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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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24573 results found.

  1. GRB 250322A: Swift-XRT refined Analysis
  2. EP250321a: TNOT Observation of Optical Counterpart
  3. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  4. SVOM/sb25032302: SVOM detection of a long X-ray transient
  5. GRB 250322B: AstroSat CZTI detection of a bright long burst
  6. GRB 250322A: VLT optical observations
  7. GRB 250322A: VLT near-infrared observations
  8. FRB 250316A: DDOTI Continued Optical Observations
  9. GRB 250322A: NOT optical upper limits
  10. GRB 250322A: Enhanced Swift-XRT position
  11. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  12. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  13. EP250321a: Liverpool Telescope optical follow-up
  14. EP250321a: Mondy AZT-33IK Optical Observations
  15. GRB 250322A: Swift detection of a short burst
  16. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  17. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  18. EP250321A: COLIBRÍ Continuing Optical Observations
  19. EP250321a: WFST optical observations
  20. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  21. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  22. GRB 250320B: Fermi GBM Observation
  23. EP250321a: Xinglong 216 decaying optical observations
  24. GRB 250321A: Swift-BAT refined analysis
  25. GRB 250321A: Swift-XRT refined Analysis
  26. EP 250321A: Optical counterpart detection by LCO.
  27. EP250321a: Kinder optical follow-up observations
  28. GRB 250321A: Swift/UVOT Upper Limits
  29. GRB 250320B: SVOM/GRM observation of a long burst
  30. EP250321a: LCO optical counterpart detection
  31. EP250321a: Swift-XRT detection of an X-ray source
  32. EP250321A: COLIBRÍ Optical Observations
  33. GRB 250320B: AstroSat CZTI detection
  34. EP250321a: REM optical/NIR afterglow detection
  35. EP250321a: TRT optical counterpart detection
  36. Swift GRB 250321A: Global MASTER-Net observations report
  37. EP250321a: Einstein Probe detection of an X-ray transient
  38. GRB 250321A: GOTO optical upper limits
  39. GRB 250314A: Keck/NIRC2 J-band upper limit
  40. EP250226a/GRB 250226A: KAIT optical observations
  41. GRB 250321A: Fermi GBM Observation
  42. GRB 250321A: Swift detection of a burst
  43. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  44. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  45. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  46. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  47. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  48. GRB 250317D: EIRSAT-1 GMOD Detection
  49. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  50. GRB 250314A: ATCA radio upper limits
  51. GRB 250317B: OHP/T193 continued follow-up
  52. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  53. GRB 250317C: SVOM/GRM observation of a long burst
  54. GRB 250317B: Leavitt Observatory optical upper limit
  55. GRB 250317B: Mondy AZT-33IK Optical Observations
  56. GRB 250317B: NOT optical observations suggest an optical plateau phase
  57. GRB 250317C: GECAM-B detection
  58. GRB 250317B: OHP/T193 optical observations
  59. GRB250312A: Swift/UVOT Upper Limits
  60. GRB 250317B: REM optical/NIR observations
  61. GRB 250317B: Swift-XRT observations
  62. GRB 250316A: Swift/UVOT Upper Limits
  63. GRB 250314A: REM optical/NIR upper limits
  64. GRB 250316A: AbAO AS-32 Optical Upper Limit
  65. EP 250317B: Fading optical counterpart detection by LCO
  66. GRB 250316A: Swift-XRT afterglow detection
  67. GRB 250317B: LCO detection of the fading optical afterglow
  68. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  69. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  70. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  71. GRB 250317B: SVOM detection of a burst
  72. GRB 250316A: Fermi GBM Observation
  73. GRB 250316A: Swift-XRT observations
  74. GRB 250314A: SVOM/GRM analysis
  75. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  76. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  77. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  78. GRB 250314A: EP-FXT afterglow detection
  79. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  80. GRB 250314A: Swift/UVOT Upper Limits
  81. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  82. GRB 250314A: Swift XRT Detection
  83. EP250315a: optical counterpart candidate detected by Gemini North
  84. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  85. EP250315a: Einstein Probe detection of an X-ray transient
  86. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  87. SVOM/MXT upper limit on GRB 250314A
  88. GRB 250314A: SVOM/VT upper limit
  89. GRB 250314A: NOT near-infrared candidate counterpart
  90. GRB 250313A: Fermi GBM Detection
  91. GRB 250312B: Fermi GBM Observation
  92. GRB 250313A: Swift-XRT observations
  93. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  94. GRB 250314A: SVOM detection of a burst
  95. GRB 250313A: AstroSat CZTI detection of a bright long burst
  96. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  97. GRB 250313A: Fermi-LAT detection
  98. EP250304a: Pan-STARRS r and i-band imaging and photometry
  99. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  100. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch

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