Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

25225 results found.

  1. GRB 250818B: Swift-XRT afterglow detection
  2. GRB 250818B: SVOM detection of a short burst
  3. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  4. GRB 250818A: Swift detection of a burst
  5. sb25081602: Swift-XRT observations
  6. GRB 250816A: SVOM/GRM observation of a short burst
  7. GRB 250814A: Swift-BAT refined analysis
  8. GRB 250813B: Liverpool Telescope optical upper limits
  9. GRB 250814A: Further COLIBRÍ optical upper limit
  10. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  11. GRB 250814A: GRAWITA TNG NIR observations
  12. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  13. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  14. GRB250814A: TRT optical upper limits
  15. GRB 250814B: SVOM/GRM observation
  16. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  17. GRB 250813B: SVOM/GRM observation
  18. GRB 250814A: P200/WIRC observations of the afterglow candidate
  19. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  20. GRB 250814A: KAIT optical upper limit
  21. GRB 250814A: Swift-XRT refined Analysis
  22. GRB 240814A: Fermi GBM Observation
  23. GRB 250814A: Possible afterglow candidate from P200/WIRC
  24. GRB 250813B: Fermi GBM Observation
  25. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  26. GRB 250814A: J-band upper limit from WINTER
  27. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  28. GRB 250813B: NOT observations of the optical afterglow
  29. GRB 250814A: COLIBRÍ optical upper limit
  30. GRB 250813A: AstroSat CZTI detection
  31. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  32. GRB 250814A: DDOTI Optical Upper Limit
  33. GRB 250813B: EP-FXT counterpart detection
  34. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  35. GRB 250813B: Swift-XRT afterglow detection
  36. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  37. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  38. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  39. GRB 250813B: SVOM detection of a bright long burst
  40. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  41. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  42. EP250812a: Nickel optical upper limit
  43. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  44. EP250812a: NOT, NTT, and GS observations
  45. GRB 250812A: Swift/UVOT Detection
  46. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  47. EP250812a: Liverpool Telescope upper limits
  48. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  49. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  50. GRB 250812A: EP-FXT counterpart detection
  51. GRB 250807B: Swift-BAT refined analysis
  52. EP 250812a: GOTO optical upper limit
  53. GRB 250812A: Kilonova-Catcher optical afterglow detection
  54. EP250812a: Swift-XRT counterpart detection
  55. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  56. EP250812a: Einstein Probe detection of an X-ray transient
  57. GRB 250812A: Swift-XRT afterglow detection
  58. GRB 250812A: TRT likely optical counterpart detection
  59. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  60. GRB 250809A: Swift-BAT refined analysis
  61. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  62. GRB 250807A: Swift-BAT refined analysis
  63. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  64. GRB 250809A: Swift/UVOT Detection
  65. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  66. Corrected Swift-XRT Refined Analysis of GRB 250809A
  67. GRB 250809A: Swift-XRT refined Analysis
  68. GRB 250809A: LCOGT Optical Upper Limits
  69. GRB 250808A: VLT X-shooter candidate counterpart
  70. GRB 250809A: Swift detection of a gamma ray burst
  71. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. GRB 250808A: Fermi GBM Observation
  73. GRB 250808A: Swift-XRT candidate counterpart detection
  74. GRB 250807B: Swift/UVOT Detection
  75. GRB 250807B: Kilonova-Catcher optical afterglow detection
  76. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 250807A: Swift/UVOT Detection
  78. GRB 250807A: Swift-XRT refined Analysis
  79. GRB 250806A: SVOM/MXT refined analysis
  80. EP250807a: NTT z-band optical upper limit
  81. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  82. GRB 250807A: SVOM/GRM observation
  83. GRB 250807A: AstroSat CZTI detection of bright long burst
  84. GRB 250807B: Swift-XRT refined Analysis
  85. EP250807a: EP-WXT detection of a fast X-ray transient
  86. EP 250807.979: GOTO optical upper limit
  87. EP250807a: COLIBRÍ optical upper limit
  88. EP250806a: Upper limit from Fermi-GBM Observations
  89. GRB 250807B: Enhanced Swift-XRT position
  90. GRB 250807A: Enhanced Swift-XRT position
  91. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  92. GRB 250807B: Swift detection of a burst with an optical counterpart.
  93. GRB 250805A: Kilonova-Catcher optical upper limits
  94. GRB 250805A: Swift/UVOT Upper Limits
  95. GRB 250806A: Swift/UVOT U-band detection
  96. EP250806a: Liverpool telescope optical upper limit
  97. GRB 250807A: Swift detection of a burst with an optical counterpart
  98. EP250802a: EP-FXT follow-up observation
  99. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  100. EP250806a: SVOM /VT optical candidate

Advanced

Download all Circulars as a .tar.gz archive:
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