Skip to main content
Circulars over Kafka event name backfill. See news and announcements

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"

17213 results found.

  1. GRB 250322A: third epoch of NOT optical observations
  2. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  3. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  4. GRB 250322A: further NOT optical observations
  5. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  6. GRB 250322A: Swift/UVOT Upper Limits
  7. EP250324A: COLIBRÍ/DDRAGO Optical Observations
  8. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  9. GRB 250321B: Swift-XRT observations
  10. EP250321a: TNOT Observation of Optical Counterpart
  11. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  12. SVOM/sb25032302: SVOM detection of a long X-ray transient
  13. GRB250322A: STEP/T80S optical limits
  14. GRB 250322A: VLT optical observations
  15. GRB 250322A: VLT near-infrared observations
  16. FRB 250316A: DDOTI Continued Optical Observations
  17. GRB 250322A: NOT optical upper limits
  18. GRB 250322A: Enhanced Swift-XRT position
  19. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  20. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  21. EP250321a: Liverpool Telescope optical follow-up
  22. EP250321a: Mondy AZT-33IK Optical Observations
  23. GRB 250322A: Swift detection of a short burst
  24. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  25. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP250321A: COLIBRÍ Continuing Optical Observations
  27. GRB 250321B: Swift ToO observations
  28. EP250321a: WFST optical observations
  29. EP250321a: Xinglong 216 decaying optical observations
  30. GRB 250321A: Swift-XRT refined Analysis
  31. GRB 250321B: SVOM detection of a sub-threshold transient event
  32. EP 250321A: Optical counterpart detection by LCO.
  33. EP250321a: Kinder optical follow-up observations
  34. GRB 250321A: Swift/UVOT Upper Limits
  35. GRB 250320B: SVOM/GRM observation of a long burst
  36. EP250321a: LCO optical counterpart detection
  37. EP250321A: COLIBRÍ Optical Observations
  38. EP250321a: REM optical/NIR afterglow detection
  39. EP250321a: TRT optical counterpart detection
  40. EP250321a: Einstein Probe detection of an X-ray transient
  41. GRB 250321A: GOTO optical upper limits
  42. GRB 250314A: Keck/NIRC2 J-band upper limit
  43. EP250226a/GRB 250226A: KAIT optical observations
  44. GRB 250321A: Swift detection of a burst
  45. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  46. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  47. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  48. GRB 250317C: SVOM/GRM observation of a long burst
  49. GRB 250317B: Leavitt Observatory optical upper limit
  50. GRB 250317B: Mondy AZT-33IK Optical Observations
  51. GRB 250317B: NOT optical observations suggest an optical plateau phase
  52. GRB 250317B: OHP/T193 optical observations
  53. GRB250312A: Swift/UVOT Upper Limits
  54. GRB 250317B: REM optical/NIR observations
  55. GRB 250316A: Swift/UVOT Upper Limits
  56. GRB 250314A: REM optical/NIR upper limits
  57. GRB 250316A: AbAO AS-32 Optical Upper Limit
  58. EP 250317B: Fading optical counterpart detection by LCO
  59. GRB 250316A: Swift-XRT afterglow detection
  60. GRB 250317B: LCO detection of the fading optical afterglow
  61. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  62. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  63. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  64. GRB 250317B: SVOM detection of a burst
  65. GRB 250316A: Swift ToO observations
  66. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  67. GRB 250314A: Swift/UVOT Upper Limits
  68. GRB 250314A: Swift XRT Detection
  69. EP250315a: optical counterpart candidate detected by Gemini North
  70. EP250315a: Einstein Probe detection of an X-ray transient
  71. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  72. SVOM/MXT upper limit on GRB 250314A
  73. GRB 250314A: SVOM/VT upper limit
  74. GRB 250314A: NOT near-infrared candidate counterpart
  75. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  76. GRB 250314A: SVOM detection of a burst
  77. GRB 250313A: Swift ToO observations
  78. EP250304a: Pan-STARRS r and i-band imaging and photometry
  79. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  80. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  81. GRB 250312A: Enhanced Swift-XRT position
  82. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  83. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  84. GRB 250312A: Swift detection of a burst
  85. GRB 241213A: VIRT Optical Upper Limit
  86. GRB 241228A: VIRT Optical Upper Limit
  87. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  88. GRB 230509B: 1.3m DFOT Optical observations
  89. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  90. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  91. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  92. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  93. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  94. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  95. GRB 250309B: PRIME near-infrared detection
  96. EP250304a: Chandra detection
  97. GRB 250225B: Swift-BAT refined analysis
  98. GRB 250311A/EP250311a: TRT optical upper limit
  99. GRB 250311A: Tiled Swift observations
  100. EP250311a/GRB 250311A: EP-WXT detection

Advanced

Download all Circulars as a .tar.gz archive:
Looking for U.S. government information and services? Visit USA.gov