Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

28056 results found.

  1. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  2. EP250831a: NOT optical observations and tentative afterglow candidate
  3. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  4. GRB 250901A: SVOM detection of a burst
  5. EP250901a: Mephisto optical upper limits
  6. GRB 250830C: GECAM-B detection
  7. EP250901a: Einstein Probe detection of an X-ray transient
  8. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  9. EP250831a: Swift-XRT observations
  10. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  11. EP250831a: EP-WXT detection of a fast X-ray transient
  12. GRB 250831A: Swift-XRT counterpart detection
  13. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 250831A: SVOM/VT upper limit with VHF data
  15. GRB 250831A: SVOM detection of a soft burst
  16. GRB 250830B: Swift-XRT observations
  17. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  18. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  19. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  20. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  21. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  22. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  23. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  24. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  25. GRB 250830B: MAXI/GSC detection
  26. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  27. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  28. GRB 250828B: Swift-BAT refined analysis
  29. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  30. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  31. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  32. EP250828a: Optical counterpart detection with Kinder observations
  33. EP250828a: Liverpool Telescope upper limits
  34. EP250828a: Global MASTER-Net observations report
  35. EP-WXT trigger 01709200800 : KAIT optical observations
  36. EP250828a: KAIT optical upper limit
  37. EP250827a: Swift/UVOT Detection
  38. EP250828a: NOT optical counterpart confirmation
  39. EP250828a: SVOM/VT optical candidate
  40. EP250828a: Seimei/TriCCS optical counterpart detection
  41. EP250828a: Optical upper limit with Kinder observations
  42. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  43. EP250827a: LCO observations show fading optical counterpart
  44. EP250828a: Einstein Probe detection of an X-ray transient
  45. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  46. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  47. EP250827a: confirmation of optical rebrightening with LCO
  48. GRB 250826A: SVOM/GRM observation
  49. EP250827A: An optical rebrightening was detected by LCO.
  50. EP250827a: Swift-XRT counterpart detection
  51. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  52. EP250827a: TRT optical observations
  53. EP250827a: Gemini-South redshift z = 1.613
  54. EP250827a: Einstein Probe detection of an X-ray transient
  55. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  56. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  57. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  58. Fermi GRB 250824B: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  60. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  61. GRB 250823A: Swift-BAT refined analysis
  62. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  63. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  64. GRB 250823A: Swift-XRT refined Analysis
  65. EP250821a: MeerKAT radio counterpart
  66. GRB 250823A: COLIBRÍ optical observations
  67. GRB 250823A: SVOM/VT optical observation
  68. GRB 250823A: Swift/UVOT Detection
  69. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  70. GRB 250823A: Fermi GBM Observation
  71. GRB 250823A: Enhanced Swift-XRT position
  72. GRB 250823A: LCOGT Optical Detection
  73. GRB 250823A: Swift detection of a burst
  74. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  75. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  76. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  77. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  78. GRB 250806A: Gemini observations of host galaxy candidate
  79. GRB 250821A: Kilonova-Catcher optical upper limits
  80. EP250821a: Swift/XRT counterpart fading
  81. GRB 250821A: Swift-BAT refined analysis
  82. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  83. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  84. GRB 250821A: VLT/FORS2 Optical Observation
  85. GRB 250821B: SVOM/GRM observation
  86. EP250821a: SVOM/VT optical observation
  87. GRB 250821A: NOT z-band upper limit
  88. GRB 250821A: KAIT optical upper limit
  89. GRB 250821A: Swift-XRT refined Analysis
  90. GRB 250821B: Fermi GBM Detection
  91. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  92. GRB 250821A: Enhanced Swift-XRT position
  93. GRB 250821A: Swift/UVOT Upper Limits
  94. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  95. EP250821a: Swift XRT and UVOT counterpart detection
  96. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  97. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  98. GRB 250821A: LCOGT Optical Upper Limits
  99. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  100. GRB 250821A: Swift detection of a burst

Advanced

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