These forms allow you to extract an ASCII version of the ASM light
curve for a desired source. You can then save this output as text for
plotting or analysis. The data will be drawn directly from the most
recent MIT weekly production data files. These files contain data
points that have passed through our reliability filter criteria, as
explained on the MIT
ASM Light Curves Page.|
The ascii-formatted data available here are provided primarily for
convenience. While MIT and the GOF hope our instructions and
information are adequate for most users, we are not prepared formally
to support users of these data. We do, however, appreciate
Note that the RXTE SOF at
NASA's GSFC has a
script very similar to this, which allows you more flexibility in
choosing your own filters, but it is most likely slower.
We ask that when results from these analyses are used, they be
referenced as "quick-look results provided by the ASM/RXTE team."
This team includes all those working on the ASM at MIT and at the
Goddard Space Flight Center SOF and GOF.
For more information, please see the MIT ASM Light Curves Page.
The ASM light curves are preserved in two default data types:
the Dwell by Dwell files contain information pertaining to each
individual 90-s observation of the source of interest. We also
maintain files with One-Day Averaged intensities. Hardness ratios
are also preserved at one-day intervals.
Each raw data point represents the fitted source flux from one 90
second dwell. The data files contain results from all three Scanning
Shadow Cameras, and are quoted as rates in ASM counts per second,
where the Crab nebula flux is about 75 ASM c/s (when at the center of
an SSC field of view, with 8 anodes operational) in the 2-10 keV band.
The ASM data are also preserved in three sub-bands
. See table below for the normalized count
rates for the Crab in each energy band.
Each "one-day average" data point represents the one-day average of
the fitted source fluxes from a number (typically 5-10) of individual
ASM dwells. The error value used in plotting the one-day averages is
the quadrature average of the estimated errors on the individual
dwells from that day (note that for sources expected to show little
flux variation on shorter time scales, the RMS of the individual flux
measurements -- fourth column of the data files -- may provide a
Start and Stop Times
The ASM light curves are given as a function of time in Modified
Julian Date (MJD). If you know the MJD values of the time interval
you require, you may enter them directly in the fields for the
MJD. If not, you may select the Year, Month, and Day, and the
web page will display the corresponding MJD automatically.
Notes on Columns
The "Data by Dwell" ASCII files contain the following columns:
The count rate and estimated error are available in all four energy bands.
- MJD of the observation (JD - 2,400,000.5)
- SSC unit number
- Dwell sequence number
- Dwell number
- Reduced chi-square of the fit
- Number of sources in the field of view
- Earth angle (degrees)
- Fitted ASM unit count rate (counts/second; Crab is ~75)
- Estimated error (counts/second)
- Exposure time (seconds)
- Long-axis angle theta (degrees)
- Short-axis angle phi (degrees)
The "One-Day Averages" ASCII data files contain five columns:
The count rate, RMS error, and RMS scatter are available in all four
energy bands. There are also two hardness ratios with associated
errors. The hardness ratio 1 is the ratio between the counts in the B
band to the counts in the A band, and the hardness ratio 2 is the
ratio of the counts in the C band to the counts in the B band. The
ASM energy channels span the following nominal energy ranges (in keV):
- MJD of the observation (JD - 2,400,000.5)
- Averaged ASM unit count rate for the day (counts/second; Crab is ~75)
- RMS estimated error (counts/second)
- RMS deviation of the points from the one-day mean (counts/second)
- Number of dwells averaged
|Band||Energy Range||Crab ASM c/s|
The output light curve will contain the columns you select in the same
order as presented here.
If you are not sure of the name of your desired source in the ASM
catalog, you may enter the coordinates here (in either decimal or
sexigesimal format), and we will choose the closest ASM source to that
location. (Equinox J2000.0 only, please.)
You may know the source name in an alternate form to what we use in
ASM Catalog. We have a list of alternate
names for ASM catalogued sources, and if you enter a source
name, or a piece of a source name, we will try to find the ASM catalog
name for you. (This form is not case sensitive, and spaces are
This page and associated code written and maintained
by Don Smith.