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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"

18004 results found.

  1. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  2. GRB 250327A: DDOTI Optical Observations
  3. GRB 250327A: COLIBRÍ optical upper limit
  4. IPN triangulation of GRB 250322B
  5. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  6. EP250321a: Mondy AZT-33IK Continued Optical Observations
  7. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  8. GRB 250322A: third epoch of NOT optical observations
  9. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  10. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  11. GRB 250322A: further NOT optical observations
  12. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  13. GRB 250322A: Swift/UVOT Upper Limits
  14. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  15. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  16. GRB 250321B: Swift-XRT observations
  17. EP250321a: TNOT Observation of Optical Counterpart
  18. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  19. GRB 250322A: VLT optical observations
  20. GRB 250322A: VLT near-infrared observations
  21. FRB 250316A: DDOTI Continued Optical Observations
  22. GRB 250322A: NOT optical upper limits
  23. GRB 250322A: Enhanced Swift-XRT position
  24. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  25. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  26. EP250321a: Liverpool Telescope optical follow-up
  27. EP250321a: Mondy AZT-33IK Optical Observations
  28. GRB 250322A: Swift detection of a short burst
  29. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  30. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  31. EP250321a: KAIT optical observations
  32. EP250321A: COLIBRÍ Continuing Optical Observations
  33. EP250321a: WFST optical observations
  34. EP250321a: Xinglong 216 decaying optical observations
  35. GRB 250321A: Swift-XRT refined Analysis
  36. EP 250321A: Optical counterpart detection by LCO.
  37. EP250321a: Kinder optical follow-up observations
  38. GRB 250321A: Swift/UVOT Upper Limits
  39. GRB 250320B: SVOM/GRM observation of a long burst
  40. EP250321a: LCO optical counterpart detection
  41. EP250321A: COLIBRÍ Optical Observations
  42. GRB 250320B: AstroSat CZTI detection
  43. EP250321a: REM optical/NIR afterglow detection
  44. EP250321a: TRT optical counterpart detection
  45. EP250321a: Einstein Probe detection of an X-ray transient
  46. GRB 250321A: GOTO optical upper limits
  47. GRB 250314A: Keck/NIRC2 J-band upper limit
  48. EP250226a/GRB 250226A: KAIT optical observations
  49. GRB 250321A: Swift detection of a burst
  50. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  51. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  52. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  53. EP250302a: VLA observations
  54. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  55. GRB 250317C: SVOM/GRM observation of a long burst
  56. GRB 250317B: Leavitt Observatory optical upper limit
  57. GRB 250317B: Mondy AZT-33IK Optical Observations
  58. GRB 250317B: NOT optical observations suggest an optical plateau phase
  59. GRB 250317B: OHP/T193 optical observations
  60. GRB250312A: Swift/UVOT Upper Limits
  61. GRB 250317B: REM optical/NIR 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. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  73. GRB 250314A: Swift/UVOT Upper Limits
  74. GRB 250314A: Swift XRT Detection
  75. EP250315a: optical counterpart candidate detected by Gemini North
  76. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  77. EP250315a: Einstein Probe detection of an X-ray transient
  78. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  79. SVOM/MXT upper limit on GRB 250314A
  80. GRB 250314A: SVOM/VT upper limit
  81. GRB 250314A: NOT near-infrared candidate counterpart
  82. GRB 250313A: Fermi GBM Detection
  83. GRB 250313A: Swift-XRT observations
  84. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  85. Konus-Wind detection of GRB 250313A
  86. GRB 250314A: SVOM detection of a burst
  87. EP250304a: Pan-STARRS r and i-band imaging and photometry
  88. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  89. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  90. GRB 250312A: Enhanced Swift-XRT position
  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 250311A: Swift-XRT observations
  97. GRB 230509B: 1.3m DFOT Optical observations
  98. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  100. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst

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