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"

32536 results found.

  1. GRB 250313A: GRBAlpha detection
  2. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  3. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  4. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  5. GRB 250314A: ATCA radio upper limits
  6. EP250302a: VLA observations
  7. GRB 250317B: OHP/T193 continued follow-up
  8. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  9. GRB 250317C: SVOM/GRM observation of a long burst
  10. GRB 250317B: Leavitt Observatory optical upper limit
  11. GRB 250309B/AT2025dws: further ATCA observations
  12. GRB 250317B: Mondy AZT-33IK Optical Observations
  13. GRB 250317C: AstroSat CZTI detection
  14. GRB 250317B: NOT optical observations suggest an optical plateau phase
  15. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  16. GRB 250317B: OHP/T193 optical observations
  17. GRB250312A: Swift/UVOT Upper Limits
  18. GRB 250317B: REM optical/NIR observations
  19. GRB 250317B: Swift-XRT observations
  20. GRB 250316A: Swift/UVOT Upper Limits
  21. GRB 250314A: REM optical/NIR upper limits
  22. GRB 250316A: AbAO AS-32 Optical Upper Limit
  23. EP 250317B: Fading optical counterpart detection by LCO
  24. GRB 250317B: LCO detection of the fading optical afterglow
  25. GRB 250317B: refined SVOM/MXT analysis
  26. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  27. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  28. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  29. GRB 250316A: Fermi GBM Observation
  30. GRB 250316A: Swift-XRT observations
  31. Fermi GRB 250316A: Global MASTER-Net observations report
  32. GRB 250314A: SVOM/GRM analysis
  33. GRB 250316A: Swift ToO observations
  34. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  35. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  36. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  37. GRB 250314A: EP-FXT afterglow detection
  38. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  39. GRB 250314A: Swift/UVOT Upper Limits
  40. GRB 250312B: GRBAlpha detection
  41. GRB 250314A: Swift XRT Detection
  42. EP250315a: optical counterpart candidate detected by Gemini North
  43. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  44. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  45. SVOM/MXT upper limit on GRB 250314A
  46. GRB 250314A: SVOM/VT upper limit
  47. GRB 250314A: NOT near-infrared candidate counterpart
  48. GRB 250313A: Fermi GBM Detection
  49. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  50. GRB 250312B: Fermi GBM Observation
  51. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  52. Konus-Wind detection of GRB 250313A
  53. Konus-Wind detection of GRB 250308A
  54. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  55. GRB 250313A: SVOM/GRM observation of a bright long burst
  56. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  57. GRB 250313A: AstroSat CZTI detection of a bright long burst
  58. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  59. GRB 250313A: Fermi-LAT detection
  60. GRB 250313A: Swift ToO observations
  61. EP250304a: Pan-STARRS r and i-band imaging and photometry
  62. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  63. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  64. Fermi GRB 250313A: Global MASTER-Net observations report
  65. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  66. EP250304a: SVOM/VT optical observation
  67. EP250311a/GRB 250311A: EP-FXT follow-up observation
  68. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  69. EP250302a: Chandra X-ray Detection
  70. Fermi GRB 250312B: Global MASTER-Net observations report
  71. GRB 250226B: Fermi GBM Observation
  72. Swift GRB 250312A: Global MASTER-Net observations report
  73. GRB 250302A: Fermi GBM Observation
  74. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  75. GRB 241213A: VIRT Optical Upper Limit
  76. GRB 241228A: VIRT Optical Upper Limit
  77. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  78. GRB 250223B: Fermi GBM Observation
  79. GRB 250311A: Swift-XRT observations
  80. GRB 250228A: Fermi GBM Observation
  81. GRB 250309B: 1.3m DFOT Optical observations
  82. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  83. EP250311a: Global MASTER-Net observations report
  84. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  85. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  86. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  87. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  88. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  89. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  90. GRB 250309B: PRIME near-infrared detection
  91. EP250304a: Chandra detection
  92. GRB 250225B: Swift-BAT refined analysis
  93. GRB 250311A/EP250311a: TRT optical upper limit
  94. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  95. GRB 250311A: Tiled Swift observations
  96. EP250311a/GRB 250311A: EP-WXT detection
  97. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  98. GRB 250309B: SVOM/VT optical observation
  99. GRB 250309B / AT2025dws: further SAO RAS optical observations
  100. IceCube-250309A: Upper limits from Fermi-GBM Observations

Advanced

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