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"

25841 results found.

  1. GRB 250902A: GECAM-B detection
  2. GRB 250903A: LCO optical observation
  3. GRB 250903A: LCO optical afterglow detection
  4. GRB 250903A: SVOM/VT optical confirmation with VHF data
  5. EP250901a: Mondy, Assy and SAO RAS optical limits
  6. GRB 250903A: TRT optical counterpart detection
  7. GRB 250902B: AstroSat CZTI detection
  8. GRB 250903A: SVOM detection of a burst
  9. EP250903a: TRT optical observations
  10. EP250903a: Einstein Probe detection of an X-ray transient
  11. EP 250827B: Detection of supernova counterpart by LCO.
  12. GRB 250902B: SVOM/GRM observation
  13. EP250827b: SVOM/VT observation of AT 2025wkm
  14. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  15. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  16. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  17. GRB 250902A: Fermi GBM Detection
  18. GRB 250901A: Swift/UVOT Upper Limit
  19. GRB 250902B: Fermi GBM Final Real-time Localization
  20. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 250830B: Swift-XRT afterglow detection
  22. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  23. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  24. GRB 250902A: SVOM/GRM observation
  25. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  26. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  27. GRB 250901A: EP-FXT follow-up observation
  28. GRB 250902A: Fermi GBM Final Real-time Localization
  29. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 250901A: SVOM/VT optical afterglow with VHF data
  31. GRB 250901A: Swift-XRT afterglow detection
  32. EP250901a: Swift-XRT observations
  33. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  34. GRB 250901A: LCO optical upper limit
  35. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  36. EP250831a: NOT optical observations and tentative afterglow candidate
  37. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  38. GRB 250901A: SVOM detection of a burst
  39. EP250901a: Mephisto optical upper limits
  40. GRB 250830C: GECAM-B detection
  41. EP250901a: Einstein Probe detection of an X-ray transient
  42. EP250831a: EP-FXT follow-up observation
  43. EP250831a: Swift-XRT observations
  44. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  45. EP250831a: EP-WXT detection of a fast X-ray transient
  46. GRB 250831A: Swift-XRT counterpart detection
  47. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. GRB 250831A: SVOM/VT upper limit with VHF data
  49. GRB 250831A: SVOM detection of a soft burst
  50. GRB 250830B: Swift-XRT observations
  51. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  52. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  53. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  54. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  55. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  56. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  57. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  58. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  59. The EP-WXT trigger 01709200994 is likely a flaring star
  60. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  61. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  62. GRB 250808B: SVOM detection of a burst through offline search
  63. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  64. EP250828a: Optical counterpart detection with Kinder observations
  65. EP250828a: Liverpool Telescope upper limits
  66. EP-WXT trigger 01709200800 : KAIT optical observations
  67. EP250828a: KAIT optical upper limit
  68. EP250827a: Swift/UVOT Detection
  69. EP250828a: NOT optical counterpart confirmation
  70. EP250828a: SVOM/VT optical candidate
  71. EP250828a: Seimei/TriCCS optical counterpart detection
  72. EP250828a: Optical upper limit with Kinder observations
  73. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  74. EP250828a: Einstein Probe detection of an X-ray transient
  75. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  76. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  77. EP250827a: confirmation of optical rebrightening with LCO
  78. GRB 250826A: SVOM/GRM observation
  79. EP250827A: An optical rebrightening was detected by LCO.
  80. EP250827a: Swift-XRT counterpart detection
  81. The EP-WXT trigger 01709200800 is likely a flaring star
  82. EP250827a: TRT optical observations
  83. EP250827a: BOOTES-7 early optical dectection
  84. EP250827a: Einstein Probe detection of an X-ray transient
  85. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  86. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  87. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  88. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  89. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  90. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  91. GRB 250823A: Swift-XRT refined Analysis
  92. EP250821a: MeerKAT radio counterpart
  93. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  94. The EP-WXT trigger 01709200707 is likely a flaring star
  95. GRB 250823A: COLIBRÍ optical observations
  96. The EP-WXT trigger 01709200706 is likely a flaring star
  97. GRB 250823A: SVOM/VT optical observation
  98. GRB 250823A: Swift/UVOT Detection
  99. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  100. GRB 250823A: Fermi GBM Observation

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