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 250308A: CALET Gamma-Ray Burst Monitor detection
  2. GRB 250311B: SVOM detection of a burst
  3. GRB 250309B / AT2025dws: further SAO RAS optical observations
  4. EP250308a: 1.6m Mephisto optical upper limits
  5. Konus-Wind detection of GRB 250309B
  6. IPN triangulation of GRB 250308A (short)
  7. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  8. GRB 250309B / AT2025dws: SAO RAS optical observations
  9. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  10. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  11. IceCube-250309A: No candidates from the Zwicky Transient Facility
  12. Fermi-LAT gamma-ray observations of IceCube-250309A
  13. GRB 230509B: Tiled Swift observations
  14. EP250308a: Einstein Probe detection of an X-ray transient
  15. EP250308a: NOT optical upper limit
  16. EP250304a: MeerKAT detection of a possible radio counterpart
  17. GRB 250305A: AstroSat CZTI detection
  18. EP250302a:Xinglong optical observations
  19. GRB 250306A: AstroSat CZTI detection
  20. GRB250101A: Radio upper limits from VLA observations
  21. GRB 250305A: SVOM/GRM observation of a burst
  22. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  23. EP250302a: Optical Observations at CrAO and SAO RAS
  24. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  25. EP 250304A: Optical counterpart detection by LCO
  26. EP250302A: 1.3m DFOT optical afterglow detection
  27. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  28. EP250304a: REM NIR upper limits
  29. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  30. EP250302a: Mondy Continued Optical Observations
  31. EP250304a: TRT optical counterpart detection
  32. EP250304a: Einstein Probe detection of an X-ray transient
  33. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  34. EP250302a: SAO RAS optical observations
  35. EP250302a : GIT optical follow-up
  36. EP250302a: Kinder optical follow-up observations
  37. EP250302a: Swift/UVOT detection
  38. EP250302a: optical observation from the INAF Asiago Observatory
  39. EP250302a: REM NIR upper limits
  40. EP250302a: Mondy Observations and Optical Light Curve
  41. EP250302a: VLT/MUSE optical redshift z = 1.131
  42. EP250302A: VLT near-infrared observations
  43. EP250302A: VLT/X-shooter tentative redshift
  44. EP250302a: OHP/T193 optical and spectroscopic observations
  45. EP250302a: Swift-XRT observations of a fading X-ray source
  46. EP250302a: Einstein Probe detection of an X-ray transient
  47. EP250302a: SVOM/C-GFT optical observations
  48. GRB 250226A: GRANDMA Optical Observations
  49. EP250302a: Montarrenti Observatory optical detection
  50. EP250302a: Nanshan/HMT optical counterpart detection
  51. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  52. GRB 250225B: VLT near-infrared afterglow confirmation
  53. EP250228a: Optical observations with Kinder and Swift/UVOT
  54. Konus-Wind detection of GRB 250226A
  55. GRB 250226A: KAO Optical Upper Limit
  56. GRB 250226A: AbAO AS-32 Optical Upper Limit
  57. EP250227a: TRT optical upper limit
  58. GRB 250225B: VLT/HAWKI near-infrared observations
  59. EP250227a: Optical upper limits with Kinder observations
  60. EP250227a: NOT optical observations
  61. EP250227a: Einstein Probe detected of a fast X-ray transient
  62. EP250228a: updates on the EP observations
  63. EP250223a: J band upper limit by SYSU 80cm telescope
  64. EP250228a: Einstein Probe detection of an X-ray transient
  65. GRB 250225B: VLT/Xshooter imaging
  66. GRB 250205A / EP250205A: further radio observations with the VLA
  67. EP250225a: NOT optical candidate counterpart
  68. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  69. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  70. EP250225a: TRT optical upper limits
  71. EP250226a/GRB 250226A: 1.6m Mephisto observations
  72. EP250226a/GRB 250226A: Kinder optical follow-up observations
  73. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  74. GRB 250225B: REM NIR upper limits
  75. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  76. EP250223a: CrAO ZTSH optical observation
  77. GRB 250225B: VLT optical and near-infrared candidate counterpart
  78. GRB 250225B: SVOM/GRM observation of a long burst
  79. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  80. EP250226a / GRB 250226A: TRT optical counterpart observation
  81. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  82. EP250223a: GMG Optical Observation
  83. EP250225a: Einstein Probe detected of a fast X-ray transient
  84. EP250223a: GROWTH-India Telescope optical observations
  85. EP250215A: J band upper limit by SYSU 80cm telescope
  86. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  87. EP250223a: Kinder optical follow-up observations
  88. GRB 250222A: SVOM/GRM observation of a burst
  89. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  90. EP250223a: REM NIR upper limit
  91. EP250223a: TRT optical afterglow observation
  92. EP250223a: refined analysis of the EP-WXT and FXT observations
  93. EP250223a: 1.6m Mephisto and 50cm array observations
  94. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  95. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  96. EP250223a: OASDG optical observations
  97. EP250223a: NOT optical afterglow candidate
  98. EP250223a: Einstein Probe detection of an X-ray transient
  99. GRB 250221A: Optical counterpart detection by LCO.
  100. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits

Advanced

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