Skip to main content
JSON Notices via Email, Kafka Cron Jobs, Submitter Profile, GCN is Hiring. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28272 results found.

  1. GRB 250902A: Fermi GBM Detection
  2. GRB 250901A: Swift/UVOT Upper Limit
  3. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  4. GRB 250830B: Swift-XRT afterglow detection
  5. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  6. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  7. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  8. GRB 250902A: SVOM/GRM observation
  9. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  10. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  11. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  12. GRB 250901A: SVOM/VT optical afterglow with VHF data
  13. GRB 250901A: Swift-XRT afterglow detection
  14. EP250901a: Swift-XRT observations
  15. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  16. GRB 250901A: LCO optical upper limit
  17. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  18. EP250827b: Gemini Spectroscopy of AT 2025wkm
  19. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  20. EP250831a: NOT optical observations and tentative afterglow candidate
  21. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  22. GRB 250901A: SVOM detection of a burst
  23. EP250901a: Mephisto optical upper limits
  24. GRB 250830C: GECAM-B detection
  25. EP250901a: Einstein Probe detection of an X-ray transient
  26. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  27. EP250831a: Swift-XRT observations
  28. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  29. EP250831a: EP-WXT detection of a fast X-ray transient
  30. GRB 250831A: Swift-XRT counterpart detection
  31. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB 250831A: SVOM/VT upper limit with VHF data
  33. GRB 250831A: SVOM detection of a soft burst
  34. GRB 250830B: Swift-XRT observations
  35. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  36. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  37. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  38. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  39. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  40. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  41. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  42. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  43. GRB 250830B: MAXI/GSC detection
  44. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  45. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  46. GRB 250828B: Swift-BAT refined analysis
  47. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  48. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  49. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  50. EP250828a: Optical counterpart detection with Kinder observations
  51. EP250828a: Liverpool Telescope upper limits
  52. EP250828a: Global MASTER-Net observations report
  53. EP-WXT trigger 01709200800 : KAIT optical observations
  54. EP250828a: KAIT optical upper limit
  55. EP250827a: Swift/UVOT Detection
  56. EP250828a: NOT optical counterpart confirmation
  57. EP250828a: SVOM/VT optical candidate
  58. EP250828a: Seimei/TriCCS optical counterpart detection
  59. EP250828a: Optical upper limit with Kinder observations
  60. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  61. EP250827a: LCO observations show fading optical counterpart
  62. EP250828a: Einstein Probe detection of an X-ray transient
  63. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  64. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  65. EP250827a: confirmation of optical rebrightening with LCO
  66. GRB 250826A: SVOM/GRM observation
  67. EP250827A: An optical rebrightening was detected by LCO.
  68. EP250827a: Swift-XRT counterpart detection
  69. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  70. EP250827a: TRT optical observations
  71. EP250827a: Gemini-South redshift z = 1.613
  72. EP250827a: Einstein Probe detection of an X-ray transient
  73. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  74. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  75. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  76. Fermi GRB 250824B: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  78. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  79. GRB 250823A: Swift-BAT refined analysis
  80. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  81. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  82. GRB 250823A: Swift-XRT refined Analysis
  83. EP250821a: MeerKAT radio counterpart
  84. GRB 250823A: COLIBRÍ optical observations
  85. GRB 250823A: SVOM/VT optical observation
  86. GRB 250823A: Swift/UVOT Detection
  87. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  88. GRB 250823A: Fermi GBM Observation
  89. GRB 250823A: Enhanced Swift-XRT position
  90. GRB 250823A: LCOGT Optical Detection
  91. GRB 250823A: Swift detection of a burst
  92. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  93. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  94. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  95. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  96. GRB 250806A: Gemini observations of host galaxy candidate
  97. GRB 250821A: Kilonova-Catcher optical upper limits
  98. EP250821a: Swift/XRT counterpart fading
  99. GRB 250821A: Swift-BAT refined analysis
  100. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts

Advanced

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