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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"

22108 results found.

  1. EP250321a: Mondy AZT-33IK Continued Optical Observations
  2. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  3. GRB 250322A: third epoch of NOT optical observations
  4. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  5. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  6. GRB 250322A: further NOT optical observations
  7. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  8. GRB 250322A: Swift/UVOT Upper Limits
  9. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  10. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  11. GRB 250321B: Swift-XRT observations
  12. EP250321a: TNOT Observation of Optical Counterpart
  13. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  14. GRB 250322B: AstroSat CZTI detection of a bright long burst
  15. GRB250322A: STEP/T80S optical limits
  16. GRB 250322A: Gemini-South optical observations
  17. GRB 250322A: VLT optical observations
  18. GRB 250322A: VLT near-infrared observations
  19. FRB 250316A: DDOTI Continued Optical Observations
  20. GRB 250322A: NOT optical upper limits
  21. GRB 250322A: Enhanced Swift-XRT position
  22. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  23. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  24. EP250321a: Liverpool Telescope optical follow-up
  25. EP250321a: Mondy AZT-33IK Optical Observations
  26. GRB 250322A: Swift detection of a short burst
  27. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  28. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  29. EP250321A: COLIBRÍ Continuing Optical Observations
  30. EP250321a: WFST optical observations
  31. EP250321a: Xinglong 216 decaying optical observations
  32. GRB 250321A: Swift-XRT refined Analysis
  33. EP 250321A: Optical counterpart detection by LCO.
  34. EP250321a: Kinder optical follow-up observations
  35. GRB 250321A: Swift/UVOT Upper Limits
  36. GRB 250320B: SVOM/GRM observation of a long burst
  37. EP250321a: LCO optical counterpart detection
  38. EP250321A: COLIBRÍ Optical Observations
  39. GRB 250320B: AstroSat CZTI detection
  40. EP250321a: REM optical/NIR afterglow detection
  41. EP250321a: TRT optical counterpart detection
  42. EP250321a: Einstein Probe detection of an X-ray transient
  43. GRB 250321A: GOTO optical upper limits
  44. GRB 250314A: Keck/NIRC2 J-band upper limit
  45. EP250226a/GRB 250226A: KAIT optical observations
  46. GRB 250321A: Swift detection of a burst
  47. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  48. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  49. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  50. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  51. GRB 250314A: ATCA radio upper limits
  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 250317C: AstroSat CZTI detection
  57. GRB 250317B: NOT optical observations suggest an optical plateau phase
  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. GRB 250317B: 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: Swift-XRT observations
  73. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  74. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  75. GRB 250314A: Swift/UVOT Upper Limits
  76. GRB 250314A: Swift XRT Detection
  77. EP250315a: optical counterpart candidate detected by Gemini North
  78. EP250315a: Einstein Probe detection of an X-ray transient
  79. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  80. SVOM/MXT upper limit on GRB 250314A
  81. GRB 250314A: SVOM/VT upper limit
  82. GRB 250314A: NOT near-infrared candidate counterpart
  83. GRB 250313A: Swift-XRT observations
  84. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  85. GRB 250314A: SVOM detection of a burst
  86. GRB 250313A: AstroSat CZTI detection of a bright long burst
  87. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  88. EP250304a: Pan-STARRS r and i-band imaging and photometry
  89. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  90. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  91. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  92. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  93. GRB 250312A: Enhanced Swift-XRT position
  94. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  95. GRB 250312A: Swift detection of a burst
  96. GRB 241213A: VIRT Optical Upper Limit
  97. GRB 241228A: VIRT Optical Upper Limit
  98. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  99. GRB 250311A: Swift-XRT observations
  100. GRB 250309B: 1.3m DFOT Optical observations

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