Skip to main content
End of Swift Science Operations, CHIME Notices Unavailable During Upgrade. 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"

15403 results found.

  1. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  2. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  3. GRB 250831A: Swift-XRT counterpart detection
  4. GRB 250831A: SVOM detection of a soft burst
  5. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  6. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  7. GRB 250830B: Swift ToO observations
  8. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  9. EP250821a: SOAR observations
  10. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  11. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  12. GRB 250808B: SVOM detection of a burst through offline search
  13. EP250828a: Liverpool Telescope upper limits
  14. EP250828a: KAIT optical upper limit
  15. EP250828a: NOT optical counterpart confirmation
  16. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  17. EP250827A: VLT/X-shooter redshift confirmation
  18. EP250827a: confirmation of optical rebrightening with LCO
  19. GRB 250826A: SVOM/GRM observation
  20. EP250827A: An optical rebrightening was detected by LCO.
  21. EP250827a: Swift-XRT counterpart detection
  22. EP250827a: BOOTES-7 early optical dectection
  23. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  24. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  25. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  26. GRB 250821B: AstroSat CZTI detection
  27. GRB 250819A: AstroSat CZTI detection
  28. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  29. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  30. GRB 250821B: Insight-HXMT detection
  31. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  32. GRB 250823A: COLIBRÍ optical observations
  33. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  34. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  35. GRB 250823A: Fermi GBM Observation
  36. GRB 250823A: BOOTES6/DPRT early optical detection
  37. Konus-Wind detection of GRB 250821B
  38. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  39. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  40. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  41. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  42. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  43. GRB 250806A: Gemini observations of host galaxy candidate
  44. EP250821a: Swift/XRT counterpart fading
  45. GRB 250812A: SVOM/ECLAIRs refined analysis
  46. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  47. EP250821a: Swift/UVOT further observations.
  48. GRB 250821A: GECAM-B detection
  49. GRB 250821B: SVOM/GRM observation
  50. GRB 250821A: NOT z-band upper limit
  51. GRB 250821A: KAIT optical upper limit
  52. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  53. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  54. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  55. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  56. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  57. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  58. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  59. GRB 250819A: Insight-HXMT detection
  60. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  61. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  62. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  63. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  64. GRB 250818B: Kilonova-Catcher optical afterglow detection
  65. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  66. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  67. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  68. GRB 250818A: AstroSat CZTI detection
  69. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  70. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  71. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  72. GRB 250818B: EP-FXT counterpart detection
  73. LIGO/Virgo/KAGRA S250818k: FTW optical and NIR observations of AT 2025ulz
  74. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  75. GRB 250813B: SVOM/ECLAIRs refined analysis
  76. GRB 250818A: Fermi GBM Observation
  77. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  78. GRB 250814A: Further GRAWITA TNG NIR observations
  79. GRB 250818B: Swift-XRT afterglow detection
  80. GRB 250818B: SVOM detection of a short burst
  81. GRB 250816A: SVOM/GRM observation of a short burst
  82. SVOM/sb25081602: detection of a likely X-ray transient
  83. GRB 250814A: GRAWITA TNG NIR observations
  84. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  85. GRB 250814B: SVOM/GRM observation
  86. GRB 250814C: SVOM/GRM observation of a short burst
  87. GRB 250813B: SVOM/GRM observation
  88. GRB 250814A: P200/WIRC observations of the afterglow candidate
  89. GRB 250814A: KAIT optical upper limit
  90. GRB 240814A: Fermi GBM Observation
  91. GRB 250814A: Possible afterglow candidate from P200/WIRC
  92. GRB 250813B: Fermi GBM Observation
  93. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  94. GRB 250814A: J-band upper limit from WINTER
  95. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  96. GRB 250813B: NOT observations of the optical afterglow
  97. Subject GRB 250813B: SVOM/MXT refined analysis
  98. GRB 250814A: COLIBRÍ optical upper limit
  99. GRB 250813A: AstroSat CZTI detection
  100. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov