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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"

39172 results found.

  1. GRB 250327B: J-band observations with WINTER
  2. GRB 250327B: MASTER detection of OT rebrightening
  3. GRB 250327B: LCO optical counterpart detection
  4. GRB 250328A: GWAC-F50A optical upper limit
  5. GRB 250328A: SVOM detection of a burst
  6. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  7. GRB 250327B: CrAO and SAO RAS Optical Observations
  8. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  9. GRB 250327B: further optical observations by LCOGT
  10. EP250315a: Pan-STARRS r and i-band imaging and photometry
  11. GRB 250327b: Liverpool Telescope optical observations
  12. GRB 250322A: GRANDMA/TNOT optical upper limits
  13. GRB 250327A: SVOM/VT upper limits on the XRT position
  14. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  15. GRB 250327B: Las Cumbres optical counterpart detection
  16. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  17. GRB 250327B: 1.6m Mephisto optical observations
  18. GRB 250327B: NOT spectroscopic redshift z = 3.035
  19. GRB 250327A: Swift-XRT refined Analysis
  20. GRB 250327B: GOTO optical counterpart detection
  21. GRB 250327B: SVOM/VT optically bright counterpart
  22. GRB 250327B: SAO RAS optical candidate
  23. GRB 250327B: SVOM detection of a burst
  24. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  25. GRB 250327A: J-band observations with WINTER
  26. GRB 250327A: SVOM/VT optical candidate
  27. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  28. GRB 250327A: Fermi GBM observation
  29. Fermi GRB 250327A: Global MASTER-Net observations report
  30. Swift GRB 250327A: Global MASTER-Net observations report
  31. GRB 250327A: DDOTI Optical Observations
  32. GRB 250327A: COLIBRÍ optical upper limit
  33. GRB 250327A: Swift detection of a burst
  34. GRB 250327A: Fermi GBM Final Real-time Localization
  35. Fermi trigger No 764700395: Global MASTER-Net observations report
  36. Konus-Wind detection of GRB 250322A (short)
  37. IPN triangulation of GRB 250322B
  38. EP250321a: Mondy AZT-33IK Continued Optical Observations
  39. GRB 250322A: third epoch of NOT optical observations
  40. GRB 250322A: Swift-BAT refined analysis
  41. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  42. GRB 250322A: further NOT optical observations
  43. GRB 250322A: Swift/UVOT Upper Limits
  44. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  45. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  46. GRB 250321B: Swift-XRT observations
  47. GRB 250322A: Swift-XRT refined Analysis
  48. EP250321a: TNOT Observation of Optical Counterpart
  49. GRB 250322A: Gemini-North redshift of candidate host galaxy
  50. SVOM/sb25032302: SVOM detection of a long X-ray transient
  51. GRB 250322A: AstroSat CZTI detection of a short burst
  52. GRB 250322B: AstroSat CZTI detection of a bright long burst
  53. GRB 250322A: Gemini-South optical observations
  54. GRB 250322A: VLT optical observations
  55. GRB 250322A: VLT near-infrared observations
  56. GRB 250322A: NOT optical upper limits
  57. GRB 250322A: Enhanced Swift-XRT position
  58. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  59. GRB 250322A: MASTER optical observation
  60. EP250321a: Mondy AZT-33IK Optical Observations
  61. GRB 250322A: Swift detection of a short burst
  62. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  63. EP250321a: KAIT optical observations
  64. GRB 250225B: GECAM-A detection
  65. GRB 250312A: GECAM-A detection
  66. GRB 250321B: Swift ToO 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 250321A: Swift-XRT refined Analysis
  74. GRB 250320B: Fermi-LAT detection
  75. GRB 250321B: SVOM detection of a sub-threshold transient event
  76. EP 250321A: Optical counterpart detection by LCO.
  77. GRB 250321A: Swift/UVOT Upper Limits
  78. GRB 250320B: SVOM/GRM observation of a long burst
  79. EP250321a: LCO optical counterpart detection
  80. GRB 250320B: AstroSat CZTI detection
  81. EP250321a: REM optical/NIR afterglow detection
  82. Fermi GRB 250320B: Global MASTER-Net observations report
  83. EP250321a: TRT optical counterpart detection
  84. EP250321a: Global MASTER-Net observations report
  85. Swift GRB 250321A: Global MASTER-Net observations report
  86. Fermi GRB 250321A: Global MASTER-Net observations report
  87. GRB 250321A: GOTO optical upper limits
  88. GRB 250321A: Swift-XRT localisation
  89. GRB 250314A: Keck/NIRC2 J-band upper limit
  90. EP250226a/GRB 250226A: KAIT optical observations
  91. GRB 250321A: Fermi GBM Observation
  92. GRB 250321A: Swift detection of a burst
  93. GRB 250321A: Fermi GBM Final Real-time Localization
  94. GRB 250320B: Fermi GBM Final Real-time Localization
  95. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  96. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  97. GRB 250320A: Fermi GBM Final Real-time Localization
  98. Fermi GRB 250319B: Global MASTER-Net observations report
  99. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  100. GRB 250313A: GRBAlpha detection

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