  8. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  9. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  10. Swift GRB 250331C: Global MASTER-Net observations report
  11. Swift GRB 250331B: Global MASTER-Net observations report
  12. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  13. GRB 250331C: Enhanced Swift-XRT position
  14. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  15. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  16. GRB 250331B: Enhanced Swift-XRT position
  17. GRB 250320C : SVOM detection of a burst through offline search
  18. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  19. GRB 250330A: VLT/FORS2 Afterglow Detection
  20. GRB20250327B: 45th Parallel Observatory upper limit
  21. GRB 250328A: Swift/UVOT Detection
  22. GRB 250328A: Swift-XRT refined Analysis
  23. Fermi-LAT gamma-ray observations of IceCube-250330A
  24. SVOM/sb25033102 is a false trigger
  25. GRB 250330A: Fermi GBM Observation
  26. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  27. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  28. GRB 250331C: Swift detection of a burst
  29. GRB 250331B: Swift detection of a burst
  30. GRB 250331A: MAXI/GSC detection
  31. SVOM/sb25033102: SVOM detection of an X-ray transient
  32. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  33. GRB 250330A: Swift/UVOT Upper Limits
  34. GRB 250330A: Swift-XRT afterglow detection
  35. GRB 250328A: 1.6m Mephisto optical observations
  36. GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
  37. GRB 250330A: VLT/FORS2 Optical Observations
  38. GRB 250329B: Swift-XRT afterglow detection
  39. GRB 250330A: Swift detection of a burst
  40. GRB 250329B: SVOM/C-GFT optical upper limit
  41. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  42. GRB 250329B: SVOM/VT optical upper limit
  43. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  44. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  45. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  46. GRB250329A: REM optical afterglow detection
  47. GRB 250329A: Swift-XRT afterglow detection
  48. GRB 250328A: SVOM/VT optical observation
  49. GRB 250329A: Fading optical counterpart detection by LCO.
  50. GRB 250328A: SVOM/C-GFT optical upper limit
  51. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  52. GRB 250329A: SVOM/VT optical counterpart confirmation
  53. GRB 250329A: SVOM detection of a burst
  54. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  55. GRB 250327B: J-band observations with WINTER
  56. GRB 250327B: LCO optical counterpart detection
  57. GRB 250328A: SVOM detection of a burst
  58. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  59. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  60. GRB 250327B: CrAO and SAO RAS Optical Observations
  61. GRB 250327b: Liverpool Telescope optical observations
  62. GRB 250322A: GRANDMA/TNOT optical upper limits
  63. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  64. GRB 250327A: SVOM/VT upper limits on the XRT position
  65. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  66. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  67. GRB 250327B: Las Cumbres optical counterpart detection
  68. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  69. GRB 250327B: 1.6m Mephisto optical observations
  70. GRB 250327A: Swift-XRT refined Analysis
  71. GRB 250327B: SVOM/VT optically bright counterpart
  72. GRB 250327B: SAO RAS optical candidate
  73. GRB 250327B: SVOM detection of a burst
  74. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  75. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  76. GRB 250327A: J-band observations with WINTER
  77. GRB 250327A: SVOM/VT optical candidate
  78. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  79. GRB 250327A: DDOTI Optical Observations
  80. GRB 250327A: COLIBRÍ optical upper limit
  81. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  82. IPN triangulation of GRB 250322B
  83. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  84. EP250321a: Mondy AZT-33IK Continued Optical Observations
  85. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  86. GRB 250322A: third epoch of NOT optical observations
  87. GRB 250322A: Swift-BAT refined analysis
  88. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  89. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  90. GRB 250322A: further NOT optical observations
  91. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  92. GRB 250322A: Swift/UVOT Upper Limits
  93. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  94. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  95. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  96. GRB 250321B: Swift-XRT observations
  97. GRB 250322A: Swift-XRT refined Analysis
  98. EP250321a: TNOT Observation of Optical Counterpart
  99. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  100. SVOM/sb25032302: SVOM detection of a long X-ray transient

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