Skip to main content
New! BOOM Notices and Schema v7.0.0. 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"

27321 results found.

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

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