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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"

26733 results found.

  1. GRB 250322A: VLT near-infrared observations
  2. FRB 250316A: DDOTI Continued Optical Observations
  3. GRB 250322A: NOT optical upper limits
  4. GRB 250322A: Enhanced Swift-XRT position
  5. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  6. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  7. EP250321a: Liverpool Telescope optical follow-up
  8. EP250321a: Mondy AZT-33IK Optical Observations
  9. GRB 250322A: Swift detection of a short burst
  10. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  11. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  12. EP250321A: COLIBRÍ Continuing Optical Observations
  13. EP250321a: WFST optical observations
  14. GRB 250320B: Fermi GBM Observation
  15. EP250321a: Xinglong 216 decaying optical observations
  16. GRB 250321A: Swift-XRT refined Analysis
  17. EP 250321A: Optical counterpart detection by LCO.
  18. EP250321a: Kinder optical follow-up observations
  19. GRB 250321A: Swift/UVOT Upper Limits
  20. GRB 250320B: SVOM/GRM observation of a long burst
  21. EP250321a: LCO optical counterpart detection
  22. EP250321a: Swift-XRT detection of an X-ray source
  23. EP250321A: COLIBRÍ Optical Observations
  24. EP250321a: VLT/X-shooter redshift z = 4.368
  25. GRB 250320B: AstroSat CZTI detection
  26. EP250321a: REM optical/NIR afterglow detection
  27. EP250321a: TRT optical counterpart detection
  28. EP250321a: Einstein Probe detection of an X-ray transient
  29. GRB 250321A: GOTO optical upper limits
  30. GRB 250314A: Keck/NIRC2 J-band upper limit
  31. EP250226a/GRB 250226A: KAIT optical observations
  32. GRB 250321A: Fermi GBM Observation
  33. GRB 250321A: Swift detection of a burst
  34. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  35. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  36. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  37. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  38. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  39. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  40. GRB 250317C: SVOM/GRM observation of a long burst
  41. GRB 250317B: Leavitt Observatory optical upper limit
  42. GRB 250317B: Mondy AZT-33IK Optical Observations
  43. GRB 250317B: NOT optical observations suggest an optical plateau phase
  44. GRB 250317B: OHP/T193 optical observations
  45. GRB250312A: Swift/UVOT Upper Limits
  46. GRB 250317B: REM optical/NIR observations
  47. GRB 250317B: Swift-XRT observations
  48. GRB 250316A: Swift/UVOT Upper Limits
  49. GRB 250314A: REM optical/NIR upper limits
  50. GRB 250316A: AbAO AS-32 Optical Upper Limit
  51. EP 250317B: Fading optical counterpart detection by LCO
  52. GRB 250316A: Swift-XRT afterglow detection
  53. GRB 250317B: LCO detection of the fading optical afterglow
  54. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  55. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  56. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  57. GRB 250317B: SVOM detection of a burst
  58. GRB 250316A: Fermi GBM Observation
  59. GRB 250316A: Swift-XRT observations
  60. GRB 250314A: SVOM/GRM analysis
  61. The EP-WXT trigger 01709132801 is likely a flaring star
  62. GRB 250314A: EP-FXT afterglow detection
  63. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  64. GRB 250314A: Swift/UVOT Upper Limits
  65. GRB 250314A: Swift XRT Detection
  66. EP250315a: optical counterpart candidate detected by Gemini North
  67. EP250315a: Einstein Probe detection of an X-ray transient
  68. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  69. SVOM/MXT upper limit on GRB 250314A
  70. GRB 250314A: SVOM/VT upper limit
  71. GRB 250314A: NOT near-infrared candidate counterpart
  72. GRB 250313A: Fermi GBM Detection
  73. GRB 250312B: Fermi GBM Observation
  74. GRB 250313A: Swift-XRT observations
  75. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  76. Konus-Wind detection of GRB 250313A
  77. Konus-Wind detection of GRB 250308A
  78. GRB 250314A: SVOM detection of a burst
  79. GRB 250313A: AstroSat CZTI detection of a bright long burst
  80. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  81. Fermi trigger No 763581136: Global MASTER-Net observations report
  82. EP250304a: Pan-STARRS r and i-band imaging and photometry
  83. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  84. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  85. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  86. GRB 250312A: Swift-XRT refined Analysis
  87. GRB 250312A: Enhanced Swift-XRT position
  88. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  89. GRB 250226B: Fermi GBM Observation
  90. GRB 250302A: Fermi GBM Observation
  91. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  92. GRB 250312A: Swift detection of a burst
  93. GRB 241213A: VIRT Optical Upper Limit
  94. GRB 241228A: VIRT Optical Upper Limit
  95. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  96. GRB 250223B: Fermi GBM Observation
  97. GRB 250311A: Swift-XRT observations
  98. GRB 250228A: Fermi GBM Observation
  99. GRB 250309B: 1.3m DFOT Optical observations
  100. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube

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