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"

43019 results found.

  1. GRB 250823A: Swift-XRT refined Analysis
  2. EP250821a: MeerKAT radio counterpart
  3. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  4. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  5. GRB 250824B: Fermi GBM Final Real-time Localization
  6. The EP-WXT trigger 01709200707 is likely a flaring star
  7. GRB 250823A: COLIBRÍ optical observations
  8. The EP-WXT trigger 01709200706 is likely a flaring star
  9. GRB 250823A: SVOM/VT optical observation
  10. GRB 250824A: Fermi GBM Final Real-time Localization
  11. GRB 250823A: Swift/UVOT Detection
  12. GRB 250823A: NOT optical observations
  13. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  14. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  15. GRB 250823A: Fermi GBM Observation
  16. GRB 250818B: MeerKAT Detection
  17. GRB 250823A: Enhanced Swift-XRT position
  18. GRB 250823A: LCOGT Optical Detection
  19. GRB 250823A: BOOTES6/DPRT early optical detection
  20. GRB 250823A: Liverpool Telescope optical detection
  21. GRB 250823A: Swift detection of a burst
  22. GRB 250823A: Fermi GBM Final Real-time Localization
  23. Swift GRB250823.84: Global MASTER-Net observations report
  24. Konus-Wind detection of GRB 250821B
  25. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  26. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  27. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  28. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  29. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  30. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  31. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  32. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  33. GRB 250806A: Gemini observations of host galaxy candidate
  34. IPN triangulation of GRB 250821B (long/bright)
  35. GRB 250821A: Kilonova-Catcher optical upper limits
  36. EP250821a: Swift/XRT counterpart fading
  37. GRB 250812A: SVOM/ECLAIRs refined analysis
  38. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  39. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  40. EP250821a: Swift/UVOT further observations.
  41. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  42. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  43. GRB 250821A: VLT/FORS2 Optical Observation
  44. GRB 250821A: GECAM-B detection
  45. GRB 250821B: SVOM/GRM observation
  46. EP250821a: SVOM/VT optical observation
  47. Fermi GRB 250821B: Global MASTER-Net observations report
  48. GRB 250821A: NOT z-band upper limit
  49. GRB 250821C: Fermi GBM Final Real-time Localization
  50. GRB 250821A: KAIT optical upper limit
  51. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  52. GRB 250821A: Swift-XRT refined Analysis
  53. Swift GRB 250821A: Global MASTER-Net observations report
  54. GRB 250821B: Fermi GBM Detection
  55. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  56. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  57. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  58. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  59. GRB 250821A: Enhanced Swift-XRT position
  60. GRB 250821A: Swift/UVOT Upper Limits
  61. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  62. EP250821a: Swift XRT and UVOT counterpart detection
  63. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  64. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  65. GRB 250821A: LCOGT Optical Upper Limits
  66. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  67. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  68. GRB 250821A: Prompt enhanced Swift-XRT position
  69. GRB 250821A: Swift detection of a burst
  70. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  71. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  72. EP250821a: Einstein Probe detection of an X-ray transient
  73. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  74. GRB 250819A: Insight-HXMT detection
  75. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  76. GRB 250818B: 10 GHz VLA detection
  77. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  78. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  79. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  80. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  81. GRB 250814A: Swift/UVOT Upper Limits
  82. GRB 250813B: Swift/UVOT Upper Limit
  83. IPN triangulation of GRB 250816A (short)
  84. IPN triangulation of GRB 250814C (short)
  85. IPN triangulation of GRB 250804B (short)
  86. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  87. GRB 250818B: Kilonova-Catcher optical afterglow detection
  88. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  89. GRB 250818B: Liverpool Telescope optical detections
  90. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  91. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  92. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  93. GRB 250818A: AstroSat CZTI detection
  94. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  95. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  96. GRB 250818B: Swift/UVOT Detection
  97. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  98. GRB 250820A: Fermi GBM Final Real-time Localization
  99. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  100. GRB 250818B: TRT Optical Observation

Advanced

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